April 2025 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 38076] GRB 250330A Swift-BAT refined analysis
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40055 SUBJECT: GRB 250330A Swift-BAT refined analysis DATE: 25/04/04 16:15:22 GMT FROM: Mike Moss at NASA GSFC <mikejmoss3(a)gmail.com> H. A. Krimm (NSF), S. D. Barthelmy (GSFC), S. B. Cenko (GSFC), R. Gupta (GSFC), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-137 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250330A (trigger #1299776) (Cenko, et al., GCN Circ. 39938). The BAT ground-calculated position is RA, Dec = 252.685, -86.875 deg which is RA(J2000) = 16h 50m 44.5s Dec(J2000) = -86d 52' 29.6" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 98%. The mask-weighted light curve shows a single well defined fast-rise exponential- decay pulse shape. the T90 (15-350 keV) is 11.27 +- 2.53 sec (estimated error including systematics). The time-averaged spectrum from T-0.16 to T+14.33 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.72 +- 0.10. The fluence in the 15-150 keV band is 9.2 +- 0.6 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+0.26 sec in the 15-150 keV band is 4.0 +- 0.2 ph/cm2/sec. 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/1299776 View this GCN Circular online at https://gcn.nasa.gov/circulars/40055. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38075] EP250321A: J band upper limit by SYSU 80cm telescope
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40054 SUBJECT: EP250321A: J band upper limit by SYSU 80cm telescope DATE: 25/04/04 15:32:10 GMT FROM: Yan Yu <yuyan35(a)mail2.sysu.edu.cn> Yan Yu, Jin-Ji Li, Jia-Qi Lin, Wei-Sen Huang, Zhong-Nan Dong, Pu Lin, Hao-Nan Yang, Hao-Ran Zhang, Chun Chen, P H Thomas Tam, Rong-Feng Shen, Bin Ma(Sun Yat-sen University) report on behalf of the SYSU 80cm telescope team: We observed the field of EP250321A (EP GCN 39800; MASTER-OAFA GCN 39803; Zhu et al., GCNs 39809; Swift-XRT GCN 39811) using the Sun Yat-sen University 80cm infrared telescope with 90 x 20 s exposures in J band. The calculated position is RA. = 179.2625 deg, DEC = 17.3628 deg J2000, from EP observation. Our observations began at 2025-3-22 13:25:00 UTC, 31.25 hours after the EP trigger. We do not detect any counterpart at the position of the optical afterglow (Fu et al., GCN 39804; Perez-Garcia et al., GCNs 39805; Brivio et al., GCNs 39807; Becerra et al., GCNs 39810; Pérez-Fournon et al., GCN 39812; Lee et al., GCN 39815; Ghosh et al., GCN 39816; Han et al., GCN 39817; Jin et al., GCN 39822; Zhu et al., GCN 39827; Gill et al., GCN 39831; Zheng et. al, GCN 39832; Pankov et al., GCN 39836; Bochenek et. al, GCN 7939837; Zhu et. al, GCN 39854), down to a 5-sigma depth of J~ 17.6 Vega magnitudes. View this GCN Circular online at https://gcn.nasa.gov/circulars/40054. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38074] EP250404a: BOOTES-4/JGT optical afterglow detection
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40053 SUBJECT: EP250404a: BOOTES-4/JGT optical afterglow detection DATE: 25/04/04 15:31:24 GMT FROM: I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg(a)iaa.es> I. Perez-Garcia, S.-Y. Wu, E. Fernandez-Garcia, M. D. Caballero-Garcia, G. Garcia-Segura, S. Guziy, R. Sanchez-Ramirez and A. J. Castro-Tirado (IAA-CSIC, Granada), C. Perez del Pulgar (Univ. de Malaga), M. Gritsevich (Univ. of Helsinki), Y.-D. Hu (GXU), and D. R. Xiong, J. M. Bai, Y. F. Fan, C. J. Wang, Y. X. Xin, X. H. Zhao, J. R. Mao, B. K. Lun, K. Ye (Yunnan Observatories/CAS, Kunming) on behalf of a larger collaboration, report: Following the detection of EP250404a by Einstein Probe (Hu et al. GCNC [40051](https://gcn.nasa.gov/circulars/40051)), the 0.6m BOOTES-4/MET robotic telescope at Lijiang Astronomical Observatory (China) automatically responded to this X-ray transient starting on 2025-04-04 14:39:39UT (20 min after detection and 15 after notification). Series of images in clear filter were gathered and we detect and uncatalogud source constistent with position reported by Xu et al. (GCN [40052](https://gcn.nasa.gov/circulars/40052)). Using GaiaDR3 Gmag as reference we measure an initial magnitude of 14.8 +/- 0.03. Within 20 minutes, the source faded to magnitude 16.1. Further analysis of the additional images is ongoing. We thank the staff at Lijiang observatory for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/40053. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38073] EP250404a: Nanshan/HMT optical counterpart detection
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40052 SUBJECT: EP250404a: Nanshan/HMT optical counterpart detection DATE: 25/04/04 15:12:14 GMT FROM: Dong Xu at NAOC/CAS <dxu(a)nao.cas.cn> S.Q. Jiang, Z.P. Zhu, J. An, X. Liu, D. Xu (NAOC), S.Y. Fu (HUST), X. Gao (Urumqi No.1 Senior High School), J.Z. Liu (XAO) report: We observed the field of EP250404a detected by EP (Hu et al., GCN 40051), which is temporally and spatially consistent with GRB 250404A detected by Fermi/GBM (GBM team, GCN 40050), using the HMT-0.5m telescope located at Nanshan, Xinjiang, China. Observations started at 14:24:59 UT on 2025-04-04, i.e., 300 s after the EP/WXT trigger time, and a series of unfiltered frames with different exposures were obtained. An uncatalogued and varying optical source is detected within the EP/FXT error circle at coordinates: R.A.(J2000) = 08:20:14.54 Dec.(J2000) = +35:31:41.57 with an uncertainty of ~0.5 arcsec. The source has R ~ 16.1 mag in the first image, calibrated with the nearby Pan-STARRS field and not corrected for Galactic extinction. Observations are still ongoing. View this GCN Circular online at https://gcn.nasa.gov/circulars/40052. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38072] EP250404a: Einstein Probe detection of an X-ray transient
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40051 SUBJECT: EP250404a: Einstein Probe detection of an X-ray transient DATE: 25/04/04 15:03:49 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> J. W. Hu (NAO, CAS), Q. C. Liu (THU), B. B. Zhang (BNU), Y. L. Hua (PMO, CAS), Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) 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 EP250404a. The transient triggered EP-WXT (ID: 01709133918) at 2025-04-04T14:19:59 (UTC). The WXT position of the source is R.A. = 125.064 deg, DEC = 35.511 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 circle, an uncatalogued X-ray source was detected at R.A. = 125.0575 deg, DEC = 35.5305 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). It is noted that EP250404a is temporally and spatially coincident with GRB 250404A (Fermi team, GCN Circ. 40050). 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/40051. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38071] GRB 250404A: Fermi GBM Final Real-time Localization
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40050 SUBJECT: GRB 250404A: Fermi GBM Final Real-time Localization DATE: 25/04/04 14:30:25 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 14:19:46 UT on 4 Apr 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250404A (trigger 765469191.347644 / 250404597). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 123.4, Dec = 34.1 (J2000 degrees, equivalent to J2000 08h 13m, 34d 06'), with a statistical uncertainty of 1.2 degrees. The angle from the Fermi LAT boresight is 42.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250404597/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250404597/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250404597/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40050. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38070] GRB 250402A: Mondy optical observations
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40049 SUBJECT: GRB 250402A: Mondy optical observations DATE: 25/04/04 14:24:06 GMT FROM: Alexei Pozanenko at IKI, Moscow <grb.alex(a)gmail.com> E. Mazaeva (IKI), E. Klunko (ISTP), N. Pankov (HSE), A. Pozanenko (IKI) report on behalf of IKI GRB-FuN: We observed GRB 250402A (Chen et al. GCN 40014) with the AZT-33IK telescope starting on 2025-04-03 (UT) 18:11:28. We found the optical counterpart (Xin et al., GCN 40015; Pérez-Fournon et al., GCN 40020; Schneider et al., GCN 40022; Magnani et al., GCN 40023) at the position reported by Xin et al., GCN 40015. Preliminary photometry of the optical counterpart is the following Date UT start t-T0 Filter Exp. OT Err. UL(3sigma) (mid, days) (s) 2025-04-03 18:11:28 0.81567 R 29*120 21.9 0.2 22.3 The photometry is based on the nearby PS1 stars (R mag by Lupton transformations). View this GCN Circular online at https://gcn.nasa.gov/circulars/40049. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38069] GRB 250403A: Swift/UVOT Upper Limits
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40048 SUBJECT: GRB 250403A: Swift/UVOT Upper Limits DATE: 25/04/04 13:28:59 GMT FROM: Sam Shilling at Lancaster University <shilling.sam(a)gmail.com> S. P. R. Shilling (Lancaster U.) and S. R. Oates (Lancaster U.) report on behalf of the Swift UVOT team: Swift/UVOT observed the field of GRB 250403A detected by Fermi GBM (Fermi team, GCN Circ. 40025) and SVOM/ECLAIRs (Julakanti et al., GCN Circ. 40026) starting at 00:02:02 UT on 25/04/04, ~8.75 hours after the initial detections. No optical afterglow is detected consistent with the position of the uncatalogued X-ray source detected by Swift/XRT (Dichiara et al., GCN Circ. 40037) or the optical afterglow detected by various facilities (Starling et al., GCN Circ. 40028; Wu et al., GCN Circ. 40029; Du et al., GCN Circ. 40031; Li et al., GCN Circ. 40032; Ghosh et al., GCN Circ. 40039; Jiang et al., GCN Circ. 40041; Pérez-Fournon et al., GCN Circ. 40043; Xin et al., GCN Circ. 40045). Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposures are: Filter Exp(s) Mag u 492 >20.3 b 386 >20.5 v 130 >19.0 w1 164 >19.3 m2 245 >19.7 w2 246 >19.8 The magnitudes in the table are not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/40048. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38068] GRB 250402A: Swift/UVOT Upper Limits
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40047 SUBJECT: GRB 250402A: Swift/UVOT Upper Limits DATE: 25/04/04 12:51:00 GMT FROM: Sam Shilling at Lancaster University <shilling.sam(a)gmail.com> S. P. R. Shilling (Lancaster U.) and S. R. Oates (Lancaster U.) report on behalf of the Swift UVOT team: Swift/UVOT observed the field of SVOM/ECLAIRs GRB 250402A (Chen et al. GCN Circ. 40014) for 2521 seconds in the U-band starting at 12:48:12 UT on 25/04/03, ~13 hours after the detection by SVOM/ECLAIRs. No optical afterglow is detected within a 5" radius of the position of the uncatalogued X-ray source detected by Swift/XRT (Dichiara et al., GCN Circ. 40027) and SVOM/MXT (Maggi et al., GCN circ. 40019) or the optical afterglow detected by SVOM/VT (Xin et al., GCN Circ. 40015), LCOGT (Pérez-Fournon et al., GCN Circ. 40020), and the SVOM/COLIBRÍ (Magnani et al., GCN Circ. 40023). The Swift/UVOT non-detection in the U-band has a preliminary 3-sigma upper limit of >21.1, calculated using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373). View this GCN Circular online at https://gcn.nasa.gov/circulars/40047. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38067] EP250402a: Optical upper limit with Kinder observations
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40046 SUBJECT: EP250402a: Optical upper limit with Kinder observations DATE: 25/04/04 12:01:23 GMT FROM: Janet Chen at National Central University <janetstars(a)gmail.com> A. Aryan, Y.-H. Lee, T.-W. Chen, W.-J. Hou (all NCU), S. Brennan (OKC), 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, M.-H. Lee, H.-Y. Hsiao, C.-S. Lin, H.-C. Lin, C.-H. Lai, 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 EP250402a (Li et al., GCN 40017, GCN 40038) using the 40cm SLT telescope 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 14:18 UT on the 3rd of April 2025 (MJD = 60768.538), ~24.43 hrs after the EP trigger. We utilized the astroalign (Beroiz et al., 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al., 2022, ApJ, 935, 167) packages to align and stack the individual frames. We did not detect any uncataloged optical counterpart candidate within the EP-WXT/EP-FXT localization error circle of radius 2.5 arcminutes/10 arcseconds. The field of FXT is only covered by SkyMapper. We further employed the Python-based package AutoPhOT (Brennan & Fraser, 2022, A&A, 667, 62) to perform PSF photometry on our stacked frames. The details of the observations and measured three sigma upper limits (in the AB system) were as follows: Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass SLT | r | 60768.538 | 24.43 | 300 * 24 | >20.5 | 1".83 | 3.11 The presented upper limit was calibrated using the field stars from the SkyMapper catalog and was not corrected for the expected Galactic foreground extinction corresponding to a reddening of A_r = 0.38 mag, respectively, in the direction of the transient (Schlafly & Finkbeiner 2011). View this GCN Circular online at https://gcn.nasa.gov/circulars/40046. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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