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

[vsnet-grb-info 39050] GRB 250706A: SAO RAS optical observations
by GCN Circulars 07 Jul '25

07 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41000 SUBJECT: GRB 250706A: SAO RAS optical observations DATE: 25/07/07 03:57:27 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin and O. Spiridonova (SAO RAS), report on behalf of a GRB follow-up collaboration. We observed the field of the GRB 250706A (Moss et al., GCN 40988) with SAO RAS 1-m telescope Zeiss-1000 equipped with CCD-photometer. We obtained 20 x 300 sec. images in Rc band on July 6, 20:04:37--22:41:35 UT (t_mid - T0 = 5.5764 hours) under a good weather conditions and the seeing of 1".6. In the XRT error circle (Moss et al., GCN 40988) we detected a bright stellar-like source with the coordinates R.A. = 18:56:04.3, Dec. = +32:19:13.5 (J2000.0) also presented in the archival images. After the PSF subtraction of this bright star we did not detect any significant sources down to the limiting magnitude of R_lim = 23.0. (based on the nearby USNO-B1.0 stars and not corrected for the Galactic extinction) Additionaly we divided whole set into two 10 x 300 sec. subsets (1st: t_mid - T0 = 4.9217 hours, 2nd: t_mid - T0 = 6.2393 hours) and found no significant residuals between two stacked images and no variability of the mentioned bright star within 0.01 mag. between two epochs. This results are in agreement with OT non-detection by Moss et al. (GCN 40988); Mohan et al. (GCN 40990) and Wu et al. (GCN 40998). View this GCN Circular online at https://gcn.nasa.gov/circulars/41000. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39049] EP250704A: NOWT Detection
by GCN Circulars 07 Jul '25

07 Jul '25

TITLE: GCN CIRCULAR NUMBER: 40999 SUBJECT: EP250704A: NOWT Detection DATE: 25/07/07 03:57:17 GMT FROM: Abdusamatjan Iskandar at XAO,CAS <abudu(a)xao.ac.cn> Letian Wang, Abdusamtjan Iskandar, Ali Esamdin, Yu Zhang, Jinzhong Liu, report on behalf of optical group of the XAO: We observed the filed of EP250704a (Li et al., GCNs 40941, 40956; Schneider et al., GCN 40942; Malesani et al., GCN 40945; Brivio et al., GCN 40947; Evans et al., GCN 40951; Perez-Garcia et al., GCN 4957; Gillanders et al., GCN 40958; Xin et al., GCN 40960; Mohan et al., GCN 40962; Moskvin et al., GCN 40963; Liu et al., GCN 40965; An et al., GCN 40966; Yang et al., GCN 4970; Martin-Carillo et al., GCN 40971; Frederiks et al., GCN 40972,Malte Busmann et al., GCN 40974, Li et al., GCN40975, Li et al., GCN 40986) with the Nanshan One-meter Wide-field Telescope (NOWT) at Nanshan Station of Xinjiang Astronomical Observatory (XAO). The observations were started at 2025-07-04T18:33:06.0 (UTC, 0.43 days after the trigger), and obtained a series of V band images. The optical afterglow was clearly detected at the position reported by Schneider et al.(GCN 40942) in the our stacked image, the preliminary photometric magnitudes is V=19.98 +- 0.16 mag (MJD 60860.7729, 6X300s). The photometric calibration was performed using nearby stars from the GAIA synthesis catalog and the magnitude is not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/40999. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39048] GRB 250706A: SVOM/C-GFT upper limit in eary phase
by GCN Circulars 07 Jul '25

07 Jul '25

TITLE: GCN CIRCULAR NUMBER: 40998 SUBJECT: GRB 250706A: SVOM/C-GFT upper limit in eary phase DATE: 25/07/07 01:42:18 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Chao WU (NAOC), Zhe Kang (CHO), Liping Xin(NAOC), Xuhui Han(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), Jinsong Deng(NAOC), Lei Huang(NAOC), Jianyan Wei (NAOC) report on behalf of the SVOM/C-GFT team: We observed the field of GRB250706A detected by Swift/BAT (GCN 40988) with LATIOS on SVOM/C-GFT. Observations started at 2025-07-06T15:49:56 UTC, ~85 seconds after the trigger. A series of g, r, and i band images were obtained. No credible candidate was detected within the error box provided by XRT (GCN 40988) in our images after preliminary processing, the three sigma upper limits are: | Date-Obs (mid-time) | Mid_t - T0 (s) | Exposure Time (s) | Band | Upper Limit (AB) | |---------------------|----------------|-------------------|------|------------------| | 2025-07-06T15:50:35 | 124 | 5×10 | i | 19.31 | | 2025-07-06T16:00:55 | 744 | 6×30 | g | 20.66 | | 2025-07-06T16:04:30 | 949 | 6×30 | r | 20.37 | The photometry was calibrated with nearby Pan-STARRS1 stars. We thank the observation assistants Bowen Li & Yinhuai Hao at Jilin observatory for their excellent support. The Chinese Ground Follow-up Telescope (C-GFT) for the SVOM mission is located at Jilin Station, Changchun Observatory, National Astronomical Observatories, CAS. It features two instruments: (1) CATCH at the Cassegrain focus with a 21 arcsec x 21 arcsec FOV for simultaneous g/r/i-band imaging, and (2) LATIOS, a 4k x 4k CMOS camera at the prime focus with a 1.28 deg x 1.28 deg FOV that images in g, r, and i bands via filter switching. View this GCN Circular online at https://gcn.nasa.gov/circulars/40998. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39047] The EP-WXT trigger 01709181580 is likely a flaring star
by GCN Circulars 07 Jul '25

07 Jul '25

TITLE: GCN CIRCULAR NUMBER: 40997 SUBJECT: The EP-WXT trigger 01709181580 is likely a flaring star DATE: 25/07/07 01:41:47 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> D. Y. Li (NAO, CAS), G. Y. Zhao (SYSU), C. Zhou, P. Y. Han (HUST) , W. D. Zhang (NAO, CAS)on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709181580 at the time of 2025-07-06T17:32:37, is likely a stellar flare associated with PM J17411+1504. 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 1.8 x 10^31 erg/s. 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/40997. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39046] The EP-WXT trigger 01709181580 is likely a flaring star
by GCN Circulars 07 Jul '25

07 Jul '25

TITLE: GCN CIRCULAR NUMBER: 40997 SUBJECT: The EP-WXT trigger 01709181580 is likely a flaring star DATE: 25/07/07 01:41:47 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> D. Y. Li (NAO, CAS), G. Y. Zhao (SYSU), C. Zhou, P. Y. Han (HUST) , W. D. Zhang (NAO, CAS)on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709181580 at the time of 2025-07-06T17:32:37, is likely a stellar flare associated with PM J17411+1504. 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 1.8 x 10^31 erg/s. 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/40997. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39045] GRB250706B: Swift-XRT counterpart detection
by GCN Circulars 06 Jul '25

06 Jul '25

TITLE: GCN CIRCULAR NUMBER: 40996 SUBJECT: GRB250706B: Swift-XRT counterpart detection DATE: 25/07/06 21:33:59 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), J.A. Kennea (PSU), D.N. Burrows (PSU), M.A. Williams (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), A. D'Ai (INAF-IASFPA) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift has performed follow-up observations of the SVOM detected burst GRB250706B (GCN 40989), collecting 1.6 ks of XRT data from 1.4 ks to 3.0 ks after the SVOM/ECLAIRs trigger. The data are entirely in Photon Counting (PC) mode. A candidate X-ray counterpart has been found with a position RA, Dec = 41.2296, -50.0604 which is equivalent to: RA (J2000): 02 44 55.11 Dec(J2000): -50 03 37.5 with an uncertainty of 3.5 arcsec (radius, 90% confidence). We consider the X-ray source the afterglow of GRB 250706B, even if this position appears only marginally consistent with the optical counterpart detected by TRT (Zhu et al., GCN 40991) and from SVOM/VT (GCN 40992). The light curve can be modelled with an initial power-law decay with an index of alpha=0.93 (+0.17, -0.21), followed by a break at T+2679 s to an alpha of 8.0 (+0.0, -1.4). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.50 (+/-0.07). The best-fitting absorption column is 1.11 (+0.24, -0.23) x 10^21 cm^-2, in excess of the Galactic value of 2.8 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 4.3 x 10^-11 (4.8 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.11 (+0.24, -0.23) x 10^21 cm^-2 Galactic foreground: 2.8 x 10^20 cm^-2 Excess significance: 5.9 sigma Photon index: 1.50 (+/-0.07) If the light curve continues to decay with a power-law decay index of 8.0, the count rate at T+24 hours will be 1.3 x 10^-11 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.6 x 10^-22 (6.2 x 10^-22) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00019912. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40996. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39044] GRB 250706B: iTelescope optical observations
by GCN Circulars 06 Jul '25

06 Jul '25

TITLE: GCN CIRCULAR NUMBER: 40995 SUBJECT: GRB 250706B: iTelescope optical observations DATE: 25/07/06 20:59:09 GMT FROM: Filipp Dmitrievich Romanov at Amateur astronomer <filipp.romanov.27.04.1997(a)gmail.com> On 2025-07-06 I observed the field of GRB 250706B (Palmerio et al., GCN Circ. 40989) remotely using the telescopes T33 (0.3-m f/9 reflector + CCD with Astrodon Series II Red filter) and T17 (0.43-m f/6.8 reflector + CMOS with Astrodon Red-E filter) of iTelescope.Net at Siding Spring Observatory, Australia. The exposure times of the photographs were 300 seconds, observations started at 19:56:23 UT (2h 50m after the trigger). I detected the optical afterglow in all images with the position (J2000.0): 02:44:55.46 -50:03:40.1. I measured the magnitudes (compared to r' magnitudes of nearby stars from the APASS DR9 catalog: Henden et al., 2016): Mid-time (UT) | Magnitude | Error | Telescope | 19:58:53.3 16.852 0.073 T33 20:04:55.9 16.790 0.046 T33 20:10:58.5 16.756 0.110 T33 20:17:00.3 16.752 0.071 T33 20:05:50.8 16.738 0.040 T17 20:11:47.9 16.875 0.054 T17 20:17:43.6 16.833 0.076 T17 Magnitudes were not corrected for Galactic extinction. F. D. Romanov (AAVSO). View this GCN Circular online at https://gcn.nasa.gov/circulars/40995. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39043] IceCube-250706A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 06 Jul '25

06 Jul '25

TITLE: GCN CIRCULAR NUMBER: 40994 SUBJECT: IceCube-250706A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/07/06 20:52:56 GMT FROM: A. Zegarelli at Ruhr University Bochum <azegarelli(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 25-07-06 at 13:14:40.04 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 Bronze alerts is 50%. This alert has an estimated false alarm rate of 0.2382 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/141104_37015490.amon) more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 25-07-06 Time: 13:14:40.04 UT RA: 266.00 (+0.57/-0.59 deg 90% PSF containment) J2000 Dec: 38.97 (+0.49/-0.47 deg 90% PSF containment) J2000 We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino. 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/40994. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39042] EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
by GCN Circulars 06 Jul '25

06 Jul '25

TITLE: GCN CIRCULAR NUMBER: 40993 SUBJECT: EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart DATE: 25/07/06 20:50:24 GMT FROM: Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo(a)ucd.ie> J. An (NAOC), A. Martin-Carrillo (UCD), D. B. Malesani (DAWN/NBI and Radboud), X. Liu (NAOC), A. K. Haris-Kiss (Helsinki Univ.), M. Korpi-Lagg (Aalto Univ.), S. Wedemeyer (Univ. Oslo), A. Casasbuenas Corral (IAC), report on behalf of a larger collaboration: We performed further observations of the field of the EP250704a (Li et al., GCN 40941) also detected by SVOM (GRB 250704B; Wang et al., GCN 40940), using the StanCam camera mounted on the Nordic Optical Telescope (NOT). We obtained 3x300 s exposures in the Bessel-R and I bands, starting at 2025-07-05 at 23:49:00 UT (~39.54 hr after the EP trigger). In our stacked image, the optical afterglow detected by COLIBRÍ (Schneider et al., GCN 40942), BOOTES-5 (Perez-Garcia et al., GCN 40957), Pan-STARRS (Gillanders et al., GCN 40958), SVOM/VT (Xin et al., GCN 40960), GROWTH-India (Mohan et al., GCN 40962), SAO RAS (Moskvitin et al., GCN 40963), JinShan (Liu et al., GCN 40965), VLT/X-shooter (An et al., GCN 40966), VLT/HAWK-I (Yang et al., GCN 40970), NOT (Martin-Carrillo et al., GCN 40971), FTW (Busmann et al., GCN 40974) and GSP (Li et al., GCN 40975), the optical counterpart is detected at a preliminary magnitude of: i = 21.56 +/- 0.14 (AB), calibrated against nearby Pan-STARRS sources and not corrected for Galactic extinction. Compared to our previous measurement (Martin-Carrillo et al., GCN 40971), the new magnitude indicates a rapid decay (effective power-law index ~ 1.8), in stark contrast with the flat / rising behavior observed over the first ~16 hr after the trigger (e.g., Gillanders et al., GCN 40958; Yang et al., GCN 40970; Martin-Carrillo et al., GCN 40971; Busmann et al., GCN 40974). View this GCN Circular online at https://gcn.nasa.gov/circulars/40993. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39041] GRB 250706B: SVOM/VT optical observation
by GCN Circulars 06 Jul '25

06 Jul '25

TITLE: GCN CIRCULAR NUMBER: 40992 SUBJECT: GRB 250706B: SVOM/VT optical observation DATE: 25/07/06 18:45:55 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> After the trigger by SVOM/ECLAIRs at 2025-07-06T17:06:04 UTC (T0), SVOM performed an automatic slew on the burst location (Palmerio et al., GCN 40989). SVOM/VT began observing the field at 2025-07-06T17:10:48, 283.83 seconds after T0, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. From a preliminary analysis of the 1-bit subimage and source list downloaded via VHF network, at least one credible candidate is identified, the details of which are presented below. VT_ID 50: This candidate was flagged as un uncatalogued source whose magnitude varied with 3 sigma significance. The position of this candidate is R.A., Dec. 41.2311, -50.0612 degrees, corresponding to: R.A. (J2000) = 2h44m55.5s Dec. (J2000) = -50d03m40.4s with an uncertainty of 1 arcsec. This location is within the R90 uncertainty region of the SVOM/MXT onboard localization. This location is consistent with the optical afterglow reported by Zhu et al. (GCN 40991). The source was detected in both VT_R and VT_B, and was fading between the first 2 VT observing sequences. The candidate's magnitudes are: | date-obs (UTC) | mid-time | exposure | band | mag(AB) | | -------------------- | ----------- | --------- | ----- | ------------- | | 2025-07-06T17:10:48 | 7.23 min | 6*50 sec | VT_B | 14.90 ± 0.01 | | 2025-07-06T17:10:48 | 7.23 min | 6*50 sec | VT_R | 14.48 ± 0.01 | | 2025-07-06T17:15:48 | 12.23 min | 6*50 sec | VT_B | 15.17 ± 0.01 | | 2025-07-06T17:15:48 | 12.23 min | 6*50 sec | VT_R | 14.65 ± 0.01 | Magnitudes were not corrected for dust extinction. Given the VT colour of the counterpart, it might be a low redshift gamma-ray burst. 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. SVOM/VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. The SVOM/VT point of contact for this burst is Jesse Palmerio: palmerio(a)cea.fr. View this GCN Circular online at https://gcn.nasa.gov/circulars/40992. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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