- vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 37683] GRB 250311A/EP250311a: TRT optical upper limit
by GCN Circulars 11 Mar '25

11 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39667 SUBJECT: GRB 250311A/EP250311a: TRT optical upper limit DATE: 25/03/11 12:48:25 GMT FROM: Wenxiong Li at NAOC <liwenxiong1992(a)gmail.com> W.X. Li (NAOC), S. Tinyanont, R. Anutarawiramkul, P. Butpan (NARIT), N.C. Sun, D. Xu, Z. Fan, Y.N. Wang (NAOC), report on behalf of a large collaboration: We observed the field of GRB 250311A/EP250311a detected by MAXI (Tatano et al. GCN 39660) and EP (Mao et al., GCN 39664), using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at Sierra Remote Observatories in California. Observations started at 12:00:05 UT on 2025-03-11, i.e., ~10 hours after the EP trigger, and 2 x 300s frames were obtained in the R band. No uncatalogued optical source is detected in the stacked R-band image within the EP/WXT error circle, down to the 3-sigma limiting magnitude of R ~ 20. View this GCN Circular online at https://gcn.nasa.gov/circulars/39667. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37682] IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
by GCN Circulars 11 Mar '25

11 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39666 SUBJECT: IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations DATE: 25/03/11 11:59:31 GMT FROM: Ichiro Takahashi at Science Tokyo <itakahashi(a)hp.phys.titech.ac.jp> Ichiro Takahashi (Science Tokyo), Kenta Taguchi (Kyoto U.), Seiji Toshikage, Masaomi Tanaka (Tohoku U.), Yousuke Utsumi (NAOJ), Ryosuke Itoh (Ibara City), Tomoki Morokuma (ARC/Chitech) report on behalf of a larger collaboration: We performed optical imaging observations of the localization area of IceCube-250309A (GCN 39631) using the optical three-color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50-cm telescope Akeno and the Tricolor CMOS Camera and Spectrograph (TriCCS) on the 3.8-m Seimei telescope. We started our observations at UT 2025-03-09 14:29 (MITSuME) and 2025-03-09 16:53 (Seimei), about 6.9 and 9.3 hours after the event, respectively. The observations with MITSuME covered the 90% probability region with 4 pointings while the observations with Seimei covered about half of the 90% probability region with 15 pointings. The data reduction and detailed examination of the data are underway. View this GCN Circular online at https://gcn.nasa.gov/circulars/39666. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37681] GRB 250311A: Tiled Swift observations
by GCN Circulars 11 Mar '25

11 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39665 SUBJECT: GRB 250311A: Tiled Swift observations DATE: 25/03/11 11:30:09 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a series of observations, tiled on the sky, of the MAXI GRB 250311A. Automated analysis of the XRT data will be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00135 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. The probability of finding serendipitous sources, unrelated to the MAXI event is high: any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/39665. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37680] EP250311a/GRB 250311A: EP-WXT detection
by GCN Circulars 11 Mar '25

11 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39664 SUBJECT: EP250311a/GRB 250311A: EP-WXT detection DATE: 25/03/11 10:28:02 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> X. Mao (NAO, CAS), Y. J. Zhang (THU), Y. L. Hua (PMO, CAS), Z. X. Ling (NAO, CAS) report on behalf of the Einstein Probe team: We report on the detection of a fast X-ray transient EP250311a at 2025-03-11T01:56:19 (UTC) by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The position of the source is R.A. = 224.691 deg, DEC = -2.850 deg (J2000) with an uncertainty of 2.8 arcmin (radius, 90% C.L. statistical and systematic). EP250311a may be associated with GRB 250311A/MAXI J1457-026 reported by the MAXI team (GCN #39660) due to their temporal and spatial coincidence. The transient event lasted for about 150 seconds, with a peak flux of about 1.6 x 10^-9 erg/s/cm^2 in 0.5-4 keV. The average spectrum during the burst can be fitted with an absorbed powerlaw model, with nH fixed at the Galactic value of 6.4 x 10^20 cm^-2 and a photon index of 1.4 (-0.8/+0.8). The unabsorbed average 0.5-4 keV flux is estimated to be 6.1 (-1.9/+3.1) x 10^-10 erg/s/cm2. The uncertainties are at the 90% confidence level for the above parameters. The FXT follow-up observations have been scheduled. Further follow-up observations are encouraged to identify the nature of this X-ray transient. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/39664. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37679] GRB 250308A: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 11 Mar '25

11 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39663 SUBJECT: GRB 250308A: CALET Gamma-Ray Burst Monitor detection DATE: 25/03/11 09:19:04 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> Y. Kawakubo, A. Yoshida, T. Sakamoto, S. Sugita (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The short GRB 250308A (SVOM/GRM observation: the SVOM team, GCN Circ. 39632, 39636; IPN triangulation: Kozyrev et al., GCN Circ. 39653) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 18:06:30.72 UTC on 8 March 2025 (https://cgbm.calet.jp/cgbm_trigger/flight/1425492335/index.html). The burst signal was seen by SGM and HXM2. The burst light curve shows a single pulse that starts at T-0.1 sec, peaks at T+0.1 sec, and ends at T+0.3 sec. The T90 and T50 durations measured by the SGM data are 0.4 +/- 0.2 sec and 0.2 +/- 0.1 sec (40-1000 keV), respectively. The ground-processed light curve is available at https://cgbm.calet.jp/cgbm_trigger/ground/1425492335/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at Waseda University. View this GCN Circular online at https://gcn.nasa.gov/circulars/39663. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37678] GRB 250311B: SVOM detection of a burst
by GCN Circulars 11 Mar '25

11 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39662 SUBJECT: GRB 250311B: SVOM detection of a burst DATE: 25/03/11 08:25:41 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> C.W. Wang (IHEP), R.C. Chen (NJU), H. Goto, D. Turpin (CEA), M. G. Bernardini (INAF-OAB, LUPM) on behalf of the SVOM mission team. At 2025-03-11T07:08:05.065 UTC (Tb) SVOM/ECLAIRs triggered on the gamma-ray burst GRB 250311B (SVOM burst-id sb25031101). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was only detected by the Count rate Trigger (CRT), from which we received 1 alert. CRT provided the alert with the best signal-to-noise-ratio (SNR) of 7.45 in the [8-120] keV energy band over a time window of 10.2 seconds starting at Tb. The localization of the best alert is R.A., Dec 146.885, 29.891 degrees: RA (J2000) = 9h47m32.36s Dec (J2000) = 29d53m26.62s with a 90% C.L. radius of 10.53 arcmin (including systematic error of 2 arcmin added in quadrature). No immediate slew was performed on this burst. A SVOM ToO has been requested. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. The Burst Advocate (BA) on shift for this burst is C.W. Wang: cwwang(a)ihep.ac.cn. Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst. View this GCN Circular online at https://gcn.nasa.gov/circulars/39662. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37677] GRB 250309B: SVOM/VT optical observation
by GCN Circulars 11 Mar '25

11 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39661 SUBJECT: GRB 250309B: SVOM/VT optical observation DATE: 25/03/11 06:47:44 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Z. M. Wang, A. Li (BNU), Y. F. Liang (PMO), L. P. Xin, Y. L. Qiu, H. L. Li, Z. H. Yao, Y. Xu, P. P. Zhang, W. J. Xie, J. Wang, X. H. Han, Y. J. Xiao, H. B. Cai, J. Y. Wei (NAOC), J. T. Palmerio (CEA/Irfu) report on behalf of the SVOM team: The SVOM/VT conducted a ToO follow-up observation of ZTF25aaitvjt / AT2025dws (Stein et al., GCN 39639) which is considered as the optical candidate of Fermi GRB 250309B (Preis & Greiner, GCN 39629; McDermott et al., GCN 39635; McDermott et al., GCN circ. 39642) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously, The optical candidate ZTF25aaitvjt / AT2025dws (Stein et al., GCN 39639; Pérez-Fournon et al., GCN 39643; Stein and Ahumada, GCN 39644; Moskvitin et al., GCN 39645; Perley et al., GCN 39646; Malesani et al., GCN 39647; Ducoin et al., GCN 39650; Shin et al, GCN 39654) is clearly detected in images. The brightness in AB manigutude was estimated to be 20.20+/0.04 mag in VT_R, and 20.72+/-0.05 mag in VT_B stacked images, with an exposure time of 46*60 seconds, at the mid time of 0.974 days post the burst. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC),CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/39661. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37676] GRB 250311A/MAXI J1457-026: MAXI/GSC detection
by GCN Circulars 11 Mar '25

11 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39660 SUBJECT: GRB 250311A/MAXI J1457-026: MAXI/GSC detection DATE: 25/03/11 03:47:32 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> K. Tatano, H. Negoro, M. Nakajima (Nihon U.), M. Serino, Y. Kawakubo (AGU), Y. Kudo, H. Shibui, K. Takagi, H. Takahashi, H. Nishio (Nihon U.), T. Mihara, S. Yamada, S. Wang, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, S. Sugita, H. Hiramatsu, H. Nishikawa, Y. Kondo, S. Sasao, A. Yoshida (AGU), Y. Tsuboi, H. Sugai, N. Nagashima (Chuo U.), M. Shidatsu, Y. Niida (Ehime U.), I. Takahashi, M. Niwano, N. Higuchi, Y. Yatsu (Tokyo Tech), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, M. Kurihara (JAXA), Y. Ueda, Y. Okada, K. Fujiwara (Kyoto U.), M. Yamauchi, Y. Otsuki, T. Hasegawa, M. Nishio (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), W. Iwakiri (Chiba U.), T. Kawamuro (Osaka U.) report on behalf of the MAXI team: The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at 01:55:22 UT on March 11, 2025. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (224.318 deg, -2.613 deg) = (14 57 16, -02 36 46) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.33 deg and 0.28 deg, respectively. The roll angle of long axis from the north direction is 9.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 75 +- 18 mCrab (4.0-10.0keV, 1 sigma error). Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners: (223.607, -1.537) deg = (14 54 25, -01 32 13) (J2000) (223.164, -1.982) deg = (14 52 39, -01 58 55) (J2000) (225.099, -3.901) deg = (15 00 23, -03 54 03) (J2000) (225.542, -3.455) deg = (15 02 10, -03 27 18) (J2000) There was no significant excess flux in the previous transit at 00:22 UT and in the next transit at 03:28 UT with an upper limit of 20 mCrab for each. We note that the source position is consistent with the position of GRB 250305A reported by Fermi-GBM (#39597). We encourage follow-up observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39660. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37675] The EP-WXT trigger 01709132425 is not a real source
by GCN Circulars 11 Mar '25

11 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39659 SUBJECT: The EP-WXT trigger 01709132425 is not a real source DATE: 25/03/11 02:14:26 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.L. Hua (PMO), Y. J. Zhang (THU), X. Mao, Z. X. Ling (NAO, CAS) report on behalf of the Einstein Probe team: Further analysis of the data suggests that the EP-WXT on-board trigger (ID: 01709132425) at 2025-03-10 18:42:15 (UTC) is not a real source. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with onboard X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics) View this GCN Circular online at https://gcn.nasa.gov/circulars/39659. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37674] GRB 250309B / AT2025dws: further SAO RAS optical observations
by GCN Circulars 10 Mar '25

10 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39658 SUBJECT: GRB 250309B / AT2025dws: further SAO RAS optical observations DATE: 25/03/10 23:50:28 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. S. Moskvitin, O. I. Spiridonova (SAO RAS), A. S. Pozanenko (IKI), A. Ghosh, S. Razzaque (CAPP, University of Johannesburg), Yu. V. Sotnikova (SAO RAS) report on behalf of a larger collaboration. We observed the field of GRB 250309B / AT2025dws (Preis and Greiner, GCN 39629; Fermi GBM team, GCN 39635; McDermott et al., GCN 39642; Wang et al., GCN 39648; Page and Evans, GCN 39649; Kozyrev et al., GCN 39652; Frederiks et al., GCN 39655; Scotton, GCN 39657) with Zeiss-1000 1-m telescope of SAO RAS, equipped with the CCD-photometer. We obtained 19 x 300 sec. images in Rc band on March 10, 21:37:13 -- 23:23:40 UT (t_mid - T0 = 1.6194 days). The optical candidate ZTF25aaitvjt / AT2025dws (Stein et al., GCN 39639; Pérez-Fournon et al., GCN 39643; Stein and Ahumada, GCN 39644; Moskvitin et al., GCN 39645; Perley et al., GCN 39646; Malesani et al., GCN 39647; Ducoin et al., GCN 39650; Shin et al, GCN 39654) is clearly detected in the stacked image with the brightness of R = 20.65 +/- 0.13. We do not performed host galaxy subtraction. The photometry is based on nearby stars from the USNO-B1.0 catalog (R2 magnitudes) and has not been corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39658. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37673] IceCube-250309A: Upper limits from Fermi-GBM Observations
by GCN Circulars 10 Mar '25

10 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39657 SUBJECT: IceCube-250309A: Upper limits from Fermi-GBM Observations DATE: 25/03/10 23:19:19 GMT FROM: Lorenzo Scotton at UAH <lscottongcn(a)outlook.com> L. Scotton (UAH) reports on behalf of the Fermi-GBM Team: For the IceCube high-energy neutrino candidate event IceCube-250309A (GCN 39631), at the event time Fermi-GBM was observing the reported neutrino location at: RA: 211.07 (+0.31 -0.30 deg 90% PSF containment) J2000 Dec: -10.73 (+0.26 -0.30 deg 90% PSF containment) J2000 Fermi-GBM detected GRB 250309B (GCNs 39635, 39642) around 146s after the time of the neutrino candidate. However, the ZTF and GROWTH collaborations reported the detection of a potential optical counterpart ZTF25aaitvjt | AT2025dws (R. Stein et al, GCN 39639), suggesting that GRB 250309B and IceCube-250309A are unrelated. The IPN triangulation (Kozyrev A. S. et al, GCN 39652) also suggests that GRB 250309B and IceCube-250309A are unrelated. An automated, blind search for short gamma-ray bursts below the onboard triggering threshold in Fermi-GBM also identified no counterpart candidates. The GBM targeted search, the most sensitive, coherent search for GRB-like signals, was run from +/-30 s around the neutrino candidate time. From this search, no significant signal was found related to IceCube-250309A. Using the representative soft, normal, and hard GRB-like templates described in arXiv:2308.13666, we set the following 3 sigma flux upper limits over 10-1000 keV (in units of 10^-7 erg/s/cm^2): Timescale Soft Normal Hard ------------------------------------------- 0.128 s: 1.0 1.8 3.7 1.024 s: 0.35 0.56 1.3 8.192 s: 0.11 0.11 0.24 These results are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/39657. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37672] EP250308a: 1.6m Mephisto optical upper limits
by GCN Circulars 10 Mar '25

10 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39656 SUBJECT: EP250308a: 1.6m Mephisto optical upper limits DATE: 25/03/10 17:46:43 GMT FROM: Brajesh Kumar at SWIFAR, YNU <brajesh(a)ynu.edu.cn> Shiyan Zhong, Jinghua Zhang, Guowang Du, Xin Chang, Bin Yan, Xingzhu Zou, Brajesh Kumar, Yuan Fang, Helong Guo, Edoardo P. Lagioia, Yuanpei Yang, Xiangkun Liu, Xiaowei Liu (all SWIFAR, YNU) report on behalf of the Mephisto Team: The field of EP250308a (Yin et al., GCN 39625) was observed with the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory. Two exposures of 180s in the MEPHISTO u band, and six exposures of 50s in the MEPHISTO g band were simultaneously (ug) obtained starting from 2025-03-09T20:07:03 (~27h after the trigger). In our stacked u and g band images, we did not detect any source at the position reported by Yin et. al., GCN 39625. The preliminary 3-sigma upper limits are below, which is consistent with previously reported GCN (Zhu et al., GCN 39624; Busmann et al., GCN 39626; Lipunov et al. GNC 39628). Start_Time(UT) | Band | Exp(s) | LimMag(AB) --------------------|------|--------|------------ 2025-03-09T20:07:03 | u | 180*2 | >22.20 2025-03-09T20:07:03 | g | 50*6 | >22.38 ------------------------------------------------------------------------------------------------- Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6-m wide-field multi-channel telescope, the first of its type in the world, capable of imaging the same field of view in three optical bands simultaneously. It provides real-time, high-quality colors of stellar objects. The on-site telescope assemblage and commissioning were carried out in September 2022. The first light in all three channels was achieved on 2023 December 21. ------------------------------------------------------------------------------------------------- View this GCN Circular online at https://gcn.nasa.gov/circulars/39656. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37671] Konus-Wind detection of GRB 250309B
by GCN Circulars 10 Mar '25

10 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39655 SUBJECT: Konus-Wind detection of GRB 250309B DATE: 25/03/10 17:17:33 GMT FROM: Dmitry Frederiks at Ioffe Institute <fred(a)mail.ioffe.ru> D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB 250309B ( Fermi-GBM BALROG localization: Preis and Greiner, GCN 39629; Fermi-GBM detection: The Fermi GBM team, GCN 39635; McDermott et al., GCN 39642; GECAM-B detection: Wang et al., GCN 39648; IPN triangulation: Kozyrev et al., GCN 39652) triggered Konus-Wind (KW) at T0=27513.791 s UT (07:38:33.791). The burst light curve shows a multi-peaked structure which starts at ~T0-0.5 s and has a total duration of ~8 s. The emission is seen up to ~1 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250309_T27513/ As observed by Konus-Wind, the burst had a fluence of (5.79 ± 0.48)x10^-6 erg/cm^2 and a 64-ms peak energy flux, measured from T0 + 1.024 s, of (4.35 ± 0.43)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+8.448 s) is best fit in the 20 keV - 15 MeV range by a power law with exponential cutoff (CPL) model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.03(-0.20,+0.22) and Ep = 106(-7,+8) keV (chi2 = 80/79 dof). Fitting this spectrum by a Band function yields the same values of alpha and Ep, and an upper limit on the high energy photon index beta of -3.1 (chi2 = 79/78 dof). Assuming the redshift z=1.898 ( Malesani et al., GCN 39647) of ZTF25aaitvjt/AT 2025dws, the candidate counterpart to GRB 250309B (Stein et al., GCN 39639), and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014), we estimate the burst isotropic energy release E_iso to (5.3 ± 0.4)x10^52 erg, the isotropic peak luminosity L_iso to (1.2 ± 0.12)x10^53 erg/s, and the rest-frame peak spectral energy Ep,z to (306 ± 21) keV. With the obtained estimates, GRB 250309B is consistent with 68% prediction band of the 'Amati' relation and 90% prediction band of the 'Yonetoku' relation for the sample of >300 long KW GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021), see http://www.ioffe.ru/LEA/GRBs/GRB250309_T27513/GRB250309B_rest_frame.pdf All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/39655. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37670] GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
by GCN Circulars 10 Mar '25

10 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39654 SUBJECT: GRB 250309B / AT2025dws: KMTNet-CTIO optical observations DATE: 25/03/10 16:46:17 GMT FROM: Min-Su Shin at Korea Astronomy and Space Science Institute <msshin(a)kasi.re.kr> Min-Su Shin (Korea Astronomy and Space Science Institute; KASI), Jae-Woo Kim (KASI), and Seo-Won Chang (Seoul National University) report on behalf of the KMTNet neutrino ToO program: We observed the area corresponding to the neutrino event IceCube-250309A with the KMTNet-CTIO for the initial coordinates of Zegarelli et. al, GCN 39631. The KMTNet-CTIO observation started at 2025-03-09 09:44 (UTC), and we acquired I-band images for four pointings covering the entire 90% uncertainty area for the alert. The source AT2025dws (Stein et al., GCN 39639, Pérez-Fournon et al. GCN 39643, Moskvitin et al. GCN 39645, Perley et al. GCN 39646) is clearly found in the images with the following photometric measurements: MJD mag err 60743.40574 17.88 0.02 60743.40723 17.87 0.02 We thank the KMTNet operators for their support. View this GCN Circular online at https://gcn.nasa.gov/circulars/39654. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37669] IPN triangulation of GRB 250308A (short)
by GCN Circulars 10 Mar '25

10 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39653 SUBJECT: IPN triangulation of GRB 250308A (short) DATE: 25/03/10 16:02:51 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin on behalf of the HEND/Mars Odyssey team, D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, Y. Zhang, C. Wang, S. Xiong, J. Wei, and B. Cordier on behalf of the SVOM-GRM team, S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu on behalf of the Swift-BAT team, E. Burns on behalf of the IPN, and W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr, and A.S. Gardner on on behalf of the GRS-Odyssey GRB team, report: The short-duration GRB 250308A (SVOM-GRM detection: Wang et al., GCN 39632, 39636) was detected by SVOM (GRM), Konus-Wind, Swift (BAT), CALET (GBM), and Mars-Odyssey (HEND) at about 65191 s UT (18:06:31). The burst was outside the coded field of view of the BAT. We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 160.761 (10h 43m 03s) +23.741 (+23d 44' 26") Corners: 160.858 (10h 43m 26s) +24.405 (+24d 24' 18") 160.981 (10h 43m 55s) +24.338 (+24d 20' 15") 160.655 (10h 42m 37s) +23.074 (+23d 04' 27") 160.536 (10h 42m 09s) +23.145 (+23d 08' 43") --------------------------------------------- The error box area is 578 sq. arcmin, and its maximum dimension is 1.3 deg (the minimum one is 7.4 arcmin). The Sun distance was 159 deg. This localization may be improved. The distance between the center of SVOM (GRM) localization (GCN 39636) and the IPN box center is 9.4 deg. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB250308_T65194/IPN/ The HEALPix triangulation map is the multi-order HEALPix in units of probability density. The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular. View this GCN Circular online at https://gcn.nasa.gov/circulars/39653. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37668] IPN triangulation of GRB 250309B
by GCN Circulars 10 Mar '25

10 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39652 SUBJECT: IPN triangulation of GRB 250309B DATE: 25/03/10 13:17:34 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin on behalf of the HEND/Mars Odyssey team, D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, A. Goldstein, M. S. Briggs, C. Wilson-Hodge, and E. Burns on behalf of the Fermi GBM team, and W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr, and A.S. Gardner on on behalf of the GRS-Odyssey GRB team, report: The long-duration GRB 250309B (Fermi-GBM BALROG localization: Preis and Greiner, GCN 39629; Fermi-GBM detection: The Fermi GBM team, GCN 39635; McDermott et al., GCN 39642; GECAM-B detection: Wang et al., GCN 39648) was detected by Fermi (GBM trigger 763198715), Konus-Wind, Mars-Odyssey (HEND), and GECAM-B at about 27510 s UT (07:38:30). We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: ------------------------------- RA(2000), deg Dec(2000), deg ------------------------------ Center: 208.8101 -12.9141 Corners: 204.1541 -23.3442 204.3621 -23.0319 213.4312 -2.9483 213.5345 -2.5970 ------------------------------- The error box area is 1.3 sq. deg, and its maximum dimension is 23 deg (the minimum one is 3.5 arcmin). The Sun distance was 135 deg. This localization may be improved. The IPN localization is consistent with, but reduces the area of, the final Fermi-GBM (GCN 39635) and BALROG (GCN 39629) localizations. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB250309_T27513/IPN/ The HEALPix triangulation map is the multi-order HEALPix in units of probability density. The localization of IceCube-250309A (IceCube Collaboration, GCN 39631) is inconsistent with the IPN localization. The optical transient ZTF25aaitvjt/AT2025dws (Stein et al., GCN 39639) is inside the IPN box, which further strengthen the interpretation of transient as the burst afterglow. The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular. View this GCN Circular online at https://gcn.nasa.gov/circulars/39652. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37667] IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
by GCN Circulars 10 Mar '25

10 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39651 SUBJECT: IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect DATE: 25/03/10 12:01:17 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> K. Labzina, K.Zhirkov, V.Lipunov, E.Gorbovskoy, A.Kuznetsov, G.Antipov, D.Vlasenko, A.Kuznetsov, N.Tyurina, P.Balanutsa, A.Chasovnikov, V.Topolev, Ya.Kechin, V.Senik, Yu.Tselik (Lomonosov MSU), O.Gress, N.Budnev, O.Ershova (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), D.Buckley (SAAO), A.Sosnovskij (Crao RAS), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) started IceCube-241224A (IC GCN #38664, trigger No 303893, trigger time 07:10:04UT, 12h 20m 13.44s , +02d 46m 01.2s, R=0.74) errorbox 16 sec after notice time (178 sec after trigger time) at 2024-12-24 07:13:02 UT, with upper limit up to 19.6 mag (Lipunov et al.GCN#38663, MASTER cover map: https://master.sai.msu.ru/site/master2/event.php?id=2720792 ) We observed it in MASTER-SAAO, MASTER-OAFA and analyzed MASTER archive images since 2016 of the sources, that can be related with this event. There is quasar PKS 1217+02 inside 3-sigma IC error-box https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=&-out.add=_r&-out.add=…) We detected its brightening up to 15.7m near alert time. MASTER archive light curve from 2016 year is available at http://observ.pereplet.ru/IC/MASTER_IC241224A.jpg We report the observation of an Zhirkov effect, discovered earlier (The Astrophysic Jornal Letters, 896, L19, 2020 https://ui.adsabs.harvard.edu/abs/2020ApJ...896L..19L/abstract ). View this GCN Circular online at https://gcn.nasa.gov/circulars/39651. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37666] GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
by GCN Circulars 10 Mar '25

10 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39650 SUBJECT: GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart DATE: 25/03/10 11:48:47 GMT FROM: F. Fortin at IRAP <ffortin.sci.edu(a)gmail.com> Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Kin Ocelotl López (UNAM), Francesco Magnani (CPPM), Stéphane Basa (UAR Pytheas), Benjamin Schneider (LAM), Alan M. Watson (UNAM), William H. Lee (UNAM), Camila Angulo (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Jean-Luc Atteia (IRAP), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Noémie Globus (UNAM), Diego López-Cámara (UNAM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), and Antonio de Ugarte Postigo (LAM) We observed the field of GRB 250309B (Preis et al., GCN 39629) using the OGSE engineering camera on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We observed from 2025-03-10T07:34:55 to 2025-03-10T08:46:13 UTC (23h 56min after the trigger) and obtained 3000 seconds of exposure in the r filter. The data were analyzed in STDWeb/STDPipe (Karpov 2021), with photometric calibration against Pan-STARRS DR1 and image subtraction against Pan-STARRS DR2. Our photometry is in the AB system and is not corrected for Galactic extinction. In our stacked image, after the subtraction, we clearly detect a source at the position of the optical candidate AT2025dws (reported by Stein et al., GCN 39639, Pérez-Fournon et al. GCN 39643, Moskvitin et al. GCN 39645, Perley et al. GCN 39646) with magnitude: r = 20.76 +/- 0.10 Further observations are planned to monitor the evolution of the transient. We warmly thank the COLIBRÍ and DDRAGO engineering teams and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/39650. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37665] GRB 250309B: Swift-XRT refined Analysis
by GCN Circulars 10 Mar '25

10 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39649 SUBJECT: GRB 250309B: Swift-XRT refined Analysis DATE: 25/03/10 07:19:06 GMT FROM: K.L. Page at U Leicester <klp5(a)leicester.ac.uk> K.L. Page and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 3.9 ks of XRT data for the Fermi/GBM-detected GRB 250309B, from 46.1 to 57.7 ks after the Fermi trigger (GCN Circs. 39635, 39642). The data are entirely in Photon Counting (PC) mode. We detect a previously uncatalogued X-ray source at the following coordinates: RA/Dec(J2000) = 210.80129, -8.50302, which is equivalent to RA (J2000): 14 03 12.31 Dec(J2000): -08 30 10.9 with an uncertainty of 3.0 arcsec (radius, 90% confidence). This source is 1.8 arcsec from the optical counterpart AT2025dws discovered by the Zwicky Transient Facility (GCN Circ. 39639), and also detected by LCO (GCN Circ. 39643), SAO RAS (GCN Circ. 39645), the Liverpool telescope (GCN Circ. 39646) and the Swift UVOT (GCN Circ. 39644). A redshift of 1.898 has been reported from OSIRIS+/GTC spectroscopy in GCN Circ. 39647. The light curve can be modelled with a power-law decay with a decay index of alpha=2.7 (+1.1, -2.6). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.74 (+0.24, -0.23). The best-fitting absorption column is consistent with the Galactic value of 3.0 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.8 x 10^-11 (4.0 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Galactic foreground column: 3.0 x 10^20 cm^-2 Photon index: 1.74 (+0.24, -0.23) If the light curve continues to decay with a power-law decay index of 2.7, the count rate at T+24 hours will be 0.015 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.7 x 10^-13 (6.0 x 10^-13) erg cm^-2 s^-1. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/39649. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37664] GRB 250309B / IceCube-250309A: GECAM-B observations
by GCN Circulars 10 Mar '25

10 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39648 SUBJECT: GRB 250309B / IceCube-250309A: GECAM-B observations DATE: 25/03/10 07:04:11 GMT FROM: Yue Wang <m18509381757(a)163.com> Yue Wang, Jia-Cong Liu, Jin-Peng Zhang, Chen-Wei Wang, Wen-Jun Tan, Wang-Chen Xue, Shao-Lin Xiong (IHEP), report on behalf of the GECAM team: GECAM-B was triggered on-ground by a long burst, GRB 250309B, at 2025-03-09T07:38:31.050 UTC (T0), which was also observed by Fermi/GBM (McDermott et al., GCN 39642). According to GECAM-B light curve, this burst mainly consists of multiple pulses with a duration (T90) of about 6.74 (+/-0.15) sec (50-300 keV). The GECAM-B light curve of GRB 250309B could be found at: https://www.bursthub.cn//admin/static/gecamgrb250309B.png The GECAM-B localization of GRB 250309B is consistent with the Fermi/GBM localization of this burst (McDermott et al., GCN 39642) and the position of optical counterpart AT 2025dws (Stein et al., GCN 39639) as well as the IceCube-250309A (The IceCube Collaboration, GCN 39631). Thus, we confirm that GRB 250309B is spatially and temporally coincident with IceCube-250309A. The time-integrated spectrum of GRB 250309B from T0-1.0 s to T0+6.0 s is best fitted by a cutoff-powerlaw function with Epeak = 109.3 +/- 6.8 keV and alpha = -1.00 +/- 0.27. The event fluence (10-1000 keV) in this time interval is (7.65 +/- 0.56)E-06 erg/cm^2. With the measured redshift z=1.898 (D. B. Malesani et al., GCN 39647), we calculate the isotropic energy Eiso is (7.4 ± 0.8)x10^52 erg. Then we note that GRB 250309B is well consistent with Type II GRBs in the 'Amati' relation diagram, as shown at: https://www.bursthub.cn//admin/static/grb250309B_amati.png Further, we note that there is no GECAM-B trigger just around the event time of IceCube-250309A (2025-03-09 at 07:36:04.75 UT, The IceCube Collaboration, GCN 39631). We implemented a targeted search [1] for burst activities from T0-330 s to T0-30 s embracing this IceCube event, but identified no candidate above 3 sigma. Thus, we calculated the upper limit of a potential precursor of GRB 250309B which is simultaneously associated with IceCube-250309A. Considering three typical GRB spectral models (i.e. soft, normal and hard Band functions), three timescales and the center region of GRB localization (RA= 211.07, Dec = -10.73), the 3 sigma upper limits of the potential GRB precursor energy flux (15 keV-5000 keV, in units of 10^-7 erg/s/cm^2) are reported below: |Timescale (s)|Soft|Normal|Hard| | ------------ | ------------ | ------------ | ------------ | |0.1|3.86|3.92|6.33| |1 |1.22|1.24|2.00| |10 |0.38|0.39|0.63| We note that these results are preliminary. Refined analysis will be reported. Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two microsatellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/39648. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37663] GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
by GCN Circulars 10 Mar '25

10 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39647 SUBJECT: GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898 DATE: 25/03/10 05:47:31 GMT FROM: Antonio de Ugarte Postigo at LAM, CNRS <adeugartepostigo(a)gmail.com> D. B. Malesani (DAWN/NBI and Radboud Univ.), A. de Ugarte Postigo (LAM), A. Martin-Carrillo (UCD), C. C. Thoene (AbAO), J. F. Agui Fernandez (CAHA), N. R. Tanvir (Univ. Leicester), L. Izzo (INAF/OACn and DARK/NBI), J. P. U. Fynbo (DAWN/NBI), S. Geier (GTC), G. Lombardi (GTC), N. A. Rakotondrainibe (LAM), F. Perez Toledo (GTC), and A. Perez (GTC) report: We observed the afterglow of GRB 250309B (Preis et al. GCN 39629; Fermi GBM team GCN 39635; Stein et al. GCN 39639; McDermott et al. GCN 39642; Perez-Fournon et al. GCN 39643; Stain et al. GCN 39644; Moskvitin et al. GCN 39645; Perley et al. GCN 39646) with OSIRIS+, mounted on te 10.4.m GTC telescope at the Roque de los Muchachos Observatory in the island of La Palma (Spain). The observation started at 2025-03-10T03:28:33.011 UT (19.83 h after the burst) and consisted of 2x900 s spectroscopy with grism R1000B, covering the range between 3600 and 7880 AA. A preliminary reduction shows a continuum across the complete spectral range with multiple spectral features which we interpret as due to SiII, SiIV, OI, CII, CIV, FeII, AlII, AlIII, ZnII, and MnII at a common redshift of 1.898, which we identify as the redshift of the GRB. Additionally, we detect a strong intervening system with features of CIV, AlII, FeII, MgII and MgI at a a redshift of 1.634. View this GCN Circular online at https://gcn.nasa.gov/circulars/39647. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37662] Liverpool Telecope observations of AT 2025dws / GRB 250309B
by GCN Circulars 10 Mar '25

10 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39646 SUBJECT: Liverpool Telecope observations of AT 2025dws / GRB 250309B DATE: 25/03/10 03:52:06 GMT FROM: Daniel Perley at Liverpool JMU <d.a.perley(a)ljmu.ac.uk> D. A. Perley (LJMU), A. Bochenek (LJMU), and A. Y. Q. Ho (Cornell) report: We obtained imaging observations of AT2025dws (Stein et al., GCN 39639), a possible optical counterpart of GRB 250309B (Preis & Greiner, GCN 39629; McDermott et al., GCN 39635) with IO:O on the Liverpool Telescope on UT 2025 March 10 between 01:46:53 and 02:01:08 UT. Two 100s exposures were acquired in each of the g, r, i, and z bands. The source was weakly detected in all four filters. We report the following photometry, calibrated relative to SDSS standards (dt is reported relative to the GRB 250309B GBM trigger time; McDermott et al., GCN 39642): MJD dt filter mag err 60744.07423 0.7558 g 20.47 0.19 60744.07708 0.7587 r 20.30 0.14 60744.07991 0.7615 i 20.07 0.19 60744.08274 0.7643 z 19.44 0.17 The red colours and significant fading are consistent with the interpretation of this source as the afterglow (see also Pérez-Fournon et al., GCN 39643; Stein et al., GCN 39644; Alexander et al., 39645). No host galaxy subtraction or extinction correction has been performed. View this GCN Circular online at https://gcn.nasa.gov/circulars/39646. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37661] GRB 250309B / AT2025dws: SAO RAS optical observations
by GCN Circulars 10 Mar '25

10 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39645 SUBJECT: GRB 250309B / AT2025dws: SAO RAS optical observations DATE: 25/03/10 02:45:01 GMT FROM: Moskvitin Alexander at SAO RAS <mosk(a)sao.ru> A. S. Moskvitin, O. I. Spiridonova (SAO RAS), A. S. Pozanenko (IKI), A. Ghosh, S. Razzaque (CAPP, University of Johannesburg), Yu. V. Sotnikova (SAO RAS) report on behalf of a larger collaboration. We partially covered the error circle of the GRB 250309B (Preis and Greiner, GCN 39629; Fermi GBM team, GCN 39635; McDermott et al., GCN 39642) with 1-m telescope of SAO RAS, Zeiss-1000, equipped with the CCD-photometer. The fields of ZTF25aaitvjt / AT2025dws (Stein et al., GCN 39639), XRT sources #1 and #3 (Evans et al., GCN 39633) were observed in Rc band on March 9/10 night. The AT2025dws source does not fit into the error circle of ground-based GBM localization (Fermi GBM group, GCN 39635), but falls into the BALROG localization field (Preis et al., GCN 39629). We obtained two epochs of observations for ZTF25aaitvjt / AT2025dws field. The 1st: on March 9, 21:58:17 -- March 9, 22:29:28 UT, t_mid - T0 = 14.5893 h = 0.60789 days (5 x 300 sec. exposure); the 2nd: on March 9, 23:52:03 -- March 10, 00:47:22 UT, t_mid - T0 = 16.6865 h = 0.69527 days (10 x 300 sec. exposure). We clearly detected ZTF25aaitvjt / AT2025dws (Stein et al., GCN 39639; Pérez-Fournon et al., GCN 39643; Stein and Ahumada, GCN 39644) in the stacked images. Preliminary photometry is the following. Date UT start t-T0 Exptime Filter OT Err UL (mid, days) (s) (3sigma) 2025-03-09 21:58:17 0.60789 5 x 300 Rc 19.52 +/- 0.04 22.0 2025-03-09 23:52:03 0.69527 10 x 300 Rc 19.66 +/- 0.02 22.6 The above photometry includes the OT and a possible host galaxy. The photometry is based on nearby stars from the USNO-B1.0 catalog (R2 magnitudes) and has not been corrected for the Galactic extinction. USNO-B1.0 reference stars RA Dec R2 14:03:06.24 -08:27:38.9 15.67 14:03:08.07 -08:26:47.1 17.30 View this GCN Circular online at https://gcn.nasa.gov/circulars/39645. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37660] GRB 250309B / AT2025dws: Swift-UVOT detection
by GCN Circulars 10 Mar '25

10 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39644 SUBJECT: GRB 250309B / AT2025dws: Swift-UVOT detection DATE: 25/03/10 02:12:00 GMT FROM: Robert David Stein at JSI <rdstein(a)umd.edu> Robert Stein (JSI), Tomas Ahumada (Caltech) report, On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations: We requested observations of AT2025dws (Stein et al., GCN 39639), the candidate counterpart to GRB 250309B (Preis & Greiner, GCN 39629; McDermott et al., GCN 39635), with the Neil Gehrels Swift Observatory. Observations were conducted beginning 2025-03-09 20:26:46 UT, ~13 hours after the GRB time (2025-03-09 07:38:30.66 UT). These observations had an exposure time of 30 minutes, in the U-band filter. We reduced the Swift UVOT data (Roming et al. 2005) using HEASoft. A source is clearly visible at the position of AT2025dws, with an apparent magnitude of m = 21.5 +/- 0.2 [AB Mag]. These observations had a limiting magnitude of m = 22.4 [AB Mag]. While we have not performed host subtraction, the source is marginally detected in archival SDSS imaging with a u-band magnitude of m=24.02. This suggests our detection is dominated by transient light. AT2025dws has been already been confirmed to be fast-fading by recent optical observations with LCO (Perez-Fournon et al., GCN 39643). While there are no earlier U-band detection of this transient, our UVOT detection is fainter than the optical detections reported in GCNs 39639 and 39643. This confirms the red nature of the transient, and is consistent with the expected red/fast-fading behaviour of a GRB aferglow. View this GCN Circular online at https://gcn.nasa.gov/circulars/39644. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37659] AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
by GCN Circulars 10 Mar '25

10 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39643 SUBJECT: AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading DATE: 25/03/10 01:28:25 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf(a)iac.es> I. Pérez-Fournon, F. Poidevin (IAC and ULL), D. Cano-Morales, I. Correa-Plasencia, and A.E. Hernández-Díaz (ULL) We report Las Cumbres Observatory Global Telescope network (LCOGT) observations of ZTF25aaitvjt / AT 2025dws, that has been proposed by Stein et al. (GCN circ. 39639) as the candidate optical counterpart of the Fermi GBM likely long Gamma-Ray Burst GRB 250309B (Preis & Greiner, GCN circ. 39629; Fermi GBM team, GCN circ. 39635; and McDermott et al., GCN circ. 39642), that may be related with the IceCube high-energy neutrino IceCube-250309A (The IceCube Collaboration, GCN circ. 39631). We observed the field of ZTF25aaitvjt / AT 2025dws with one of the LCOGT 1-m telescopes, equipped with Sinistro cameras, located at the LCOGT node at Sutherland Observatory (South Africa). We obtained a 180-sec exposure in each of the SDSS g', r', and i' filters starting at about 21.77 hours after the Fermi trigger. We detect ZTF25aaitvjt / AT 2025dws in the three filters. We measure the following magnitudes, calibrated against Pan-STARRS DR2 stars and not corrected for Galactic extinction: Date | UT start | t_mid - t0 (hours) | mag | error | filter | ---------------------------------------------------------------------- 2025-03-09 22:28:06 21.79 20.38 0.15 g' 2025-03-09 22:31:46 21.85 20.12 0.14 r' 2025-03-09 22:35:16 21.91 19.87 0.14 i' The fast fading in the g' and r' bands compared with the Zwicky Transient Facility (ZTF) detections reported by Stein et al. (GCN circ. 39639 and TNS Astronomical Transient Report No. 247224) supports that ZTF25aaitvjt / AT 2025dws is the likely optical afterglow of GRB 250309B. This work makes use of observations from the Las Cumbres Observatory global telescope network (LCOGT observing programme IAC2025A-009, SGLF). View this GCN Circular online at https://gcn.nasa.gov/circulars/39643. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37658] GRB 250309B: Fermi GBM Observation
by GCN Circulars 10 Mar '25

10 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39642 SUBJECT: GRB 250309B: Fermi GBM Observation DATE: 25/03/10 00:47:24 GMT FROM: Lorenzo Scotton at UAH <lscottongcn(a)outlook.com> P. McDermott (UCD), P. Veres (UAH) and L. Scotton (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 07:38:30.66 UT on 09 March 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250309B (trigger 763198715/250309318). The Fermi GBM on-ground location was reported in GCN 39635. The angle from the Fermi LAT boresight is 77 degrees. The GBM light curve consists of an emission episode with multiple peaks, with a duration (T90) of about 6.4 s (50-300 keV). The time-averaged spectrum from T0+0.003 to T0+8.192 s is best fit by a Band function with Epeak = 93 +/- 5 keV, alpha = -0.98 +/- 0.06 and beta = -2.40 +/- 0.08. The event fluence (10-1000 keV) in this time interval is (1.07 +/- 0.02)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+3.8 s in the 10-1000 keV band is 23 +/- 0.4 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/39642. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37657] Fermi GRB 250309B: Global MASTER-Net observations report
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39641 SUBJECT: Fermi GRB 250309B: Global MASTER-Net observations report DATE: 25/03/09 22:31:38 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 250309B ( Fermi GBM team, GCN 39635) errorbox 53228 sec after notice time and 53238 sec after trigger time at 2025-03-09 22:25:49 UT, with upper limit up to 17.4 mag. The observations began at zenith distance = 61 deg. The sun altitude is -48.7 deg. The galactic latitude b = 44 deg., longitude l = 331 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2805642 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 53269 | 2025-03-09 22:25:49 | MASTER-Kislovodsk | (13h 59m 30.46s , -13d 45m 18.7s) | C | 60 | 17.4 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/39641. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37656] Fermi GRB 250309A: Global MASTER-Net observations report
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39640 SUBJECT: Fermi GRB 250309A: Global MASTER-Net observations report DATE: 25/03/09 22:31:05 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 250309A ( Fermi GBM team, GCN 39623) errorbox 71845 sec after notice time and 71879 sec after trigger time at 2025-03-09 20:40:03 UT, with upper limit up to 16.2 mag. The observations began at zenith distance = 81 deg. The sun altitude is -50.2 deg. The galactic latitude b = 0 deg., longitude l = 140 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2805313 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 71900 | 2025-03-09 20:40:03 | MASTER-Kislovodsk | (02h 47m 28.83s , +38d 43m 03.4s) | C | 40 | 15.5 | 71955 | 2025-03-09 20:40:03 | MASTER-Kislovodsk | (02h 47m 28.84s , +38d 43m 03.3s) | C | 150 | 16.2 | Coadd 71965 | 2025-03-09 20:41:03 | MASTER-Kislovodsk | (02h 47m 28.70s , +38d 42m 52.8s) | C | 50 | 15.4 | 72040 | 2025-03-09 20:42:13 | MASTER-Kislovodsk | (02h 47m 28.63s , +38d 42m 43.8s) | C | 60 | 15.6 | 72130 | 2025-03-09 20:43:33 | MASTER-Kislovodsk | (02h 47m 28.55s , +38d 42m 35.0s) | C | 80 | 15.7 | 72240 | 2025-03-09 20:43:33 | MASTER-Kislovodsk | (02h 47m 28.54s , +38d 42m 34.9s) | C | 300 | 16.1 | Coadd 72240 | 2025-03-09 20:45:13 | MASTER-Kislovodsk | (02h 47m 28.42s , +38d 42m 25.5s) | C | 100 | 15.8 | 72370 | 2025-03-09 20:47:13 | MASTER-Kislovodsk | (02h 47m 28.29s , +38d 42m 16.6s) | C | 120 | 15.7 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/39640. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37655] GRB250309B: One candidate counterpart from the Zwicky Transient Facility
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39639 SUBJECT: GRB250309B: One candidate counterpart from the Zwicky Transient Facility DATE: 25/03/09 18:25:09 GMT FROM: Robert David Stein at JSI <rdstein(a)umd.edu> Robert Stein (JSI), Tomas Ahumada (Caltech), Jannis Necker, Akshay Eranhalodi (DESY), and Anna Franckowiak (Ruhr University Bochum), Jesper Sollerman (Stockholm) report: On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations: We observed the localisation of Gamma-Ray Burst GRB 250309B (McDermott et al., GCN 39635) with the Palomar 48-inch telescope equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). This GRB was reported to be in spatial/temporal coincidence with high-energy neutrino IC250309A (Zegarelli et. al, GCN 39631), and our observations included ToO observations (Stein et al., GCN 39638) conducted as part of the ZTF neutrino follow up program (Stein et al. 2023). We started serendiptious observations of the GRB skymap in the g- and r-band beginning at 2025-03-09 07:51 UTC, approximately 0.3 hours after event time. We covered 80% of the reported localization region. This estimate accounts for chip gaps. The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019, Stein et al. 2021) was used to search the alerts database for candidates. We reject stellar sources (Tachibana and Miller 2018) and moving objects, and apply machine learning algorithms (Mahabal et al. 2019). After applying standard candidate vetting procedures, we identified the following candidate optical afterglow: ±–––––––––––––––––––––––––––––––––––––––-+ | ZTF Name | IAU Name | RA (deg) | DEC (deg) | Filter | Mag | MagErr | ±–––––––––––––––––––––––––––––––––––––––-+ | ZTF25aaitvjt | AT2025dws | 210.801761 | -8.502842 | r | 18.48| 0.107 | ±–––––––––––––––––––––––––––––––––––––––-+ Using the smaller BALROG localisation (Greiner et al, GCN 39629), we covered 76.8% (1.9 sq deg) of the reported localization region. This estimate accounts for chip gaps. Repeating the same search, AT2025dws is again the only candidate found within the error contour of the GRB. AT2025dws is red (g−r>0.4 mag) and is coincident with a faint Legacy Survey source that appears to be a possible host galaxy. From the ATLAS forced photometry service, we find that the transient had deeper upper limit (m>19.2) 1.67 hours before the GRB trigger. This suggests that AT2025dws is both fast-evolving, and temporally coincident with the GRB. Given this, we consider AT2025dws to be the likely afterglow counterpart. We encourage spectroscopic observations to confirm the nature of AT2025dws as an afterglow. ToO observations have been requested with the Neil Gehrels Swift Observatory. We note that none of ZTF25aaitvjt/AT2025dws is located 2.24 degrees from the center of the neutrino localisation. If this is indeed the afterglow, then the offset to the reported neutrino uncertainty region is >5 sigma, suggesting that the neutrino and GRB are not associated. We will continue to observe this field as part of our standard ToO cadence for high-energy neutrinos (Stein et al. 2023). Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Award #2407588 and a partnership including Caltech, USA; Caltech/IPAC, USA; University of Maryland, USA; University of California, Berkeley, USA; University of Wisconsin at Milwaukee, USA; Cornell University, USA; Drexel University, USA; University of North Carolina at Chapel Hill, USA; Institute of Science and Technology, Austria; National Central University, Taiwan; Operations are conducted by Caltech's Optical Observatory (COO), Caltech/IPAC, and the University of Washington at Seattle, USA. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert database searches are done by AMPEL (Nordin et al. 2019). Alert filtering is performed with the nuztf (Stein et al. 2021, https://github.com/desy-multimessenger/nuztf ). View this GCN Circular online at https://gcn.nasa.gov/circulars/39639. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37654] IceCube-250309A: No candidates from the Zwicky Transient Facility
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39638 SUBJECT: IceCube-250309A: No candidates from the Zwicky Transient Facility DATE: 25/03/09 18:24:08 GMT FROM: Robert David Stein at JSI <rdstein(a)umd.edu> Robert Stein (JSI), Jannis Necker, Akshay Eranhalodi (DESY), and Anna Franckowiak (Ruhr University Bochum), Tomas Ahumada (Caltech), Jesper Sollerman (Stockholm) report: On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations: As part of the ZTF neutrino follow up program (Stein et al. 2023), we observed the localization region of the neutrino event IceCube-250309A (Zegarelli et. al, GCN 39631) with the Palomar 48-inch telescope, equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). We started deep observations in the g- and r-band beginning at 2025-03-09 10:16 UTC while the same field was also observed by the routine ZTF survey at 08:18 UTC, approximately 0.7 hours after event time. We covered 92.9% (0.3 sq deg) of the reported localization region. This estimate accounts for chip gaps. Each exposure was 300s with a typical depth of 21.0 mag. The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019, Stein et al. 2021) was used to search the alerts database for candidates. We reject stellar sources (Tachibana and Miller 2018) and moving objects, and apply machine learning algorithms (Mahabal et al. 2019). We are left with one candidate within the 90.0% localization of the skymap. ±–––––––––––––––––––––––––––––––––––––––-+ | ZTF Name | IAU Name | RA (deg) | DEC (deg) | Filter | Mag | MagErr | ±–––––––––––––––––––––––––––––––––––––––-+ | ZTF25aaiurnn | –––- | 211.3537073 | -10.4938701 | g | 20.82 | 0.18 | ±–––––––––––––––––––––––––––––––––––––––-+ ZTF25aaiurnn was first detected on 2025-03-02 in the r-band, roughly one week before the neutrino arrival. It has a match in the MILLIQUAS catalog at a distance of 0.18 arcsec as a 95% probable QSO. The match in the AllWISE source catalog (WISEA J140524.90-102938.0, 0.22 arcsec) shows a red color of W1-W2=1), consistent with an AGN. Although there is only one detection per band, there is no clear evidence for coincident flaring activity. We will continue to observe this field as part of our standard ToO cadence for high-energy neutrinos (Stein et al. 2023). Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Award #2407588 and a partnership including Caltech, USA; Caltech/IPAC, USA; University of Maryland, USA; University of California, Berkeley, USA; University of Wisconsin at Milwaukee, USA; Cornell University, USA; Drexel University, USA; University of North Carolina at Chapel Hill, USA; Institute of Science and Technology, Austria; National Central University, Taiwan; Operations are conducted by Caltech's Optical Observatory (COO), Caltech/IPAC, and the University of Washington at Seattle, USA. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert database searches are done by AMPEL (Nordin et al. 2019). Alert filtering is performed with the nuztf (Stein et al. 2021, https://github.com/desy-multimessenger/nuztf ). View this GCN Circular online at https://gcn.nasa.gov/circulars/39638. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37653] Fermi-LAT gamma-ray observations of IceCube-250309A
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39637 SUBJECT: Fermi-LAT gamma-ray observations of IceCube-250309A DATE: 25/03/09 17:38:48 GMT FROM: Sara Buson at DESY, Univ. of Wurzburg <sara.buson(a)gmail.com> S. Buson (DESY, Univ. of Wuerzburg), S. Garrappa (Weizmann Institute of Science), L. Pfeiffer (Univ. of Wuerzburg), N. Di Lalla (Stanford Univ.), M. Arimoto (Kanazawa University), R. Gupta (NASA GSFC) and A. Holzmann Airasca (UniTrento and INFN Bari) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC250309A neutrino event (GCN 39631) with all-sky survey data from the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. The IceCube event was detected on 2025-03-09 07:36:04.75 UTC (T0) with J2000 position RA = 211.07 (+0.31, -0.30) deg, Decl. = -10.73 (+0.26, -0.30) deg 90% PSF containment. No cataloged gamma-ray sources are found within the 90% IC250309A localization error (The Fourth Fermi-LAT catalog, 4FGL-DR4, The Fermi-LAT collaboration 2023, arXiv:2307.12546). We searched for the existence of intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (>5sigma) new excess emission (> 100 MeV) within the IC250309A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IceCube best-fit position, the >100 MeV flux upper limit (95% confidence) is <2.4e-10 ph cm^-2 s^-1 for ~16-years (2008-08-04 / T0), <6.8e-09 (<9.3 e-8) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. The IceCube event IC250309A occurred near the GRB 250309B (GCN 39635), with a detection time 145.91 seconds after the Fermi-GBM trigger and a positional separation of 0.50 deg. An analysis of the LAT data conducted over a ±1000-second window centered on T0, shows no significant excess emission, neither associated with IC250309A nor GRB 250309B. The >100 MeV flux upper limit (95% confidence) at IC250309A best-fit position for this time interval is < 5.3 e-6 ph cm^-2 s^-1. Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. For this source, the Fermi-LAT contact person is S. Buson (sara.buson at uni-wuerzburg.de). The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. View this GCN Circular online at https://gcn.nasa.gov/circulars/39637. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37652] GRB 250308A: SVOM/GRM detection of QPO in the tail emission
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39636 SUBJECT: GRB 250308A: SVOM/GRM detection of QPO in the tail emission DATE: 25/03/09 16:00:23 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Wen-Jun Tan, Zheng-Hang Yu, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Nicolas Dagoneau (CEA), Maria-Grazia Bernardini (INAF-OAB), Jean-Luc Atteia (IRAP), Frédéric Piron (LUPM) Report on behalf of the SVOM team: The bright short burst, GRB 250308A (GCN #39632), consists of a narrow spike followed by a short tail emission (from T0-0.15 to T0+0.15 s), which shows a feature of QPO, with a center frequency at approximately 31 Hz. The on-ground localization of this burst is (J2000): RA: 170.9 deg DEC: 25.6 deg Error: 5.2 deg (1sigma, statistical only) We caution that the calibration of SVOM/GRM is undergoing and this localization is subject to systematic errors. With this localization, the time-averaged spectrum from T0-0.3 to T0+0.2 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.28 +/- 0.04 and the cutoff energy, parameterized as Epeak, is 452 +/- 56 keV. The event fluence (10-1000 keV) in this time interval is (4.9 +/- 0.2)E-06 erg/cm^2. The feature of QPO in the tail emission and the spectrum parameters are consistent with the scenario of magnetar giant flare. Follow-up observations are strongly encouraged. We note that these results are preliminary. Refined analysis will be reported later. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM/GRM point of contact for this burst is: Chen-Wei Wang (IHEP) (cwwang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/39636. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37651] GRB 250309B: Fermi GBM Final Localization
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39635 SUBJECT: GRB 250309B: Fermi GBM Final Localization DATE: 25/03/09 15:47:40 GMT FROM: Padraig McDermott at University College Dublin <padraig.mcdermott(a)ucdconnect.ie> The Fermi GBM team reports the detection of a likely LONG GRB "At 07:38:30.66 UT on 09 March 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250309B (trigger 763198715/250309318). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 210.58, Dec = -10.86 (J2000 degrees, equivalent to J2000 14h 02m, -10d 51'), with a statistical uncertainty of 1.2 degrees. The angle from the Fermi LAT boresight is 77 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250309318/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250309318/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250309318/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/39635. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37650] Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39634 SUBJECT: Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A! DATE: 25/03/09 13:20:55 GMT FROM: P.A. Evans at U. Leicester <pae9(a)leicester.ac.uk> P.A. Evans reports on behalf of the Swift-XRT team, There was an error in GCN Circ. 39633 — Swift is not observing a 22-month old GRB, but is in fact observing combined error locatlisation of GRB 250309B and IceCube 250309A. Apologies for any confusion caused by my errant fingers, and thanks to Kim Page for spotting this. We will request a correction in the GCN archives. View this GCN Circular online at https://gcn.nasa.gov/circulars/39634. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37649] GRB 230509B: Tiled Swift observations
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39633 SUBJECT: GRB 230509B: Tiled Swift observations DATE: 25/03/09 13:15:21 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a series of observations, tiled on the sky, of the Fermi/GBM GRB 230509B. Automated analysis of the XRT data will be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00134 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. The probability of finding serendipitous sources, unrelated to the Fermi/GBM event is high: any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/39633. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37648] GRB 250308A: SVOM/GRM observation of a bright short burst
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39632 SUBJECT: GRB 250308A: SVOM/GRM observation of a bright short burst DATE: 25/03/09 12:40:35 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Zheng-Hang Yu, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Nicolas Dagoneau (CEA), Maria-Grazia Bernardini (INAF-OAB), Jean-Luc Atteia (IRAP), Frédéric Piron (LUPM) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by GRB 250308A (SVOM trigger reference: sb25030804) at 2025-03-08T18:06:30.1 (T0), which is also detected by CALTE/GBM (TRIGGER ID: 1425492335) and Konus-Wind. With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multi-pulses with a T90 of 1.9 +0.9/-0.8 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250308A.png The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM/GRM point of contact for this burst is: Chen-Wei Wang (IHEP) (cwwang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/39632. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37647] IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39631 SUBJECT: IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/03/09 11:48:28 GMT FROM: A. Zegarelli at Ruhr University Bochum <azegarelli(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 2025-03-09 at 07:36:04.75 UT IceCube detected a track-like event with a high probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_GOLD alert stream. The average astrophysical neutrino purity for Gold alerts is 50%. This alert has an estimated false alarm rate of 0.1759 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection. After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/140626_1288692.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 2025-03-09 Time: 07:36:04.75 UT RA: 211.07 (+0.31 -0.30 deg 90% PSF containment) J2000 Dec: -10.73 (+0.26 -0.30 deg 90% PSF containment) J2000 The inferred neutrino energy of this alert is ~4 PeV, making it the fourth-highest energy known detection by IceCube over the past decade. The alert coincides with the Fermi GRB250309B (Fermi-GBM trigger 763198715 at 07:38:30.66 on 09 March 2025; https://gcn.gsfc.nasa.gov/other/763198715.fermi) with a time delay of 145.91 seconds relative to the GRB trigger time. The angular distance to the most updated reconstruction released by the GBM team, which has a 1σ statistical error of 1.60 deg, is 0.77 degrees. An alternative algorithm results in a shifted direction (https://gcn.nasa.gov/circulars/39629) with an angular distance from the best fit neutrino direction of 3.18 degrees and has a 1σ statistical error of 1.3 degree and a systematic error of 1 degree. We strongly encourage follow-up observations of the neutrino region of interest and the uncertainty region of GRB250309B. No known gamma-ray sources listed in the Fermi 4FGL-DR4 or 3FHL catalogs are located within the 90% uncertainty region of the event. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu View this GCN Circular online at https://gcn.nasa.gov/circulars/39631. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37646] IceCube Alert 250309.32: Global MASTER-Net observations report
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39630 SUBJECT: IceCube Alert 250309.32: Global MASTER-Net observations report DATE: 25/03/09 09:39:41 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the IceCube Alert 250309.32 (trigger No 1288692,14h 03m 12.24s , -10d 26m 24.0s, R=0.51) errorbox 9 sec after notice time and 109 sec after trigger time at 2025-03-09 07:37:54 UT, with upper limit up to 21.3 mag. The observations began at zenith distance = 21 deg. The sun altitude is -35.6 deg. The galactic latitude b = 48 deg., longitude l = 331 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2805613 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 120 | 2025-03-09 07:37:54 | MASTER-OAFA | (14h 12m 24.48s , -09d 45m 33.8s) | C | 20 | 18.1 | 135 | 2025-03-09 07:37:54 | MASTER-OAFA | (14h 12m 24.47s , -09d 45m 33.7s) | C | 50 | 18.7 | Coadd 120 | 2025-03-09 07:37:54 | MASTER-OAFA | (14h 03m 05.50s , -10d 07m 35.4s) | C | 20 | 20.1 | 155 | 2025-03-09 07:37:54 | MASTER-OAFA | (14h 03m 05.50s , -10d 07m 35.4s) | C | 90 | 21.1 | Coadd 490 | 2025-03-09 07:37:54 | MASTER-OAFA | (14h 03m 05.50s , -10d 07m 35.4s) | C | 760 | 21.0 | Coadd 154 | 2025-03-09 07:38:34 | MASTER-OAFA | (14h 12m 24.51s , -09d 45m 31.7s) | C | 10 | 17.5 | 165 | 2025-03-09 07:38:34 | MASTER-OAFA | (14h 03m 05.53s , -10d 07m 33.6s) | C | 30 | 20.4 | 196 | 2025-03-09 07:39:10 | MASTER-OAFA | (14h 12m 24.55s , -09d 45m 29.5s) | C | 20 | 18.1 | 206 | 2025-03-09 07:39:10 | MASTER-OAFA | (14h 03m 05.54s , -10d 07m 32.1s) | C | 40 | 20.6 | 247 | 2025-03-09 07:39:56 | MASTER-OAFA | (14h 12m 24.59s , -09d 45m 27.0s) | C | 30 | 18.6 | 292 | 2025-03-09 07:39:56 | MASTER-OAFA | (14h 12m 24.59s , -09d 45m 27.0s) | C | 120 | 19.6 | Coadd 257 | 2025-03-09 07:39:57 | MASTER-OAFA | (14h 03m 05.56s , -10d 07m 30.4s) | C | 50 | 20.7 | 322 | 2025-03-09 07:39:57 | MASTER-OAFA | (14h 03m 05.56s , -10d 07m 30.5s) | C | 180 | 21.0 | Coadd 308 | 2025-03-09 07:40:52 | MASTER-OAFA | (14h 12m 24.62s , -09d 45m 24.4s) | C | 40 | 18.7 | 318 | 2025-03-09 07:40:53 | MASTER-OAFA | (14h 03m 05.58s , -10d 07m 28.6s) | C | 60 | 20.8 | 379 | 2025-03-09 07:41:58 | MASTER-OAFA | (14h 12m 24.64s , -09d 45m 21.7s) | C | 50 | 18.9 | 389 | 2025-03-09 07:41:59 | MASTER-OAFA | (14h 03m 05.59s , -10d 07m 26.6s) | C | 70 | 20.8 | 466 | 2025-03-09 07:43:15 | MASTER-OAFA | (14h 12m 24.68s , -09d 45m 18.7s) | C | 70 | 19.0 | 566 | 2025-03-09 07:43:15 | MASTER-OAFA | (14h 12m 24.69s , -09d 45m 18.7s) | C | 270 | 20.2 | Coadd 476 | 2025-03-09 07:43:15 | MASTER-OAFA | (14h 03m 05.61s , -10d 07m 24.2s) | C | 90 | 20.9 | 596 | 2025-03-09 07:43:15 | MASTER-OAFA | (14h 03m 05.61s , -10d 07m 24.2s) | C | 330 | 21.3 | Coadd 572 | 2025-03-09 07:44:51 | MASTER-OAFA | (14h 12m 24.72s , -09d 45m 15.1s) | C | 90 | 19.3 | 582 | 2025-03-09 07:44:51 | MASTER-OAFA | (14h 03m 05.63s , -10d 07m 21.3s) | C | 110 | 20.9 | 698 | 2025-03-09 07:46:47 | MASTER-OAFA | (14h 12m 24.74s , -09d 45m 11.3s) | C | 110 | 19.5 | 708 | 2025-03-09 07:46:47 | MASTER-OAFA | (14h 03m 05.66s , -10d 07m 17.9s) | C | 130 | 20.8 | 849 | 2025-03-09 07:49:03 | MASTER-OAFA | (14h 12m 24.76s , -09d 45m 07.0s) | C | 140 | 19.5 | 1009 | 2025-03-09 07:49:03 | MASTER-OAFA | (14h 12m 24.76s , -09d 45m 07.0s) | C | 460 | 20.3 | Coadd 859 | 2025-03-09 07:49:03 | MASTER-OAFA | (14h 03m 05.69s , -10d 07m 14.1s) | C | 160 | 20.7 | 1039 | 2025-03-09 07:49:03 | MASTER-OAFA | (14h 03m 05.69s , -10d 07m 14.1s) | C | 520 | 20.5 | Coadd 1025 | 2025-03-09 07:51:50 | MASTER-OAFA | (14h 12m 24.78s , -09d 45m 02.4s) | C | 160 | 19.7 | 1036 | 2025-03-09 07:51:50 | MASTER-OAFA | (14h 03m 05.70s , -10d 07m 09.7s) | C | 180 | 20.6 | 1212 | 2025-03-09 07:54:56 | MASTER-OAFA | (14h 12m 24.76s , -09d 44m 57.9s) | C | 160 | 19.6 | 1222 | 2025-03-09 07:54:56 | MASTER-OAFA | (14h 03m 05.69s , -10d 07m 05.4s) | C | 180 | 20.6 | 1398 | 2025-03-09 07:58:02 | MASTER-OAFA | (14h 12m 24.74s , -09d 44m 53.3s) | C | 160 | 19.8 | 1558 | 2025-03-09 07:58:02 | MASTER-OAFA | (14h 12m 24.74s , -09d 44m 53.3s) | C | 480 | 20.3 | Coadd 1408 | 2025-03-09 07:58:03 | MASTER-OAFA | (14h 03m 05.69s , -10d 07m 00.9s) | C | 180 | 20.6 | 1588 | 2025-03-09 07:58:03 | MASTER-OAFA | (14h 03m 05.69s , -10d 07m 00.9s) | C | 540 | 20.5 | Coadd 1584 | 2025-03-09 08:01:08 | MASTER-OAFA | (14h 12m 24.74s , -09d 44m 49.1s) | C | 160 | 19.7 | 1594 | 2025-03-09 08:01:08 | MASTER-OAFA | (14h 03m 05.70s , -10d 06m 56.7s) | C | 180 | 20.6 | 1770 | 2025-03-09 08:04:15 | MASTER-OAFA | (14h 12m 24.73s , -09d 44m 44.9s) | C | 160 | 19.6 | 1781 | 2025-03-09 08:04:15 | MASTER-OAFA | (14h 03m 05.73s , -10d 06m 52.4s) | C | 180 | 20.7 | 1957 | 2025-03-09 08:07:21 | MASTER-OAFA | (14h 12m 24.72s , -09d 44m 40.7s) | C | 160 | 19.7 | 2117 | 2025-03-09 08:07:21 | MASTER-OAFA | (14h 12m 24.72s , -09d 44m 40.7s) | C | 480 | 20.3 | Coadd 1967 | 2025-03-09 08:07:22 | MASTER-OAFA | (14h 03m 05.75s , -10d 06m 48.3s) | C | 180 | 20.5 | 2147 | 2025-03-09 08:07:22 | MASTER-OAFA | (14h 03m 05.76s , -10d 06m 48.4s) | C | 540 | 20.5 | Coadd 2143 | 2025-03-09 08:10:27 | MASTER-OAFA | (14h 12m 24.71s , -09d 44m 36.8s) | C | 160 | 19.6 | 2153 | 2025-03-09 08:10:28 | MASTER-OAFA | (14h 03m 05.79s , -10d 06m 44.3s) | C | 180 | 20.6 | 2329 | 2025-03-09 08:13:34 | MASTER-OAFA | (14h 12m 24.71s , -09d 44m 33.2s) | C | 160 | 19.7 | 2340 | 2025-03-09 08:13:34 | MASTER-OAFA | (14h 03m 05.84s , -10d 06m 40.6s) | C | 180 | 20.8 | 2515 | 2025-03-09 08:16:39 | MASTER-OAFA | (14h 12m 24.68s , -09d 44m 29.5s) | C | 160 | 19.7 | 2675 | 2025-03-09 08:16:39 | MASTER-OAFA | (14h 12m 24.68s , -09d 44m 29.5s) | C | 480 | 20.3 | Coadd 2526 | 2025-03-09 08:16:40 | MASTER-OAFA | (14h 03m 05.85s , -10d 06m 36.6s) | C | 180 | 20.6 | 2706 | 2025-03-09 08:16:40 | MASTER-OAFA | (14h 03m 05.85s , -10d 06m 36.6s) | C | 540 | 20.7 | Coadd 2702 | 2025-03-09 08:19:46 | MASTER-OAFA | (14h 12m 24.68s , -09d 44m 25.6s) | C | 160 | 19.6 | 2712 | 2025-03-09 08:19:46 | MASTER-OAFA | (14h 03m 05.90s , -10d 06m 32.8s) | C | 180 | 20.7 | 2888 | 2025-03-09 08:22:52 | MASTER-OAFA | (14h 12m 24.64s , -09d 44m 22.0s) | C | 160 | 19.6 | 2898 | 2025-03-09 08:22:52 | MASTER-OAFA | (14h 03m 05.91s , -10d 06m 28.7s) | C | 180 | 20.7 | 3074 | 2025-03-09 08:25:58 | MASTER-OAFA | (14h 12m 24.59s , -09d 44m 18.7s) | C | 160 | 19.6 | 3234 | 2025-03-09 08:25:58 | MASTER-OAFA | (14h 12m 24.59s , -09d 44m 18.6s) | C | 480 | 20.5 | Coadd 3084 | 2025-03-09 08:25:59 | MASTER-OAFA | (14h 03m 05.93s , -10d 06m 25.4s) | C | 180 | 20.8 | 3264 | 2025-03-09 08:25:59 | MASTER-OAFA | (14h 03m 05.93s , -10d 06m 25.3s) | C | 540 | 20.6 | Coadd 3260 | 2025-03-09 08:29:05 | MASTER-OAFA | (14h 12m 24.55s , -09d 44m 15.1s) | C | 160 | 19.7 | 3271 | 2025-03-09 08:29:05 | MASTER-OAFA | (14h 03m 05.93s , -10d 06m 21.3s) | C | 180 | 20.6 | 3447 | 2025-03-09 08:32:11 | MASTER-OAFA | (14h 12m 24.52s , -09d 44m 11.8s) | C | 160 | 19.6 | 3457 | 2025-03-09 08:32:11 | MASTER-OAFA | (14h 03m 05.91s , -10d 06m 17.9s) | C | 180 | 20.6 | 3633 | 2025-03-09 08:35:18 | MASTER-OAFA | (14h 12m 24.48s , -09d 44m 08.4s) | C | 160 | 19.7 | 3793 | 2025-03-09 08:35:18 | MASTER-OAFA | (14h 12m 24.48s , -09d 44m 08.5s) | C | 480 | 20.4 | Coadd 3644 | 2025-03-09 08:35:18 | MASTER-OAFA | (14h 03m 05.92s , -10d 06m 14.4s) | C | 180 | 20.6 | 3824 | 2025-03-09 08:35:18 | MASTER-OAFA | (14h 03m 05.92s , -10d 06m 14.3s) | C | 540 | 20.5 | Coadd 3819 | 2025-03-09 08:38:24 | MASTER-OAFA | (14h 12m 24.44s , -09d 44m 05.3s) | C | 160 | 19.7 | 3830 | 2025-03-09 08:38:24 | MASTER-OAFA | (14h 03m 05.93s , -10d 06m 11.1s) | C | 180 | 20.6 | 4006 | 2025-03-09 08:41:30 | MASTER-OAFA | (14h 12m 24.42s , -09d 44m 02.4s) | C | 160 | 19.7 | 4016 | 2025-03-09 08:41:30 | MASTER-OAFA | (14h 03m 05.95s , -10d 06m 07.8s) | C | 180 | 20.6 | 4192 | 2025-03-09 08:44:36 | MASTER-OAFA | (14h 12m 24.38s , -09d 43m 59.5s) | C | 160 | 19.7 | 4352 | 2025-03-09 08:44:36 | MASTER-OAFA | (14h 12m 24.38s , -09d 43m 59.4s) | C | 480 | 20.4 | Coadd 4202 | 2025-03-09 08:44:36 | MASTER-OAFA | (14h 03m 05.96s , -10d 06m 04.4s) | C | 180 | 20.6 | 4382 | 2025-03-09 08:44:36 | MASTER-OAFA | (14h 03m 05.96s , -10d 06m 04.4s) | C | 540 | 20.6 | Coadd 4378 | 2025-03-09 08:47:42 | MASTER-OAFA | (14h 12m 24.33s , -09d 43m 56.5s) | C | 160 | 19.6 | 4388 | 2025-03-09 08:47:42 | MASTER-OAFA | (14h 03m 05.98s , -10d 06m 01.1s) | C | 180 | 20.6 | 4564 | 2025-03-09 08:50:48 | MASTER-OAFA | (14h 12m 24.26s , -09d 43m 53.8s) | C | 160 | 19.7 | 4574 | 2025-03-09 08:50:48 | MASTER-OAFA | (14h 03m 06.00s , -10d 05m 58.2s) | C | 180 | 20.6 | 4750 | 2025-03-09 08:53:54 | MASTER-OAFA | (14h 12m 24.22s , -09d 43m 51.1s) | C | 160 | 19.8 | 4910 | 2025-03-09 08:53:54 | MASTER-OAFA | (14h 12m 24.22s , -09d 43m 51.1s) | C | 480 | 20.4 | Coadd 4760 | 2025-03-09 08:53:54 | MASTER-OAFA | (14h 03m 06.02s , -10d 05m 55.4s) | C | 180 | 20.7 | 4940 | 2025-03-09 08:53:54 | MASTER-OAFA | (14h 03m 06.02s , -10d 05m 55.4s) | C | 540 | 20.7 | Coadd 4936 | 2025-03-09 08:57:00 | MASTER-OAFA | (14h 12m 24.13s , -09d 43m 48.7s) | C | 160 | 19.6 | 4946 | 2025-03-09 08:57:00 | MASTER-OAFA | (14h 03m 06.02s , -10d 05m 52.7s) | C | 180 | 20.6 | 5122 | 2025-03-09 09:00:06 | MASTER-OAFA | (14h 12m 24.08s , -09d 43m 46.1s) | C | 160 | 19.7 | 5132 | 2025-03-09 09:00:06 | MASTER-OAFA | (14h 03m 06.03s , -10d 05m 50.1s) | C | 180 | 20.6 | 5307 | 2025-03-09 09:03:12 | MASTER-OAFA | (14h 12m 24.05s , -09d 43m 43.6s) | C | 160 | 19.7 | 5467 | 2025-03-09 09:03:12 | MASTER-OAFA | (14h 12m 24.05s , -09d 43m 43.6s) | C | 480 | 20.3 | Coadd 5318 | 2025-03-09 09:03:12 | MASTER-OAFA | (14h 03m 06.04s , -10d 05m 47.4s) | C | 180 | 20.7 | 5498 | 2025-03-09 09:03:12 | MASTER-OAFA | (14h 03m 06.04s , -10d 05m 47.4s) | C | 540 | 20.6 | Coadd 5493 | 2025-03-09 09:06:18 | MASTER-OAFA | (14h 12m 24.00s , -09d 43m 41.3s) | C | 160 | 19.6 | 5504 | 2025-03-09 09:06:18 | MASTER-OAFA | (14h 03m 06.04s , -10d 05m 44.8s) | C | 180 | 20.6 | 5680 | 2025-03-09 09:09:24 | MASTER-OAFA | (14h 12m 23.93s , -09d 43m 39.2s) | C | 160 | 19.6 | 5690 | 2025-03-09 09:09:24 | MASTER-OAFA | (14h 03m 06.09s , -10d 05m 42.5s) | C | 180 | 20.6 | 5866 | 2025-03-09 09:12:30 | MASTER-OAFA | (14h 12m 23.88s , -09d 43m 37.0s) | C | 160 | 19.6 | 6026 | 2025-03-09 09:12:30 | MASTER-OAFA | (14h 12m 23.88s , -09d 43m 37.0s) | C | 480 | 20.3 | Coadd 5876 | 2025-03-09 09:12:31 | MASTER-OAFA | (14h 03m 06.10s , -10d 05m 40.2s) | C | 180 | 20.6 | 6056 | 2025-03-09 09:12:31 | MASTER-OAFA | (14h 03m 06.10s , -10d 05m 40.2s) | C | 540 | 20.4 | Coadd 6052 | 2025-03-09 09:15:36 | MASTER-OAFA | (14h 12m 23.83s , -09d 43m 35.0s) | C | 160 | 19.6 | 6062 | 2025-03-09 09:15:36 | MASTER-OAFA | (14h 03m 06.11s , -10d 05m 38.0s) | C | 180 | 20.6 | 6238 | 2025-03-09 09:18:42 | MASTER-OAFA | (14h 12m 23.77s , -09d 43m 33.0s) | C | 160 | 19.6 | 6248 | 2025-03-09 09:18:42 | MASTER-OAFA | (14h 03m 06.11s , -10d 05m 35.8s) | C | 180 | 20.7 | 6424 | 2025-03-09 09:21:48 | MASTER-OAFA | (14h 12m 23.72s , -09d 43m 31.3s) | C | 160 | 19.5 | 6584 | 2025-03-09 09:21:48 | MASTER-OAFA | (14h 12m 23.72s , -09d 43m 31.3s) | C | 480 | 20.3 | Coadd 6434 | 2025-03-09 09:21:49 | MASTER-OAFA | (14h 03m 06.12s , -10d 05m 33.9s) | C | 180 | 20.6 | 6610 | 2025-03-09 09:24:54 | MASTER-OAFA | (14h 12m 23.65s , -09d 43m 29.5s) | C | 160 | 19.5 | 6620 | 2025-03-09 09:24:55 | MASTER-OAFA | (14h 03m 06.14s , -10d 05m 31.9s) | C | 180 | 20.6 | 6796 | 2025-03-09 09:28:00 | MASTER-OAFA | (14h 12m 23.59s , -09d 43m 27.9s) | C | 160 | 19.4 | 6806 | 2025-03-09 09:28:01 | MASTER-OAFA | (14h 03m 06.16s , -10d 05m 30.1s) | C | 180 | 20.5 | 6983 | 2025-03-09 09:31:07 | MASTER-OAFA | (14h 12m 23.52s , -09d 43m 26.7s) | C | 160 | 19.2 | 6993 | 2025-03-09 09:31:07 | MASTER-OAFA | (14h 03m 06.19s , -10d 05m 28.9s) | C | 180 | 20.4 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/39630. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37645] GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39629 SUBJECT: GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318) DATE: 25/03/09 08:04:59 GMT FROM: Jochen Greiner at MPE <jcgrog(a)mpe.mpg.de> T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report: The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger 763198715 at 07:38:30 on 09 March 2025 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60). The best-fit position is: RA(2000.0) = 210.5 deg Decl.(2000.0) = -7.6 deg The 1 sigma statistical error radius is 1.3 deg. We estimate an additional systematic error of 1 deg. Further details are available at: https://grb.mpe.mpg.de/grb/GRB250309318/ The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB250309318/healpix The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB250309318/json View this GCN Circular online at https://gcn.nasa.gov/circulars/39629. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37644] EP250308a: Global MASTER-Net observations report
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39628 SUBJECT: EP250308a: Global MASTER-Net observations report DATE: 25/03/09 06:09:33 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP250308a ( EP Team et al., GCN 39625) errorbox 194 sec after notice time and 44884 sec after trigger time at 2025-03-09 05:32:01 UT, with upper limit up to 20.4 mag. The observations began at zenith distance = 57 deg. The sun altitude is -52.8 deg. The galactic latitude b = 71 deg., longitude l = 9 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2805476 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 44915 | 2025-03-09 05:32:01 | MASTER-OAFA | (14h 02m 29.31s , +18d 46m 58.8s) | C | 60 | 20.4 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/39628. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37643] EP250308a: GSP optical upper limit
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39627 SUBJECT: EP250308a: GSP optical upper limit DATE: 25/03/09 05:36:15 GMT FROM: Wenxiong Li at NAOC <liwenxiong1992(a)gmail.com> W. X. Li, S. J. Xue (NAOC), M. Andrews, J. Farah, D. A. Howell, M. Newsome, E. Padilla Gonzalez, C. McCully, and G. Terreran (Las Cumbres Observatory), on behalf of a larger collaboration, report: Following the detection of the fast X-ray transient EP250308a by the Einstein Probe (trigger ID: 01709132392; Yin et al., GCN 39625), we initiated observations of its location starting on 2025 March 9th at 05:07 UT (~12 hours after the EP/WXT trigger) in the i band. These observations were conducted using the 1-meter telescope at the Las Cumbres Observatory node located at Cerro Tololo Inter-American Observatory in Chile. No new optical source was detected in the co-added images within the EP/FXT error box down to ~21.5 mag. These observations were taken as part of the Global Supernova Project. View this GCN Circular online at https://gcn.nasa.gov/circulars/39627. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37642] EP250308a: FTW optical and NIR upper limits
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39626 SUBJECT: EP250308a: FTW optical and NIR upper limits DATE: 25/03/09 05:35:45 GMT FROM: Brendan O'Connor at Carnegie Mellon University <boconno2(a)andrew.cmu.edu> Malte Busmann (LMU), Brendan O’Connor (Carnegie Mellon U.), Daniel Gruen (LMU) and Antonella Palmese (Carnegie Mellon U.) report: We observed the 90% of EP-WXT trigger 01709132392, corresponding to EP250308a, with the Three Channel Imager (3KK) at the Fraunhofer Telescope at Wendelstein Observatory (FTW) in the r, i and J band simultaneously for 19 x 180 s starting at 2025-03-09T03:27:28 UT (0.43 days after the trigger). We performed difference imaging in the i-band with templates from Legacy Survey and detect no new or changing source. The 3 sigma mean depth of our observations are: r > 24.0 AB mag i > 23.8 AB mag The magnitudes are calibrated against the PS1 catalog and not corrected for Galactic extinction. We thank Michael Schmidt from the Wendelstein Observatory staff for obtaining these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39626. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37641] EP250308a: Einstein Probe detection of an X-ray transient
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39625 SUBJECT: EP250308a: Einstein Probe detection of an X-ray transient DATE: 25/03/09 05:27:54 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.-H. I. Yin (NJU), Q. Y. Wu (NAO, CAS), J. H. Wu (GZHU), H. W. Pan (NAO, CAS) report on behalf of the Einstein Probe team: We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP250308a. The transient triggered EP-WXT (ID: 01709132392) at 2025-03-08T17:03:57 (UTC). The WXT position of the source is R.A. = 210.581 deg, DEC = 18.515 deg (J2000) with an uncertainty of 2.9 arcmin in radius (90% C.L. statistical and systematic). The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a Galactic hydrogen column density of 2.37 x 10^20 cm^-2 and a photon index of 2.36 (-0.59/+0.61). The derived average unabsorbed 0.5-4 keV flux is 3.62 (-0.82/+1.18) x 10^(-10) erg/s/cm^2. The Follow-up X-ray Telescope (FXT) on board EP observed this source autonomously about 165 seconds after the trigger with an exposure time of 5.5 ks. On-ground analysis of the FXT data found an uncatalogued source at R.A. = 210.5875, DEC = 18.4967 (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic), which is consistent positionally with the WXT transient. The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a Galactic hydrogen column density of 2.37 x 10^20 cm^-2 and a photon index of 2.59 (-0.07/+0.08). The derived average unabsorbed 0.5-10 keV flux is 9.71 (-0.42/+0.45) x 10^(-13) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. No previously known bright X-ray sources are found within the error circle around the transient position. Further follow-up observations are encouraged to identify the nature of this X-ray transient. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/39625. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37640] EP250308a: NOT optical upper limit
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39624 SUBJECT: EP250308a: NOT optical upper limit DATE: 25/03/09 05:18:36 GMT FROM: Zipei Zhu at NAOC <zpzhu(a)nao.cas.cn> Z.P. Zhu, X. Liu, Jie An, S.Q. Jiang, D. Xu (NAOC), S.Y. Fu (HUST, NAOC), D. B. Malesani (DAWN/NBI and Radboud U.), P. Jonker (Radboud U.), A. H. Fuente (NOT) report on behalf of a large collaboration: We observed the field of EP250308a detected by EP/WXT (Trigger ID: 01709132392), using the ALFOSC instruments mounted on the Nordic Optical Telescope (NOT), with 3 x 300 s in the SDSS-r band. Preliminary analysis shows that no new source is detected within the EP/WXT error circle, down to the 5-sigma upper limits of r > ~ 22.7 (AB) at ~ 0.41 day after the EP trigger, calibrated with nearby Pan-STARRS stars and without Galactic extinction correction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39624. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37639] GRB 250309A: Fermi GBM Final Real-time Localization
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39623 SUBJECT: GRB 250309A: Fermi GBM Final Real-time Localization DATE: 25/03/09 00:53:02 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely SHORT GRB At 00:42:03 UT on 9 Mar 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250309A (trigger 763173728.785018 / 250309029). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 46.7, Dec = 58.0 (J2000 degrees, equivalent to J2000 03h 06m, 58d 00'), with a statistical uncertainty of 22.9 degrees. The angle from the Fermi LAT boresight is 22.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250309029/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250309029/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250309029/… View this GCN Circular online at https://gcn.nasa.gov/circulars/39623. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37638] GRB 250306A: EIRSAT-1 GMOD detection
by GCN Circulars 08 Mar '25

08 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39622 SUBJECT: GRB 250306A: EIRSAT-1 GMOD detection DATE: 25/03/08 19:48:12 GMT FROM: Cuán de Barra at UCD <cuan.debarra(a)ucdconnect.ie> C. de Barra, D. Murphy, C. McKenna, A. Ulyanov, P. McDermott, G. Finneran, M. Doyle, R. Dunwoody, J. Mangan, G. Corcoran, L. Cotter, A. Empey, J. Fisher, F. Gibson Kiely, J. Thompson, D. McKeown, A. Martin-Carrillo, L. Hanlon, S. McBreen, on behalf of the EIRSAT-1 team: EIRSAT-1 reports the detection of the long gamma-ray burst GRB250306A by the Gamma-ray Module (GMOD) instrument, which was also detected by Swift BAT (GCN 39606), AstroSat CZTI (GCN 39611), and NuSTAR (GCN 39616) The GMOD detection was made starting at 2025-03-06 16:30:05.7 UTC. The GMOD light-curve for GRB250306A with 1.2s binning shows two distinct pulses consistent with the observation seen by Swift-BAT. The spacecraft location at the time of detection was 37.285 S, 98.479 E, at an altitude of 439.15 km. The GMOD light curve for this event can be found here: https://grb.eirsat1.ie/250306A/250306A_LC_onboard_preliminary.png EIRSAT-1 is Ireland’s first satellite (Doyle et al. Proceedings of the 4th SSEA, 2022). It is a 2U CubeSat and carries onboard a number of experiments including the Gamma-Ray Module (GMOD), a novel, compact, gamma-ray detector (Murphy et al, Experimental Astronomy, 53, 961–990, 2022). GMOD consists of a 25 mm × 25 mm × 40 mm Cerium Bromide scintillator coupled to SiPMs and is designed to detect gamma-ray bursts in the ~ 60 keV - 1.5 MeV range. EIRSAT-1 was developed in University College Dublin with support from ESA’s Fly Your Satellite! programme and was launched on 1st December 2023. View this GCN Circular online at https://gcn.nasa.gov/circulars/39622. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37637] The EP-WXT trigger 01709132387 is likely a flaring star
by GCN Circulars 08 Mar '25

08 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39621 SUBJECT: The EP-WXT trigger 01709132387 is likely a flaring star DATE: 25/03/08 02:02:24 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Q. C. Liu (THU), Y.-H. I. Yin (NJU), H. Y. Liu, W. Yuan (NAO, CAS) report on behalf of the Einstein Probe team: The EP-WXT trigger (ID: 01709132387) on 2025-03-07 18:51:20 (UTC) is likely a stellar flare associated with a young stellar object candidate Gaia DR3 6093234407369953024. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with onboard X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/39621. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37636] Fermi GRB 250307A: Global MASTER-Net observations report
by GCN Circulars 08 Mar '25

08 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39620 SUBJECT: Fermi GRB 250307A: Global MASTER-Net observations report DATE: 25/03/08 00:30:39 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 250307A ( Fermi GBM team, GCN 39618) errorbox 12559 sec after notice time and 12601 sec after trigger time at 2025-03-07 23:27:54 UT, with upper limit up to 17.9 mag. The observations began at zenith distance = 70 deg. The sun altitude is -42.9 deg. The galactic latitude b = 16 deg., longitude l = 27 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2803750 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 12631 | 2025-03-07 23:27:54 | MASTER-Kislovodsk | (17h 39m 34.52s , +03d 16m 16.2s) | C | 60 | 16.0 | 13390 | 2025-03-07 23:40:34 | MASTER-Kislovodsk | (17h 47m 30.44s , +03d 15m 20.9s) | C | 60 | 16.9 | 13470 | 2025-03-07 23:41:53 | MASTER-Kislovodsk | (17h 39m 36.28s , +03d 16m 01.7s) | C | 60 | 17.1 | 13550 | 2025-03-07 23:43:13 | MASTER-Kislovodsk | (17h 38m 11.65s , +01d 21m 58.9s) | C | 60 | 16.9 | 15377 | 2025-03-08 00:13:10 | MASTER-Kislovodsk | (17h 40m 28.55s , +02d 25m 26.0s) | C | 120 | 17.0 | 15517 | 2025-03-08 00:15:30 | MASTER-Kislovodsk | (17h 40m 32.95s , +02d 24m 17.6s) | C | 120 | 17.7 | 15656 | 2025-03-08 00:17:49 | MASTER-Kislovodsk | (17h 40m 27.31s , +00d 23m 17.3s) | C | 120 | 17.9 | 15796 | 2025-03-08 00:20:09 | MASTER-Kislovodsk | (17h 40m 31.50s , +00d 23m 28.7s) | C | 120 | 17.9 | 16015 | 2025-03-08 00:24:18 | MASTER-Kislovodsk | (17h 40m 31.73s , +02d 23m 54.6s) | C | 60 | 17.1 | 16095 | 2025-03-08 00:25:39 | MASTER-Kislovodsk | (17h 46m 12.95s , +01d 24m 43.6s) | C | 60 | 17.4 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/39620. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37635] Konus-Wind detection of GRB 250306A
by GCN Circulars 07 Mar '25

07 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39619 SUBJECT: Konus-Wind detection of GRB 250306A DATE: 25/03/07 22:30:19 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, A. Tsvetkova, M. Ulanov, and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 250306A (Swift-BAT detection: Evans et al., GCN 39606; Astrosat-CZTI detection: Tembhurnikar et al., GCN 39611) triggered Konus-Wind at T0=59404.612 s UT (16:30:04.612). The burst light curve shows a double-peaked structure which starts at ~T0-0.5 s and has a total duration of ~15 s. The emission is seen up to ~3 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250306_T59404/ As observed by Konus-Wind, the burst had a fluence of 2.32(-0.15,+0.16)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+1.120 s, of 1.40(-0.12,+0.12)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+18.176 s) is best fit in the 20 keV - 20 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.94(-0.08,+0.08), the high energy photon index beta = -2.78(-0.33,+0.19), the peak energy Ep = 179(-10,+11) keV (chi2 = 84/97 dof). The spectrum near the maximum count rate (measured from T0+0.256 to T0+1.792 s) is best fit in the 20 keV - 20 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.62(-0.08,+0.09), the high energy photon index beta = -2.59(-0.13,+0.10), the peak energy Ep = 217(-13,+14) keV (chi2 = 55/54 dof). All the quoted errors are at the 68% confidence level. All the quoted values are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/39619. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37634] GRB 250307A: Fermi GBM Final Real-time Localization
by GCN Circulars 07 Mar '25

07 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39618 SUBJECT: GRB 250307A: Fermi GBM Final Real-time Localization DATE: 25/03/07 20:08:14 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 19:57:53 UT on 7 Mar 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250307A (trigger 763070278.733804 / 250307832). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 265.6, Dec = 2.2 (J2000 degrees, equivalent to J2000 17h 42m, 2d 12'), with a statistical uncertainty of 2.7 degrees. The angle from the Fermi LAT boresight is 82.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250307832/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250307832/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250307832/… View this GCN Circular online at https://gcn.nasa.gov/circulars/39618. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37633] GRB 250306A: Swift-BAT refined analysis
by GCN Circulars 07 Mar '25

07 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39617 SUBJECT: GRB 250306A: Swift-BAT refined analysis DATE: 25/03/07 18:38:30 GMT FROM: Rahul Gupta at NASA GSFC <rahul.gupta(a)nasa.gov> T. Parsotan (GSFC), S. D. Barthelmy (GSFC), P. A. Evans (U Leicester), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-240 to T+961 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250306A (trigger #1293340) (Evans et al., GCN Circ. 39606). The BAT ground-calculated position is RA, Dec = 354.724, -47.998 deg which is RA(J2000) = 23h 38m 53.7s Dec(J2000) = -47d 59' 52.8" with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 13%. The mask-weighted BAT light curve shows a distinct peak at around BAT trigger time, followed by a rapid decay and a quieter post-peak phase. T90 (15-350 keV) is 11.44 +- 2.44 sec (estimated error including systematics). The time-averaged spectrum from T-1.52 to T+19.04 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.87 +- 0.24, and Epeak of 132.8 +- 45.6 keV (chi squared 62.11 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 8.9 +- 0.3 x 10^-06 erg/cm2 and the 1-sec peak flux measured from T+0.18 sec in the 15-150 keV band is 35.9 +- 1.6 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.37 +- 0.05 (chi squared 75.58 for 57 d.o.f.). All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1293340 View this GCN Circular online at https://gcn.nasa.gov/circulars/39617. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37632] GRB 250306A: NuSTAR detection of the prompt emission
by GCN Circulars 07 Mar '25

07 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39616 SUBJECT: GRB 250306A: NuSTAR detection of the prompt emission DATE: 25/03/07 17:27:29 GMT FROM: Brian Grefenstette at Caltech/NuSTAR <bwgref(a)srl.caltech.edu> B. Grefenstette (Caltech) reports on behalf of the NuSTAR Search for INteresting Gamma-ray Signals (SINGS) working group: The NuSTAR SINGS working group reports the detection of prompt emission from the Long GRB 250306A in both the NuSTAR CsI anti-coincidence shields. This GRB was identified through a blind search using the CsI shield rates. Details of the search algorithm will be described in a future paper. The NuSTAR SINGS algorithm triggered at 2025-03-06 16:30:03 (with a resolution ~5-seconds). This is consistent with the detections by the Neil Gehrels Swift BAT (Evans et al, GCN circ. 39606) and ASTROSAT (Tembhurnikar et al., GCN circ. 39611). The NuSTAR CsI shield data are recorded at 1 Hz. The GRB appears to be composed of a single, narrow burst with a duration of a few seconds with a peak rate of ~4,000 counts per second. The baseline rate is ~1,000 cps during this time period. We also see a single short burst above 100 keV in the CdZnTe detectors. Using the localization from Swift/BAT at RA = 354.730, Dec = -47.993 implies an offset from the NuSTAR boresight of 64.95 deg (e.g., through the side of the instrument) and the offset from the geocenter of 114-deg Discovery report and preliminary analysis for this GRB can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2025/250306A/ Information on NuSTAR SINGS can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/ NuSTAR is a NASA Small Explorer mission led by Caltech and managed by JPL for NASA’s Science Mission Directorate in Washington. View this GCN Circular online at https://gcn.nasa.gov/circulars/39616. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37631] EP250304a: MeerKAT detection of a possible radio counterpart
by GCN Circulars 07 Mar '25

07 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39615 SUBJECT: EP250304a: MeerKAT detection of a possible radio counterpart DATE: 25/03/07 16:30:01 GMT FROM: Francesco Carotenuto at INAF/OAR <francesco.carotenuto(a)inaf.it> F. Carotenuto (INAF/OAR), J. Bright (University of Oxford), P. G. Jonker (Radboud University) report on behalf of a larger collaboration: We observed the Fast X-ray Transient EP250304a (Chen et al., GCN 39580) with the MeerKAT radio telescope at 3.0 GHz for a total of 1 hour starting on March 7th 2024 at 04:36 UTC. J1939-6342 and PKS 1320-446 were used as flux and complex gain calibrators, respectively. Using the South African Radio Astronomy Observatory Science Data Pipeline image, we find an unresolved source at the position of the optical counterpart of the FXT (Liu et al., GCN 39583, Saccardi et al., GCN 39585) with a flux density of ~100 uJy/beam. The rms noise in the field is 6.5 uJy/beam. Further MeerKAT observations are planned. We thank the staff at the South African Radio Astronomy Observatory for the rapid scheduling of these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39615. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37630] IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
by GCN Circulars 07 Mar '25

07 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39614 SUBJECT: IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect DATE: 25/03/07 13:19:38 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> K. Labzina, K.Zhirkov, V.Lipunov, E.Gorbovskoy, A.Kuznetsov, G.Antipov, D.Vlasenko, A.Kuznetsov, N.Tyurina, P.Balanutsa, A.Chasovnikov, V.Topolev, Ya.Kechin, V.Senik, Yu.Tselik (Lomonosov MSU), O.Gress, N.Budnev, O.Ershova (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), D.Buckley (SAAO), A.Sosnovskij (Crao RAS), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER Global Robotic Net ( Lipunov et al., Advances in Astronomy, 2010, 30L ) started IceCube-241016A alert (GCN#37794, trigger No 2910365,07h 29m 18.96s , -33d 31m 44.4s, R=0.87) errorbox 69 sec after notice time (167 sec after trigger time) at 2024-10-16 01:01:19 UT with upper limit up to 17.7 mag (Lipunov et al.GCN#37793) MASTER cover map: https://master.sai.msu.ru/site/master2/observ.php?id=2639656 We observed it in MASTER-SAAO and MASTER-OAFA and analyzed MASTER archive images since 2015 of the sources, that can be related with this event. We detected variability of blazar 5BZU J073038.29-320820.2, located inside 3 sigma IC error-box https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=&-out.add=_r&-out.add=… We detected its brightening up to 16.0m at alert time at MASTER archive light curve from 2015 year: http://observ.pereplet.ru/IC/MASTER_IC241016A.jpg Light curve also shows that a few days after neutrino alert this blazar returned to its original state. This, we report observation of an Zhirkov effect, discovered earlier (The Astrophysic Jornal Letters, 896, L19, 2020 https://ui.adsabs.harvard.edu/abs/2020ApJ...896L..19L/abstract ). View this GCN Circular online at https://gcn.nasa.gov/circulars/39614. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37629] GRB 250305A: AstroSat CZTI detection
by GCN Circulars 07 Mar '25

07 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39613 SUBJECT: GRB 250305A: AstroSat CZTI detection DATE: 25/03/07 12:11:29 GMT FROM: Gaurav Waratkar at IIT Bombay <gauravwaratkar(a)iitb.ac.in> M. Tembhurnikar (IUCAA), J. Joshi (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of GRB 250305A which was also detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 39597), and SVOM/GRM (Jin-Peng Zhang et al., GCN Circ. 39602). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-03-05 15:28:58.3 UTC. The measured peak count rate associated with the burst is 517 (+151, -123) counts/s above the background in the combined data of all quadrants, with a total of 135 (+57, -41) counts. We caution that there is a 0.3 s readout dead time in CZT data during the burst which affects the calculated total counts. The local mean background count rate was 271 (+8, -14) counts/s. Using cumulative rates, we measure a T90 of 0.9 (+0.2, -0.7) s. The source was also weakly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The measured peak count rate associated with the burst is 161 (+53, -55) counts/s above the background in the combined data of all quadrants, with a total of 298 (+140, –157) counts. The local mean background count rate was 897.1 (+5.5, –6.3) counts/s. Due to the intrinsic 1 s binning of veto data, we cannot reliably estimate a T90 from it. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/39613. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37628] EP250302a:Xinglong optical observations
by GCN Circulars 07 Mar '25

07 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39612 SUBJECT: EP250302a:Xinglong optical observations DATE: 25/03/07 09:55:58 GMT FROM: Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) <xinglong(a)nao.cas.cn> Junjie-Jin (NAOC), Haiyang-Mu (NAOC), Jinlei-Zhang (NAOC), Pengliang-Du (NAOC), Zhou-Fan (NAOC), Hong-Wu (NAOC) report: We performed optical observations of the field of a fast X-Ray transient EP250302a (Zhu et. al, GCN 39550; ) in the g, i and r filter using Tsinghua-NAOC 0.8-m telescope (TNT) located at Xinglong, Hebei, China. In each band a 600 s exposures were taken , with a median observation time of 2025-03-02T20:32:28, approximately 5 hours after the EP FXT trigger (2025-03-02T15:36:04). The optical object reported by Zhu et al. (GCN #39550) is detected in our image. We measure a preliminary magnitude of g = 17.98 +/- 0.46, i = 18.64 +/- 0.42 and r=18.41+/- 0.56 mag (AB), calibrated against nearby stars from the Pan-STARRS catalog. We summarize our observation results as follows: Obs. No. | Time (UTC) | Exposure Time (s) | Filter | Apparent mag (AB) | Telescope Name 1 | 2025-03-02T16:46:26.6 | 600 s | g |17.98 +/- 0.46| Tsinghua-NAOC 0.8-m telescope (TNT) 2 | 2025-03-02T17:06:50.4 | 600 s | i |18.64 +/- 0.42| Tsinghua-NAOC 0.8-m telescope (TNT) 3 | 2025-03-02T16:46:26.6 | 600 s | r |18.41 +/- 0.56| Tsinghua-NAOC 0.8-m telescope (TNT) View this GCN Circular online at https://gcn.nasa.gov/circulars/39612. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37627] GRB 250306A: AstroSat CZTI detection
by GCN Circulars 07 Mar '25

07 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39611 SUBJECT: GRB 250306A: AstroSat CZTI detection DATE: 25/03/07 05:36:41 GMT FROM: Gaurav Waratkar at IIT Bombay <gauravwaratkar(a)iitb.ac.in> M. Tembhurnikar (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long duration GRB 250306A which was also detected by Swift/BAT (P. A. Evans et al., GCN Circ. 39606). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-03-06 16:30:09.5 UTC. The measured peak count rate associated with the burst is 298 (+41, -38) counts/s above the background in the combined data of three quadrants (out of four), with a total of 717 (+168, -110) counts. The local mean background count rate was 220 (+3, -6) counts/s. Using cumulative rates, we measure a T90 of 7.2 (+1.5, -1.5) s. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-03-06 16:30:09.0 UTC. The measured peak count rate associated with the burst is 1146 (+81, -74) counts/s above the background in the combined data of all quadrants, with a total of 3170 (+271, -287) counts. The local mean background count rate was 1370 (+7, -8) counts/s. We measure a T90 of 6.8 (+0.7, -1.1) s from the cumulative Veto light curve. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/39611. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37626] Fermi trigger No 762963055: Global MASTER-Net observations report
by GCN Circulars 07 Mar '25

07 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39610 SUBJECT: Fermi trigger No 762963055: Global MASTER-Net observations report DATE: 25/03/07 03:31:23 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB250306.59 (trigger No 762963055,06h 29m 04.08s , -54d 04m 58.8s, R=50) errorbox 19549 sec after notice time and 19583 sec after trigger time at 2025-03-06 19:37:13 UT, with upper limit up to 19.3 mag. The observations began at zenith distance = 44 deg. The sun altitude is -30.8 deg. MASTER-OAFA robotic telescope located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB250306.59 errorbox 35961 sec after notice time and 35994 sec after trigger time at 2025-03-07 00:10:45 UT, with upper limit up to 20.7 mag. Observations started at twilight. The observations began at zenith distance = 6 deg. The sun altitude is -15.1 deg. The galactic latitude b = -25 deg., longitude l = 263 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2802407 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 19613 | 2025-03-06 19:37:13 | MASTER-SAAO | (04h 20m 33.85s , -55d 04m 29.3s) | C | 60 | 17.8 | 19692 | 2025-03-06 19:38:32 | MASTER-SAAO | (04h 20m 41.18s , -55d 05m 26.6s) | B | 60 | 17.9 | 19942 | 2025-03-06 19:42:42 | MASTER-SAAO | (07h 23m 40.55s , -50d 13m 46.6s) | C | 60 | 18.8 | 20021 | 2025-03-06 19:44:01 | MASTER-SAAO | (07h 35m 57.04s , -50d 14m 19.6s) | C | 60 | 18.7 | 20101 | 2025-03-06 19:45:21 | MASTER-SAAO | (06h 59m 31.94s , -57d 50m 20.3s) | C | 60 | 19.1 | 20180 | 2025-03-06 19:46:40 | MASTER-SAAO | (07h 14m 17.76s , -57d 51m 12.6s) | C | 60 | 18.9 | 20259 | 2025-03-06 19:47:59 | MASTER-SAAO | (06h 53m 09.68s , -59d 43m 41.7s) | C | 60 | 19.3 | 20339 | 2025-03-06 19:49:19 | MASTER-SAAO | (07h 08m 50.79s , -59d 44m 59.4s) | C | 60 | 19.1 | 20418 | 2025-03-06 19:50:38 | MASTER-SAAO | (06h 38m 47.19s , -55d 56m 27.1s) | C | 60 | 18.9 | 20497 | 2025-03-06 19:51:57 | MASTER-SAAO | (06h 52m 56.67s , -55d 55m 18.5s) | C | 60 | 18.9 | 20576 | 2025-03-06 19:53:17 | MASTER-SAAO | (04h 20m 40.87s , -55d 05m 06.1s) | C | 60 | 17.4 | 20855 | 2025-03-06 19:57:55 | MASTER-SAAO | (04h 20m 41.15s , -55d 05m 19.8s) | B | 60 | 17.8 | 21511 | 2025-03-06 20:08:52 | MASTER-SAAO | (07h 23m 44.10s , -50d 12m 41.1s) | C | 60 | 18.9 | 21591 | 2025-03-06 20:10:11 | MASTER-SAAO | (07h 36m 14.00s , -50d 13m 36.1s) | C | 60 | 18.7 | 21671 | 2025-03-06 20:11:31 | MASTER-SAAO | (06h 59m 37.99s , -57d 50m 34.1s) | C | 60 | 19.1 | 21750 | 2025-03-06 20:12:50 | MASTER-SAAO | (07h 14m 35.51s , -57d 50m 12.8s) | C | 60 | 19.0 | 21829 | 2025-03-06 20:14:10 | MASTER-SAAO | (06h 53m 20.12s , -59d 42m 57.5s) | C | 60 | 19.2 | 22516 | 2025-03-06 20:25:36 | MASTER-SAAO | (07h 09m 03.43s , -59d 41m 59.2s) | C | 60 | 19.1 | 22595 | 2025-03-06 20:26:55 | MASTER-SAAO | (06h 39m 05.00s , -55d 55m 13.9s) | C | 60 | 19.0 | 22675 | 2025-03-06 20:28:15 | MASTER-SAAO | (06h 53m 08.87s , -55d 56m 07.8s) | C | 60 | 19.0 | 23012 | 2025-03-06 20:33:52 | MASTER-SAAO | (07h 23m 52.89s , -50d 13m 01.7s) | C | 60 | 18.9 | 23091 | 2025-03-06 20:35:11 | MASTER-SAAO | (07h 36m 17.11s , -50d 11m 56.0s) | C | 60 | 18.8 | 23171 | 2025-03-06 20:36:31 | MASTER-SAAO | (06h 59m 51.87s , -57d 48m 49.5s) | C | 60 | 19.1 | 23250 | 2025-03-06 20:37:50 | MASTER-SAAO | (07h 14m 37.85s , -57d 49m 43.0s) | C | 60 | 18.9 | 23329 | 2025-03-06 20:39:09 | MASTER-SAAO | (06h 53m 30.83s , -59d 43m 41.5s) | C | 60 | 19.2 | 23583 | 2025-03-06 20:43:24 | MASTER-SAAO | (07h 09m 06.81s , -59d 42m 35.4s) | C | 60 | 19.1 | 23663 | 2025-03-06 20:44:43 | MASTER-SAAO | (06h 39m 02.04s , -55d 53m 45.9s) | C | 60 | 18.9 | 23742 | 2025-03-06 20:46:02 | MASTER-SAAO | (06h 53m 18.74s , -55d 54m 38.5s) | C | 60 | 18.9 | 24154 | 2025-03-06 20:52:54 | MASTER-SAAO | (07h 24m 04.89s , -50d 11m 37.4s) | C | 60 | 18.9 | 24233 | 2025-03-06 20:54:14 | MASTER-SAAO | (07h 36m 22.74s , -50d 12m 22.2s) | C | 60 | 18.8 | 24313 | 2025-03-06 20:55:33 | MASTER-SAAO | (06h 59m 48.96s , -57d 47m 13.8s) | C | 60 | 19.0 | 24392 | 2025-03-06 20:56:52 | MASTER-SAAO | (07h 14m 48.32s , -57d 48m 07.9s) | C | 60 | 18.9 | 24471 | 2025-03-06 20:58:12 | MASTER-SAAO | (06h 53m 27.53s , -59d 43m 09.8s) | C | 60 | 19.3 | 24724 | 2025-03-06 21:02:24 | MASTER-SAAO | (07h 09m 15.67s , -59d 42m 55.8s) | C | 60 | 19.2 | 24804 | 2025-03-06 21:03:44 | MASTER-SAAO | (06h 39m 12.98s , -55d 53m 12.3s) | C | 60 | 18.9 | 24883 | 2025-03-06 21:05:03 | MASTER-SAAO | (06h 53m 17.91s , -55d 54m 02.0s) | C | 60 | 19.0 | 25374 | 2025-03-06 21:13:14 | MASTER-SAAO | (07h 24m 10.09s , -50d 10m 53.7s) | C | 60 | 18.8 | 25453 | 2025-03-06 21:14:33 | MASTER-SAAO | (07h 36m 29.33s , -50d 11m 44.1s) | C | 60 | 18.7 | 25532 | 2025-03-06 21:15:52 | MASTER-SAAO | (06h 59m 55.42s , -57d 46m 33.9s) | C | 60 | 18.9 | 25611 | 2025-03-06 21:17:12 | MASTER-SAAO | (07h 14m 54.90s , -57d 47m 28.2s) | C | 60 | 18.8 | 25691 | 2025-03-06 21:18:31 | MASTER-SAAO | (06h 53m 33.13s , -59d 42m 29.2s) | C | 60 | 19.1 | 26024 | 2025-03-06 21:24:04 | MASTER-SAAO | (07h 09m 24.68s , -59d 40m 41.5s) | C | 60 | 19.1 | 26103 | 2025-03-06 21:25:24 | MASTER-SAAO | (06h 39m 10.31s , -55d 53m 24.4s) | C | 60 | 19.0 | 26183 | 2025-03-06 21:26:43 | MASTER-SAAO | (06h 53m 20.72s , -55d 52m 17.4s) | C | 60 | 18.5 | 26681 | 2025-03-06 21:35:01 | MASTER-SAAO | (07h 24m 19.80s , -50d 10m 26.5s) | C | 60 | 17.3 | 26761 | 2025-03-06 21:36:21 | MASTER-SAAO | (07h 36m 38.64s , -50d 11m 15.0s) | C | 60 | 17.4 | 26840 | 2025-03-06 21:37:40 | MASTER-SAAO | (07h 00m 03.51s , -57d 46m 05.9s) | C | 60 | 17.6 | 26919 | 2025-03-06 21:38:59 | MASTER-SAAO | (07h 15m 04.43s , -57d 46m 59.8s) | C | 60 | 16.8 | 26999 | 2025-03-06 21:40:19 | MASTER-SAAO | (06h 53m 40.23s , -59d 42m 01.2s) | C | 60 | 17.6 | 27330 | 2025-03-06 21:45:50 | MASTER-SAAO | (07h 09m 30.05s , -59d 40m 08.9s) | C | 60 | 19.1 | 27409 | 2025-03-06 21:47:09 | MASTER-SAAO | (06h 39m 13.36s , -55d 52m 47.5s) | C | 60 | 18.9 | 27488 | 2025-03-06 21:48:28 | MASTER-SAAO | (06h 53m 25.38s , -55d 51m 40.4s) | C | 60 | 19.1 | 36055 | 2025-03-07 00:10:45 | MASTER-OAFA | (06h 39m 01.49s , -36d 27m 29.2s) | C | 120 | 20.0 | 36175 | 2025-03-07 00:10:45 | MASTER-OAFA | (06h 39m 01.49s , -36d 27m 29.2s) | C | 360 | 20.5 | Coadd 36492 | 2025-03-07 00:18:13 | MASTER-OAFA | (06h 50m 23.77s , -36d 05m 00.8s) | C | 100 | 18.4 | 36592 | 2025-03-07 00:18:13 | MASTER-OAFA | (06h 50m 23.77s , -36d 05m 00.8s) | C | 300 | 19.1 | Coadd 36503 | 2025-03-07 00:18:13 | MASTER-OAFA | (06h 39m 02.29s , -36d 26m 20.3s) | C | 120 | 19.9 | 36626 | 2025-03-07 00:20:26 | MASTER-OAFA | (06h 50m 31.45s , -36d 05m 57.5s) | C | 100 | 18.5 | 36636 | 2025-03-07 00:20:27 | MASTER-OAFA | (06h 39m 09.85s , -36d 27m 17.1s) | C | 120 | 20.1 | 36763 | 2025-03-07 00:22:43 | MASTER-OAFA | (06h 50m 26.25s , -36d 06m 54.0s) | C | 100 | 18.5 | 36773 | 2025-03-07 00:22:44 | MASTER-OAFA | (06h 39m 04.58s , -36d 28m 13.9s) | C | 120 | 20.0 | 36893 | 2025-03-07 00:22:44 | MASTER-OAFA | (06h 39m 04.58s , -36d 28m 13.9s) | C | 360 | 20.6 | Coadd 36899 | 2025-03-07 00:24:59 | MASTER-OAFA | (06h 50m 31.50s , -36d 06m 22.8s) | C | 100 | 18.5 | 36909 | 2025-03-07 00:25:00 | MASTER-OAFA | (06h 39m 09.97s , -36d 27m 43.2s) | C | 120 | 20.1 | 37253 | 2025-03-07 00:30:54 | MASTER-OAFA | (06h 50m 28.93s , -36d 06m 37.9s) | C | 100 | 18.5 | 37264 | 2025-03-07 00:30:54 | MASTER-OAFA | (06h 39m 07.66s , -36d 28m 03.4s) | C | 120 | 20.0 | 37674 | 2025-03-07 00:38:24 | MASTER-OAFA | (03h 08m 25.09s , -30d 36m 24.1s) | C | 40 | 18.0 | 37714 | 2025-03-07 00:38:24 | MASTER-OAFA | (03h 08m 25.09s , -30d 36m 24.0s) | C | 120 | 18.9 | Coadd 37684 | 2025-03-07 00:38:24 | MASTER-OAFA | (02h 57m 52.08s , -30d 57m 32.7s) | C | 60 | 20.0 | 37744 | 2025-03-07 00:38:24 | MASTER-OAFA | (02h 57m 52.07s , -30d 57m 32.8s) | C | 180 | 20.6 | Coadd 37854 | 2025-03-07 00:41:24 | MASTER-OAFA | (02h 47m 43.33s , -45d 51m 10.7s) | C | 40 | 18.1 | 37894 | 2025-03-07 00:41:24 | MASTER-OAFA | (02h 47m 43.32s , -45d 51m 10.6s) | C | 120 | 18.8 | Coadd 37864 | 2025-03-07 00:41:24 | MASTER-OAFA | (02h 34m 39.52s , -46d 11m 20.6s) | C | 60 | 20.0 | 37924 | 2025-03-07 00:41:24 | MASTER-OAFA | (02h 34m 39.52s , -46d 11m 20.6s) | C | 180 | 20.7 | Coadd 38489 | 2025-03-07 00:51:59 | MASTER-OAFA | (03h 08m 20.31s , -30d 35m 34.4s) | C | 40 | 18.0 | 38499 | 2025-03-07 00:51:59 | MASTER-OAFA | (02h 57m 47.83s , -30d 56m 40.0s) | C | 60 | 19.7 | 38567 | 2025-03-07 00:53:18 | MASTER-OAFA | (02h 47m 44.07s , -45d 50m 28.4s) | C | 40 | 18.1 | 38578 | 2025-03-07 00:53:18 | MASTER-OAFA | (02h 34m 40.86s , -46d 10m 33.0s) | C | 60 | 19.9 | 39176 | 2025-03-07 01:03:27 | MASTER-OAFA | (03h 08m 26.89s , -30d 36m 25.0s) | C | 40 | 18.0 | 39187 | 2025-03-07 01:03:27 | MASTER-OAFA | (02h 57m 54.21s , -30d 57m 33.5s) | C | 60 | 19.9 | 39256 | 2025-03-07 01:04:46 | MASTER-OAFA | (02h 47m 39.18s , -45d 50m 51.5s) | C | 40 | 17.9 | 39266 | 2025-03-07 01:04:47 | MASTER-OAFA | (02h 34m 35.84s , -46d 10m 58.8s) | C | 60 | 20.1 | 39769 | 2025-03-07 01:13:19 | MASTER-OAFA | (03h 08m 27.01s , -30d 37m 51.1s) | C | 40 | 18.0 | 39809 | 2025-03-07 01:13:19 | MASTER-OAFA | (03h 08m 27.01s , -30d 37m 51.0s) | C | 120 | 18.7 | Coadd 39779 | 2025-03-07 01:13:19 | MASTER-OAFA | (02h 57m 54.90s , -30d 58m 54.2s) | C | 60 | 19.7 | 39839 | 2025-03-07 01:13:19 | MASTER-OAFA | (02h 57m 54.90s , -30d 58m 54.2s) | C | 180 | 20.4 | Coadd 40225 | 2025-03-07 01:20:55 | MASTER-OAFA | (02h 47m 38.97s , -45d 50m 05.2s) | C | 40 | 17.9 | 40235 | 2025-03-07 01:20:55 | MASTER-OAFA | (02h 34m 36.00s , -46d 10m 14.5s) | C | 60 | 20.1 | 40574 | 2025-03-07 01:26:45 | MASTER-OAFA | (03h 08m 27.40s , -30d 38m 14.0s) | C | 40 | 17.7 | 40585 | 2025-03-07 01:26:45 | MASTER-OAFA | (02h 57m 55.08s , -30d 59m 20.9s) | C | 60 | 19.6 | 41242 | 2025-03-07 01:37:42 | MASTER-OAFA | (02h 34m 44.51s , -46d 11m 34.8s) | C | 60 | 19.1 | 41646 | 2025-03-07 01:44:36 | MASTER-OAFA | (03h 08m 24.70s , -30d 38m 19.6s) | C | 40 | 17.9 | 41656 | 2025-03-07 01:44:37 | MASTER-OAFA | (02h 57m 52.88s , -30d 59m 23.8s) | C | 60 | 19.3 | 41875 | 2025-03-07 01:48:25 | MASTER-OAFA | (02h 47m 42.83s , -45d 51m 36.8s) | C | 40 | 17.9 | 41885 | 2025-03-07 01:48:25 | MASTER-OAFA | (02h 34m 40.19s , -46d 11m 44.0s) | C | 60 | 19.6 | 47204 | 2025-03-07 03:17:15 | MASTER-OAFA | (12h 16m 47.66s , -65d 25m 24.4s) | C | 40 | 16.7 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/39610. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37625] Fermi Gamma-ray Burst Monitor trigger 762963055/250306591 is not a GRB
by GCN Circulars 06 Mar '25

06 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39609 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 762963055/250306591 is not a GRB DATE: 25/03/06 22:57:36 GMT FROM: Matt Godwin <msg0028(a)uah.edu> Matt Godwin (UAH) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 762963055/250306591 at 14:10:50.74 UT on 06 March 2025, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to an accidental trigger." View this GCN Circular online at https://gcn.nasa.gov/circulars/39609. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37624] Swift GRB 250306A: Global MASTER-Net observations report
by GCN Circulars 06 Mar '25

06 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39608 SUBJECT: Swift GRB 250306A: Global MASTER-Net observations report DATE: 25/03/06 18:13:38 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB 250306A ( P. A. Evans et al., GCN 39606) errorbox 4918 sec after notice time and 5733 sec after trigger time at 2025-03-06 18:05:42 UT, with upper limit up to 18.3 mag. Observations started at twilight. The observations began at zenith distance = 74 deg. The sun altitude is -12.9 deg. The galactic latitude b = -65 deg., longitude l = 332 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2802578 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 5823 | MASTER-SAAO | C | 180 | 18.3 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/39608. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37623] LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
by GCN Circulars 06 Mar '25

06 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39607 SUBJECT: LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume DATE: 25/03/06 17:03:36 GMT FROM: David Cook at Caltech/IPAC-NED <dcook(a)ipac.caltech.edu> David O. Cook (Caltech/IPAC), Rick Ebert (Caltech/IPAC), George Helou (Caltech/IPAC), Joseph M. Mazzarella (Caltech/IPAC), Marion Schmitz (Caltech/IPAC), and Leo Singer (NASA/GSFC) On behalf of the NASA/IPAC Extragalactic Database (NED) Team. We spatially cross-matched the LVK S250207bg-5-Update sky localization with the NED Local Volume Sample (NED-LVS; Cook et al. 2023), which is a subset of NED with a redshift or redshift-independent distance less than 1000 Mpc. We find 369 galaxies within the 90% containment volume, and we list here the top 20 galaxies sorted by the joint probability of the 3D localization and the WISE W1 luminosity (an observable proxy for stellar mass). For the full or top 20 list of galaxies in the 90% volume go either to the NED Gravitational Wave Followup service at https://ned.ipac.caltech.edu/uri/NED::GWF/ or click on the following links: Full List Download: https://ned.ipac.caltech.edu/uri/NED::GWFglist/fits/S250207bg/5 Top 20 List Download: https://ned.ipac.caltech.edu/uri/NED::GWFglist/fits/S250207bg/5/20 *** We note that the version of NED-LVS used in this analysis is from Jan 2025 that was released on Feb 10 2025, whereas the S250207bg-4-Update analysis used the previous version. This new version has an additional 203K galaxies in the full sample the majority of which are from DESI-EDR. The NED-GWF service provides downloadable galaxy lists and visualizations for candidate host galaxies. For each GW alert, these products are automatically generated and made available within minutes to expedite efficient electromagnetic follow-up observations. The NED top 20 list is sorted by the joint probability of the 3D localization and the WISE W1 luminosity, but users can sort on additional pre-computed prioritization metrics (star formation rate, P_3D * P_SFR; and specific star formation rate, P_3D * P_sSFR; etc.) which are available via downloading the entire galaxy list inside the event's probability volume. | objname| ra| dec|objtype| DistMpc|DistMpc_unc| m_NUV| m_NUV_unc| m_Ks| m_Ks_unc| m_W1| m_W1_unc| P_3D|P_3D_LumW1| |-------------------------|--------------|--------------|-------|-----------|-----------|------------|------------|------------|------------|------------|------------|--------|----------| | CGCG 184-039| 164.42690| 37.65455| G| 162.22| 26.21| null| null| 10.680| 0.054| 10.878| 0.006|8.03e-05| 1.12e-06| | MCG +06-24-041| 164.47481| 37.54192| G| 162.22| 26.21| 20.279| 0.148| 11.298| 0.055| 11.331| 0.007|9.63e-05| 8.84e-07| | CGCG 184-023| 162.54517| 35.03369| G| 183.12| 0.03| 17.688| 0.031| 12.087| 0.052| 11.752| 0.008|8.79e-05| 6.97e-07| | CGCG 184-033| 163.24603| 37.61345| G| 187.51| 0.05| null| null| 11.034| 0.043| 11.024| 0.006|4.07e-05| 6.62e-07| |WISEA J105523.87+362209.7| 163.84948| 36.36938| G| 151.73| 0.05| 21.139| 0.087| 12.289| 0.075| 12.390| 0.018|2.11e-04| 6.38e-07| |WISEA J105133.05+360501.0| 162.88772| 36.08364| G| 188.40| 44.45| null| null| 12.941| 0.092| 12.598| 0.010|1.58e-04| 6.09e-07| | MCG +06-24-040| 164.47226| 37.51474| G| 149.83| 0.04| 19.652| 0.099| 11.734| 0.062| 11.636| 0.007|1.01e-04| 5.94e-07| | 2MFGC 08396| 161.78556| 34.83804| G| 195.44| 0.05| null| null| 12.218| 0.063| 11.971| 0.009|7.37e-05| 5.44e-07| |WISEA J105802.45+364004.6| 164.51022| 36.66795| G| 141.05| 33.28| 21.365| 0.346| 12.356| 0.057| 12.181| 0.007|1.63e-04| 5.17e-07| |WISEA J104944.42+362416.4| 162.43511| 36.40456| G| 181.79| 0.05| null| null| 12.607| 0.089| 12.522| 0.009|1.21e-04| 4.65e-07| |WISEA J105909.94+371504.2| 164.79142| 37.25117| G| 187.86| null| 18.157| 0.034| 11.855| 0.050| 11.585| 0.007|4.77e-05| 4.64e-07| | 2MFGC 08535| 164.22259| 37.59752| G| 157.75| 0.07| 21.513| 0.332| 12.030| 0.059| 11.685| 0.007|7.16e-05| 4.48e-07| |WISEA J105800.68+374606.5| 164.50287| 37.76849| G| 151.47| 0.04| 20.580| 0.135| 11.774| 0.046| 11.693| 0.007|7.45e-05| 4.27e-07| |WISEA J104451.00+353606.0| 161.21250| 35.60167| G| 229.57| 0.05| null| null| 13.208| 0.103| 11.860| 0.009|3.62e-05| 4.09e-07| | 2MFGC 08400| 161.86882| 36.82418| G| 158.37| 0.05| null| null| 10.992| 0.033| 10.891| 0.006|2.92e-05| 3.83e-07| |WISEA J105511.98+365943.1| 163.79993| 36.99531| G| 194.37| 0.04| 19.438| 0.024| 12.725| 0.093| 12.580| 0.012|7.82e-05| 3.26e-07| |WISEA J105456.98+375126.3| 163.73744| 37.85731| G| 153.99| 0.12| null| null| 15.333| 0.275| 11.308| 0.007|3.85e-05| 3.25e-07| |WISEA J105258.79+371636.7| 163.24498| 37.27688| G| 190.48| 0.05| null| null| 12.533| 0.066| 12.424| 0.008|6.96e-05| 3.21e-07| |WISEA J105855.76+370625.3| 164.73237| 37.10705| G| 157.95| 0.10| 18.116| 0.038| 12.805| 0.115| 12.824| 0.010|1.29e-04| 2.83e-07| |WISEA J105412.49+373218.9| 163.55205| 37.53859| G| 135.45| 0.04| 20.135| 0.181| 11.549| 0.047| 11.403| 0.006|4.57e-05| 2.73e-07| Table 1: Top 20 galaxies in NED-LVS that fall in the 90% probability volume for S250207bg sorted by the joint probability of 3D position and WISE W1 luminosity (P_3D * P_LumW1). Galaxy is the NED preferred name. RA and Dec are the Equatorial coordinates in degrees (J2000). Objtype is the object type of the galaxy candidate. Distance is the distance to the galaxy in Mpc. m_NUV and mErr_NUV are the apparent magnitude and error from GALEX. m_Ks and mErr_Ks are the apparent magnitude and error from 2MASS. m_W1 and mErr_W1 are the apparent magnitude and error from AllWISE. P_3D is the probability that the galaxy is in the volume given the distance of GW event. P_3D_LumW1 is the joint probability within the volume weighted by the WISE1 luminosity of the galaxy (P_3D * P_LumW1). View this GCN Circular online at https://gcn.nasa.gov/circulars/39607. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37622] GRB 250306A: Swift detection of a burst
by GCN Circulars 06 Mar '25

06 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39606 SUBJECT: GRB 250306A: Swift detection of a burst DATE: 25/03/06 16:51:42 GMT FROM: David Palmer at LANL <palmer(a)lanl.gov> P. A. Evans (U Leicester), R. Gupta (NASA GSFC), J. A. Kennea (PSU), K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift Observatory Team: At 16:30:08 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250306A (trigger=1293340). Swift did not slew to the burst. The BAT on-board calculated location is RA, Dec 354.730, -47.993 which is RA(J2000) = 23h 38m 55s Dec(J2000) = -47d 59' 35" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 10 sec. The peak count rate was ~14,000 counts/sec (15-350 keV), at ~0 sec after the trigger. Due to a Sun observing constraint, Swift cannot slew to the BAT position until 01:23 UT on 2025 March 18. There will thus be no XRT or UVOT data for this trigger before this time. Burst Advocate for this burst is P. A. Evans (pae9 AT leicester.ac.uk). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/) View this GCN Circular online at https://gcn.nasa.gov/circulars/39606. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37621] LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
by GCN Circulars 06 Mar '25

06 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39605 SUBJECT: LIGO/Virgo/KAGRA S250207bg: Updated Sky localization DATE: 25/03/06 16:37:39 GMT FROM: Sylvia Biscoveanu at Northwestern CIERA <sylvia.biscoveanu(a)ligo.org> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We have conducted further analysis of the LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S250207bg (GCN Circulars 39201 and 39242). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.offline1.multiorder.fits,0, distributed via GCN Notice, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S250207bg For the Bilby.offline1.multiorder.fits,0 sky map, the 90% credible region is well fit by an ellipse with an area of 19 deg2 described by the following DS9 region (right ascension, declination, semi-major axis, semi-minor axis, position angle of the semi-minor axis): icrs; ellipse(10h51m, +36d04m, 3.72d, 1.66d, 139.66d) Marginalized over the whole sky, the a posteriori luminosity distance estimate is 180 +/- 38 Mpc (a posteriori mean +/- standard deviation). At the time of the candidate, the Hanford detector was being brought online and was not in observing mode. However, it was determined that the Hanford data are sufficiently robust to inform our estimate of the sky localization. The well-measured arrival time of the signal at Hanford, while consistent with the Livingston and Virgo data, breaks the degeneracy in sky localization inherent in a 2-detector analysis, and significantly shifts the posterior distribution with respect to the earlier localization. Further investigations are ongoing to understand how the operational state of Hanford at the time of the event impacts this analysis. The estimated sky localization may change slightly based on these studies, but this skymap represents our best understanding of the event at this time. For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. (2023) arXiv:2307.13380 View this GCN Circular online at https://gcn.nasa.gov/circulars/39605. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37620] GRB250101A: Radio upper limits from VLA observations
by GCN Circulars 06 Mar '25

06 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39604 SUBJECT: GRB250101A: Radio upper limits from VLA observations DATE: 25/03/06 15:57:17 GMT FROM: Arvind Balasubramanian <arvind6895(a)gmail.com> A. Balasubramanian (IIA), A.P. Saikia (IITB), V. Swain (IITB), G.C. Anupama (IIA), S. Barway (IIA), V. Bhalerao (IITB) report We observed the field of the gamma ray burst GRB250101A (Page et al. GCN 38752, Li et al. GCN 38753, Mohan et al. GCN 38754, Zhu et al. GCN 38755, Budnev et al. GCN 38756, Wu et al. GCN 38758, Odeh et al. GCN 38763, Balasubramanian et al. GCN 39307) with the Jansky Very Large Array (VLA) under the DDT 24B-529 (PI: A. Balasubramanian) on 13th February 2025 in S Band (3 GHz) for about 1.5 hours starting at 02:06 hours UTC. We do not detect any significant radio emission at the position of the optical counterpart (Li et al. GCN 38753). We used 3C47 for the flux calibration and J0238+1636 for complex gain and phase calibration. The CASA calibration and imagining pipeline (version 6.5.4.9) was used for data calibration and imaging. We compute a 3-sigma upper limit of ~805 uJy at 3 GHz. Further analysis is in progress. We thank the TAC and operations team of VLA for making these observations possible. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. View this GCN Circular online at https://gcn.nasa.gov/circulars/39604. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37619] LIGO/Virgo/KAGRA S250306ej: Retraction of GW compact binary merger candidate
by GCN Circulars 06 Mar '25

06 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39603 SUBJECT: LIGO/Virgo/KAGRA S250306ej: Retraction of GW compact binary merger candidate DATE: 25/03/06 15:31:48 GMT FROM: Mayank Chaturvedi at RRCAT, INDORE. <mayankc1947(a)gmail.com> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: The trigger S250306ej is no longer considered to be a candidate of interest. This candidate was initially identified by one or more early-warning analyses by matching partial signal templates to the data. Analysis of additional data up to the putative merger time, with full signal templates, did not make a significant detection, indicating that the initial candidate was likely due to transient noise. Specifically, low-frequency transient noise was present in the LIGO Hanford and Livingston detectors in the minute before the time of the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/39603. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37618] GRB 250305A: SVOM/GRM observation of a burst
by GCN Circulars 06 Mar '25

06 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39602 SUBJECT: GRB 250305A: SVOM/GRM observation of a burst DATE: 25/03/06 09:51:52 GMT FROM: zhangjinpeng(a)ihep.ac.cn SVOM/GRM team: Jin-Peng Zhang, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Nicolas Dagoneau (CEA), Maria-Grazia Bernardini (INAF-OAB), Jean-Luc Atteia (IRAP), Frédéric Piron (LUPM) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by GRB 250305A (SVOM burst-id sb25030508) at 2025-03-05T15:28:58.100 (T0), which was also observed by Fermi/GBM (Fermi GBM team, GCN #39597). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multi-pulses with a T90 of 4.6 +1.5/-0.9 s in the 15-5000 keV band. In addition, the position of this burst, as determined by Fermi/GBM (GCN #39597, RA: 223.7 deg, DEC: -3.0 deg, Error: 5.0 deg), is located at about 63 degrees from the SVOM optical axis, and outside the ECLAIRs field of view. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250305A.png The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM/GRM point of contact for this burst is: Jin-Peng Zhang (IHEP) (zhangjinpeng(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/39602. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37617] The EP-WXT trigger 01709132323 is likely a flaring star
by GCN Circulars 06 Mar '25

06 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39601 SUBJECT: The EP-WXT trigger 01709132323 is likely a flaring star DATE: 25/03/06 09:42:08 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.-H. I. Yin (NJU), H. Sun, X. P. Xu, C. C. Jin (NAO, CAS) report on behalf of the Einstein Probe team: The EP-WXT trigger (ID: 01709132323) on 2025-03-06 09:04:17 (UTC) is likely a stellar flare associated with a star TYC 2497-986-1. The estimated flux of the flare is around 1.2 x 10^-10 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 2.3 x 10^33 erg/s. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with onboard X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/39601. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37616] EP250304A: Upper limits from Fermi-GBM Observations
by GCN Circulars 06 Mar '25

06 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39600 SUBJECT: EP250304A: Upper limits from Fermi-GBM Observations DATE: 25/03/06 09:13:06 GMT FROM: mariaedvige.ravasio(a)ru.nl M. E. Ravasio (Radboud Univ.), E. Burns (LSU), and P.G. Jonker (Radboud Univ.) report on behalf of the Fermi-GBM Team: At the starting time T0=2025-03-04T01:29:49 UTC of the EP-WXT event EP250304A (Zhang et al., GCN 39591), Fermi was in South Atlantic Anomaly (SAA). Fermi-GBM had exited SAA approximately 50 seconds after T0. There was no Fermi-GBM onboard trigger around EP-WXT time. The GBM targeted search [1], the most sensitive, coherent search for GRB-like signals, was run in the time interval [T0-50;T0+500] s, seeking signals between 64 ms and 32.768 s in duration. No signal consistent with the EP transient both temporally and spatially is identified, as confirmed by visual inspection of the data. Assuming a “soft” spectral template (Band function with Epeak = 70 keV, alpha = -1.9, beta = -3.7), and a duration of 8.192 s, we derive a sky-averaged flux upper limit of 3.9e-08 erg/cm2/s in the energy band 10-1000 keV. [1] Goldstein et al. 2019 arXiv:1903.12597 View this GCN Circular online at https://gcn.nasa.gov/circulars/39600. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37615] Fermi GRB 250305A: Global MASTER-Net observations report
by GCN Circulars 05 Mar '25

05 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39599 SUBJECT: Fermi GRB 250305A: Global MASTER-Net observations report DATE: 25/03/05 21:32:49 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 250305A ( Fermi GBM team, GCN 39597) errorbox 20388 sec after notice time and 20424 sec after trigger time at 2025-03-05 21:09:22 UT, with upper limit up to 18.6 mag. The observations began at zenith distance = 78 deg. The sun altitude is -45.2 deg. The galactic latitude b = 47 deg., longitude l = 353 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2801332 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 20455 | 2025-03-05 21:09:22 | MASTER-SAAO | (14h 34m 50.28s , -02d 29m 23.3s) | C | 60 | 18.3 | 20534 | 2025-03-05 21:10:41 | MASTER-SAAO | (14h 42m 45.22s , -02d 30m 38.4s) | C | 60 | 18.4 | 20613 | 2025-03-05 21:12:01 | MASTER-SAAO | (14h 36m 36.01s , -04d 22m 25.4s) | C | 60 | 18.6 | 20772 | 2025-03-05 21:14:39 | MASTER-SAAO | (14h 44m 39.80s , -04d 22m 36.6s) | C | 60 | 18.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/39599. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37614] Fermi-LAT Gamma-ray Observations of IceCube-250302A
by GCN Circulars 05 Mar '25

05 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39598 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-250302A DATE: 25/03/05 18:12:45 GMT FROM: chiara.bartolini-1(a)unitn.it C. Bartolini (INFN Bari), S. Buson (DESY, Univ. of Wuerzburg), S. Garrappa (Weizmann Institute of Science), L. Pfeiffer (Univ. of Wuerzburg) and P. M. Veres (Ruhr University Bochum) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC250302A neutrino event (GCN 39549) with all-sky survey data from the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. The IceCube event was detected on 2025-03-02 03:20:52.90 UTC (T0) with J2000 position RA = 348.05 (+0.38, -0.43) deg, Decl. = 3.77 (+0.42, -0.41) deg 90% PSF containment. No cataloged gamma-ray sources are found within the 90% IC250302A localization error (The Fourth Fermi-LAT catalog, 4FGL-DR4, The Fermi-LAT collaboration 2023, arXiv:2307.12546). We searched for the existence of intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (>5sigma) new excess emission (> 100 MeV) within the IC250302A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IceCube best-fit position, the >100 MeV flux upper limit (95% confidence) is <9.21e-10 ph cm^-2 s^-1 for ~16-years (2008-08-04 / T0), <9.22e-09(<6.48e-8) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. For this source, the Fermi-LAT contact person is C. Bartolini (chiara.bartolini at ba.infn.it). The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. View this GCN Circular online at https://gcn.nasa.gov/circulars/39598. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37613] GRB 250305A: Fermi GBM Final Real-time Localization
by GCN Circulars 05 Mar '25

05 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39597 SUBJECT: GRB 250305A: Fermi GBM Final Real-time Localization DATE: 25/03/05 15:39:31 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 15:28:57 UT on 5 Mar 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250305A (trigger 762881342.919284 / 250305645). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 223.7, Dec = -3.0 (J2000 degrees, equivalent to J2000 14h 54m, -3d 00'), with a statistical uncertainty of 5.0 degrees. The angle from the Fermi LAT boresight is 60.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250305645/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250305645/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250305645/… View this GCN Circular online at https://gcn.nasa.gov/circulars/39597. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37612] EP250302a: Optical Observations at CrAO and SAO RAS
by GCN Circulars 05 Mar '25

05 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39596 SUBJECT: EP250302a: Optical Observations at CrAO and SAO RAS DATE: 25/03/05 12:52:41 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI), A. Moskvitin (SAO RAS), O. I. Spiridonova (SAO RAS), A. Pozanenko (IKI), E. Klunko (ISTP) report on behalf of IKI-GRB-FuN: We performed optical observations of the field of a fast X-Ray transient EP250302a (Dai et al., GCN 39556; Page et al., GCN 39557) in the R filter with the 2.6-meter telescope of the Crimean Astrophysical Observatory (CrAO) and the 1-meter Zeiss-1000 telescope of the Special Astrophysical Observatory of the RAS (SAO RAS). The observations began on 2025-03-03 (UT) 01:51:40, i.e. 1.42750 days since trigger. The optical source (Zhu et al., GCN 39550; Busmann et al., GCN 39551; Leonini et al., GCN 39553; Wu et al., GCN 39555; Xin et al., GCN 39558; Adami et al., GCN 39560; Yang et al., GCN 39561; Becerra et al., GCN 39562; Izzo et al., GCN 39564; Pankov et al., GCN 39565; Reguitti, GCN 39568; Komesh et al., GCN 39569; Shilling and Breeveld, GCN 39570; Aryan et al., GCN 39572; Moskvitin et. al, GCN 39576; Wu et. al, GCN 39578; Pankov et. al, GCN 39586; Gupta et. al, GCN 39593) is not detected in the stacked images from both telescopes. The preliminary upper limits are as follows: Date UT start t-T0 Exptime Filter UL Telescope (mid, days) (s) (3sigma) 2025-03-03 01:51:40 1.44460 9*300 Rc 22.7 Zeiss-1000/SAO RAS 2025-03-04 23:21:23 2.33286 14*120 R 23.3 ZTSh/CrAO The photometry is based on nearby stars from the USNO-B1.0 catalog (R2 magnitudes) and has not been corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39596. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37611] GRB 250219A: SVOM/C-GFT optical upper limit at early phase
by GCN Circulars 05 Mar '25

05 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39595 SUBJECT: GRB 250219A: SVOM/C-GFT optical upper limit at early phase DATE: 25/03/05 12:41:57 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Zhe Kang (CHO), F. Daigne (IAP), M. Gnaoui (IAP), Liping Xin(NAOC), Xuhui Han(NAOC), Chao WU (NAOC), Pinpin Zhang (NAOC), Xiaomeng Lu (NAOC), Zhenwei Li (CHO), You Lv (CHO), Ruosong Zhang (NAOC), Yujie Xiao(NAOC), Yulei, Qiu(NAOC), Jing Wang(NAOC), Jianyan Wei (NAOC) report on behalf of the SVOM/C-GFT team: We observed the field of GRB 250219A (SVOM/ECLAIRs burst-id:sb25021904, Daigne et al. GCN 39376) starting at 2025-02-19T16:03:29 UT, ~10.68 mins after the burst trigger with C-GFT. A series of g, r and i band images were obtained with exposure time of 10s for each frame. No source consistent with the XRT (Kennea et al., GCN 39379; Turpin et al., GCN 39456) was detected. The optical counterpart (Xin et al., GCN 39380; Magnani et al., GCN 39382; Fu et al., GCN 39383; ) was not detected in our images. The upper limit at early phase are, (T-T0)_mid(sec) exptime(s) limiting_mag(3sigma) band ------------------------------------------------------ 678 6x10s >19.57 (6x10s) i 1013 6x10s >20.11 (6x10s) g 1102 6x10s >20.03 (6x10s) r The photometry was calibrated with nearby stars in UCAC4 catalog. It is consistent with those results reported by Lagioia et al. (GCN 39381), Adami et al. (GCN 39384), Breeveld et al (GCN 39385), Turpin et al. (GCN 39407) and Komesh et al. (GCN 39419). We thank the observation assistant Guangsheng Zhang and Chunlei Guo at Jilin observatory for their excellent support. Chinese Ground Follow-up Telescope of SVOM mission is located at Jilin, Changchun Observatory, National Astronomical Observatories, CAS. It has FOV of 1.28 deg x 1.28 deg with a 4k*4k CMOS detector mounted on the primary focus of 1.2-meter-aperure telescope. View this GCN Circular online at https://gcn.nasa.gov/circulars/39595. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37610] EP 250304A: Optical counterpart detection by LCO
by GCN Circulars 05 Mar '25

05 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39594 SUBJECT: EP 250304A: Optical counterpart detection by LCO DATE: 25/03/05 09:43:20 GMT FROM: ankur ghosh at CAPP, University of Johannesburg <ghosh.ankur1994(a)gmail.com> Ankur Ghosh, Soebur Razzaque (CAPP, University of Johannesburg), Alexander Moskvitin, Yulia Sotnikova (SAO RAS), Naveen Dukiya (ARIES), Rahul Gupta (NASA GSFC) on behalf of a larger collaboration. We observed the field of the EP 250304A triggered by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Chen et al., GCN 39580) in r filter of the 1-meter Sinistro telescope at the Las Cumbres Observatory Global Telescope (LCOGT) node located at South African Astronomical Observatory (SAAO), South Africa. The 1-m Sinistro telescope is equipped with a 4K x 4K CCD (FOV: 26 x 26 arcmin, scale: 0.39 arcsec/pixel). Observations began on March 04, 2025, starting 19.80 hours after the GRB trigger. We clearly detect the optical transient (OT) reported by GCNs (Xu et al, GCN 39583, Page et al., GCN 39584, Saccardi et al., GCN 39585, Shilling et al., 39587) in our r band image. |Date| |UTstart| |t-T0 (hours)| |Exp (sec)| |Filter| |Magnitude| -------------------------------------------------------------------------------------------------- 2025-03-04 21:20:52.80 19.80 1 x 1000 r r = 20.00 +/- 0.08 The field was calibrated against nearby APASS stars, with magnitudes converted using Lupton (2005) equations, and has not been corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39594. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37609] GCN Announcement: End of INTEGRAL Operations
by GCN Announcements 04 Mar '25

04 Mar '25

Beginning March 4, 2025 at 12:08:04 UT, data from the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) will no longer be transmitted to the INTEGRAL Science Data Centre (ISDC), due to the end of scientific operations, more than 22 years after its launch. As a consequence, the INTEGRAL Burst Alert System (IBAS) will be discontinued and GCN Notices will no longer be distributed. The full archive of INTEGRAL GCN Notices is available at https://gcn.gsfc.nasa.gov/integral.html. The IBAS team thank the scientific community for the continuous support. The GCN team thank INTEGRAL for being an important contributor to GCN over the last 22 years. The mission pages for GCN Notice producers that are no longer operational have been moved to a submenu for archived missions, including AGILE, BurstCube, and INTEGRAL (https://gcn.nasa.gov/missions/archive). This news was also reported by the INTEGRAL team in GCN Circular 39563. For more details on this new feature and an archive of GCN news and announcements, see https://gcn.nasa.gov/news. For questions, issues, or bug reports, please contact us via: - Contact form: https://gcn.nasa.gov/contact - GitHub issue tracker: https://github.com/nasa-gcn/gcn.nasa.gov/issues --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37608] EP250302A: 1.3m DFOT optical afterglow detection
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39593 SUBJECT: EP250302A: 1.3m DFOT optical afterglow detection DATE: 25/03/04 15:36:13 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Amit K. Ror, Kuntal Misra, and Shashi B. Pandey (ARIES) report: We observed the field of EP250302A detected by EP-WXT (Trigger ID: 01709132186) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2025-03-02 at 20:15:46 UT, i.e., ~ 4.66 hours after the EP-WXT trigger. We have taken multiple frames with an exposure time of 300 s in the R filter. We stacked the images after the alignment. We clearly detected optical afterglow in our stacked image within the error box of the EP/WXT coordinates (GCN 39550). We obtained the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (hour) Filter Exp time (s) magnitude ========================================================================= 2025-03-02 20:15:46 ~4.66 hour R 300*12 19.990 +- 0.004 Our detection is consistent with Zhu et al. 2025 (GCN 39550); Busmann et al. 2025 (GCN 39551); Leonini et al. 2025 (GCN 39553); WU et al. 2025 (GCN 39555); Xin et al. 2025 (GCN 39558); Lipunov et al. 2025 (GCN 39559); Adami et al. 2025 (GCN 39560); Yang et al. 2025 (GCN 39561); Becerra et al. 2025 (GCN 39562); Izzo et al. 2025 (GCN 39564); Pankov et al. 2025(GCN 39565); Reguitti et al. 2025 (GCN 39568); Komesh et al. 2025 (GCN 39569); Shilling et al. 2025 (GCN 39570); Aryan et al. 2025 (GCN 39572); Eappachen wt al. 2025 (GCN 39575); Moskvitin et al. 2025(GCN 39576); Wu et al. 2025 (GCN 39578) and Pankov et al. 2025 (GCN 39586). The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the USNO-B1.0 catalog. This circular may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/39593. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37607] IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39592 SUBJECT: IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube DATE: 25/03/04 14:56:45 GMT FROM: Jessie Thwaites at IceCube/U Wisc-Madison <thwaites(a)wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search [1] for additional track-like muon neutrino events arriving from the direction of IceCube-250302A (https://gcn.nasa.gov/circulars/39549) in a time range of 1000 seconds centered on the alert event time (2025-03-02 03:12:32.900 UTC to 2025-03-02 03:29:12.900 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero track-like events are found within the 90% containment region of IceCube-250302A. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-250302A is 1.4e-01 GeV cm^-2 in a 1000 second time window. 90% of events IceCube would detect from a source at this declination with an E^-2.5 spectrum have energies in the approximate energy range between 3e+02 GeV and 1e+05 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2025-03-01 03:20:52.900 UTC to 2025-03-03 03:20:52.900 UTC). In this case, we report a p-value of 1.00, consistent with no significant excess of track events. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-250302A is 1.6e-01 GeV cm^-2 in a 2 day time window. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu. [1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021) View this GCN Circular online at https://gcn.nasa.gov/circulars/39592. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37606] EP250304a: refined analysis of the EP-WXT and EP-FXT observations
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39591 SUBJECT: EP250304a: refined analysis of the EP-WXT and EP-FXT observations DATE: 25/03/04 14:33:38 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.J. Zhang (THU), C. Y. Dai (NJU), W. Chen, W. X. Wang (NAO, CAS), Y. Liu (NAO, CAS) report on behalf of the Einstein Probe team: The X-ray transient EP250304a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Chen et al., GCN 39580), and followed up by several telescopes (Xu et al, GCN 39583, Page et al., GCN 39584, Saccardi et al., GCN 39585, Shilling et al., 39587), with an optical counterpart detected at a redshift of 0.200 (Saccardi et al., GCN 39585). Refined analysis of the WXT data shows that the event started at T0=2025-03-04T01:29:49 (UTC) and lasted for about 1200 s. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a Galactic hydrogen column density of 5 x 10^20 cm^-2 and a photon index of 2.2 (-/+0.1). The derived average unabsorbed 0.5-4 keV flux is 5.3(-/+0.4) x 10^(-10) erg/s/cm^2. The Follow-up X-ray Telescope (FXT) on board EP observed this source autonomously about 200 seconds after T0. On-ground analysis of the FXT data found an uncatalogued source at R.A. = 208.3953, DEC = -42.8050 (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic), which is consistent positionally with the WXT transient. The FXT observation suffered from significant pile up at the begining of the observation. The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a Galactic hydrogen column density of 5 x 10^20 cm^-2 and a photon index of 2.11 (-/+0.05). The derived average unabsorbed 0.5-10 keV flux is 1.75 (-/+0.06) x 10^(-10) erg/s/cm^2 during the time interval from 500 to 1200 seconds after the start of the observation. Further FXT observation started about 4000 seconds after the trigger and showed an average unabsorbed 0.5-10 keV flux of 6.5 (-2.3/+3.5) x 10^(-12) erg/s/cm^2 with an exposure time of about 300 seconds. The uncertainties are at the 90% confidence level for the above parameters. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/39591. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37605] Konus-Wind detection of GRB 250222A
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39590 SUBJECT: Konus-Wind detection of GRB 250222A DATE: 25/03/04 13:35:08 GMT FROM: Dmitry Frederiks at Ioffe Institute <fred(a)mail.ioffe.ru> D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long GRB 250222A (SVOM-GRM detection: Wang et al., GCN 39454; IPN triangulation: Svinkin et al., GCN 39588) triggered Konus-Wind (KW) at T0=51862.905 s UT (14:24:22.905). The burst light curve shows a bright, multi-peaked pulse, with the duration of ~2.5 s, followed by a weaker, decaying emission. The total duration of the burst is ~13 s. The emission is seen up to ~10 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250222_T51862/ As observed by Konus-Wind, the burst had a fluence of (1.79 ± 0.19)x10^-5 erg/cm^2 and a 64-ms peak energy flux, measured from T0 + 0.064 s, of (1.53 ± 0.20)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+16.640 s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.51 (-0.22,+0.26), the high energy photon index beta = -2.28 (-0.14,+0.11), the peak energy Ep = 173 (-21,+23) keV, chi2 = 98/97 dof. The spectrum near the peak count rate (measured from T0 to T0+0.256 s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = 0.40 (-0.61,+1.09), the high energy photon index beta = -1.97 (-0.13,+0.10), the peak energy Ep = 169 (-39,+46) keV, chi2 = 42/43 dof. All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/39590. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37604] EP250304a: REM NIR upper limits
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39589 SUBJECT: EP250304a: REM NIR upper limits DATE: 25/03/04 13:00:46 GMT FROM: Riccardo Brivio at INAF-OAB <riccardo.brivio(a)inaf.it> R. Brivio, M. Ferro (INAF-OAB), D. B. Malesani (DAWN/NBI and Radboud), P. D’Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of EP250304a (Chen et al., GCN 39580) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the J, H, and K bands, started on 2025 March 04 at 01:46:18 UT (i.e. 0.23 hr after the burst), and lasted for about 2 hours. From preliminary analysis, we do not find any NIR counterpart at the position of the reported optical afterglow (Liu et al., GCN 39583; Saccardi et al., GCN 39585) down to the following 3sigma limit: J > 17.5 (Vega; calibrated against the 2MASS catalogue), at a mid-time of 1.46 hours after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/39589. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37603] IPN triangulation of GRB 250222A
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39588 SUBJECT: IPN triangulation of GRB 250222A DATE: 25/03/04 12:59:51 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, Y. Zhang, C. Wang, S. Xiong, J. Wei, and B. Cordier on behalf of the SVOM-GRM team, E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, A. Goldstein, M. S. Briggs, C. Wilson-Hodge, and E. Burns on behalf of the Fermi GBM team, S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu on behalf of the Swift-BAT team, report: The long-duration GRB 250222A (SVOM-GRM detection: Wang et al., GCN 39454) was detected by SVOM (GRM), Konus-Wind, and INTEGRAL (SPI-ACS) at about 51859 s UT (14:24:19). Fermi (GBM) and Swift (BAT) were taking data, but shows no rate increase at the burst time. We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 359.336 (23h 57m 21s) +0.946 ( +0d 56' 47") Corners: 335.308 (22h 21m 14s) +25.783 (+25d 47' 00") 352.637 (23h 30m 33s) +12.776 (+12d 46' 35") 6.156 (00h 24m 37s) -19.368 (-19d 22' 04") 2.915 (00h 11m 40s) -9.794 ( -9d 47' 40") --------------------------------------------- The error box area is 38.5 sq. deg, and its maximum dimension is 54 deg (the minimum one is 3 deg). The Sun distance was 25 deg. This localization may be improved. The SVOM (GRM) localization (GCN 39454) is inconsistent with the IPN localization and also with burst non-detection by Fermi (GBM) and Swift (BAT). A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB250222_T51862/IPN/ The HEALPix triangulation map is the multi-order HEALPix in units of probability density. The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular. View this GCN Circular online at https://gcn.nasa.gov/circulars/39588. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37602] EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39587 SUBJECT: EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve DATE: 25/03/04 12:18:09 GMT FROM: Sam Shilling at Lancaster University <shilling.sam(a)gmail.com> S. P. R. Shilling (Lancaster U.) reports on behalf of the Swift UVOT team: Swift/UVOT observed the field of EP250304a (Chen et al., GCN 39580) for a total of 2 ks in the U-band starting at 02:48:13 UT, 1.25 hours after the detection by Einstein Probe WXT. An optical source consistent with the EP-FXT position (Chen et al., GCN 39580) is detected and appears to be rising in brightness. The preliminary detection magnitudes reported below are calculated using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373). The magnitude at the start of the observation is 19.29 +/- 0.09 (1.25 hours post trigger) and rises to 18.91 +/- 0.15 (~2.75 hours post trigger). We note that an X-ray source at this position was independently observed by the Swift/XRT (Page et al., GCN 39584). We also note that, in addition to the Swift/UVOT detection, an optical counterpart at this position has been detected by the TRT (Liu et al., GCN 39583) but has not been detected by MASTER (Lipunov et al., GCN 39581). Finally, that the source has a spectroscopic redshift, observed with the VLT/X-shooter, of z=0.2 (Saccardi et al., GCN 39585). View this GCN Circular online at https://gcn.nasa.gov/circulars/39587. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37601] EP250302a: Mondy Continued Optical Observations
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39586 SUBJECT: EP250302a: Mondy Continued Optical Observations DATE: 25/03/04 10:06:19 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunko (ISTP), A. Moskvitin (SAO RAS) report on behalf of IKI-GRB-FuN: We performed optical observations of the field of a fast X-Ray transient EP250302a (Dai et al., GCN 39556; Page et al., GCN 39557) in the R filter with the 1.5-meter telescope of Sayan Solar Observatory (Mondy). The observations began on 2025-03-03 (UT) 19:29:15, i.e. ~1.18 days since trigger. The optical source (Zhu et al., GCN 39550; Busmann et al., GCN 39551; Leonini et al., GCN 39553; Wu et al., GCN 39555; Xin et al., GCN 39558; Adami et al., GCN 39560; Yang et al., GCN 39561; Becerra et al., GCN 39562; Izzo et al., GCN 39564; Pankov et al., GCN 39565; Reguitti, GCN 39568; Komesh et al., GCN 39569; Shilling and Breeveld, GCN 39570; Aryan et al., GCN 39572; Moskvitin et. al, GCN 39576; Wu et. al, GCN 39578) is detected in the stacked image of 28*120 seconds. The preliminary photometry is as follows: Date UT start t-T0 Exptime Filter OT Err. UL (mid, days) (s) (3sigma) 2025-03-03 19:29:15 1.18136 28*120 R 22.12 0.14 23.4 The photometry is based on nearby stars from the USNO-B1.0 catalog (R2 magnitudes) and has not been corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39586. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37600] EP250304a: VLT/X-shooter redshift z = 0.200
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39585 SUBJECT: EP250304a: VLT/X-shooter redshift z = 0.200 DATE: 25/03/04 09:54:03 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University <d.malesani(a)astro.ru.nl> A. Saccardi (CEA/Irfu), Z. P. Zhu (NAOC), B. Schneider (LAM), D. Xu (NAOC), L. Izzo (INAF/OAC and DARK/NBI), A. J. Levan (Radboud and Warwick), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), N. R. Tanvir (U. Leicester), S. D. Vergani (CNRS - Paris Observatory/LUX) report on behalf of the Stargate collaboration: We observed the optical counterpart (Liu et al., GCN 39583; see also Page et al., GCN 39584) of the fast X-ray transient EP250304a (Chen et al., GCN 39580) using the ESO VLT UT3 (Melipal) equipped with the X-shooter spectrograph. In a 30-s r-band image taken with the acquisition camera (mid-time 2025 Mar 4.302 UT, or 5.7 hr after trigger), we detect the optical counterpart with a magnitude r = 20.97 +/- 0.03 (AB), calibrated against nearby stars from the SkyMapper catalog (Wolf et al. 2018, doi:10.4225/41/593620ad5b574). Our spectra cover the wavelength range 3000-21000 AA, and consist of 4 exposures of 600 s each. The observation mid time was 2025 Mar 4.3248 UT (6.254 hr after the GRB). In a preliminary reduction of the spectra, we detect continuum over the entire covered wavelength range. We detect emission lines in the VIS arm, which we identify as Halpha and [O III] 5007 AA at the common redshift of z = 0.200. We also identify the Mg II doublet (2796,2804) in absorption at a consistent redshift. The spectrum continues to rise towards the blue end down to the cut-off of the UVB arm (~3100 AA). This spectral shape is qualitatively similar to what was seen in EP250108a / AT2025kg (e.g., Zhu et al., GCN 38908). We encourage further follow-up of this potentially interesting target. We acknowledge expert support from the ESO staff in Paranal, in particular Diego Parraguez. View this GCN Circular online at https://gcn.nasa.gov/circulars/39585. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37599] EP250304a: Swift-XRT detection of a fading X-ray source
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39584 SUBJECT: EP250304a: Swift-XRT detection of a fading X-ray source DATE: 25/03/04 09:18:19 GMT FROM: K.L. Page at U Leicester <klp5(a)leicester.ac.uk> K.L. Page, P.A. Evans (U.Leicester) and J. DeLaunay (PSU) report on behalf of the Swift XRT Team: On 2025 March 04 at 02:59 UT, Swift started observing EP250304a, 5.2 ks after the Einstein Probe trigger (GCN Circ. 39580). A fading X-ray source was identified, at a position of RA, Dec = 208.39408, -42.8046, which is equivalent to RA (J2000): 13h 53m 34.58s Dec (J2000): -42d 48′ 16.7″ with an uncertainty of 4.1 arcsec (radius, 90% confidence). This is consistent with the FXT position (GCN Circ. 39580), as well as the TRT optical counterpart given in GCN Circ. 39583. The mean observed X-ray flux in the first snapshot was (3.5 +/- 0.4) x 10^-12 erg cm^-2 s^-1 (0.3 - 10 keV). By the time of the second snapshot, at 10.3 ks after the trigger, the source was no longer detected, having faded to a 3-sigma upper limit of 2.1 x 10^-12 erg cm^-2 s^-1. View this GCN Circular online at https://gcn.nasa.gov/circulars/39584. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37598] EP250304a: TRT optical counterpart detection
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39583 SUBJECT: EP250304a: TRT optical counterpart detection DATE: 25/03/04 08:17:49 GMT FROM: Dong Xu at NAOC/CAS <dxu(a)nao.cas.cn> X. Liu, J. An, N.C. Sun (NAOC), S. Tinyanont, R. Anutarawiramkul, P. Butpan (NARIT), S.Q. Jiang, S.Y. Fu, Z.P. Zhu, D. Xu, Z. Fan, W.X. Li, Y.N. Wang (NAOC) report on behalf of a large collaboration: We observed the field of EP250304a (Chen et al, GCN 39580), using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at Cerro Tololo Inter-American Observatory, Chile. Observations started at 02:18:49 UTC on 2025-03-04, i.e., ~1.12 hr after the EP/WXT trigger. A series of B-/V-/R-/I- band frames were obtained. An uncatalogued and varying optical source is detected within the EP/FXT error circle (Chen et al, GCN 39580) at coordinates R.A. (J2000) = 13:53:34.68 Dec. (J2000) = -42:48:16.71 with an uncertainty of ~ 1 arcsec. Preliminary photometry shows that the source has B = 20.5 +/- 0.1 mag at 1.39 hr post-trigger, and R = 20.8 +/- 0.1 mag at 2.4 hr post-trigger, calibrated with SkyMapper DR2 catalog converted using Lupton (2005) equations and not corrected for Galactic extinction. We thus think this source is the optical counterpart of EP250304a. View this GCN Circular online at https://gcn.nasa.gov/circulars/39583. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37597] LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39582 SUBJECT: LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate DATE: 25/03/04 06:58:51 GMT FROM: Pan Guo at KAGRA <panguocas(a)gmail.com> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S250304cb during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2025-03-04 06:22:45.568 UTC (GPS time: 1425104583.568). The candidate was found by the GstLAL [1] and MBTA [2] analysis pipelines. S250304cb is an event of interest because its false alarm rate, as estimated by the online analysis, is 5.6e-08 Hz, or about one in 6 months. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S250304cb The classification of the GW signal, in order of descending probability, is BBH (96%), Terrestrial (4%), NSBH (<1%), or BNS (<1%). Assuming the candidate is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is <1%. [3] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [3] Both HasNS and HasRemnant consider the support of several neutron star equations of state. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is 2%. Two sky maps are available at this time and can be retrieved from the GraceDB event page: * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [4], distributed via GCN notice about 28 seconds after the candidate event time. * bayestar.multiorder.fits,2, an initial localization generated by BAYESTAR [4], distributed via GCN notice about 5 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,2. For the bayestar.multiorder.fits,2 sky map, the 90% credible region is 1569 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1768 +/- 541 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. (2023) arXiv:2305.05625 [2] Aubin et al. CQG 38, 095004 (2021) doi:10.1088/1361-6382/abe913 [3] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [4] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/39582. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37596] EP250304a: Global MASTER-Net observations report
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39581 SUBJECT: EP250304a: Global MASTER-Net observations report DATE: 25/03/04 03:00:51 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP250304a ( EP Team et al., GCN 39580) errorbox 148 sec after notice time and 4018 sec after trigger time at 2025-03-04 02:39:28 UT, with upper limit up to 19.4 mag. The observations began at zenith distance = 59 deg. The sun altitude is -41.7 deg. The galactic latitude b = 18 deg., longitude l = 315 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2799155 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 4049 | 2025-03-04 02:39:28 | MASTER-OAFA | (13h 52m 43.16s , -42d 51m 39.4s) | C | 60 | 19.4 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/39581. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37595] EP250304a: Einstein Probe detection of an X-ray transient
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39580 SUBJECT: EP250304a: Einstein Probe detection of an X-ray transient DATE: 25/03/04 02:35:25 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> W. Chen, W. X. Wang (NAO, CAS), Y. J. Zhang (THU), C. Y. Dai (NJU), Y.Liu (NAO, CAS) report on behalf of the Einstein Probe team: We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP250304a. The transient triggered EP-WXT (ID: 01709132237 ) at 2025-03-04 01:32:30 (UTC). The WXT position of the source is R.A. = 208.394 deg, DEC = -42.818 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error cirlce, an uncatalogued X-ray source was detected at R.A. = 208.3965 deg, DEC = -42.8067 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). Further information will be updated when the telemetry data is received. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/39580. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37594] The EP-WXT trigger 01709132212 is not a real source
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39579 SUBJECT: The EP-WXT trigger 01709132212 is not a real source DATE: 25/03/04 02:18:44 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> J. W. Hu, M. H. Zhang (NAOC, CAS), C. Y. Dai (NJU), Y. Q. Zhao (USTC, PRIC), W. D. Zhang (NAOC, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709132212 at 16:00:13 UTC on 3th March 2025, is not a real source. View this GCN Circular online at https://gcn.nasa.gov/circulars/39579. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37593] EP250302a: SVOM/VT optical observation
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39578 SUBJECT: EP250302a: SVOM/VT optical observation DATE: 25/03/04 02:15:58 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> C. Wu, D. H. Zhao, Y. N. Ma, L. P. Xin, Y. L. Qiu, H. L. Li, Z. H. Yao, Y. Xu, P. P. Zhang, W. J. Xie, J. Wang, X. H. Han, Y. J. Xiao, H. B. Cai, J. Y. Wei(NAOC), J. T. Palmerio(CEA/Irfu) report on behalf of the SVOM team: The SVOM/VT conducted a ToO follow-up observations of the EP250302a (Zhu et al., GCN 39550) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously. The optical counterpart of EP250302a(Trigger ID: 01709132186, Zhu et al., GCN 39550; Busmann et al., GCN 39551; Leonini et al., GCN 39553; Wu et al., GCN 39555; Xin et al., GCN 39558; Adami et al., GCN 39560; Yang et al., GCN 39561; Becerra et al., GCN 39562; Izzo et al., GCN 39564; Pankov et al., GCN 39565; Reguitti, GCN 39568; Komesh et al., GCN 39569; Shilling and Breeveld, GCN 39570; Aryan et al., GCN 39572, Moskvitin et al., GCN 39576) was clearly detected in VT_R and VT_B images. The brightness in AB manigutude was estimated to be 21.41 +/-0.09 mag in VT_R (stacked image: 50x60s), and 22.68 +/-0.14 mag in VT_B (stacked iamge: 50x60s), measured at the mid time of 1.03 days post the burst. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC),CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/39578. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37592] LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
by GCN Circulars 03 Mar '25

03 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39577 SUBJECT: LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits DATE: 25/03/03 19:55:29 GMT FROM: noelklin(a)umbc.edu Noel Klingler (NASA-GSFC / UMBC / CRESST II), Sam Shilling (Lancaster U.), P.A. Evans (U. Leicester), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), S.B. Cenko (NASA/GSFC), R.A.J. Eyles-Ferris (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), A.A. Breeveld (UCL-MSSL), S. Campana (INAF-OAB), J.J. Delaunay (PSU), M. De Pasquale (University of Messina), S. Dichiara (PSU), P. D'Avanzo (INAF-OAB), A. D'Aì (INAF-IASFPA) , V. D'Elia (ASI-SSDC & INAF-OAR), C. Gronwall (PSU), D. Hartmann (Clemson University), N. Klingler (NASA-GSFC / UMBC / CRESST II), N.P.M. Kuin (UCL-MSSL), S. Laha (NASA/GSFC), S.R. Oates (U. Birmingham), J.P. Osborne (U. Leicester), P. O'Brien (U. Leicester), M.J. Page (UCL-MSSL), S. Ronchini (PSU), T. Sbarrato (INAF-OAB), B. Sbarufatti (INAF-OAB), M.H. Siegel (PSU), G. Tagliaferri (INAF-OAB), E. Troja (U Tor Vergata, INAF) report on behalf of the Swift team: Swift/UVOT has carried out 1 observation of the combined LVK/Swift-BAT-GUANO error region for the GW trigger S250223dk (GCN 39443), centered on the most-probable location (RA,Dec = 85.4260, -47.5420 [J2000]; GCN 39485). UVOT collected 4.9 ks of data from 106 ks to 140 ks after the LVK trigger, using the White filter. For the X-ray sources reported by Evans et al. (GCN 39485): X1, X5, and X6 are outside of the UVOT field of view. X2 is not detected, with a 3 sigma detection limit > 21.54 mag (AB). X3 is not detected, with a 3 sigma detection limit > 23.01 mag (AB). X7 is not detected, with a 3 sigma detection limit > 23.09 (AB). X4 is detected (20.14 +/- 0.03 mag, AB) but its position is coincident with a known source (classified as an AGN in the AllWISE catalog), WISEA J054219.27-473400.6. No uncatalogued/transient sources are detected, with an average 3 sigma limit > 23.0 mag (AB) over the UVOT field of view. View this GCN Circular online at https://gcn.nasa.gov/circulars/39577. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37591] EP250302a: SAO RAS optical observations
by GCN Circulars 03 Mar '25

03 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39576 SUBJECT: EP250302a: SAO RAS optical observations DATE: 25/03/03 16:32:59 GMT FROM: Moskvitin Alexander at SAO RAS <mosk(a)sao.ru> A. S. Moskvitin, O. A. Maslennikova (SAO RAS), A. Pozanenko (IKI) and N. Pankov (HSE, IKI) report on behalf of larger collaboration. We observed the field of the X-ray transient EP250302a (Dai et al., GCN 39556; Page et al., GCN 39557) with SAO RAS 1-m telescope Zeiss-1000 equipped with CCD-photometer under mediocre weather conditions. We obtained two sets of 300-sec images in Rc band. 1st set: 2025.03.02, 20:33:49 -- 2025.03.02, 22:09:49 UT (t_mid - T0 = 0.24010 days = 5.7625 hours); 2nd set: 2025.03.02, 23:55:53 -- 2025.03.03, 01:00:10 UT, (t_mid - T0 = 0.36942 days = 8.8660 hours). The OT (Zhu et al., GCN 39550; Busmann et al., GCN 39551; Leonini et al., GCN 39553; Wu et al., GCN 39555; Xin et al., GCN 39558; Adami et al., GCN 39560; Yang et al., GCN 39561; Becerra et al., GCN 39562; Izzo et al., GCN 39564; Pankov et al., GCN 39565; Reguitti, GCN 39568; Komesh et al., GCN 39569; Shilling and Breeveld, GCN 39570; Aryan et al., GCN 39572) is clearly detected in our stacked frames with the following brightness. Date UT start t-T0 (mid),d Exp.,s Filter OT Err. UL(3sigm) 2025.03.02 20:33:49 0.24010 8x300 R 20.18 0.09 22.5 2025.03.02 23:55:53 0.36942 7x300 R 20.51 0.10 22.5 Above photometry is preliminary and calibrated against R2 magnitudes of nearby USNO-B1 stars and not corrected for the Galaxy extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39576. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37590] EP250302a : GIT optical follow-up
by GCN Circulars 03 Mar '25

03 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39575 SUBJECT: EP250302a : GIT optical follow-up DATE: 25/03/03 16:09:43 GMT FROM: V. Swain at IIT Bombay <vishwajeet.s(a)iitb.ac.in> D. Eappachen (IIA), V. Swain (IITB), A.P. Saikia (IITB), V. Bhalerao (IITB), G.C. Anupama (IIA), S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team: We observed the field of EP250302a (Dai et al., GCN 39556) with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2025-03-02 20:51:47 UT, i.e., 5.26 hours after the EP trigger. We obtained two exposures of 360 seconds each in both r' and g' filters. We clearly detected the optical counterpart in our stacked images at the position given by HMT-0.5m telescope (Zhu et al., GCN 39550). The photometry results are as follow: | JD (mid) | t-t0 (hours) | Filter | Exposure (s) | Mag (AB) | | ----------------- | ----------- |------- | ------------------ | -------------- | | 2460737.373565 | 5.36 | r' | 2x360s | 20.40+/- 0.11 | | 2460737.390706 | 5.78 | g' | 2x360s | 20.66+/- 0.10 | Our results are consistent with Zhu et al., (GCN 39550); Busmann et al., (GCN 39551); Leonini et al., (GCN 39553); WU et al., (GCN 39555); Xin et al., (GCN 39558); Adami et al., (GCN 39560); Pankov et al., (GCN 39565); Reguitti et al., (GCN 39568); Komesh et al., (GCN 39569); Shilling et al., (GCN 39570). The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. The GROWTH India Telescope (GIT; Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/. View this GCN Circular online at https://gcn.nasa.gov/circulars/39575. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37589] EP250302a: VLT/X-shooter redshift confirmation
by GCN Circulars 03 Mar '25

03 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39574 SUBJECT: EP250302a: VLT/X-shooter redshift confirmation DATE: 25/03/03 15:53:51 GMT FROM: Yu-Han Yang at University of Rome Tor Vergata <yyang(a)roma2.infn.it> Yu-Han Yang (U Rome), Eleonora Troja (U Rome), and Rosa Becerra (U Rome) report on behalf of the ERC BHianca team: A further analysis was performed on the VLT/X-shooter spectrum reported by Yang et al. (GCN 39561). Whereas no significant features are visible in the VIS and NIR arms, we note the presence of absorption features at the edge of the UVB spectrum, consistent with Fe II (2600, 2587, 2383, 2374, 2344) at redshift z=1.131 as reported by Izzo et al. (GCN 39564). We therefore confirm this as the likely redshift of the EP transient. View this GCN Circular online at https://gcn.nasa.gov/circulars/39574. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37588] EP250225a: the candidate optical counterpart is an AGN
by GCN Circulars 03 Mar '25

03 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39573 SUBJECT: EP250225a: the candidate optical counterpart is an AGN DATE: 25/03/03 15:25:46 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University <d.malesani(a)astro.ru.nl> D. B. Malesani (DAWN/NBI and Radboud Univ.), D. Mata-Sanchez (IAC and ULL), A. Martin-Carrillo (UCD), A. J. Levan (Radboud Univ.), P. G. Jonker (Radboud Univ.), report on behalf of a larger collaboration: We observed again the variable object (Malesani et al., GCN 39516) located inside the X-ray localization of the fast X-ray transient EP250225a (Jiang et al., GCN 39475; Jiang et al., GCN 39529) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. The observation mid time was 2025 Feb 27.93 UT (2.42 days after the trigger) and a total of 5x300 s was secured in the r band. The object is detected with a flux consistent with our previous observation (Malesani et al., GCN 39516) to within ~0.1 mag, and still brighter than the archival value from the Legacy Survey. Image subtraction confirms no significant variability between the two NOT epochs. A spectrum of this source was secured with the Gran Telescopio Canarias (GTC). Observations started on 2025 Feb 28.98 UT (3.47 days after the trigger), and consisted of a single 1800 s exposure with grism R1000R, yielding usable data in the wavelength range 5000-9000 AA. Detection of two broad features (FWHM ~ 3500 km s^-1), identified as Hbeta and Hgamma, as well as of narrow [O III] 5008, allows us to measure a redshift z = 0.587. The large velocities and the point-like PSF indicate that this is an active galactic nucleus. Given the slow variability and the AGN nature of this source, its relationship to EP250225b is unclear, and the two may well be unrelated. We acknowledge significant support from the observing staff at the NOT, in particular, Alejandra Diaz Teodori (NOT and Turku Univ.), Roar Rasmussen (NOT and Aarhus Univ.), and Saskia Schlagenhauf (QUB), and at the GTC, in particular Antonio Cabrera-Lavers (GTC). View this GCN Circular online at https://gcn.nasa.gov/circulars/39573. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37587] EP250302a: Kinder optical follow-up observations
by GCN Circulars 03 Mar '25

03 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39572 SUBJECT: EP250302a: Kinder optical follow-up observations DATE: 25/03/03 14:21:48 GMT FROM: Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941(a)gmail.com> A. Aryan, T.-W. Chen, C.-S. Lin (all NCU), A. K. H. Kong (NTHU), J. Gillanders (Oxford), S. J. Smartt (Oxford/QUB), Y. J. Yang, A. Sankar. K, Y.-C. Pan, C.-C. Ngeow, W.-J. Hou, M.-H. Lee, H.-C. Lin, C.-H. Lai, H.-Y. Hsiao, J.-K. Guo (all NCU), S. Yang, L. L. Fan, Z. N. Wang, G. H. Sun (all HNAS), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz and M. Huber (both IfA, Hawaii) report: We observed the field of the fast X-ray transient EP250302a (Zhu et al., GCN 39550; Dai et al., GCN 39556) using the 40cm SLT at Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen & Yang et al. 2024, arXiv:2406.09270). The first SLT epoch of observations in the r band started at 18:30 UT on the 2nd of March 2025 (MJD = 60736.771), ~2.91 hrs after the EP trigger. We took a total of 12 frames in r-band spanning a period of about 2.91hr to 5.22hr since the EP-WXT trigger. The optical counterpart candidate proposed by Zhu et al., (GCN 39550 ) and confirmed by several other observations (Busmann et al., GCN 39551; Leonini et al., GCN 39553; Wu et al., GCN 39555; Xin et al., GCN 39558; Adami et al., GCN 39560; Yang et al., GCN 39561; Becerra et al., GCN 39562; and Izzo et al., GCN 39564), was clearly detected in almost each of the individual frame (besides the last frame). We utilized the Python-based package AutoPhOT (Brennan & Fraser, 2022, A&A, 667, A62) to perform PSF photometry on individual frames. The details of the observation and measured photometry from the first frame (in the AB system) were as follows: Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | Seeing | Airmass SLT | r | 60736.771 | 2.91 | 300 * 1 | 19.60 +/- 0.05 | 1".25 | 1.14 The presented magnitude was calibrated using the field stars from the Pan-STARRS1 catalog and was not corrected for the expected Galactic foreground extinction corresponding to a reddening of A_r = 0.06 mag, respectively, in the direction of the transient (Schlafly & Finkbeiner 2011). View this GCN Circular online at https://gcn.nasa.gov/circulars/39572. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37586] LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
by GCN Circulars 03 Mar '25

03 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39571 SUBJECT: LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search DATE: 25/03/03 13:51:37 GMT FROM: Zsuzsa Marka at IceCube/Columbia University <zsuzsa(a)astro.columbia.edu> IceCube Collaboration (http://icecube.wisc.edu/) reports: We have performed a search for track-like muon neutrino candidate events detected by IceCube consistent with the sky localization of the low-significance gravitational-wave candidate event S250302av in a time range of 1000 seconds centered on the alert event time (2025-03-02 13:57:15 UTC to 2025-03-02 14:13:55 UTC) [1,2]. During this time period, IceCube was collecting good quality data. A single hypothesis test was conducted using a Bayesian approach to quantify the joint GW + neutrino event significance, which assumes a binary merger scenario and accounts for known astrophysical priors, such as GW source distance, in the statistical significance estimation [3]. Two track-like events were found in spatial and temporal coincidence with the gravitational-wave candidate S250302av calculated from the map circulated in the S250302av-2-Preliminary notice. This represents an overall p-value of 0.0084 for the Bayesian search. The p-value measures the consistency of the observed track-like events with the known atmospheric backgrounds for this single map (not accounting for statistical trials from multiple GW events). Further details are available at https://gcn.nasa.gov/missions/icecube and at https://roc.icecube.wisc.edu/public/LvkNuTrackSearch. Properties of the coincident event are shown below: dt(s) RA(deg) Dec(deg) Angular uncertainty(deg) p-value(Bayesian) ------------------------------------------------------------------------------------- 76.86 114.87 3.25 1.16 0.0298 211.98 191.11 58.45 5.39 0.0137 where: dt = Time of track event minus time of GW trigger (sec) Angular uncertainty = Angular uncertainty of track event: the radius of a circle representing 90% CL containment by area. p-value = the individual p-value for the specific track event from this search. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu [1] M. G. Aartsen et al 2020 ApJL 898 L10 [2] Abbasi et al. Astrophys.J. 944 (2023) 1, 80 [3] I. Bartos et al. 2019 Phys. Rev. D 100, 083017 View this GCN Circular online at https://gcn.nasa.gov/circulars/39571. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37585] EP250302a: Swift/UVOT detection
by GCN Circulars 03 Mar '25

03 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39570 SUBJECT: EP250302a: Swift/UVOT detection DATE: 25/03/03 12:58:05 GMT FROM: Sam Shilling at Lancaster University <shilling.sam(a)gmail.com> S. P. R. Shilling (Lancaster U.) and A. A. Breeveld (UCL-MSSL) reports on behalf of the Swift UVOT team: Swift/UVOT observed the field of EP250302a (Dai et al., GCN 39556) for 1029 seconds in the U-band starting at 16:36:56 UT, 1 hour after the detection by Einstein Probe WXT. A source consistent with the EP-FXT position (Dai et al., GCN 39556) is detected and appears to be fading. The preliminary detection magnitudes reported below are calculated using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373). The magnitude at the start of the observation is 17.64 +/- 0.05 (1 hour post trigger) and decays to 18.88 +/- 0.12 (~2 hours post trigger). We note that an X-ray source at the EP-FXT position was independently observed by the Swift/XRT (Page et al., GCN 39557). We also note that, in addition to the Swift/UVOT, various other facilities have observed an optical counterpart at this position (Zhu et al., GCN 39550; Busmann et al., GCN 39551; Leonini et al., GCN 39553; Wu et al., GCN 39555; Xin et al., GCN 39558; Lipunov et al., GCN 39559; Adami et al., GCN 39560; Becerra et al., GCN 39562; Pankov et al., GCN 39565; Reguitti et al., GCN 39568; Komesh et al., GCN 39569). View this GCN Circular online at https://gcn.nasa.gov/circulars/39570. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37584] EP250302a: NUTTelA-TAO Early Measurments
by GCN Circulars 03 Mar '25

03 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39569 SUBJECT: EP250302a: NUTTelA-TAO Early Measurments DATE: 25/03/03 12:18:23 GMT FROM: Toktarkhan Komesh at Nazarbayev University <toktarkhan.komesh(a)nu.edu.kz> T. Komesh (NU), Z. Abdullayev (NU), Z. Maksut (NU), D. Berdikhan (NU), B. Grossan (UCB, NU), M. Krugov (FAI) and E. Abdikamalov (NU) report on behalf of the Energetic Cosmos Laboratory: The Nazarbayev University Transient Telescope at Assy-Turgen Astrophysical Observatory (NUTTelA-TAO) pointed at EP250302a on receipt of an automated GCN / EP position alert, observing in Sloan g' and r' bands, with the Burst Simultaneous Three-Channel Imager (BSTI; Grossan, Kumar & Smoot 2019, JHEA, 32, 14). We started observations at 15:42:43 UT on 2025-03-02, 399 seconds after the Einstein Probe trigger (Dai et al., GCN 39556). Observations were made in partially cloudy conditions. A new and changing source consistent with the XRT position (Page et al., GCN 38761) was detected. We report the following photometric values for the optical transient: tc-t0(s) g'(mag) err r'(mag) err exposure_time (s) -------------------------------------------------------------- 424 - 18.36 0.08 50 628 - 18.35 0.08 300 928 - 18.80 0.13 300 1273 - 18.76 0.07 240 1513 - 18.55 0.06 240 1753 - 18.12 0.04 240 1993 - 17.71 0.03 240 2233 - 17.58 0.02 240 2686 - 17.48 0.03 240 2926 - 17.54 0.02 240 3166 - 17.58 0.02 240 3406 - 17.65 0.02 240 3646 - 17.68 0.03 240 3886 - 17.73 0.03 240 4126 - 17.85 0.03 240 4366 - 17.88 0.04 240 4606 - 17.95 0.03 240 4846 - 18.08 0.04 240 5086 - 18.11 0.03 240 5326 - 18.18 0.04 240 5566 - 18.32 0.04 240 5806 - 18.47 0.04 240 6046 - 18.56 0.04 240 6348 18.93 0.05 18.56 0.04 240 6588 18.99 0.06 18.76 0.04 240 6828 19.01 0.05 18.86 0.05 240 7068 19.05 0.05 18.86 0.05 240 7308 19.06 0.05 18.90 0.05 240 7548 19.12 0.05 18.94 0.05 240 7788 19.28 0.07 19.01 0.06 240 8028 19.43 0.08 19.01 0.06 240 8269 19.53 0.08 19.19 0.07 240 8509 19.34 0.06 19.19 0.06 240 tc-t0 = trigger time minus image center time. Calibration was done with 4 bright Pan-STARRS catalog stars on our images. Our results are in agreement with those reported in previously published circulars (Zhu et. al, GCN 39550; Wu et. al, GCN 39555; Xin et. al, GCN 39558; Pankov et al., GCN 39565). We caution the reader that these are preliminary results, without color or other corrections, and will likely change in small measure. Please also note that times are approximate. ---------------------------------- NU = Nazarbayev University, Astana, Kazakhstan UCB = University of California, Berkeley, USA FAI = Fesenkov Astrophysical Institute, Kazakhstan This research has been funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan (Grant No. AP26103591). The NUTTelA-TAO Team acknowledges the support of the staff of the Assy-Turgen Astrophysical Observatory, Almaty, Kazakhstan, and the Fesenkov Astrophysical Institute, Almaty, Kazkhstan. View this GCN Circular online at https://gcn.nasa.gov/circulars/39569. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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