TITLE: GCN CIRCULAR
NUMBER: 42234
SUBJECT: Fermi GRB 251013B: Global MASTER-Net observations report
DATE: 25/10/13 23:31:09 GMT
FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru>
V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko,
G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),
O.Gress, N.Budnev (ISU),
C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A.Sosnovskij (CrAO),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),
D.Buckley (SAAO),
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 251013B ( Fermi GBM team, GCN 42215) errorbox 48818 sec after notice time and 48841 sec after trigger time at 2025-10-13 21:58:28 UT, with upper limit up to 19.4 mag. The observations began at zenith distance = 41 deg. The sun altitude is -49.5 deg.
The galactic latitude b = -52 deg., longitude l = 97 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=3013666
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
48872 | 2025-10-13 21:58:28 | MASTER-SAAO | (23h 34m 30.91s , +04d 40m 04.5s) | C | 60 | 19.4 |
48872 | 2025-10-13 21:58:29 | MASTER-SAAO | (23h 32m 43.17s , +04d 55m 22.1s) | C | 60 | 19.2 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
View this GCN Circular online at https://gcn.nasa.gov/circulars/42234.
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TITLE: GCN CIRCULAR
NUMBER: 42233
SUBJECT: Fermi GRB 251013D: Global MASTER-Net observations report
DATE: 25/10/13 22:31:33 GMT
FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru>
V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko,
G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),
O.Gress, N.Budnev (ISU),
C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A.Sosnovskij (CrAO),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),
D.Buckley (SAAO),
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 251013D ( Fermi GBM team, GCN 42224) errorbox 12470 sec after notice time and 12506 sec after trigger time at 2025-10-13 21:45:26 UT, with upper limit up to 19.2 mag. The observations began at zenith distance = 54 deg. The sun altitude is -48.9 deg.
The galactic latitude b = -41 deg., longitude l = 167 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=3013985
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
12536 | 2025-10-13 21:45:26 | MASTER-SAAO | (02h 43m 45.87s , +12d 29m 46.5s) | C | 60 | 18.9 |
12536 | 2025-10-13 21:45:26 | MASTER-SAAO | (02h 45m 35.22s , +12d 14m 30.3s) | C | 60 | 19.0 |
12729 | 2025-10-13 21:48:39 | MASTER-SAAO | (02h 42m 32.93s , +10d 34m 14.1s) | C | 60 | 19.1 |
12729 | 2025-10-13 21:48:39 | MASTER-SAAO | (02h 44m 21.71s , +10d 18m 58.2s) | C | 60 | 19.2 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
View this GCN Circular online at https://gcn.nasa.gov/circulars/42233.
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TITLE: GCN CIRCULAR
NUMBER: 42232
SUBJECT: GRB 251013C: Swift-XRT counterpart detection
DATE: 25/10/13 22:23:39 GMT
FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk>
P.A. Evans (U. Leicester), J.A. Kennea (PSU), E. Ambrosi (INAF-IASFPA) , A.P.
Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), R. Brivio (INAF-OAB), D.N.
Burrows (PSU), S. Campana (INAF-OAB), M. Capalbi (INAF-OAR), A. D'Ai (INAF-IASFPA),
P. D'Avanzo (INAF-OAB), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), M. Ferro
(INAF-OAB), A. Melandri (INAF-OAR), J.P. Osborne (U. Leicester), K.L. Page (U.
Leicester), M. Perri (SSDC & INAF-OAR), C. Salvaggio (INAF-OAB), T. Sbarrato
(INAF-OAB), B. Sbarufatti (INAF-OAB), M.A. Williams (PSU) report on behalf of the
Swift-XRT team:
Swift-XRT has performed follow-up observations of the SVOM/ECLAIRs-detected source
GRB 251013C (Rakotondrainibe et al., GCN 42222), collecting 1.8 ks of Photon
Counting (PC) mode data between T0+344 s and T0+5.5 ks after the trigger. A bright,
fading counterpart has been found, coincident with the VT optical, fading source
reported by Palmerio et al. (GCN 42223), which has a redshift of 0.572
(Martin-Carrillo et al., GCN 42227). Thus, we can conclude that this is the XRT
counterpart of GRB 251013C. The details of this source are:
Source 1 (SWIFT J230320.5-001235):
==================================
RA (J2000.0): 345.8358 = 23 03 20.59
Dec (J2000.0): -0.2100 = -00 12 36.0
Error: 3.5 (arcsec, radius, 90% confidence).
Detect flag: GOOD
Distance: 3.6 arcmin from the SVOM/ECLAIRs position.
Mean rate: 2.356 +/- 0.081 ct s^-1
Mean flux: (8.71 +/- 0.30)e-11 erg cm^-2 s^-1
Peak rate: 10.2 +/- 1.9 ct s^-1
Peak flux: (3.76 +/- 0.69)e-10 erg cm^-2 s^-1
ECF: 3.70e-11 erg cm^-2 ct^-1
assuming NH=6.48e+20 cm^-2, gamma=1.78
determined from a spectral fit.
XMM UL: 6.3e-13 erg cm^-2 s^-1, (0.3-10 keV)
so the source is 5.4-sigma above this 3-sigma upper limit.
All fluxes are 0.3-10 keV, observed. For all flux conversions and comparisons with
catalogues and upper limits from other missions, we assumed a power-law spectrum
with NH=3x10^20 cm^-2 and photon index (Gamma)=1.7 unless otherwise stated.
The results of the XRT-team automatic analysis of the XRT observations, including a
position-specific upper limit calculator, are available at
https://www.swift.ac.uk/SVOM/SVOM_FIELD00041.
This circular is an official product of the Swift-XRT team.
View this GCN Circular online at https://gcn.nasa.gov/circulars/42232.
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TITLE: GCN CIRCULAR
NUMBER: 42231
SUBJECT: GRB 251013C: GOTO optical afterglow detection
DATE: 25/10/13 22:14:00 GMT
FROM: Ben Gompertz at U of Birmingham <b.gompertz(a)bham.ac.uk>
B. P. Gompertz, B. Godson, D. O'Neill, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, D. Steeghs, D. K. Galloway, V. Dhillon, G. Ramsay, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, and J. Casares report on behalf of the GOTO collaboration:
We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to GRB 251013C (Fermi GBM Team, GCN 42221; Rakotondrainibe et al, GCN 42222). Targeted observations were taken at 2025-10-13 21:40:06 UT (4.1h post trigger). The observations consisted of 4x45s exposures in the GOTO L-band (400-700 nm). Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations.
We detect the optical counterpart (Palmerio et al., GCN 42223; Perez-Garcia et al., GCN 42225; Konno et al., GCN 42226; Martin-Carrillo et al., GCN 42227; Masi, GCN 42228; Palmerio et al., GCN 42229; Moskvitin et al., GCN 42230) with an AB magnitude of L = 17.11 ± 0.02 mag.
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).
View this GCN Circular online at https://gcn.nasa.gov/circulars/42231.
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TITLE: GCN CIRCULAR
NUMBER: 42230
SUBJECT: GRB 251013C: SAO RAS optical observations
DATE: 25/10/13 21:31:40 GMT
FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru>
A. S. Moskvitin, O. I. Spiridonova, V. V. Vlasyuk (SAO RAS),
N. Pankov (HSE, IKI), A. Pozanenko (IKI), A. Ghosh, S. Razzaque
(CAPP, University of Johannesburg), Tao An and Yuanqi Liu
(Shanghai Astronomical Observatory) report on behalf of GRB follow-up
collaboration and IKI-GRB-FuN.
We observed the field of the GRB 251013C (The Fermi GBM team,
GCN 42221; Rakotondrainibe et al., GCN 42222) with the 1-m SAO RAS
telescope Zeiss-1000 equipped with the CCD-photometer.
The observations started on 2025.10.13T19:47:54 UT
(t_mid - T0 = 2.1369 hours).
The OT (Palmerio et al., GCN 42223; Perez-Garcia et al., GCN 42225;
Konno et al., GCN 42226; Martin-Carrillo et al., GCN 42227; Masi,
GCN 42228; Palmerio et al, GCN 42229) is clearly detected
in the individual images with the following brightness.
Date UT start t-T0 Exp. Filter OT Err.
(mid, d) (s)
2025.10.13 19:47:54 0.03631 300 Rc 15.84 +/- 0.01
2025.10.13 20:04:02 0.04033 100 Rc 16.05 +/- 0.01
2025.10.13 20:15:34 0.04353 100 Rc 16.21 +/- 0.01
Preliminary photometry is based on the nearby SDSS objects
(magnitudes converted with Lupton 2005 equations)
and has not corrected for the Galactic extinction.
The observations with the 1-m telescope in BVRI filters
and also with the 0.5-m telescope AS-500/2 are ongoing.
View this GCN Circular online at https://gcn.nasa.gov/circulars/42230.
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TITLE: GCN CIRCULAR
NUMBER: 42229
SUBJECT: GRB 251013C: LCO optical afterglow detection
DATE: 25/10/13 21:13:53 GMT
FROM: SVOM_group <svomgroup(a)bao.ac.cn>
J. T. Palmerio, D. Turpin, A. Saccardi, B. Cordier (CEA/Irfu), L. P. Xin (NAOC), C. Wu (NAOC), report on behalf of the SVOM mission team:
We observed the field of GRB 251013C (SVOM/ECLAIRs and GRM, Rakotondrainibe et al. GCN 42223; Fermi/GBM, Fermi GBM team, GCN 42221) with the LCO 1m telescope at South African Astronomical Observatory equipped with the Sinistro instrument. Our observation started at 2025-10-13T19:27:33.084 about 1.8 hours after the SVOM/ECLAIRs T0 time.
We obtained 3 series of 3x200 s exposures in the SDSS gri filters. The bright optical counterpart detected by SVOM/VT (Palmerio et al. GCN 42223), BOOTES-6 (Perez-Garcia et al., GCN 42225), LAST (Konno et al., GCN 42226), NOT (Martin-Carrillo et al., GCN 42227 and the Visual Telescope Project (Masi et al., GCN 42228) is clearly detected in our first images subtracted to the Pan-STARRS DR2 catalog image. We measure the following magnitude:
g = 16.30 +/- 0.01 (AB), at Tmid-T0 = 2.1 hours
r = 15.99 +/- 0.01 (AB), at Tmid-T0 = 2.0 hours
i = 15.70 +/- 0.01 (AB), at Tmid-T0 =1.8 hours
Further observations are planned and spectroscopic observations are encouraged.
This project is funded by the SVOM collaboration.
View this GCN Circular online at https://gcn.nasa.gov/circulars/42229.
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TITLE: GCN CIRCULAR
NUMBER: 42228
SUBJECT: GRB 251013C: Optical Observations via Virtual Telescope Project, Italy
DATE: 25/10/13 21:07:58 GMT
FROM: Gianluca Masi at Virtual Telescope Project <gianluca(a)bellatrixobservatory.org>
Gianluca Masi, Virtual Telescope Project (Italy), reports:
We attempted to observe the optical counterpart of GRB 251013C (Rakotondrainibe et al., GCN 42222) with the 14” robotic unit available at the Virtual Telescope Project facility in Manciano, Italy, equipped with a KAF-3200E based CCD camera, its QE peaking (90%) in the red part of the spectrum.
We collected three, 120-second unfiltered exposures, then we averaged them. The central time of the resulting stack was 13 Oct., 20:54:57 UTC, that is about 3.25 hours after the burst.
We detected a bright object at the following position (J2000.0):
R.A.: 23 03 20.56
Decl.: -00 13 37.1
mean residuals < 1” on both axes
R= 15.9 (assuming R-mags from Gaia DR2 for the reference stars).
This position is consistent with Palmerio et al. (GCN 42223)and Perez-Garcia et al., GCN 42225.
View this GCN Circular online at https://gcn.nasa.gov/circulars/42228.
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TITLE: GCN CIRCULAR
NUMBER: 42227
SUBJECT: GRB 251013C: NOT spectroscopic redshift z = 0.572
DATE: 25/10/13 21:02:05 GMT
FROM: Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo(a)ucd.ie>
A. Martin-Carrillo (UCD), L. Izzo (INAF/OACN and DARK/NBI), D. B. Malesani (DAWN/NBI and Radboud), G. Corcoran (UCD), B. Schneider (LAM), A. de Ugarte Postigo (LAM), A. Saccardi (CEA/Irfu), B. P. Gompertz (Birmingham), K. Valeckas (NOT and NBI) report on behalf of a larger collaboration:
We observed the optical afterglow (Palmerio et al., GCN 42223; Perez-Garcia et al., GCN 42225; Konno et al., GCN 42226) of GRB 251013C (Rakotondrainibe et al., GCN 42222; Fermi GBM team, GCN 42221) with the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. A spectrum using grism #4 was secured starting on 2025-10-13 at 19:46:24 UT (2.11 hr after the GRB), under good conditions. The exposure time was 2x1200 s and the covered wavelength range is 3500-9600 AA.
In a preliminary reduction of the spectra, we clearly detect a continuum over the whole covered wavelength range. From the detection of multiple absorption features, including Fe II 2600, the Mg II doublet, weak Mg I, and the Ca II doublet, we infer a redshift of z = 0.572.
Photometry of the afterglow was carried out in the ugriz filters. In a 30-s r-band image, we measure r = 16.52 +/- 0.02 AB (at a time of 2.88 hr after the GRB), calibrated against the Pan-STARRS catalog, and not corrected for Galactic extinction.
View this GCN Circular online at https://gcn.nasa.gov/circulars/42227.
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TITLE: GCN CIRCULAR
NUMBER: 42226
SUBJECT: GRB 251013C: LAST detection of optical counterpart
DATE: 25/10/13 20:58:35 GMT
FROM: Ruslan Konno at Weizmann Institute of Science <ruslankonno(a)gmail.com>
R. Konno (WIS), S. Garrappa (WIS), E. A. Zimmerman (WIS), A. Horowicz (WIS), E. O. Ofek (WIS), S. Ben-Ami (WIS), D. Polishook (WIS), O. Yaron (WIS), S. Fainer (WIS), A. Krassilchtchikov (WIS), Y. M. Shani (WIS), E. Segre (WIS), A. Gal-Yam (WIS), and S. Spitzer (WIS) report on behalf of the LAST Collaboration.
We report observations of GRB 251013C, detected by SVOM (Rakotondrainibe et al., GCN 42222) and Fermi (Fermi GBM Team, GCN 42221). Observations were conducted with the Large Array Survey Telescope (LAST; Ofek et al. 2023, PASP 135, 5001; Ben-Ami et al. 2023, PASP 135, 5002).
We observed the field of GRB 251013C using four parallel telescopes (each with a 7.4 deg^2 FoV) in clear band (similar to the Gaia Bp band) over several epochs. Each coadd consists of 20x20 s exposures, yielding a limiting magnitude of about 20.5 AB mag.
We clearly detect the optical counterpart reported by Palmerio et al. (GCN 42223) and Perez-Garcia et al. (GCN 42225). The earliest detection (20x20 s coadd) is confirmed at 2025-10-13 18:10:27 UTC (T − T0 = 0.51 h) with AB mag 16.14 +/- 0.02. Preliminary automated photometry shows a rise to 15.20 +/- 0.01 mag at 18:32:15 UTC (T − T0 = 0.87 h), followed by a power-law decay. The source remains detectable.
We encourage continued multi-wavelength follow-up of this bright optical counterpart.
LAST is a survey telescope array of the Weizmann Astrophysical Observatory (https://www.weizmann.ac.il/wao/).
View this GCN Circular online at https://gcn.nasa.gov/circulars/42226.
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TITLE: GCN CIRCULAR
NUMBER: 42225
SUBJECT: GRB 251013C: BOOTES-6 early optical detection
DATE: 25/10/13 19:07:16 GMT
FROM: I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg(a)iaa.es>
I. Perez-Garcia, S.-Y. Wu, E. Fernandez-Garcia, M.D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy and A. J. Castro-Tirado (IAA-CSIC, Granada), P. J. Meintjes and H. J. van Heerden (UFS, South Africa), A. Martin-Carrillo and L. Hanlon (UCD, Ireland), M. Gritsevich (Univ. of Helsinki) and C. J. Perez del Pulgar (UMA, Malaga), on behalf of a larger collaboration, report:
Following the detection of GRB 251013C by SVOM (Rakotondrainibe et al., GCN 42222), the BOOTES-6/DPRT 0.6m robotic telescope at Boyden Observatory in Maselspoort (South Africa) responded to this high-energy event starting on Oct 13, 17:42:32 UT (i.e., 170 sec after detection). Series of images in clear filter were gathered and we detect an optical source consistent with the one reported by Palmerio et al. (GCN 42223). Using GaiaDR3 Gmag as reference we report our photometry analysis:
| UT mid exposure | mag | error | filter | exposure time (sec) |
| ------------------- | ----- | ----- | ------ | ------------------- |
| 2025-10-13 17:43:02 | 14.42 | 0.02 | clear | 60 |
| 2025-10-13 17:44:31 | 14.82 | 0.02 | clear | 60 |
| 2025-10-13 17:50:23 | 14.79 | 0.03 | clear | 60 |
| 2025-10-13 17:51:52 | 15.03 | 0.02 | clear | 60 |
| 2025-10-13 17:57:44 | 15.77 | 0.03 | clear | 60 |
| 2025-10-13 17:59:13 | 15.79 | 0.03 | clear | 60 |
| 2025-10-13 18:05:04 | 16.07 | 0.03 | clear | 60 |
Further analysis of the additional images is ongoing.
We thank the staff at Boyden Observatory for their excellent support.
View this GCN Circular online at https://gcn.nasa.gov/circulars/42225.
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