GRB 250502A
GCN Circular 40313
Subject
GRB 250502A: SVOM detection of a burst
Date
2025-05-02T09:51:06Z (a month ago)
Edited On
2025-05-09T15:01:38Z (20 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
Y. Wang (PMO, CAS), J.X Cao (GXU), L. Bouchet, M. Brunet (IRAP), C. Plasse (CEA)
on behalf of the SVOM mission team.
SVOM/ECLAIRs triggered on the gamma-ray burst GRB 250502A (SVOM burst-id sb25050205) starting at 2025-05-02T08:46:29.27 UTC (Tb)
The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network.
The burst was detected by the Image Trigger (IMT). A sequence of 3 alerts was produced. IMT provided the alert with the best signal-to-noise-ratio (SNR) of 8.94 in the 8-50 keV energy band over a time window of 40.96 seconds starting at Tb.
The localization of the best alert is R.A., Dec. 206.479, -10.643 degrees:
R.A. (J2000) = 13h45m54.84s
Dec. (J2000) = -10h38m34.49a
with a 90% confidence level (C.L.) radius of 8.84 arcmin (including systematic error of 2 arcmin added in quadrature).
SVOM slewed to the burst.
MXT began observing the field after the slew. The analysis of MXT data will be published in a future circular.
VT began observing the field after the slew. The analysis of the recorded images will be published in a future circular gathering information on the follow-up of the SVOM optical instruments.
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 Y. Wang: wangyun@pmo.ac.cn.
Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst.
GCN Circular 40315
Subject
GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
Date
2025-05-02T10:25:06Z (a month ago)
Edited On
2025-05-02T17:24:45Z (a month ago)
From
Ny Avo Rakotondrainibe at LAM <nyavo.rakotobe@gmail.com>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Ny Avo Rakotondrainibe at LAM <nyavo.rakotobe@gmail.com>
Via
Web form
Ny Avo Rakotondrainibe (LAM), Enrique Moreno Méndez (UNAM), Jean-Grégoire Ducoin (CPPM), Benjamin Schneider (LAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), 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), Margarita Pereyra (UNAM), Antonio de Ugarte Postigo (LAM) and Y. Wang (PMO, CAS) report:
We imaged the field of the SVOM/ECLAIRs GRB 250502A (sb25050205) with the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico.
We observed from 2025-05-02 08:58 UTC to 09:17 UTC (682 to 1848 seconds after the trigger) and obtained 16 minutes of exposure in the i filter. The data were coadded with the COLIBRÍ pipeline and analyzed in STDWeb/STDPipe (Karpov 2025), with photometric calibration against Pan-STARRS DR1. Our photometry is in the AB system and is not corrected for Galactic extinction.
Within the SVOM/ECLAIRs error box, we detect a bright uncatalogued source at:
RA (J2000) = 13:46:05.60 = 206.5233d
Dec (J2000) = -10:45:31.9 = -10.7588d
The preliminary magnitude derived for that source is:
i = 17.41 +/- 0.03
Further observations are planned.
We warmly thank the COLIBRÍ and DDRAGO engineering teams and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir.
GCN Circular 40319
Subject
GRB 250502A: TRT optical afterglow confirmation
Date
2025-05-02T12:05:04Z (a month ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
Via
Web form
J. An (NAOC), K. Noysena, S. Tinyanont, K. Chanchaiworawit (NARIT), S.Y. Fu (HUST), X. Liu, Z.P. Zhu, S.Q. Jiang, D. Xu (NAOC) report on behalf of a large collaboration:
We observed the field of GRB 250502A detected by SVOM/ECLAIRs (Wang et al., GCN 40313), using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at New South Wales, Australia (SBO). Observations started at 10:30:05 UTC on 2025-05-02, i.e., ~1.73 hr after the SVOM trigger and a series of frames in the B/V/R/I bands were obtained.
The optical afterglow of the burst (Rakotondrainibe et al., GCN 40315) is clearly detected in our individual images. Preliminary photometry shows that the afterglow has decayed to I ~ 18.6 mag at 2.00 hr post-trigger, calibrated with Pan-STARRS DR2 catalog and not corrected for Galactic extinction.
Observations are ongoing.
GCN Circular 40320
Subject
GRB 250502A: SVOM/VT optical bump
Date
2025-05-02T12:21:30Z (a month ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), Y. Wang (PMO), R.Z. Li (YNAO), J.X. Cao (GXU), D.F. Kong (GXU) report on behalf of the SVOM/VT Instrument Center:
GRB 250502A (sb25050205) (Wang et al., GCN 40313) was observed by on-board SVOM/VT after the automatic slew of the satellite. The VT conducted observations in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously.
With the downlinked X-band data, the optical counterpart (Rakotondrainibe et al., GCN 40315; An et al., GCN 40319) was observed with single exposure of 50 seconds in both VT_B and VT_R bands. The earliest observation started on 2025-05-02T08:51:36 UT (i.e. 334 seconds after the burst).
The light curve shows a brightening with a peak brightness of 17.02+/-0.01 mag in VT_R and 17.86+/-0.02 mag at 584 seconds after the burst. The photometry is in the AB system and is not corrected for Galactic extinction.
Given the color of VT_B-VT_R~0.8 mag, it might be a low or intermediate redshift GRB.
Observation is ongoing.
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.
GCN Circular 40322
Subject
GRB 250502A: Early optical counterpart detection by LCO.
Date
2025-05-02T12:52:02Z (a month ago)
From
ankur ghosh at CAPP, University of Johannesburg <ghosh.ankur1994@gmail.com>
Via
Web form
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 250502A triggered by the SVOM/ECLAIRs(Wang et al., GCN 40313) in the V, 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 May 02, 2025, starting 2.00 hours after the GRB trigger.
We clearly detect the optical transient (OT) reported by GCNs (Rakotondrainibe et al., GCN 40315; An et al., GCN 40319, Li et al., GCN 40320) in our V, r band image.
------------------------------------------------------------------------------------------------------
|Date| |JD start| |t-T0 (hours)| |Exp (sec)| |Filter| |Magnitude|
------------------------------------------------------------------------------------------------------
2025-05-02 2460797.94930 2.00 1 x 600 V V = 19.08 +/- 0.04
2025-05-02 2460797.95500 2.15 1 x 600 r r = 19.02 +/- 0.04
------------------------------------------------------------------------------------------------------
The field was calibrated against nearby APASS stars, with magnitudes converted using Lupton (2005) equations, and has not been corrected for Galactic extinction.
GCN Circular 40328
Subject
GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
Date
2025-05-03T02:52:49Z (a month ago)
From
Antonio de Ugarte Postigo at LAM, CNRS <adeugartepostigo@gmail.com>
Via
email
A. de Ugarte Postigo (LAM), J. F. Agui Fernandez (CAHA), C. C. Thoene (AbAO), B. Schneider (LAM), N. A. Rakotondrainibe (LAM), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), M. A. Aloy (UV), J. P. U. Fynbo (DAWN/NBI), L. Galbany (IEEC-CSIC), S. Geier (GTC), L. Izzo (INAF/OACN and DARK/NBI), G. Lombardi (GTC), N. R. Tanvir (Univ. Leicester), A. Tejero (GTC) and D. Garcia-Alvarez (GTC) report
We observed the afterglow of the SVOM GRB 250502A (Wang et al. GCN 40313; Rakotondrainibe et al. GCN 40315; An et al. GCN 40319; Li et al. GCN 40320; Ghosh et al. GCN 40322) using OSIRIS+ on the 10.4m GTC telescope, at Roque de los Muchachos Observatory (La Palma, Spain). The observation started at 2025-05-03T00:34:49 UT (15.806 hrs after the burst) and consisted of acquisition imaging in r-band followed by 3x1200s exposures of spectroscopy using grism R1000B, covering the range between 3600 and 7800 AA at a resolving power of ~ 600.
In the acquisition image the afterglow is detected at an AB magnitude of r = 21.00 +/- 0.03, as compared to PanSTARRS field stars.
The spectrum shows a clear continuum over the complete spectral range with multiple absorption features that we identify as Ly-alpha, SII, OI, SiII, SiII*, CII, SiIV, CIV, FeII, FeII*, AlII, AlIII at a common redshift of z = 2.163, which we identify as the redshift of the GRB. We also note the presence of a prominent emission of Lyman alpha.
GCN Circular 40329
Subject
GRB 250502A: Swift ToO observations
Date
2025-05-03T04:45:12Z (a month ago)
Edited On
2025-05-03T17:52:38Z (a month ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of K.L. Page at U Leicester <klp5@leicester.ac.uk>
Via
email
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the SVOM/ECLAIRs-detected event
GRB 250502A. Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021827
Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the SVOM/ECLAIRs event. 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.
GCN Circular 40330
Subject
GRB 250502A: LCO optical counterpart detection
Date
2025-05-03T08:01:13Z (a month ago)
From
Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf@iac.es>
Via
Web form
I. Pérez-Fournon, F. Poidevin (IAC and ULL), D. Cano-Morales, A.E. Hernández-Díaz, I. Correa-Plasencia (ULL), and A. López-Oramas (IAC and ULL)
Following the detection of the SVOM/ECLAIRs gamma-ray burst GRB 250502A (SVOM burst-id sb25050205,
Wang et al., GCN circ. 40313), we observed the GRB field with the two Las Cumbres Observatory Global Telescope network (LCOGT) 1-m telescopes, equipped with Sinistro cameras, located at the LCOGT node at Teide Obervatory (Tenerife, Spain) in the SDSS r, i, and g filters. The observations started at 2025-05-02 22:13:16 UTC, about 13.45 hours after the SVOM trigger. An uncatalogued source is clearly detected at the optical counterpart position first reported by Rakotondrainibe et al. (GCN circ. 40315) and with other optical detections reported by An et al. (GCN circ. 40319), Li et al. (GCN circ. 40320), Ghosh et al. (GCN circ. 40322), and de Ugarte Postigo et al. (redshift of z = 2.163, GCN circ. 40328).
We measure the following magnitudes, calibrated against Pan-STARRS DR2 stars, that are not corrected for Galactic extinction:
Date | UT start | mag | error | filter | exposure time (sec) |
------------------------------------------------------------------------
2025-05-02 22:13:16 20.66 0.13 r 300
2025-05-02 22:20:27 20.68 0.17 i 300
2025-05-02 22:48:15 21.39 0.16 g 300
This work makes use of observations from the Las Cumbres Observatory global telescope network
(LCOGT observing programme IAC2025A-009, SGLF).
GCN Circular 40331
Subject
GRB 250502A: AKO Optical Afterglow Detection
Date
2025-05-03T08:39:13Z (a month ago)
From
Mohammad Odeh at Al Khatim Observatory M44 <mshodeh@gmail.com>
Via
email
Mohammad Odeh (Al-Khatim Observatory, AKO, operated by the International
Astronomical Center in Abu Dhabi, UAE), and Nidhal Guessoum (American
University of Sharjah, UAE), report:
We observed the field of GRB 250502A detected by SVOM (Wang et al., GCN
40313), using our 0.36m f/7.7 robotic telescope. The observation session
began on 02 May 2025 at 15:40 UT, with a midpoint at 16:43 UT, approximately
8 hours after the trigger.
We obtained multiple 180-second exposures using the Ic filter. The optical
afterglow was marginally detected at:
R.A. (J2000): 13:46:05.4
Dec. (J2000): -10:45:32.4
Our detection is consistent with the results of (Rakotondrainibe et al., GCN
40315; An et al., GCN 40319; Li et al., GCN 40320; Ghosh et al., GCN 40322;
de Ugarte Postigo et al., GCN 40328; Pérez-Fournon et al., GCN 40330).
The following observation was calculated using the Atlas catalogue as a
reference:
----------------------------------------------------------------------------
-
ObsTime (mid), Exposure (sec), Filter, Mag
----------------------------------------------------------------------------
-
2025-05-02T16:43:29Z, 40 x 180s (stacked), Ic, 19.74 +/- 0.31
----------------------------------------------------------------------------
-
The magnitude is not corrected for galactic extinction.
GCN Circular 40333
Subject
GRB 250502a: Liverpool Telescope optical follow-up
Date
2025-05-03T11:37:18Z (a month ago)
From
A. Bochenek at Liverpool John Moores University <a.m.bochenek@2023.ljmu.ac.uk>
Via
Web form
A. Bochenek and D. A. Perley (LJMU) report:
We observed the SVOM-detected GRB250502a (Wang et al., GCN 40313) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 6x100s exposures in the SDSS r’ filter starting at 2025-05-02 23:54:39 UT, approximately 15.28 hours after the trigger. The first exposure had to be discarded, due to a tracking error.
We report a detection in the stacked image at the position of the optical counterpart (Rakotondrainibe et al., GCN 40315; An et al., GCN 40319). The magnitude of the afterglow is r = 21.04 ± 0.05, which is in agreement with observations by de Ugarte Postigo et al. (GCN 40328) and Pérez-Fournon et al. (GCN 40330). The photometry was calibrated using nearby PanSTARRS secondary standards and was not corrected for extinction.
GCN Circular 40334
Subject
GRB 250502A: NOT optical observations
Date
2025-05-03T12:59:00Z (a month ago)
From
Gregory Corcoran at University College Dublin <gregory.corcoran@ucdconnect.ie>
Via
Web form
G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud Univ.), A. Martin-Carrillo (UCD), A. de Ugarte Postigo (LAM), D. Xu (NAOC), A. Saccardi (CEA/Irfu), N. Pyykkinen (NOT and Turku), report on behalf of a larger collaboration:
We observed the field of GRB 250502A detected by SVOM/ECLAIRs (Wang et al., GCN 40313), using the ALFOSC camera mounted on the Nordic Optical Telescope (NOT). We obtained exposures in the SDSS g, r, i (3x300 s each) and z (5x200 s) bands, starting at 21:41:17 UT on 2025-05-02 (12.914 hr after the SVOM/ECLAIRs trigger).
The optical counterpart reported by Rakotondrainibe et al. (GCN 40315), An et al. (GCN 40319), Li et al. (GCN 40320), Ghosh et al. (GCN 40322), de Ugarte Postigo et al. (GCN 40328), Pérez-Fournon et al. (GCN 40330), Odeh & Guessoum (GCN 40331), Bochenek & Perley (GCN 40333) with a redshift of z = 2.163 (de Ugarte Postigo et al., GCN 40328) is well detected in all our frames. We measure the following preliminary magnitude (mid time 13.23 hr after the trigger):
r = 20.71 +/- 0.03 (AB).
The photometric calibration was performed using nearby stars from the Pan-STARRS catalog and the magnitudes are not corrected for Galactic extinction.
GCN Circular 40336
Subject
GRB 250502A: Swift-XRT afterglow detection
Date
2025-05-03T19:00:30Z (a month ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
S. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU), K.L. Page (U.
Leicester), A.P. Beardmore (U. Leicester), A. D'Ai (INAF-IASFPA), A.
Melandri (INAF-OAR), T. Sbarrato (INAF-OAB) and P.A. Evans (U.
Leicester) reports on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the
SVOM/ECLAIRs-detected burst GRB 250502A (GCN 40313). We searched for
X-ray sources in 4.6 ks of Photon Counting (PC) mode data. The total
exposure at the position of the afterglow (see below) is 4.6 ks,
obtained between T0+72.1 ks and T0+105.5 ks.
An uncatalogued X-ray source is detected consistent with the
SVOM/COLIBRI error region (GCN 40315) and is believed to be the
afterglow. Using 2113 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 = 206.52396, -10.75879
which is equivalent to:
RA (J2000): 13h 46m 05.75s
Dec(J2000): -10d 45' 31.6"
with an uncertainty of 4.5 arcsec (radius, 90% confidence). This
position is 2.3 arcsec from the SVOM/COLIBRI position. The source has
a mean count rate of 1.3e-02 ct/sec; we cannot determine at the present
time whether it is fading. However, given the coincidence in position
with the optical counterpart (GCNs 40315, 40319, 40320, 40322, 40330,
40331, 40333, 40334) at a redshift of 2.163 (GCN 40328), we confirm
this as the X-ray afterglow.
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.4 (+1.6, -0.7). The
best-fitting absorption column is consistent with the Galactic value
of 5.0 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 3.1 x 10^-11 (3.6 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 5 (+/-31) x 10^20 cm^-2
Galactic foreground: 5.0 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index: 2.4 (+1.6, -0.7)
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00021827.
The results of the full analysis of the XRT observations are available
at https://www.swift.ac.uk/ToO_GRBs/00021827.
This circular is an official product of the Swift-XRT team.
GCN Circular 40337
Subject
GRB 250502A: Montarrenti Observatory optical detection
Date
2025-05-03T21:54:31Z (a month ago)
From
Simone Leonini at Montarrenti Observatory (Siena, Italy) <s.leonini@iol.it>
Via
Web form
S. Leonini, M. Conti, P. Rosi, L.M. Tinjaca Ramirez (Montarrenti Observatory, Siena, Italy, part of UAI/SSV-GRB section), M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy) and K. Kalinowski (Aarhus University, Department of Physics and Astronomy) report:
we observed the field of GRB 250502A detected by SVOM/ECLAIRs (Wang et al., GCN 40313) with the automated and remoted 0.53m Ritchey-Chretien telescope at Montarrenti Observatory (Siena, Italy, IAU code C88).
The observations were started at 2025-05-02 20:42:17 UT (approximately 12 hours after burst) stacking a set of Rc-band CCD images. Observations were performed under thin cloud cover in the second part of the night.
The optical afterglow (Rakotondrainibe et al., GCN 40315; An et al., GCN 40319; Li et al., GCN 40320; Gosh et al., GCN 40322; de Ugarte Postigo et al. with a redshift of z = 2.163, GCN 40328 ; Perez-Fournon et al., GCN 40330; Odeh & Guessoum, GCN 40331; Bochenek & Perley, GCN 40333; Corcoran et al., GCN 40334 and Dichiara et al., GCN 40336) was barely detected (S/N =2.1) at the following position:
RA (J2000.0) 13h 46m 05.60s +/-0.23
Decl. (J2000.0) -10° 45' 31.70" +/-0.16
Preliminary photometry was obtained using nearby PanSTARRS stars as follows:
Observation Mid-Time T-T0 (hr) Exposure Filter Mag. Err.
2025-05-02 21:31:19 UT 12.75 140x40s Rc 20.70 +/- 0.15
Magnitude was calibrated with the nearby PanSTARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied.
GCN Circular 40338
Subject
GRB 250502A: KAIT optical observations
Date
2025-05-04T08:20:51Z (25 days ago)
From
Weikang Zheng at UC Berkeley <weikang@berkeley.edu>
Via
email
WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and
Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, observed the field of SVOM GRB 250502A (Wang
et al., GCN 40313) starting at 08:58, May 02 UT, about 12 minutes
after the burst. Observations were performed in 3 x 3 tiling mode,
a set of clear (roughly R) filter images were obtained. We detected
the optical afterglow (Rakotondrainibe et al., GCN 40315; An et al.,
GCN 40319; Li et al., GCN 40320; Gosh et al., GCN 40322; de Ugarte
Postigo et al., GCN 40328; Perez-Fournon et al., GCN 40330; Odeh &
Guessoum, GCN 40331; Bochenek & Perley, GCN 40333; Corcoran et al.,
GCN 40334 and Leonini et al., GCN 40337), which decayed from
17.4 +/- 0.1 mag (Vega) at 963s to 18.7 +/- 0.2 mag at 7.6ks after
the burst.
GCN Circular 40339
Subject
GRB 250502A: Mondy and Tien-Shan Optical Observations
Date
2025-05-04T11:59:20Z (25 days ago)
From
Nicolai Pankov at HSE, IKI RAS <colinsergesen@gmail.com>
Via
Web form
N. Pankov (HSE, IKI), E. Klunko (ISTP), I. Reva (FAI), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN:
We performed follow-up observations of the optical counterpart (Rakotondrainibe et. al, GCN 40315) to GRB 250502A (Wang et al., GCN 40313) using the 1.5-meter AZT-33IK telescope of the Sayan Solar Observatory (Mondy), and the 1-meter Zeiss-1000 telescope of the Tien-Shan Astronomical Observatory (TSHAO). The optical source was observed also by (An et. al, GCN 40319; Li et. al, GCN 40320; Ghosh et. al, GCN 40322; Ugarte Postigo et. al, GCN 40328; Pérez-Fournon et. al, GCN 40330; Odeh et. al, GCN 40331; Bochenek & Perley, GCN 40333; Corcoran et. al, GCN 40334; Leonini et. al, GCN 40337; Zheng et. al, GCN 40338). The redshift z = 2.163 was determined by Ugarte Postigo et. al, GCN 40328. The X-Ray counterpart was detected by XRT (Dichiara et. al, GCN 40336). Our observations began on 02.05.2025 (UT) 15:48 at Mondy Observatory and 2025-05-03 18:25:43 at Tien-Shan Observatory. We detect the optical counterpart in the stacked image in the first observation. The preliminary photometry is as follows:
Date UTstart Exptime t-T0 Filter OT Err UL
(s) (mid, days) (3sigma)
2025-05-02 15:48:58 30*120 0.31425 R 19.74 0.10 22.5
2025-05-03 18:25:43 20*120 1.41617 R n/d n/d 21.0
The photometry is based on nearby USNO-B1.0 stars and has not been corrected for the Galactic extinction.
Reference stars
RA Dec R2
206.5862 -10.7663 14.69
206.4706 -10.7622 16.20
206.5453 -10.7644 17.95
GCN Circular 40340
Subject
GRB 250502A: Swift/UVOT Follow up
Date
2025-05-04T20:03:01Z (25 days ago)
From
Paul Kuin at MSSL <npkuin@gmail.com>
Via
email
Paul Kuin (MSSL/UCL) reports on behalf of the Swift/UVOT team:
The Swift/UVOT began observations of the field of SVOM detected GRB
250502A 72ks after the SVOM ECLAIR trigger (Wang et al., GCN Circ.
40313).
A source consistent with the position reported by Ny Avo
Rakotondraine et al. (GCN Circ. 40315) has been
detected in the initial UVOT exposures.
The detections using the UVOT photometric system (Breeveld et al.
2011, AIP Conf. Proc. 1358, 373) for the early exposures are:
Filter T_start T_stop Exp(s) Mag (Vega)
Wh 78ks 95ks 880 21.5+/- 0.35
u 72ks 106ks 3664 >21.3 (3-sigma UL)
GCN Circular 40349
Subject
GRB 250502A: REM optical/NIR observations
Date
2025-05-05T10:33:25Z (24 days ago)
From
Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>
Via
Web form
R. Brivio, M. Ferro, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team:
We observed the field of GRB 250502A detected by SVOM/ECLAIRs (Wang et al., GCN 40313) 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 May 02 at 22:59:17 UT (i.e. 14.2 hr after the burst), and lasted for about 1 hour.
From preliminary inspection, we do not detect any counterpart at the position of the optical afterglow (Rakotondrainibe et al., GCN. 40315; An et al., GCN 40319; Li et al., GCN 40320; Ghosh et al, GCN 40322; de Ugarte Postigo et al., GCN 40328; Pérez-Fournon et al., GCN 40330; Odeh et al., GCN 40331; Bochenek & Perley, GCN 40333; Corcoran et al., GCN 40334; Leonini et al., GCN 40337; Zheng et al., GCN 40338; Pankov et al., GCN 40339) down to the following 3sigma limits:
r > 19.8 (AB; calibrated against the Pan-STARRS catalogue),
at a mid-time of 14.7 hours after the trigger;
H > 16.0 (Vega; calibrated against the 2MASS catalogue),
at a mid-time of 14.2 hours after the trigger.
GCN Circular 40370
Subject
GRB 250502A: Bassano Bresciano Observatory upper limit
Date
2025-05-06T18:58:00Z (23 days ago)
From
Ulisse Quadri at Bassano Bresciano Observatory <osservatoriobassano@gmail.com>
Via
Web form
U.Quadri, L.Strabla and P.Madurini (Bassano Bresciano Astronomical Observatory)
Members of:
GRB/UAI - Gamma ray Burst section of Unione Astrofili Italiani.
AAVSO - American Association of Variable Star Observers.
GAC - Gruppo Astrofili Cremonesi.
In a large collaboration with:
M.G. Dainotti (National Astronomical Observatory of Japan),
Y. Niino (Tokyo University, Institute of Astronomy),
K. Kalinowski (Aarhus University, Department of Physics and Astronomy),
report:
We imaged the field of GRB 250502A detected by SVOM with the robotic telescope of (IAU station 565) Bassano Bresciano Observatory, Italy.
The observations started 12h 23m after the trigger with our Newton telescope D=250 mm F/D=4.8.
We co-added 2 series of 100 exposures of 30 sec each.
Start T0+ End T0+ V lim.
12h 23m 13h 21m 19.0
13h 22m 14h 25m 19.0
We did not found any optical uncatalogued object within the SVOM error circle.
Our upper limit is consistent with other observations reported by Wang et al. GCN 40313; Rakotondrainibe et al. GCN 40315; An et al. GCN 40319; Li et al. GCN 40320; Ghosh et al. GCN 40322; A. de Ugarte Postigo et al. GCN 40328
Magnitudes were estimated with the pan-STARRS cat and are derived using Lupton (2005) equations.
Not corrected for galactic dust extinction.
Reference:
http://www.osservatoriobassano.altervista.org
The message may be cited.
GCN Circular 40397
Subject
GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
Date
2025-05-08T14:26:33Z (21 days ago)
From
Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, Messina, Italy <giovannicalapai@tiscali.it>
Via
Web form
Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, (Messina) Italy
Member of: GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani.
Report:
we observed the field of GRB 250502A detected by SVOM/ECLAIRs (Wang et al. GCN 40313) with the 11 inches Schmidt-Cassegrain (Celestron 11) telescope F/D=6,3.
The observations were started at 2025-05-02 21:24 UT (approximately 12.62 hours after burst) stacking a set of unfiltered CCD image. The observations were carried out with clear skies
and good visibility conditions.
We detected a very faint object at the following position:
RA (J2000.0) 13h 46m 05.62s
Decl. (J2000.0) -10° 45' 32.3"
Photometry was obtained using nearby PanSTARRS stars as follows:
Observation Mid-Time T-T0 (hr) Exposure Filter Mag. Mag. err.
2025-05-02 23:44:41 UT 14.97 200x60s CR 20.70 +/-0.16
Magnitude was calibrated with the nearby PanSTARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied.
Our observations are consistent with other already reported Rakotondrainibe et al. GCN 40315; An et al. GCN 40319; Li et al. GCN 40320; Ghosh et al. GCN 40322; de Ugarte Postigo et al. GCN 40328; Pérez-Fournon et al. GCN 40330; Odeh et al. GCN 40331; Bochenek & Perley GCN 40333; Corcoran et al. GCN 40334; Leonini et al. GCN 40337; Zheng et al. GCN 40338; Pankov et al. GCN 40339; Brivio et al. GCN 40349; Quadri et al. GCN 40370.
The message may be cited.
GCN Circular 40459
Subject
GRB 250502A: TESS observations
Date
2025-05-14T20:02:36Z (15 days ago)
From
Rahul Jayaraman at MIT <rjayaram@mit.edu>
Via
Web form
R. Jayaraman (MIT), M.M. Fausnaugh (TTU), S. Chastain (TTU), R. Vanderspek (MIT), and G.R. Ricker (MIT) report:
The Transiting Exoplanet Survey Satellite (TESS; Ricker et al., JATIS 1 2015) observed GRB 250502A (Wang et al., GCN 40313) during Sector 91 of its scheduled sky survey.
We performed forced difference-imaging photometry at the location of the confirmed X-ray afterglow (Dichiara et al., GCN 40336) using the full-frame images from the publicly-available TICA data archived at MAST (https://archive.stsci.edu/hlsp/tica). Our data reduction routine is described in Fausnaugh et al. 2023 (ApJ 956(2):108).
The light curve shows a rapidly rising afterglow in the three 200s exposures from after the trigger. The light curve peaks roughly ~700 s after the burst at a magnitude of 16.44 ± 0.14 (uncorrected for Galactic extinction), followed by a decay to the detection limit of 17.6 (3-sigma) over ~4 x 10^3 s. These results are consistent with measurements of the early afterglow from Rakotondrainibe et al. (GCN 40315), Xu et al. (GCN 40319), and Li et al. (GCN 40320).
This circular includes data collected with the TESS mission, obtained from the MAST data archive at the Space Telescope Science Institute (STScI). Funding for the TESS mission is provided by the NASA Explorer Program. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.
GCN Circular 40510
Subject
GRB 250502A: Tautenburg observations
Date
2025-05-21T14:09:26Z (8 days ago)
From
Sylvio Klose at TLS Tautenburg <klose@tls-tautenburg.de>
Via
email
K. Kritik, L. Berthel, T. Ranganathan, J. Kahl, S. Schmidl (all FSU Jena),
M. Hartmann, B. Stecklum, S. Klose (all Tautenburg) report:
We observed the field of GRB 250502A (Wang et. al., GCN 40313) with
the 1.3m Schmidt telescope using the prime focus CCD
camera. Observations started on May 2, 2025, at 22:18:13 UT, about
13.5 hrs after the SVOM trigger, at a mean airmass of 2.2.
The optical transient first reported by Rakotondrainibe et. al. (GCN
40315) was clearly detected. Based on 40 min of exposure, at a midtime
of 22:38 UT, we measure a preliminary r-band magnitude (AB) of 20.88
+/- 0.20 mag, calibrated against Pan-STARRS DR1. We apologize for the
late submission of this circular.