EP250205a, GRB 250205A
GCN Circular 39154
Subject
GRB 250205A: SVOM detection of a burst
Date
2025-02-05T22:18:47Z (5 months ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
A. Saccardi, T. Sadibekova, N. Dagoneau, H. Goto, S. Schanne (CEA), Ch. Van Hove (IJCLab)
report on behalf of the SVOM mission team:
The SVOM/ECLAIRs telescope triggered and located the long duration GRB
250205A (sb25020504) starting at 2025-02-05T21:24:38 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 both the on-board Count-Rate Trigger (CRT) and
Image Trigger (IMT) and 8 alerts were received. The best detection is
obtained by IMT with a signal-to-noise ratio of 19.3 in the 8-120 keV energy
band over a time window of 40.96 s starting at Tb.
The localization of the best Alert is RA, Dec = 113.459, 32.365 (J2000).
The uncertainty on this position is 4.5 arcminutes at 90% C.L. which
includes 2 arcminutes of systematic uncertainty in quadrature.
SVOM performed an automatic slew on this burst.
MXT began observing the field at 2025-02-05T21:34:32, 593 seconds after the SVOM trigger.
Using onboard processed data we found an uncatalogued X-ray source located in J2000 at RA, Dec 113.534, 32.370 degrees
RA (J2000) = 7h34m08s
Dec (J2000) = 32d22m14s
with an uncertainty radius at 90% C.L. of 80 arcseconds.
This location is 3.8 arcminutes from the ECLAIRs onboard position. This position may be improved as more data is received.
VT began observing the field at 2025-02-05T21:41:52, 1033 seconds after the SVOM trigger. 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 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 Advocates (BAs) on shift for this burst are Andrea Saccardi, Tatyana Sadibekova (andrea.saccardi@cea.fr). Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst.
GCN Circular 39156
Subject
GRB 250205A: Liverpool Telescope optical counterpart candidate detection
Date
2025-02-05T22:53:06Z (5 months ago)
From
Ben Gompertz at U of Birmingham <b.gompertz@bham.ac.uk>
Via
email
B. P. Gompertz (U. Birmingham), D. B. Malesani (DAWN/NBI and Radboud) and A. J. Levan (Radboud) report on behalf of a larger collaboration:
We initiated follow-up observations of GRB 250205A (Saccardi et al., GCN 39154) with the IO:O camera on the 2m robotic Liverpool Telescope (LT). Observations began at 21:56:04, 32 minutes after the ECLAIRS trigger, and consisted of 5x120 s exposures in the SDSS r filter.
A new optical source, not present in archival PS1 imaging, is detected at RA = 07:34:02.64, Dec +32:22:18.79 (J2000). In a preliminary analysis, we measure an AB magnitude of r = 20.91 +/- 0.06, calibrated against nearby Pan-STARRS stars and not corrected for galactic extinction. Follow-up observations to assess the evolution of the candidate are encouraged.
GCN Circular 39157
Subject
GRB 250205A: OHP/T193 optical counterpart candidate
Date
2025-02-05T23:18:19Z (5 months ago)
From
Benjamin Schneider at MIT <bschn@mit.edu>
Via
Web form
B. Schneider (LAM) and C. Adami (LAM/Pytheas/AMU)
We observed the field of the GRB 250205A (Saccardi et al., GCN 39154) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. We obtained three exposures (300 s + 2x500 s) in the r-band starting at 22:06:27UT on 2025-02-05 (42 min after the trigger). In the stacked image, we clearly detected a new source not visible in the Legacy Survey and consistent with the MXT error at:
RA(J200) = 7:34:02.62
DEC(J200) = +32:22:18.98
with an uncertainty of 0.5 arcsec.
The preliminary magnitude derived for that source is
r = 21.01 +/- 0.07 mag (AB)
The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the magnitude is not corrected for Galactic extinction.
This source is consistent with the one reported by Gompertz et al. GCN 39156.
Further observations are ongoing.
We acknowledge the excellent support from Observatoire de Haute-Provence and in particular Jean-Pierre Troncin for the MISTRAL observations.
GCN Circular 39158
Subject
GRB 250205A: GOTO optical upper limits
Date
2025-02-05T23:30:43Z (5 months ago)
From
Ben Gompertz at U of Birmingham <b.gompertz@bham.ac.uk>
Via
email
B. P. Gompertz, S. Belkin, D. O'Neill, G. Ramsay, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, F. Jimenez-Ibarra, A. Kumar, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, E. Pall'e and D. Pollacco report on behalf of the GOTO collaboration:
We report on observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to GRB 250205A, detected by EP and SVOM (Saccardi et al., GCN 39154). Targeted observations were performed by GOTO-North (La Palma) at 21:43:59 on 2025-02-05 (19 minutes after the ECLAIRs trigger time). The observation consisted of 4x90s exposures in the GOTO L-band (400-700 nm).
Images were processed immediately after acquisition using the GOTO pipeline. The optical counterpart reported by Gompertz et al. (GCN 39156) and Schneider et al. (GCN 39157) is not detected to a 3-sigma limiting AB magnitude of L > 19.7 mags.
Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction.
GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC).
GCN Circular 39159
Subject
GRB250205A: SVOM/VT optical afterglow detection
Date
2025-02-05T23:50:19Z (5 months ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
GRB 250205A: SVOM/VT optical counterpart confirmation
J. T. Palmerio (CEA), S. Vergani (Obs.Paris), L.P. Xin, Y. L. Qiu (NAOC), A. Saccardi (CEA), H.L. Li., C. Wu, Z.H. Yao, Y.N. Ma, X.H. Han, H.B. Cai, J.Y. Wei (NAOC), report on behalf of the SVOM team:
After the trigger by SVOM/ECLAIRs at 2025-02-05T21:24:38 UTC (Tb), SVOM performed an automatic slew on the burst. The VT observing time reported in (Saccardi et al. GCN 39154) is incorrect, rather SVOM/VT began observing the field at 2025-02-05T21:32:08, 449 seconds after the SVOM trigger, in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
An uncatalogued source was detected within the error box of SVOM/MXT (Saccardi et al. GCN 39154) using the VT VHF pipeline at ra=113.51107, dec=32.37187 (J2000), corresponding to:
RA (J2000) = 07h34m02.7s
Dec (J2000) = +32d22m18.7s
with an uncertainty of 1 arcsec.
consistent with the optical afterglow reported by Gompertz et al. (GCN 39156) and Schneider et al. (GCN 39157).
The source was detected in both VT_R and VT_B, though the presence of light bloom from a bright source in the image prevents the determination of the VT_R magnitude from the VHF pipeline. The source was fading between the first 2 VT observing sequences, the magnitudes are given below:
mag(AB) VT_B | mag err | mid-observing time since trigger (minutes)
20.91 | 0.06 | 8.75
21.18 | 0.05 | 12.5
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 39160
Subject
GRB 250205A: Redshift from OSIRIS+/GTC z = 3.55
Date
2025-02-06T00:28:38Z (5 months ago)
From
Antonio de Ugarte Postigo at LAM/OCA, CNRS <deugarte@oca.eu>
Via
email
A. de Ugarte Postigo (LAM), D. B. Malesani (DAWN/NBI and Radboud Univ.), 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), A. M. Garcia Rodriguez (GTC), D. González González (GTC) report,
We have observed the counterpart of GRB 250205A (Saccardi et al. GCN 39154, also detected by EP as trigger id 01709131283), also discovered in parallel by Gompertz et al. (GCN 39156) and Schneider et al. (GCN 39157) and detected by SVOM/VT (Palmerio et al. GCN 39159), with OSIRIS+ on the 10.4 m GTC, located at the Roque de los Muchachos Observatory in the island of La Palma (Spain). Our observation consisted of a 30 s acquisition in r-band followed by 4x900s of spectroscopy using grism R1000B, which covers the spectral range between 3600 and 7800 AA.
The optical counterpart is well detected in the acquisition obtained at 23:10:36 UT (mean epoch 1.7661 hrs after the burst) with an r-band AB magnitude of 21.78 +/- 0.06 mag, as compared with 4 field stars from the Sloan catalogue.
The spectra show a faint trace with clear absorption features. In a preliminary reduction, we identify features of Ly-alpha, SII, SiII, SiII*, OI, CII, SiIV, CIV, FeII, FeII* at a common redshift of 3.55, which we identify as the redshift of the GRB. Further analysis is ongoing.
GCN Circular 39161
Subject
GRB 250205A: Swift/XRT detection
Date
2025-02-06T00:52:30Z (5 months ago)
From
Jamie Kennea at Penn State <jak51@psu.edu>
Via
Web form
J. A. Kennea (PSU), B. Sbarufatti (INAF-OAB) and P. A. Evans (Leicester) report on behalf of the Swift/XRT team:
At 22:38:21UT Swift began a target of opportunity observation of GRB 250205A (GCN #39154), approximately 74 minutes after the trigger. We detect a bright previously uncatalogued X-ray source at the following coordinates: RA/Dec(J2000) = 113.51144, 32.37196, which is equivalent to:
RA (J2000): 07h 34m 02.75s,
Dec (J2000): +32d 22' 19.1",
with an estimated error of 3.8 arc-seconds radius (90% confidence). This position lies 69 arc-seconds from the SVOM/MXT position reported in GCN #39154, and 1.7 arc-seconds from the SVOM.VT optical counterpart (GCN #39159). The mean flux during the 1.4 ks XRT observation was 4.9 (±0.4) x 10^-12 erg cm^-2 s^-1 (0.3-10 keV).
Further observations of GRB 250205A with Swift are planned.
GCN Circular 39162
Subject
GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
Date
2025-02-06T05:06:58Z (5 months ago)
From
Alan Watson at UNAM <alan@astro.unam.mx>
Via
email
Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee
(UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Sarah Antier (OCA),
Jean-Luc Atteia (IRAP), Rosa L. Becerra (Università degli Studi di
Roma Tor Vergata), Nathaniel R. Butler (ASU), Damien Dornic (CPPM),
Francis Fortin (IRAP), Jean-Grégoire Ducoin (CPPM), Francesco Magnani
(CPPM), Margarita Pereyra (UNAM), and Benjamin Schneider (LAM) report:
We imaged the field of the SVOM/ECLAIRs GRB 250205A (Saccardi et al.,
GCN Circ. 39154) with the DDRAGO wide-field camera on the COLIBRÍ
(SVOM/F-GFT) telescope at the Observatorio Astronómico Nacional on the
Sierra de San Pedro Mártir in Mexico.
We observed from 2025-02-06 03:01 to 04:48 UTC, with a midpoint of
6.34 hours after the event, and obtained 3840 seconds of exposure in
the r filter in good weather conditions. The data were reduced and
stacked using custom software and then calibrated against the PS1
catalog and analysed using STDPipe (Karpov 2021).
We detect the afterglow (Gompertz et al., GCN Circ. 39156, and
Schneider & Adami, GCN Circ. 39157) with
r = 22.89 +/- 0.11
This magnitude is not corrected for Galactic extinction.
Our measurement is significantly fainter than the earlier r magnitudes
reported by Gompertz et al. (GCN Circ. 39156), Schneider & Adami (GCN
Circ. 39157), Palmerio et al. (GCN Circ. 39159), and de Ugarte Postigo
et al. (GCN Circ. 39160), confirming that this is the afterglow.
Compared to the magnitude reported by de Ugarte Postigo et al., our
measurement implies a temporal index of -0.80 +/- 0.08 between 1.76
and 6.34 hours.
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 39165
Subject
EP250205a/GRB 250205A: Einstein Probe observation
Date
2025-02-06T09:14:37Z (5 months ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
Z. Y. Liu (USTC), M. H. Zhang, M. J. Liu, H. N. Yang, W. Yuan (NAO, CAS) report on behalf of the Einstein Probe team
We report on the detection of an X-ray transient, designated EP250205a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, which triggered the on-board processing unit at 2025-02-05 21:32:08 (UTC) (trigger ID: 01709131283). The source position is R.A. = 113.522 deg, DEC = 32.363 deg (J2000) with an uncertainty of about 2.5 arcmin (radius, 90% C.L. statistical and systematic). An autonomous follow-up observation of EP250205a was performed by the Follow-up X-ray Telescope (FXT) on board EP, 256s after the WXT trigger. An uncatalogued X-ray source was detected at R.A. = 113.509 deg, DEC = 32.373 deg (J2000) with an uncertainty of less than 10 arcsec (radius, 90% C.L. statistical and systematic), consistent with the WXT position of EP250205a.
The 0.5-4.0 keV WXT spectrum can be fitted with an absorbed power law with a fixed Galactic absorption with column density 4.4 x 10^20 cm^-2 and an intrinsic absorber with a redshift of 3.55. The fitted equivalent hydrogen column density of the intrinsic absorber is 6.5(+9.8/-6.5) x 10^22 cm^-2, the photon index 2.5(+1.7/-1.2), and the unabsorbed 0.5-4 keV flux 4.2 (+1.1/-1.1) x 10^-10 erg/s/cm^2.
The average 0.5-10 keV spectrum of the follow-up observation obtained by EP-FXT can be fitted with an absorbed power law with a photon index of 2.82 (+0.06/-0.04) (with a galactic column density fixed at 4.4 x 10^20 cm^-2), yielding an average unabsorbed 0.5-10 keV flux of 3.65 (+0.07/-0.09) x 10^-11 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters.
EP250205a is spatially and temporally consistent with GRB 250205A (Saccardi et al. GCN 39154) at a redshift of 3.55 (de Ugarte Postigo et al. GCN 39160). EP250205a was first detected by WXT at 2025-02-05T21:31:28 (UTC), about 410 seconds after the SVOM/ECLAIRs trigger time (2025-02-05T21:24:38), due to Earth obscuration of the WXT FoV from 2025-02-05T20:26:42 to 2025-02-05T21:31:28.
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). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES.
GCN Circular 39166
Subject
EP250205a/GRB 250205A: correction to the source localization
Date
2025-02-06T10:07:31Z (5 months ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
Z. Y. Liu (USTC), M. H. Zhang, M. J. Liu, H. N. Yang, W. Yuan (NAO, CAS) report on behalf of the Einstein Probe team
The EP-FXT observation source localization given in GCN 39165 is incorrect. The correct source localization should be R.A. = 113.5107, DEC = 32.3718 (J2000). We apologize for the mistake.
GCN Circular 39168
Subject
GRB 250205A: Swift/UVOT Upper Limits
Date
2025-02-06T12:21:23Z (5 months ago)
From
Alice Breeveld at MSSL-UCL <a.breeveld@ucl.ac.uk>
Via
email
A. A. Breeveld (UCL-MSSL) and R. Brivio (INAF-OAB) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of SVOM/ECLAIRs detected burst GRB 250205A 4593 s after the trigger (Saccardi et al., GCN Circ. 39154).
The afterglow reported by Gompertz et al., GCN Circ. 39156, Schneider & Adami, GCN Circ. 39157, Palmerio et al., GCN Circ. 39159, de Ugarte Postigo et al., GCN Circ. 39160, Kennea et al., GCN Circ. 39161 and Watson et al., GCN Circ. 39162, is not detected in the single U-band exposure.
Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposure is:
Filter T_start(s) T_stop(s) Exp(s) Mag
u 4593 6243 1625 >20.9
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.046 in the direction of the burst (Schlegel et al. 1998).
GCN Circular 39169
Subject
EP250205a/GRB 250205A: FTW optical and NIR observations of the counterpart
Date
2025-02-06T13:31:09Z (5 months ago)
From
Malte Busmann at Ludwig-Maximilians-Universität München <m.busmann@physik.lmu.de>
Via
Web form
Malte Busmann (LMU), Daniel Gruen (LMU), Brendan O’Connor (Carnegie Mellon U.) and Antonella Palmese (Carnegie Mellon U.) report:
We observed the counterpart of EP250205a/GRB 250205A (Saccardi et al., GCN 39154; Gompertz et al., GCN 39156; Schneider and Adami, GCN 39157; Gompertz et al., GCN 39158; Palmerio et al., GCN 39159; de Ugarte Postigo et al., GCN 39160; Kennea et al., GCN 39161; Watson et al., GCN 39162; Liu et al., GCN 39165; Breeveld et al., GCN 39168) with the Three Channel Imager (3KK) at the Fraunhofer Telescope Wendelstein (FTW) in the r, i and J band simultaneously for 40 x 180 s starting at 2025-02-05T23:04:26 UT (1.66 hours after the trigger). We detect the counterpart in the single exposures. In the first exposure at
r = (21.95 +/- 0.17) mag
i = (21.26 +/- 0.13) mag
J = (20.25 +/- 0.16) mag.
The r- and i-band manitudes are calibrated against the PS1 catalog and the J-band is calibrated with the 2MASS Catalog. All magnitudes are provided in the AB system and are not corrected for Galactic extinction.
We thank Christoph Ries from the Wendelstein Observatory for obtaining these observations.
GCN Circular 39170
Subject
GRB 250205A: REM NIR upper limit
Date
2025-02-06T13:36:20Z (5 months ago)
From
Matteo Ferro at INAF-OAB <matteo.ferro@inaf.it>
Via
Web form
M. Ferro, R. Brivio, P. D’Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team:
We observed the field of GRB 250205A detected by SVOM (Saccardi et al., GCN 39154) and Einstein Probe (Liu et al., GCN 39165) with the REM 60cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the J, H, K bands, starting on 2025 February 06 at 00:34:51 UT (i.e. 3.17 hours after the trigger), and lasting for about 1 hour.
From preliminary photometry we do not detect any NIR counterpart consistent with the candidate optical/NIR afterglow (Gompertz et al., GCN 39156; Schneider et al., GCN 39157; Palmerio et al., GCN 39159; de Ugarte Postigo et al., GCN 39160; Watson et al., GCN 39162; Busmann et al., GCN 39169), down to the following 3sigma magnitude upper limit:
H > 16.5 (Vega; calibrated against the 2MASS catalogue)
at a mid-time of t - t0 = 3.6 hr after the trigger.
GCN Circular 39171
Subject
GRB 250205A: Fermi GBM Observation
Date
2025-02-06T15:42:40Z (5 months ago)
From
oindabimukherjee@gmail.com
Via
Web form
O. Mukherjee (USRA) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:
"At 21:25:33.72 UT on 05 February 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250205A (trigger 760483538/250205893).
which was also detected by SVOM (Saccardi et al. 2025, GCN 39154), Swift XRT (Kennea et al. 2025, GCN 39161),
and OSIRIS+/GTC with z = 3.55 (Postigo et al. 2025, GCN 39160).
The Fermi GBM on-ground location is consistent with the SVOM position.
The angle from the Fermi LAT boresight is 59 degrees.
The GBM light curve consists of multiple peaks with a duration (T90)
of about 105 s (50-300 keV). The time-averaged spectrum
from T0-63 to T0+75 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -0.2 +/- 0.1 and the cutoff energy,
parameterized as Epeak, is 83 +/- 3 keV. A Band function
with Epeak = 80 +/- 5 keV,
alpha = -0.2 +/- 0.16 and beta = -3.11 +/- 0.39 fits the spectrum equally well.
The event fluence (10-1000 keV) in this time interval is
(6.6 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+0.38 s in the 10-1000 keV band is 2 +/- 0.2 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/"
GCN Circular 39240
Subject
GRB 250205A: 1.3m DFOT optical upper limit
Date
2025-02-08T17:27:46Z (4 months ago)
From
ANSHIKA GUPTA at ARIES <anshika05180@gmail.com>
Via
Web form
Anshika Gupta, Amit K. Ror, Kuntal Misra and Shashi B. Pandey (ARIES) report:
We observed the field of GRB 250205A detected by SVOM/ECLAIRs (Saccardi et al. 2025, GCN 39154) 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 2025-02-06 at 17:00:56 UT, i.e., ~ 0.81 days after the SVOM 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 could not detect the optical emission in our stacked image within the error box of SVOM telescope (Palmerio et al. 2025, GCN 39159) and Swift-XRT (Kennea et al. 2025, GCN 39161). We obtain the following 3-sigma upper limit in the stacked image:
Date Start_UT T_start-T0 (days) Filter Exp time (s) Magnitude
============================================================
2025-02-06 17:00:56 ~0.81 R 300s*12 > 22.0
The non-detection of the burst is consistent with the GCN reported by Gompertz et al. GCN 39156, 39158; Schneider et al. GCN 39157; Palmerio et al. GCN 39159; de Ugarte Postigo et al. GCN 39160; Watson et al. GCN 39162; Breeveld et al. GCN 39168; Busmann et al. GCN 39169; Ferro et al. GCN 39170.
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 catalogue. This circular may be cited.
GCN Circular 39289
Subject
GRB 250205A / EP250205A: radio detection with the VLA
Date
2025-02-11T16:51:06Z (4 months ago)
From
Stefano Giarratana at INAF-OAB <s.giarratana@ira.inaf.it>
Via
email
S. Giarratana (INAF-OAB), M. Giroletti (INAF-IRA),
G. Ghirlanda (INAF-OAB), N. Di Lalla (Stanford Univ.),
N. Omodei (Stanford Univ.), O. S. Salafia (INAF-OAB)
At 08:59:34 UT on 2025 Feb 7 (T_mid = 1.51 days post-burst)
the Karl G. Jansky VLA observed the field of GRB 250205A /
EP250205A (Saccardi et al., GCN 39154; Mukherjee et al., GCN 39171)
in three bands, with central frequencies of 6, 10 and 15 GHz.
The standard 3C286 was used as bandpass and flux density
calibrator, while J0741+3112 was used as phase calibrator.
From a preliminary analysis, an unresolved radio source
is detected at a position (J2000):
RA: 07:34:02.649 +- 0.003
Dec: 32:22:18.84 +- 0.05
consistent with the X-ray (Kennea et al., GCN39161;
Liu et al., GCN 39165) and optical (Gompertz et al., GCN 39156;
Palmerio et al., GCN 39159; de Ugarte Postigo et al., GCN 39160;
Watson et al., GCN 39162; Busmann et al., GCN 39169) position
of the transient.
The preliminary analysis yields the following results:
================================================================
T_mid Freq Peak r.m.s. Beam PA
[days] [GHz] [uJy/b] [uJy/b] [arcsec^2] [deg]
================================================================
1.51 6 27 7 0.49x0.32 66
1.51 10 44 8 0.32x0.19 65
1.51 15 40 7 0.19x0.13 66
================================================================
No source is detected with a >3sigma confidence at the
aforementioned position in previous radio surveys (NVSS, FIRST,
VLASS), all of which have r.m.s. noise levels above
100 uJy/b.
We would like to thank the staff of the VLA for approving, executing,
and processing the observations.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc.
These observations were carried out as part of project SF171028,
approved in the framework of the Fermi - NRAO joint program agreement.
GCN Circular 39302
Subject
GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
Date
2025-02-12T17:38:07Z (4 months 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 imaged the field of GRB 250205A detected by SVOM/ECLAIRs telescope (Saccardi et al. GCN 39154),
with the 11 inches Schmidt-Cassegrain (Celestron 11) telescope F/D=6,3.
The observations were started at 2025-02-05 23:12 UT (approximately 1.79 hours after burst) stacking a set of unfiltered CCD image. The observations were carried out with clear skies and good visibility conditions.
We co-added 183 exposures of 60 sec each.
Start T0+ End T0+ CR lim
1.79 hour 5.88 hour 20.2
We did not found any optical counterpart in the error box of the XRTcandidate.
Kennea et al. GCN 39161
Magnitudes were estimated with the PanSTARRS cat. and
are not corrected for galactic dust extinction.
Our observations are consistent with other already reported Gompertz et al. (GCN 39156), Schneider et al. (GCN 39157), Gompertz et al. (GCN 39158), Palmerio et al. (GCN 39159), A. de Ugarte Postigo et al. (GCN 39160), Watson et al. (GCN 39162), Breeveld et al. (GCN 39168), Busmann et al. (GCN 39169), Ferro et al. (GCN 39170).
The message may be cited.
GCN Circular 39314
Subject
GRB 250205A: Leavitt Observatory optical upper limit
Date
2025-02-13T21:56:42Z (4 months ago)
From
leavittob@gmail.com
Via
Web form
E. Pavoni and L. Moretti (Leavitt Observatory, Manciano, Italy)
Members of:
GRB/UAI - Gamma Ray Burst Section of Unione Astrofili Italiani
ATA - Associazione Tuscolana di Astronomia
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 observed the field of GRB 250205A (Saccardi et al. GCN 39154) with our RC telescope (D=250 mm, F/D=8) of Leavitt Observatory, Manciano, Italy.
The observations started approximately 43 minutes after the SVOM/ECLAIRs trigger time, with good weather conditions, and consisted of 8 individual frames of 240sec each in the R (Cousins) band.
Images were processed using the astropy package (Astropy Collaboration et al., 2022ApJ...935..167A).
In the stacked frame, we did not found any optical uncatalogued object within the SVOM error circle.
Mid Time (UTC) Limit (R filter) Err.
2025-02-05T22:28:28 >19.1 0.1
The non-detection of the burst is consistent with detection and upper limits already reported (Gompertz et al. GCN 39156; Schneider et al., GCN 39157; Gompertz et al., GCN 39158; Palmerio et al., GCN 39159; A. de Ugarte Postigo et al., GCN 39160; Watson et al., GCN 39162; Breeveld et al., GCN 39168; Busmann et al., GCN 39169; Ferro et al., GCN 39170; Gupta et al., GCN 39240; Calapai et al., GCN 39302).
Magnitude was calibrated with the nearby Pan-STARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied.
The message may be cited.
Reference:
https://leavittobservatory.altervista.org
GCN Circular 39315
Subject
GRB 250205A: VIRT Optical Upper Limit
Date
2025-02-13T22:07:44Z (4 months ago)
From
Priya Gokuldass at ERAU <gokuldap@my.erau.edu>
Via
Web form
K. Smith (UVI), P. Gokuldass (ERAU), N. Orange (OrangeWave Innovative Science, LLC), B. Gendre (UVI), D. Morris (NASA), T. Lombardi (Eckerd College), F. George (ERAU), D. Smith (UVI), and C. Watson (UVI) report:
We observed the field of GRB250205A (Saccardi et al., GCN 39154) with the 0.5m Virgin Islands Robotic Telescope (VIRT) at the University of the Virgin Islands' Etelman Observatory on 2025-02-06 starting at 1:04:43 (T-mid ~ T0 + 4.66 hrs). We performed a series of exposures in an R filter with a total exposure of 3560s. The weather conditions were partly cloudy during the hours of observation with an average airmass of 1.06.
We do not detect any source within the XRT position (Kennea et al. GCN 39161). This non-detection is consistent with reported detections (Palmerio et al., GCN 39159; Gompertz et al., GCN 39156; Schneider et al., GCN 39157; Busmann et al., GCN 39169; and de Ugarte Postigo et al., GCN 39160 ), detection of afterglow (Watson et al., GCN 39169) and upper limits (Gompertz et al., GCN 39158; Breeveld et al., GCN 39168; Ferro et al., GCN 39170; and Gupta et al., GCN 39240 ). We report the following 3-sigma upper limit:
T_mid ||Exposure ||Filter ||Limit
T+ 4.66 hrs || 3560 s || R || > 21.14
The limit is estimated from comparison to nearby USNO B1 stars and is not corrected for Galactic extinction.
We acknowledge financial support from NASA EPSCoR award 80NNSC22M0063, NSF PAARE award 2319415, and NASA EPSCoR award 80NSSC24M0112. This message can be cited.
GCN Circular 39520
Subject
GRB 250205A / EP250205A: further radio observations with the VLA
Date
2025-02-27T15:43:06Z (4 months ago)
From
Stefano Giarratana at INAF-OAB <s.giarratana@ira.inaf.it>
Via
email
S. Giarratana (INAF-OAB), M. Giroletti (INAF-IRA),
G. Ghirlanda (INAF-OAB), N. Di Lalla (Stanford Univ.),
N. Omodei (Stanford Univ.), O. S. Salafia (INAF-OAB)
At 06:32:26 UT on 2025 Feb 8 (T_mid = 2.41 days post-burst) and
at 05:58:32 UT on 2025 Feb 13 (T_mid = 7.39 days post-burst)
the Karl G. Jansky VLA observed the field of GRB 250205A /
EP250205A (Saccardi et al., GCN 39154; Mukherjee et al., GCN 39171)
in three bands, with central frequencies of 6, 10 and 15 GHz.
The standard 3C286 was used as bandpass and flux density
calibrator, while J0741+3112 was used as phase calibrator.
The preliminary analysis yields the following results:
================================================================
T_mid Freq Peak U.L. r.m.s. Beam PA
[days] [GHz] [uJy/b] [uJy] [uJy/b] [arcsec^2] [deg]
================================================================
2.41 6 - 21 7 0.34x0.31 47
2.41 10 38 - 8 0.23x0.20 49
2.41 15 - 21 7 0.14x0.12 34
7.39 6 - 24 8 0.38x0.31 65
7.39 10 - 21 7 1.47x0.16 68
7.39 15 - 24 8 0.16x0.12 54
================================================================
where U.L. are the upper limits (3 sigma) for the non-detections.
We would like to thank the staff of the VLA for approving, executing,
and processing the observations.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc.
These observations were carried out as part of project SF171028,
approved in the framework of the Fermi - NRAO joint program agreement.