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

[vsnet-grb-info 37778] GRB 250316A: Swift/UVOT Upper Limits
by GCN Circulars 17 Mar '25

17 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39762 SUBJECT: GRB 250316A: Swift/UVOT Upper Limits DATE: 25/03/17 13:26:57 GMT FROM: Mike Siegel at PSU/Swift MOC <mhs18(a)psu.edu> M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team: Swift/UVOT observed the field of GRB250316A (GCN 39737) for a total of 3.3 ks in the white filter from 21.8 ks to 29 ks after the Fermi trigger. We detect no optical/UV source at the position of the XRT afterglow (Beardmore et al., GCN Circ. 39758) to an upper limit of white > 22.53. The magnitude is not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.017 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/39762. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37777] GRB 250314A: REM optical/NIR upper limits
by GCN Circulars 17 Mar '25

17 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39761 SUBJECT: GRB 250314A: REM optical/NIR upper limits DATE: 25/03/17 13:09:40 GMT FROM: Riccardo Brivio at INAF-OAB <riccardo.brivio(a)inaf.it> R. Brivio, M. Ferro, S. Covino, P. D'Avanzo, S. Campana (INAF-OAB), D. B. Malesani (DAWN/NBI and Radboud), A. Melandri (INAF-OAR), D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of the SVOM GRB 250314A (Wang et al., GCN 39719), followed-up by Swift/XRT (Kennea et al., GCN 39734) and EP/FXT (Turpin et al., GCN 39739), with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H, and K bands, started on 2025 March 15 at 01:18:28 UT (i.e. 12.4 hr after the burst), and lasted for about 1 hour. From preliminary inspection, we do not find any counterpart at the position of the reported NIR afterglow (Malesani et al., GCN 39727; Malesani et al., GCN 39732) down to the following 3sigma limits: r > 18.1 (AB; calibrated against the Pan-STARRS catalogue), at a mid-time of 12.9 hours after the trigger, H > 16.1 (Vega; calibrated against the 2MASS catalogue), at a mid-time of 12.8 hours after the trigger, J > 16.8 (Vega; calibrated against the 2MASS catalogue) at a mid-time of 13.0 hours after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/39761. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37776] GRB 250316A: AbAO AS-32 Optical Upper Limit
by GCN Circulars 17 Mar '25

17 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39760 SUBJECT: GRB 250316A: AbAO AS-32 Optical Upper Limit DATE: 25/03/17 12:43:30 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI), R. Ya. Inasaridze (AbAO), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN: We performed optical observations of the field of GRB 250316A (The Fermi GBM team, GCN 39741; Ronchini et. al, GCN 39744; Evans, GCN 39745; Lipunov et. al, GCN 39747; Kennea et. al, GCN 39750; Bala & Meegan, GCN 39751; Beardmore et. al, GCN 39758) in the R filter with the 0.7-meter AS-32 telescope of the Abastumani Astrophysical Observatory (AbAO). The observations started on (UT) 2025-03-17 00:17:41, i.e. about 0.67 days since trigger. We do not find any new optical source within the error circle of the most probable candidate afterglow Swift XRT #1 (Beardmore et. al, GCN 39758). The preliminary upper limit is as follows: Date UT start t-T0 Exp. Filter OT UL(3sigma) (mid, days) (s) 2025-03-17 00:17:41 0.67447 107*60 R n/d 19.7 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/39760. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37775] EP 250317B: Fading optical counterpart detection by LCO
by GCN Circulars 17 Mar '25

17 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39759 SUBJECT: EP 250317B: Fading optical counterpart detection by LCO DATE: 25/03/17 11:21:28 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 GRB 250317B triggered by SVOM/ECLAIRs (Zhao et al., GCN circ. 39752 and GCN circ. 39753) and SVOM/MXT(Zhao et al., GCN circ. 39752 and GCN circ. 39753; and Götz et al., GCN circ. 39756) in r filter of the 0.4-m SCICAM QHY600 at the Las Cumbres Observatory Global Telescope (LCOGT) node located at Haleakala Observatory, Hawai . The 0.4 m SCICAM QHY600 is equipped with 9576 x 6388 pixel CCD (FOV: 1.9 x 1.2 degrees, scale: 0.74 arcsec/pixel) but we only used the FOV of 30 x 30 arcmin for our observation. Observations began on March 17, 2025, starting 6.46 hours after the GRB trigger. We clearly detect the optical transient (OT) reported by GCNs (Watson et al., GCN circ. 39754, Palmerio et al., GCN circ. 39755, Pérez-Fournon et al., GCN 39757) in our r band image. |Date| |UTstart| |t-T0 (hours)| |Exp (sec)| |Filter| |Magnitude| -------------------------------------------------------------------------------------------------- 2025-03-17 08:39:27.93 6.46 2 x 300 r r = 19.48 +/- 0.11 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/39759. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37774] GRB 250316A: Swift-XRT afterglow detection
by GCN Circulars 17 Mar '25

17 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39758 SUBJECT: GRB 250316A: Swift-XRT afterglow detection DATE: 25/03/17 09:48:06 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> A.P. Beardmore (U. Leicester), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) , J.A. Kennea (PSU), D.N. Burrows (PSU), M. A. Williams (PSU), J.P. Osborne (U. Leicester) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has conducted further observations of the field of the Swift/BAT-detected burst GRB 250316A. The observations now extend from T0+21.7 ks to T0+51.0 ks and have a total exposure time of 4.6 ks. . The source previously reported, "Source 1", is believed to be the afterglow. Using 3006 s of PC mode data and 2 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 219.59644, +14.89108 which is equivalent to: RA (J2000): 14h 38m 23.15s Dec(J2000): +14d 53' 27.9" with an uncertainty of 3.0 arcsec (radius, 90% confidence). This position is 118 arcsec from the Swift/BAT position. The source is fading with alpha >0.9. A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.7 (+0.9, -0.7). The best-fitting absorption column is 5.1 (+4.0, -2.8) x 10^21 cm^-2, in excess of the Galactic value of 1.5 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 3.0 x 10^-11 (8.4 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 5.1 (+4.0, -2.8) x 10^21 cm^-2 Galactic foreground: 1.5 x 10^20 cm^-2 Excess significance: 2.9 sigma Photon index: 2.7 (+0.9, -0.7) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00021823. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00021823. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/39758. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37773] GRB 250317B: LCO detection of the fading optical afterglow
by GCN Circulars 17 Mar '25

17 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39757 SUBJECT: GRB 250317B: LCO detection of the fading optical afterglow DATE: 25/03/17 09:34:57 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 the field of GRB 250317B, discovered by SVOM/ECLAIRs (Zhao et al., GCN circ. 39752 and GCN circ. 39753) and SVOM/MXT (Zhao et al., GCN circ. 39752 and GCN circ. 39753; and Götz et al., GCN circ. 39756). We observed the field of GRB 250317B with one of the two LCOGT 1-m telescopes, equipped with Sinistro cameras, located at the LCOGT node at McDonald Observatory (Texas). We obtained a 300-sec exposure in the SDSS r' filter starting at 2025-03-17 07:26:01 UT, about 5.23 hours after the SVOM trigger. An uncatalogued source is clearly detected at the position of the optical afterglow detected by SVOM/F-GFT (COLIBRÍ) (Watson et al., GCN circ. 39754) and SVOM/VT (Palmerio et al., GCN circ. 39755). We measure the following AB magnitude, calibrated against Pan-STARRS DR2 stars and not corrected for Galactic extinction: Time (UT, mid term) | mag | error | filter | ---------------------------------------------- 2025-03-17T07:28:31 19.27 0.05 r' 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/39757. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37772] GRB 250317B: refined SVOM/MXT analysis
by GCN Circulars 17 Mar '25

17 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39756 SUBJECT: GRB 250317B: refined SVOM/MXT analysis DATE: 25/03/17 08:04:00 GMT FROM: Diego Gotz at CEA <diego.gotz(a)cea.fr> D. Götz (CEA), F. Robinet (IJCLab), H. Goto (CEA), C. Plasse (CEA), P. Maggi (ObAS), M. Moita (CEA), C. van Hove (IJCLab) on behalf of the MXT team report: We performed further analysis of the GRB 250317B (Zhao et al., GCN 39753) MXT X-ray data, using promptly downloaded photons through the VHF band. We can improve the X-ray afterglow position. The new J2000 coordinates are R.A. = 14h 06m 32s Dec. = +40d 05mm 02ss with a 90% c.l. error radius of 48 arc seconds, including systematics. This position supersedes the one reported in GCN 39753, which was affected by early satellite instability after the slew. We note that this position is consistent with the SVOM/F-GFT (COLIBRÍ) position (Watson et al. GCN 39754) and the VT one (Palmeiro et al. GCN 39755). 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. MXT has been developed by CNES in collaboration with CEA, IJCLab, University of Leicester and MPE. View this GCN Circular online at https://gcn.nasa.gov/circulars/39756. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37771] GRB250317B: SVOM/VT detection of an optical candidate from VHF data
by GCN Circulars 17 Mar '25

17 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39755 SUBJECT: GRB250317B: SVOM/VT detection of an optical candidate from VHF data DATE: 25/03/17 06:48:34 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> J. T. Palmerio (CEA) reports on behalf of the SVOM/VT team: After the trigger by SVOM/ECLAIRs at 2025-03-17T02:12:08 UTC (Tb), SVOM performed an automatic slew on the burst. SVOM/VT began observing the field at 2025-03-17T02:18:21, 362 seconds after the SVOM trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. An uncatalogued source is detected within the error box of SVOM/ECLAIRs (Zhao et al. GCN 39753) using the VT VHF pipeline at ra=211.643617, dec=40.079524 (J2000), corresponding to: RA (J2000) = 14h06m34.5s Dec (J2000) = +40:04:46.3s with an uncertainty of 0.5 arcsec. consistent with the optical afterglow reported by Watson et al. (GCN 39754) The source is detected in both VT_R and VT_B and was fading between the third and fourth VT observing sequences (starting at 5574 and 8474 seconds after the trigger respectively), the magnitudes are given below: date-obs | exposure time (s) | mag(AB) | mag err | band 2025-03-17T03:45:13 | 6x50 | 17.48 | 0.02 | VT_R 2025-03-17T04:33:33 | 5x50 | 17.82 | 0.01 | VT_R 2025-03-17T03:45:13 | 6x50 | 18.89 | 0.01 | VT_B 2025-03-17T04:33:33 | 5x50 | 18.97 | 0.02 | VT_B The source was undetected in the first two sequences (starting at 362 and 512 seconds after the trigger, respectively) and is outside the reported SVOM/MXT position. 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/39755. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37770] GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
by GCN Circulars 17 Mar '25

17 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39754 SUBJECT: GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart DATE: 25/03/17 06:31:31 GMT FROM: Sarah Antier at OCA <sarah.antier(a)oca.eu> Alan M. Watson (UNAM), Sarah Antier (OCA/IJCLAB), Jean-Luc Atteia (IRAP), Jean-Grégoire Ducoin (CPPM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Antonio de Ugarte Postigo (LAM), Benjamin Schneider (LAM) and C. Wu (NAOC) report: We imaged the field of the SVOM/ECLAIRs GRB 250317B (Zhao et al. GCN Circ. 39752, Zhao et el. GCN Circ. 39753) with the OGSE test camera imager on the COLIBRÍ (SVOM/F-GFT) telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We observed from 2025-03-17 04:21 to 04:56 UTC (2.15 to 2.73 hours after the trigger) and obtained 23 minutes of exposure in the r filter at high airmass. The data were coadded with custom software and analyzed in STDWeb/STDPipe (Karpov 2024), 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. We detect an uncatalogued source at RA = 211.64367 degrees and Dec = 40.07953 degrees (J2000) with a magnitude of r = 18.18 +/- 0.03 The source is observed to fade in later observations and is not present in Legacy Survey DR10, which strongly suggests it is the afterglow of the GRB. This source is 81 arcsec from the MXT position reported by Zhao et al. (GCN Circ. 39752) and significantly beyond the reported 25 arcsec 90% confidence radius. Further observations are planned. We acknowledge excellent support from the staff of the Observatorio Astronómico Nacional. View this GCN Circular online at https://gcn.nasa.gov/circulars/39754. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37769] GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
by GCN Circulars 17 Mar '25

17 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39753 SUBJECT: GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752 DATE: 25/03/17 05:29:56 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Donghua Zhao, Yinuo Ma, Wenjin XIE(NAOC), Li Zhang (IHEP), F. Robinet (IJCLab), Liping Xin (NAOC) on behalf of the SVOM mission team. At 2025-03-17T02:12:08 UTC (Tb) SVOM/ECLAIRs triggered on the gamma-ray burst GRB 250317B (SVOM burst-id sb25031701). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was detected both by the Count-Rate Trigger (CRT) and the Image Trigger (IMT), which produced a sequence of 13 alerts. CRT provided the alert with the best signal-to-noise-ratio (SNR) of 14.27 in the [5-8] keV energy band over a time window of 40.96 seconds starting at Tb. The light curve showed a broad peak structure with a T90 duration of about 145.67 (-0.16 +0.16). The localization of the best alert is R.A., Dec 211.665, 40.056 degrees (J2000) with a 90% C.L. radius of 5.75 arcmin (including systematic error of 2 arcmin added in quadrature). SVOM slewed to the burst. MXT began observing the field at 2025-03-17T02:14:36 UTC, 148 seconds after Tb. Using onboard processed data we found a bright and rapidly fainting uncatalogued X-ray source located at R.A., Dec 211.648, 40.057 degrees: RA (J2000) = 14h06m35s DEC (J2000) = 40d03m23s with a 90% C.L. radius of 25 arcseconds. This location is 48 arcseconds away from the ECLAIRs onboard position. VT began to observe the field after the slew. No uncatalogued sources were detected within MXT errors compared to DESI catalog based on the VHF sequences. The 3 sigma limit magnitude is about VT_R~21 mag (AB) at about 10 minutes after the trigger. More analysis will be performed after receiving the X band data later. 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 Donghua Zhao (zhaodh(a)bao.ac.cn). Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst. We apologize for any confusion and inconvenience caused by this mistake. View this GCN Circular online at https://gcn.nasa.gov/circulars/39753. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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