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GRB 241025A, EP241025a

GCN Circular 38298

Subject
GRB 241025A: VIRT Optical Upper Limit
Date
2024-11-22T16:34:38Z (2 years ago)
From
Priya Gokuldass at ERAU <gokuldap@my.erau.edu>
Via
Web form
R. Querrard (UVI), P. Gokuldass (ERAU), N. Orange (OrangeWave Innovative Science, LLC), D. Morris (NASA), T. Lombardi (Eckerd College), F. George (ERAU), K. Noonan (UVI), D. Smith (UVI), K. Smith (UVI), C. Watson (UVI) report:

We observed the field of GRB241025A detected by Swift (Ambrosi et al., GCN 37859), Fermi (Fermi GBM team, GCN 37860), SVOM (SVOM/GRM team, GCN 37863), and EP (Li et al., GCN 37864) with the 0.5m Virgin Island Robotic Telescope (VIRT) at the University of the Virgin Islands' Etelman Observatory on 2024-10-25 starting at 22:37:31 (T-mid ~T0+21.8 hrs). We performed a series of exposures in an R filter with a total exposure of 2800s. The weather conditions were partly cloudy during the hours of observation with an average airmass of 2.4. 

We do not detect any source within the enhanced XRT position (Goad et al. GCN 37868). This non-detection is consistent with detections  (Jiang et al. GCN 37862; Pereyra et al. GCN 37865; Xu et al. GCN 37866; Qiu et al. GCN 37871; Lipunov et al. GCN 37873; Qiu et al. GCN 37871; Abdi et al. GCN 37882; Alan et al. GCN 37889; Mohan et al. GCN 37890; Vinko et al. GCN 37891; Gupta et al. GCN 37893; Pankov et al. GCN 37912; Moskvitin  et al. GCN 37914; Klingler et al. GCN 37919; Moskvitin  et al. GCN 37923; Wang et al. GCN 37926; and Rossi et al. GCN 38114) and upper limits  (Lipunov et al. GCN 37873) reported by others. We report the following 3-sigma upper limit:


T_mid                ||Exposure   ||Filter   ||Limit 
T+ 21.8 hrs          || 2800 s    || R       || > 19.8

The limit is estimated from comparison to nearby PANSTAARS and is not corrected for Galactic extinction. The VIRT is still in the commissioning phase. 

We acknowledge financial support from NASA EPSCoR award 80NNSC22M0063, NSF PAARE award 2319415, and NASA EPSCoR award 80NSSC24M0112. We also acknowledge the use of STDWeb interface to verify our result. This message can be cited.

GCN Circular 38162

Subject
GRB 241025A: VZLUSAT-2 detection
Date
2024-11-11T10:34:18Z (2 years ago)
From
Marianna Dafčíková at Masaryk University <500025@mail.muni.cz>
Via
Web form
M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory), N. Werner  (Masaryk U.), M. Ohno (Hiroshima U.),  L. Meszaros, B. Csak (Konkoly Observatory), H. Takahashi (Hiroshima U.), F. Munz , M. Topinka, F. Hroch, N. Husarikova, J.-P. Breuer (Masaryk U.), J. Hudec, J. Kapus, M. Frajt, M. Rezenov (Spacemanic s.r.o), R. Laszlo (Needronix), G. Galgoczi (Wigner Research Center/Eotvos U.), N. Uchida (ISAS/JAXA), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), Y. Fukazawa, K. Hirose, H. Matake (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), L. L. Kiss (Konkoly Observatory),  T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), K. Torigoe (Hiroshima U.), P. Svoboda, V. Daniel, J. Dudas, M. Junas, J. Gromes (VZLU), I. Vertat (FEL ZCU)  -- the VZLUSAT-2/GRB payload collaboration.

The long-duration GRB 241025A (Fermi/GBM detection: GCN 37886; Swift/BAT detection: GCN 37859; SVOM/GRM detection: GCN 37863; EP detection: GCN 37864; Konus/Wind detection: GCN 37927) was detected by the GRB detector on board of the VZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/).

The data acquisition was performed by the GRB detector unit no. 1. The detection was confirmed at the peak time 2024-10-25 01:36:50 UTC. The T90 duration is 63 s and the significance during T90 reaches 10 sigma.

The light curve obtained by VZLUSAT-2 is available here:
https://vzlusat2.konkoly.hu/static/share/GRB241025A_GCN_VZLUSAT2.pdf

All VZLUSAT-2 detections are listed at: https://monoceros.physics.muni.cz/hea/VZLUSAT-2/
The GRB detectors on VZLUSAT-2 are a demonstration payload for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). Two GRB modules of VZLUSAT-2 are placed in a perpendicular manner and each consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~30 keV to ~1000 keV. VZLUSAT-2 was launched on 2022 January 13 from Cape Canaveral.

GCN Circular 38130

Subject
GRB 241025A: radio detection with the VLA
Date
2024-11-08T16:21:52Z (2 years 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 19:11:50 UT on 2024 Oct 25 (T_mid = 0.76 days post-burst)
the Karl G. Jansky VLA observed the field of GRB 241025A
(Ambrosi et al., GCN 37859; Fermi GBM team, GCN 37860;
SVOM team, GCN 37863; Li et al., GCN 37864; Svinkin et al.,
GCN 37927) in three bands, with central frequencies of 6,
10 and 15 GHz.

The standard 3C286 was used as bandpass and flux density
calibrator, while J2344+8226 was used as phase calibrator.

From a preliminary analysis, an unresolved radio source
is clearly detected at a position (J2000):

RA: 22:14:36.859 +- 0.001
Dec: +83:34:32.27 +- 0.02

consistent with the optical (Ambrosi et al., GCN 37859;
Klingler et al., GCN 37919) and X-ray (Goad et al., GCN 37868)
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]
=============================================================
0.76	6	51	7	0.65x0.27	-71
0.76	10	119	8	0.35x0.17	-78
0.76	15	163	8	0.24x0.12	-65
=============================================================

No source is detected with a >3sigma confidence at the
aforementioned position in previous radio surveys (FIRST, NVSS,
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 38114

Subject
GRB 241025A: LBT optical observations
Date
2024-11-07T15:41:56Z (2 years ago)
From
Andrea Rossi at INAF <andrea.rossi@inaf.it>
Via
Web form
A. Rossi, E. Maiorano (INAF/OAS), D. B. Malesani (DAWN/NBI and Radboud Univ.), A. Melandri, D. Paris, and E. Marini (INAF-OAR), report on behalf of a larger collaboration: 

We observed the optical counterpart of GRB 241025A  (Ambrosi et al., GCN 37859; Fermi GBM team, GCN 37860; Wang et al., GCN 37863; Li et al., GCN 37864) with the LBC camera mounted on LBT (Mt. Graham, AZ, USA) in the r', i', and z' bands with approximate midtime 04:54:00 UT on 2024-10-28, or 3.14 days after the burst. Observations were performed under an average seeing of ~1.2" but with a few passing cirrus.

The optical afterglow (Ambrosi et al., GCN 37859; Jiang et al., GCN 37862; Pereyra et al., GCN 37865; Xu et al., GCN 37866; SVOM/VT team, GCN 37871; Abdi et al., GCN 37882; Watson et al., GCN 37889; Mohan et al., GCN 37890; Vinko et al., GCN 37891; Gupta et al., GCN 37893; Pankov et al., GCN 37912; Moskvitin and Spiridonova, GCN 37914 and 37923; Klingler and Ambrosi, GCN 37919; Wang et al., GCN 37926) is well detected in all bands. We measure a preliminary AB magnitude of  

r' = 23.6+-0.1,

calibrated against Pan-STARRS field stars, and not corrected for the foreground Galactic extinction.

We acknowledge excellent support from the LBTO and LBT-INAF staff, particularly O. Kuhn and R. Ansaldi.

GCN Circular 37964

Subject
GRB 241025A: The discovery of a BdHN I from data of Swift, Fermi, SVOM and Einstein Probe telescopes
Date
2024-10-30T12:11:00Z (2 years ago)
From
Remo Ruffini at ICRA <ruffini@icra.it>
Via
Web form
R. Ruffini, L. Becerra, C.L. Bianco, M. Della Valle, Liang Li, G.J. Mathews, M.T. Mirtorabi, R. Moradi, F. Rastegar Nia, J.A. Rueda and Y. Wang
	
We are comparing and contrasting the seven episodes of BdHN I observed in GRB 241025A with Eiso = 5.5 x 10^53 erg (GCN 37927) and GRB 220101A with Eiso = 3.7 x 10^54 erg (GCN 31365). Both are highly energetic and located at a redshift greater than 4 (GCN 37866, GCN 31353), which allows a zoom-in investigation due to cosmological expansion. By examining the onset of black hole formation and the ultra-relativistic prompt emission (UPE), we gain insight into the rotational dynamics within these systems. This investigation requires additional observational data, particularly optical emission measurements from the newly born pulsar and extended X-ray afterglow data up to more than 10^6 seconds. Concurrent monitoring by Fermi-LAT will be crucial for capturing high-energy emissions, while the already performed Fermi-GBM observations enable the identification of the jetted emission. On this basis, the energy extraction process from a newly formed black hole will be determine.

GCN Circular 37927

Subject
Konus-Wind detection of GRB 241025A
Date
2024-10-28T14:33:58Z (2 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
Via
Web form
D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia,
A. Tsvetkova,  M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:

The long-duration GRB 241025A
(Swift-BAT detection: Ambrosi et al., GCN 37859;
Fermi-GBM detection: Fermi GBM team, GCN 37860;
Godwin, GCN 37886;
SVOM-GRM detection: Wang et al., GCN 37863;
EP-WXT detection: Li et al., GCN 37864)
was detected by Konus-Wind (KW) in the waiting mode
at T0~5786 s UT (01:36:26).

A Bayesian block analysis of the KW  waiting mode data
in the 20-300 keV band reveals a >20 sigma count rate
increase in the interval from T0-13 s to ~T0+128 s.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB241025A/

The total burst fluence is 1.58(-0.14,+0.14)x10^-5 erg/cm^2,
and the 2.944 s peak energy flux, measured from T0+0.143 s,
is 4.5(-0.5,+0.5)x10^-7 erg/cm^2.
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst,
measured from T0-13 s to T0+128 s,
can be described by a power law with exponential cutoff (CPL) model
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.85(-0.13,+0.15) and Ep = 238(-33,+38) keV.

The spectrum near the peak count rate, measured from T0+12 s to T0+30 s,
can be described by a CPL model with
alpha = -0.04(-0.17,+0.20) and Ep = 261(-23,+24) keV.

Assuming the redshift z=4.20 (Xu et al., GCN 37866)
and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315,
and Omega_Lambda = 0.685 (Planck Collaboration, 2014),
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is (5.5+/-0.5)x10^53 erg,
the peak luminosity L_iso is (8.2+/-0.9)x10^52 erg/s,
the rest-frame peak energy of the time-averaged spectrum
Ep,i,z is (1238+/-182) keV, and the spectrum near the maximum count rate 
Ep,p,z is (1357+/-120) keV.

With the obtained estimates, GRB 241025A is inside 68% prediction bands for 
'Amati' and 'Yonetoku' relations for the sample of >300 long KW GRBs with 
known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021), 
see http://www.ioffe.ru/LEA/GRBs/GRB241025A/GRB241025A_rest_frame.pdf

All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.

GCN Circular 37926

Subject
GRB 241025A (EP241025a): Optical afterglow observations with the Tsinghua-Nanshan Optical Telescope
Date
2024-10-28T14:07:49Z (2 years ago)
Edited On
2024-10-28T14:14:20Z (2 years ago)
From
Xiaofeng Wang at Tsinghua University <wang_xf@mail.tsinghua.edu.cn>
Edited By
Leo P. Singer at NASA/GSFC <leo.p.singer@nasa.gov> on behalf of Xiaofeng Wang at Tsinghua University <wang_xf@mail.tsinghua.edu.cn>
Via
Web form
X. F. Wang (THU), A. Iskandar（XAO), J. L. Liu (THU)，L. T. Wang (XAO), J. Mo (THU), Y.S. Yan (THU), S. Antier (OCA)，and W. X. Li (NAOC) report the optical detections of the afterglow of GRB 241025A/EP241025a (Ambrosi et al., GCN 37859; Fermi GBM team, GCN 37860; Jiang et al., GCN 37862; Wang et al., GCN 37863; Li et al., GCN 37864; Pereyra et al., GCN 37865; Xu et al., GCN 37866; Lipunov et al., GCN 37873; Abdi et al., GCN 37882).

We obtained 300sx9 (~12.8 hrs after the burst) and 100sx30 (~13.3 hrs after the burst) r-band images with the 80~cm Tsinghua-Nanshan Optical Telescope (TNOT) located at Nanshan Station of Xinjiang Astronomy Observatory. The afterglow is clearly detected on the stacked images, with the following magnitudes:
 
r = 21.12 +- 0.08 mag (MJD = 60608.60)
r = 21.17 +- 0.10 mag (MJD = 60608.62)

The above photometric results are calibrated using the field stars from the Pan-STARRS1 catalog and are not corrected for the Galactic extinction.

GCN Circular 37923

Subject
GRB 241025A: further SAO RAS optical observations
Date
2024-10-28T03:22:13Z (2 years ago)
From
Moskvitin Alexander at SAO RAS <mosk@sao.ru>
Via
legacy email
A. S. Moskvitin and O. I. Spiridonova (SAO RAS), report
on behalf of the GRB follow-up team.

We observed the field of GRB 241025A (Ambrosi et al. GCN 37859;
The Fermi GBM team, GCN 37860; Godwin, GCN 37886)
with the 1-m telescope of SAO RAS equipped with the CCD-photometer.
We obtained 12 x 300 sec. images in Rc band on October 27,
19:33:44--20:42:52 UT (t_mid - T0 = 2.7719 days).

The OT (Ambrosi et al., GCN 37859; Jiang et al., GCN 37862;
Pereyra et al., GCN 37865; Xu et al., GCN 37866; SVOM/VT team,
GCN 37871; Abdi et al., GCN 37882; Watson et al., GCN 37889;
Mohan et al., GCN 37890; Vinko et al., GCN 37891; Gupta et al.,
GCN 37893; Pankov et al., GCN 37912; Moskvitin and Spiridonova,
GCN 37914; Klingler and Ambrosi, GCN 37919) is clearly detected
in our stacked frame with the brightness of R = 22.98 +/- 0.11
(R_lim = 24.1).

This preliminary photometry is based on nearby USNO-B1.0 stars
and not corrected for the Galaxy extinction.

GCN Circular 37919

Subject
GRB 241025A: Swift/UVOT Detection
Date
2024-10-28T01:28:28Z (2 years ago)
From
noelklin@umbc.edu
Via
Web form
N. J. Klingler (GSFC/UMBC/CRESTII) and E. Ambrosi (INAF-IASFPA)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 241025A
126 s after the BAT trigger (Ambrosi et al., GCN Circ. 37859).
A source consistent with the XRT position (Evans et al.; GCN Circ. 37868) 
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  22:14:36.83 = 333.65346 (deg.)
    Dec (J2000) = +83:34:32.2  =  83.57562 (deg.)
with an estimated uncertainty of 0.43 arc sec. (radius, 90% confidence).

Preliminary detections and 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: 

Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white              126          275          147         17.55 +/- 0.04
v                  671         5229          274        >19.4
b                  595         1347           78        >20.2
u                  339         1322          304        >20.5
w1                 722         5483          101        >21.0
m2                5234         5434          197        >20.2
w2                1030         1050           19        >19.5

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.249 in the direction of the burst
(Schlegel et al. 1998).

GCN Circular 37914

Subject
GRB 241025A: SAO RAS optical observations
Date
2024-10-27T20:14:31Z (2 years ago)
From
Moskvitin Alexander at SAO RAS <mosk@sao.ru>
Via
legacy email
A. S. Moskvitin and O. I. Spiridonova (SAO RAS), report
on behalf of the GRB follow-up team.

We observed the field of Swift GRB 241025A (Ambrosi et al. GCN 37859)
with the 1-m telescope of SAO RAS equipped with the CCD-photometer.
We obtained 12 x 300 sec. images in Rc band on October 26,
19:28:34--20:36:33 UT (t_mid - T0 = 1.7679 days)

The OT (Ambrosi et al., GCN 37859; Jiang et al., GCN 37862;
Pereyra et al., GCN 37865; Xu et al., GCN 37866; SVOM/VT team,
GCN 37871; Abdi et al., GCN 37882; Watson et al., GCN 37889;
Mohan et al., GCN 37890; Vinko et al., GCN 37891; Gupta et al.,
GCN 37893; Pankov et al., GCN 37912) is clearly detected in our
stacked frame with the brightness of R = 22.17 +/- 0.09.

This preliminary photometry is based on nearby USNO-B1.0 stars
and not corrected for the Galaxy extinction.

GCN Circular 37912

Subject
GRB 241025A: Mondy optical observations
Date
2024-10-27T15:31:29Z (2 years ago)
From
Alexei Pozanenko at IKI, Moscow <grb.alex@gmail.com>
Via
legacy email
 N. Pankov (HSE), E. Klunko (ISTP), A. Pozanenko (IKI), S. Belkin (IKI)
report on behalf of GRB IKI FuN:

We observed the field of Swift GRB 241025A (Ambrosi et al. GCN 37859) with
AZT-33IK telescope of Mondy observatory in R-filter on 2024-10-26 starting
(UT) 17:13:51. We detect optical afterglow (Ambrosi et al., GCN 37859;
Jiang et al., GCN 37862; Pereyra et al., GCN 37865; Xu et al., GCN 37866;
SVOM/VT team, GCN 37871; Abdi et al., GCN 37882; Watson et al., GCN 37889;
Mohan et al., GCN 37890; Vinko et al., GCN 37891; Gupta et al., GCN 37893).
Preliminary photometry of first images is the following

Date UT start t-T0 Exp. Filter OT Err. UL(3sigma)
(mid, days) (s)

2024-10-26 17:13:51 1.66876 26x120 R 21.7 0.2 22.8

The photometry is based on nearby USNO-B1.0 stars.

GCN Circular 37893

Subject
GRB241025A: 1.3m DFOT optical afterglow detection
Date
2024-10-26T16:20:45Z (2 years ago)
From
ANSHIKA GUPTA at ARIES <anshika05180@gmail.com>
Via
Web form
Anshika Gupta, Amit K. Ror, Sneh Lata, Dorothy Museo, Kuntal Misra and Shashi B. Pandey (ARIES) report:


We observed the field of GRB 241025A detected by Swift-BAT (GCN 37859) 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 2024-10-25 at 14:13:20 UT, i.e., ~ 12.60 hours after the BAT 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 clearly detected optical afterglow in our stacked image within the error box of the enhanced Swift-XRT position by Goad et al. 2024 (GCN 37868). We obtained the following preliminary magnitude in the stacked image:


Date Start_UT T_start-T0 (hour) Filter  Exp time (s)   magnitude

===============================================================

2024-10-25 14:13:20     ~12.60     R     300*12       20.45 +- 0.05


Our detection is consistent with Jiang et al. 2024 (GCN 37862); Pereyra et al. 2024 (GCN 37865); Xu et al. 2024 (GCN 37866); SVOM Team(GCN 37871); Abdi et al. 2024 (GCN 37882); Watson et al. 2024(GCN 37889); Mohan et al. 2024(GCN 37890), and Vinko et al. 2024 (GCN 37891).

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 catalog. This circular may be cited.

GCN Circular 37891

Subject
​GRB 241025A: optical photometry from Konkoly
Date
2024-10-26T09:55:26Z (2 years ago)
From
Jozsef Vinko at Konkoly Observator <vinko@konkoly.hu>
Via
legacy email
GRB 241025A: optical photometry from Konkoly 

J. Vinko, K. Sarneczky, Zs. Bora, A. Horti-David, R. Konyves-Toth, L. Kriskovics, A. Pal, R. Szakats 
(Konkoly Observatory, Hungary) 

We report detection and photometry of the optical afterglow of GRB 241025A 
(Ambrosi et al., GCN 37859; Fermi GBM team GCN 37860; Wang et al. GCN 37863) 
taken with the RC80 robotic telescope at Piszkesteto Station of Konkoly 
Observatory, Hungary. The observations started on 2024-10-25 16:48:09.79 UT, 
15.19 hours after the trigger. 7 sets of 300 sec frames were collected through. 
Sloan r'- and i' bands. 

The optical afterglow (Jiang et al. GCN 37862; Pereyra et al. GCN 37865; SVOM/VT team GCN 37871; 
Abdi et al. GCN 37882; Watson et al. GCN 37889; Mohan et al. GCN 37890) 
was detected on the stacked frames with the following magnitudes, calibrated 
via nearby PS1 stars: 

Date       UT-middle   t-T0(days) Exp(s) r'(AB)       i'(AB) 
2024-10-25 17:18:57.70 0.65425    7x300  22.04 (0.35) 20.07 (0.17) 

The magnitudes above are not corrected for galactic extinction.

GCN Circular 37890

Subject
GRB 241025A: GROWTH-India Telescope optical observations
Date
2024-10-26T05:36:27Z (2 years ago)
From
Varun Bhalerao at IIT Bombay <varunb@iitb.ac.in>
Via
Web form

T. Mohan, V. Swain, R. Kumar, V. Bhalerao (IITB), G.C. Anupama, S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team:

We observed the field of GRB 241025A observed by SVOM/GRM (GCN 37863

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), Fermi/GBM (Fermi GBM Team, GCN 37860), Swift/BAT (E. Ambrosi et al., GCN 37859) with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2024-10-25 15:50:58, i.e., 14.23 hours after the Swift-BAT trigger. We obtained multiple exposures of 360 seconds in the i' filter. In our stacked images, we detected the optical afterglow at the coordinates reported by Swift UVOT. The photometry results follow as:

MJD (mid)FilterTotal Exposure (s)Magnitude (AB)
60608.6728935i'6x36020.3 +/- 0.08

Above optical afterglow is also observed by Jiang et al., (GCN 37862

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), Pereyra et al., (GCN 37865), SVOM/VT (GCN 37871), Abdi et al., (GCN 37882), Watson et al. (GCN 37889).

The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction.

The GROWTH India Telescope (GIT; Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/.

GCN Circular 37889

Subject
GRB 241025A: COLIBRÍ Detection of the Afterglow
Date
2024-10-26T05:09:44Z (2 years ago)
From
Alan Watson at UNAM <alan@astro.unam.mx>
Via
legacy email
Alan M. Watson (UNAM), Margarita Pereyra (UNAM), Stéphane Basa (UAR
Pytheas), William H. Lee (UNAM), S. Antier (OCA), Jean-Luc Atteia (IRAP),
Nathaniel R. Butler (ASU), Damien Dornic (CPPM), J.-G. Ducoin (CPPM),
Francis Fortin (IRAP), Simona Lombardo (LAM), and Francesco Magnani (CPPM)
report:

We imaged the field of GRB 241025A detected by Swift/BAT, Fermi/GBM, and
SVOM/GRM (GCN Circ. 37859, 37860, 37863) during the commissioning of the
COLIBRÍ (SVOM/F-GFT) telescope at the Observatorio Astronómico Nacional on
the Sierra de San Pedro Mártir in Mexico.

The observations started 39 minutes after the GRB trigger. We observed with
the engineering test camera in a red filter that approximates SDSS r. The
data were reduced using custom software and then analysed and calibrated
against the PS1 catalog using the STDWeb service.

In 1980 seconds of exposure from 2024-10-25 02:15 to 03:00, we detect the
optical counterpart with:

    r = 19.64 +/- 0.04

This magnitude is consistent with other optical observations (GCN Circ.
37862, 37865, 37871, and 37882).

We warmly thank the COLIBRI engineering team and the staff of the
Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir.

GCN Circular 37888

Subject
GRB 241025A: Swift-XRT refined Analysis
Date
2024-10-26T01:24:05Z (2 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
K.L. Page (U. Leicester), T. Sbarrato (INAF-OAB), P. D'Avanzo
(INAF-OAB), M.G. Bernardini (INAF-OAB), S. Dichiara (PSU), J.A. Kennea
(PSU), D.N. Burrows (PSU), A.P. Beardmore (U. Leicester) and P.A. Evans
report on behalf of the Swift-XRT team:

We have analysed 6.8 ks of XRT data for GRB 241025A, from 109 s to 80.1
ks after the  BAT trigger. The data comprise 321 s in Windowed Timing
(WT) mode (the first 4 s were taken while Swift was slewing) with the
remainder in Photon Counting (PC) mode. 

The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=8.0 (+0.0, -0.5). At T+126 s  the decay
flattens to an alpha of 3.15 (+0.20, -0.21) before breaking again at
T+221 s to a final decay with index alpha=1.071 (+0.026, -0.025).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.77 (+/-0.05). The
best-fitting absorption column is  3.6 (+/-1.1) x 10^22 cm^-2, at a
redshift of 4.2, in addition to the Galactic value of 1.2 x 10^21 cm^-2
(Willingale et al. 2013). The PC mode spectrum has a photon index of
1.68 (+/-0.12) and a best-fitting absorption column of 2.4 (+2.4, -2.1)
x 10^22 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum  is 4.3 x 10^-11 (5.1 x
10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Galactic foreground: 1.2 x 10^21 cm^-2
Intrinsic column:    2.4 (+2.4, -2.1) x 10^22 cm^-2 at z=4.2
Photon index:	     1.68 (+/-0.12)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01262165.

This circular is an official product of the Swift-XRT team.

GCN Circular 37886

Subject
GRB 241025A: Fermi GBM Observation
Date
2024-10-25T21:10:23Z (2 years ago)
From
Matt Godwin <msg0028@uah.edu>
Via
Web form
Matt Godwin (UAH) reports on behalf of the Fermi Gamma-ray Burst Monitor Team:

"At 01:36:26.89 UT on 25 October 2024, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 241025A (trigger 751512991/241025067).
which was also detected by Swift BAT (V. D'Elia et al. 2024, GCN 37859) and Einstein Probe (D.Y. Li et al. 2024, GCN 37864)
The Fermi GBM on-ground location is consistent with the Swift BAT position.

The angle from the Fermi LAT boresight is 47 degrees.

The GBM light curve consists of multiple close peaks with a duration (T90)
of about 124 s (50-300 keV). The time-averaged spectrum
from T0+2.3 to T0+125.2 s is best fit by a Band function.
The power law index is -0.93 +/- 0.06 and the cutoff energy,
parameterized as Epeak, is 235 +/- 22 keV.

The event fluence (10-1000 keV) in this time interval is
(1.46 +/- 0.06)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+46 s in the 10-1000 keV band is 3 +/- 0.2 ph/s/cm^2.

A power law function with an exponential high-energy cutoff fits the spectrum equally well.
The power law index is -0.92 +/- 0.05 and the cutoff energy, parameterized as
Epeak, is 232 +/- 18 keV.

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 37882

Subject
GRB 241025A: GRANDMA and Kilonova-Catcher optical afterglow detections and upperlimits
Date
2024-10-25T17:49:36Z (2 years ago)
From
Emma de Bruin at University of Minnesota <debru045@umn.edu>
Via
Web form
I. Abdi (AUS), E. de Bruin (UMN), C. Andrade (UMN), T.Hussenot (IJCLAB), M. Masek(FZU),
S. Antier (OCA), S. Karpov (FZU), M. Coughlin (UMN), I. Tosta e Melo (UniCT-DFA), P. Hello, N. Leroy (IJCLAB), P-A Duverne (APC), T. Pradier (Unistra/IPHC), N. Guessoum (AUS), M. Tanasan (NARIT), K. Noysena (NARIT), D.Turpin (CEA-Saclay/Irfu), M. Freeberg (KNC), D. St-Gelais (KNC) on behalf of the GRANDMA and Kilonova-Catcher collaborations:

We observed the Swift/UVOT localisation of GRB 241025A, detected by Swift/BAT (GCN 37859) with the GRANDMA network and its citizen science project Kilonova-catcher (KNC). Our observations started 70 min after the trigger.

We detect at the Swift/UVOT coordinates the afterglow already observed by TRT (GCN 37862) DDOTI (GCN 37865) and SVOM/VT (GCN 37871), and we obtain the following magnitudes and 5-sigma upperlimits:

| Tstart (UTC)  | Telescope | Exposure | Filter | Magnitude (Vega) |
	 	 	 	
| 2024-10-25T02:46:16 | KNC-iT11 | 4x180s | R | >18.5 (U.L) |
| 2024-10-25T03:28:43 | KNC-iT21 | 10x180s | V | >18.5 (U.L) |
| 2024-10-25T04:04:36 | KNC-iT21 | 10x180s | R | 19.29 +- 0.15 |
| 2024-10-25T04:58:39 | TRT-SRO | 5x300s | R | 19.66 +- 0.05  |
| 2024-10-25T06:05:10 | KNC-iT11 | 20x180s | R | 19.97 +- 0.22 |
| 2024-10-25T06:35:00 | TRT-SRO | 5x300s | I | 18.90 +- 0.08 |
| 2024-10-25T07:25:25 | TRT-SRO | 5x200s | B | > 21.4 (U.L) |
| 2024-10-25T07:50:17 | TRT-SRO | 5x200s | V | >21.1 (U.L) |
| 2024-10-25T08:04:33 | TRT-SRO | 5x200s | R | 20.23 +- 0.08 |
| 2024-10-25T08:25:49 | TRT-SRO | 5x200s | I | 19.08 +- 0.17 |

The V-band image of TRT-SRO contains a marginal 4-sigma detection at V=21.11+-0.23, just under the V>21.1 5-sigma upperlimit.

TRT-SRO images were calibrated using the PanSTARRS catalog. KNC images were calibrated using the Gaia DR3 Synphot catalog.

All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). We use the SkyPortal application (skyportal.io) to monitor our observational campaign.

GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/).

GCN Circular 37874

Subject
Fermi GRB 241025A: Global MASTER-Net observations report
Date
2024-10-25T11:15:35Z (2 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
legacy email
V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik,  D. Vlasenko,
G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra
(The Instituto de Astrofisica de Canarias),

D. Buckley
(South African Astronomical Observatory),

O.A. Gress, N.M. Budnev, O.Ershova
(Irkutsk State University, API),

L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez
(INAOE, Guillermo Haro Astrophysics Observatory),

A. Tlatov, D. Dormidontov
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich
(Blagoveschensk Educational State University)

MASTER-Tunka robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 241025A ( Fermi GBM team, GCN 37860) errorbox  33528 sec after notice time and 33571 sec after trigger time at 2024-10-25 10:55:58 UT, with upper limit up to  18.6 mag. Observations started at twilight.  The observations began at zenith distance = 34 deg. The sun  altitude  is -10.3 deg. 

The galactic latitude b = 20 deg., longitude l = 116 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2648590

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

   33587 | 2024-10-25 10:55:58 |        MASTER-Tunka | (22h 21m 51.83s , +83d 24m 29.9s) |   C |    30 | 17.7 |        
   33630 | 2024-10-25 10:56:41 |        MASTER-Tunka | (22h 21m 57.07s , +83d 23m 31.1s) |   C |    30 | 17.7 |        
   33674 | 2024-10-25 10:57:25 |        MASTER-Tunka | (22h 21m 50.77s , +83d 22m 33.0s) |   C |    30 | 17.8 |        
   33716 | 2024-10-25 10:58:08 |        MASTER-Tunka | (22h 21m 56.24s , +83d 22m 37.1s) |   C |    30 | 17.8 |        
   33860 | 2024-10-25 11:00:31 |        MASTER-Tunka | (22h 21m 59.88s , +83d 22m 43.0s) |   C |    30 | 18.1 |        
   33919 | 2024-10-25 11:01:27 |        MASTER-Tunka | (22h 22m 05.43s , +83d 24m 20.8s) |   C |    36 | 18.3 |        
   34038 | 2024-10-25 11:03:26 |        MASTER-Tunka | (22h 21m 56.61s , +83d 24m 43.0s) |   C |    36 | 18.6 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.

GCN Circular 37873

Subject
Swift GRB 241025A: Global MASTER-Net observations report
Date
2024-10-25T11:03:30Z (2 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
legacy email
V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik,  D. Vlasenko,
G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra
(The Instituto de Astrofisica de Canarias),

D. Buckley
(South African Astronomical Observatory),

O.A. Gress, N.M. Budnev, O.Ershova
(Irkutsk State University, API),

L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez
(INAOE, Guillermo Haro Astrophysics Observatory),

A. Tlatov, D. Dormidontov
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich
(Blagoveschensk Educational State University)

MASTER-Tunka robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the Swift GRB 241025A ( E. Ambrosi et al., GCN 37859) errorbox  33497 sec after notice time and 33548 sec after trigger time at 2024-10-25 10:55:58 UT, with upper limit up to  17.8 mag. Observations started at twilight.  The observations began at zenith distance = 34 deg. The sun  altitude  is -10.3 deg. 

The galactic latitude b = 22 deg., longitude l = 119 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2648532

We obtain a following upper limits.  

Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

   33563 |        MASTER-Tunka |   C |    30 | 17.7 |        
   33606 |        MASTER-Tunka |   C |    30 | 17.7 |        
   33650 |        MASTER-Tunka |   C |    30 | 17.8 |        
   33693 |        MASTER-Tunka |   C |    30 | 17.8 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.

GCN Circular 37872

Subject
EP241025a (GRB 241025A): EP observations update
Date
2024-10-25T10:20:16Z (2 years ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
D. Y. Li (NAO, CAS), Z. Y. Liu, M. Q. Huang (USTC), J. Q. Peng (IHEP, CAS), C. C. Jin (NAO, CAS) report on behalf of the Einstein Probe team:

The preliminary analysis of the telemetry EP-WXT data shows that the bright transient EP241025a (GRB 241025A, Swift GCN 37859, Fermi GBM GCN 37860, SVOM/GRM GCN 37863, EP GCN 37864) began at (T0) 2024-10-25T01:35:29 (UTC), and lasted for around 300 seconds, with the peak flux in 0.5-4.0 keV to be around 1e-8 erg/s/cm2. The EP-FXT autonomous observation began at T0+3min and caught the latter half of the bright transient, followed by lasting fainter emission. The ground calculated EP-FXT position is RA=333.6550 deg, DEC=83.5750 deg (J2000), with an uncertainty of 10 arcsecs (radius, 90% C.L. statistical and systematic), which is consistent with the enhanced XRT position (GCN 37868). The averaged EP-FXT spectrum can be fitted with an absorbed powerlaw, with a photon index of (1.41 +/- 0.09), and an absorption of NH= (2.2 +/- 0.4) e21 cm^(-2). The derived average unabsorbed flux in 0.5-4.0 keV is (1.6 +/- 0.7) e-10 erg/s/cm2. All the errors of the parameters quoted are at 90% C.L. 

Please note that the temporal and spectral analyses presented above are preliminary. The final results will be presented in future publications. EP-FXT will also keep monitoring this transient in the following days.

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).

GCN Circular 37871

Subject
GRB 241025A : SVOM/VT optical afterglow observations
Date
2024-10-25T09:59:39Z (2 years ago)
From
Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>
Via
Web form
SVOM/VT commissioning team: Y. L. Qiu, H. L. Li, C. Wu, L. P. Xin, X. H. Han, J. Wang, W. J. Xie,  H. B. Cai, Y. Xu, Y. J. Xiao, P. P. Zhang, J. S. Deng, L. Lan, X. M. Lu, R. S. Zhang, (NAOC), J. Zhang, L. J.  Dan, G. Y. Zou, C. J. Wang, Y. F. Du, C. Huang (XIOPM), H. Zhou (PMO), S. L. Xiong(IHEP) 

SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang (IHEP), Stéphane Basa (LAM), Olivier Godet (IRAP), Arnaud Claret (CEA), Zi-Gao Dai (USTC), Frédéric Daigne (IAP), Jin-Song Deng (NAOC), Andrea Goldwurm (APC), Diego Götz (CEA), Xu-Hui Han (NAOC), Cyril Lachaud (APC), En-Wei Liang (GXU), Yu-Lei Qiu (NAOC), Susanna Vergani (Obs.Paris), Jing Wang (NAOC), Chao Wu (NAOC), Li-Ping Xin (NAOC), Bing Zhang (UNLV)

report on behalf of the SVOM team:

VT started to observe the field of GRB 241025A (Ambrosi et al., GCN#37859; Fermi GBM team, GCN#37860; Wang et al., GCN#37863; Li et al., GCN 37864)via ToO observations started at 2024-10-25T04:03:55 UT, about 2.45 hours after the burst. The VT conducted observations simultaneously in two channels: VT_B (400nm-650nm) and VT_R (650nm-1000nm).

The counterpart (Ambrosi et al., GCN#37859; Jiang et al., GCN#37862, Pereyra et al., GCN#37865; Xu et al., GCN#37866)  was clearly detected in both bands with VT_B=20.8+/-0.2 mag and VT_R=19.07+/-0.07 mag at 2.45 hours post the burst. 

More observations are on-going. 

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 37868

Subject
GRB 241025A: Enhanced Swift-XRT position
Date
2024-10-25T09:19:14Z (2 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 947 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 241025A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 333.65769, +83.57588 which is equivalent
to:

RA (J2000): 22h 14m 37.85s
Dec (J2000): +83d 34' 33.2"

with an uncertainty of 2.2 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.

GCN Circular 37866

Subject
GRB 241025A: NOT spectroscopic redshift of z = 4.20
Date
2024-10-25T06:17:59Z (2 years ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
Via
Web form
D. Xu (NAOC), L. Izzo (INAF/OACn and DARK/NBI), Z.P. Zhu, S.Y. Fu (NAOC), N. Koivisto (NOT), T. Bäcker, M. Varding, R. Tuomainen, A. Willstedt Justel, T. Gobold (UH) report on behalf of a larger collaboration:

We have observed the optical counterpart (Ambrosi et al., GCN#37859; Jiang et al., GCN#37862) of GRB 241025A (Ambrosi et al., GCN#37859; Fermi GBM team, GCN#37860; Wang et al., GCN#37863; Li et al., GCN 37864), using the Nordic Optical Telescope (NOT) equipped with the ALFOSC spectrograph. Grism #4 was used, covering the wavelength range 3650-9500 AA. Four spectra of 1200 s exposure time each have been obtained, with the first sequence starting at 02:07:32 UT on 2024-10-25, i.e., 0.51 hr after the Swift trigger.

Preliminary analysis of the data reveals a bright continuum in the red part of the spectrum, with a clear break around 6310 AA, which we interpret as due to Lyman alpha. We also identify the 
Lyman limit, the Lyman forest, and several metal absorption features, interpreted as due to Si II, Si IV, O I, C II, C IV, Fe II and Al II, all at a common redshift of z = 4.20.

GCN Circular 37865

Subject
GRB 241025A: DDOTI Afterglow detection
Date
2024-10-25T04:50:00Z (2 years ago)
From
Margarita Pereyra Talamantes at IA-UNAM Ensenada <mpereyra@astro.unam.mx>
Via
Web form
Margarita Pereyra (UNAM),  Alan M. Watson (UNAM), Nat Butler (ASU), Rosa Becerra (UTOV), Simone Dichiara (PSU), Tzveti Dimitrova (ASU), Océlotl López (UNAM), Camila Angulo (UNAM), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM) and Eleonora Troja (UTOV) report:

We observed the field of the GRB 241025A detected by Swift (Ambrosi et al., GCN 37859; Fermi GBM team, GCN 37860) with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir (http://ddoti.astroscu.unam.mx) on 2024-10-25 from 02:28 to 02:43 UTC, 51min to 1.1hrs after the event, obtaining a total of 11 minutes of exposure in the w filter.

We detect a source at 22:14:36.94 +83:34:31.9, consistent with the position of the UVOT afterglow (Ambrosi et al., GCN 37859 ; Jiang et al, GCN 37862), with the following magnitude and 10-sigma uncertainty: w = 20.20 +/- 0.19 mag.

Our photometry is calibrated against the APASS catalog, on an approximate AB system, and is not corrected for Galactic extinction in the direction of the GRB.

We thank the DDOTI technical team and the staff of the Observatorio Astronómico Nacional.

GCN Circular 37864

Subject
EP241025a (GRB 241025A): EP on-board trigger and autonomous follow-up observation
Date
2024-10-25T04:34:13Z (2 years ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
D. Y. Li (NAO, CAS), Z. Y. Liu, M. Q. Huang (USTC), J. Q. Peng (IHEP, CAS), C. C. Jin (NAO, CAS) report on behalf of the Eintein Probe team:

We report on the detection of an X-ray transient detected by EP-WXT, EP241025a, which triggered the on-board processing unit at 2024-10-25T01:36:45 (UTC) (trigger ID: 01709111485). The trigger flux is estimated to be around 2e-10 erg/s/cm2 in 0.5-4 keV, assuming a spectral shape of absorbed power-law with a photon index of 2. An autonomous observation on the X-ray transient was performed by the EP-FXT about 3 minutes later, which also detected an X-ray source at R.A. = 333.6408 deg, DEC = 83.5772 deg (J2000) with an uncertainty of about 10 arcsecs (radius, 90% C.L. statistical and systematic), consistent with the position of the WXT transient within the uncertainties. The source flux is estimated to be around 5e-11 erg/s/cm2. We note that the trigger time and position of this X-ray transient are consistent with that of GRB 241025A (Swift GCN 37859, Fermi GBM GCN 37860, SVOM/GRM GCN 37863).

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).

GCN Circular 37863

Subject
GRB 241025A: SVOM/GRM observation
Date
2024-10-25T03:57:54Z (2 years ago)
From
Chenwei Wang at IHEP <cwwang@ihep.ac.cn>
Via
Web form
SVOM/GRM team: Chen-Wei Wang, Shi-Jie Zheng, Yong-Wei Dong, Jiang-Tao Liu, Jian-Chao Sun, Yue Huang, Jiang He, Min Gao, Hao-Xuan Guo, Lu Li, Yong-Ye Li, Hong-Wei Liu, Xin Liu, Hao-Li Shi, Li-Ming Song, You-Li Tuo, Wen-Long Zhang, Wen-Jun Tan, Hao-Xi Wang, Jin Wang, Jin-Zhou Wang, Ping Wang, Rui-Jie Wang, Yu-Xi Wang, Bo-Bing Wu, Shao-Lin Xiong, Jian-Ying Ye, Yi-Tao Yin, Wen-Hui Yu, Fan Zhang, Li Zhang, Peng Zhang, Shuang-Nan Zhang, Yan-Qiu Zhang, Yan-Ting Zhang, Shu-Min Zhao, Xiao-Yun Zhao, Chao Zheng (IHEP), Maria-Grazia Bernardini (LUPM/INAF-OAB), Laurent Bouchet (IRAP), David Corre (CEA), Tais Maiolino (LUPM), Frédéric Piron (LUPM), Stéphane Schanne (CEA), Jingwei Wang (IAP), JeanLuc Attéia (IRAP)

SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang (IHEP), Stéphane Basa (LAM), Arnaud Claret (CEA), Zi-Gao Dai (USTC), Frédéric Daigne (IAP), Jin-Song Deng (NAOC), Olivier Godet (IRAP),  Andrea Goldwurm (APC), Diego Götz (CEA), Xu-Hui Han (NAOC), Cyril Lachaud (APC), En-Wei Liang (GXU), Yu-Lei Qiu (NAOC), Susanna Vergani (Obs.Paris), Jing Wang (NAOC), Chao Wu (NAOC), Li-Ping Xin (NAOC),  Shao-Lin Xiong (IHEP), Bing Zhang  (UNLV)

report on behalf of the SVOM team:

During the commissioning phase, the SVOM/GRM was triggered in-flight by GRB 241025A at 2024-10-25T01:36:40 UT (T0), which was also observed by Fermi/GBM (Fermi GBM Team, GCN 37860), Swift/BAT (E. Ambrosi et al., GCN 37859).

The real-time alert data and light curves of SVOM/GRM were downlinked to the ground through the VHF system with low latency. The GRM light curve shows that this burst consists of multiple pulses with a T90 of 37.6 +1.7/-1.1 s.

The GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb241025A.png

The telecommand for the ToO observation related to this burst has been successfully uploaded to SVOM.

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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS.

The SVOM point of contact for this burst is: Chen-Wei Wang (IHEP)(cwwang@ihep.ac.cn)

GCN Circular 37862

Subject
GRB 241025A: TRT optical afterglow observation
Date
2024-10-25T03:35:44Z (2 years ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
Via
Web form
S.Q. Jiang (NAOC), S. Tinyanont, R. Anutarawiramkul, P. Butpan (NARIT), Z.P. Zhu, S.Y. Fu, J. An, X. Liu, Z. Fan, W.X. Li, N.C. Sun, Y.N. Wang, D. Xu (NAOC) report on behalf of a large collaboration:

We observed the field of GRB 241025A detected by Swift (Ambrosi et al., GCN 37859), EP (EP241025a, ID: 01709111485), Fermi (Fermi GBM team, GCN 37860), using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at Fresno, California, US. Observations started at 02:24:10.976 UTC on 2024-10-25, i.e., 47.34 mins after the Swift trigger, and a series of 200 s frames were obtained in R-band.

The optical afterglow by Swift/UVOT (Ambrosi et al., GCN 37859) is clearly detected in our individual as well as stacked images. Its brightness is varying and has R = 19.68 +/- 0.12 mag in the first image at a median time 0.817 hr after the Swift trigger, calibrated with PanSTARRS and not corrected for Galactic extinction.

GCN Circular 37860

Subject
GRB 241025A: Fermi GBM Final Real-time Localization
Date
2024-10-25T01:47:05Z (2 years ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
Via
email
The Fermi GBM team reports the detection of a likely LONG GRB

At 01:36:26 UT on 25 Oct 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 241025A (trigger 751512991.890046 / 241025067).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 326.2, Dec = 80.3 (J2000 degrees, equivalent to J2000 21h 44m, 80d 17'), with a statistical uncertainty of 3.6 degrees.

The angle from the Fermi LAT boresight is 46.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn241025067/quicklook/glg_skymap_all_bn241025067.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn241025067/quicklook/glg_healpix_all_bn241025067.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn241025067/quicklook/glg_lc_medres34_bn241025067.gif

GCN Circular 37859

Subject
GRB 241025A: Swift detection of a burst with an optical counterpart
Date
2024-10-25T01:46:15Z (2 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
Via
email
E. Ambrosi (INAF-IASFPA), A. D'Ai (INAF-IASFPA),
V. D'Elia (SSDC & INAF-OAR), R. Gupta (NASA GSFC), J. A. Kennea (PSU),
D. M. Palmer (LANL), T. M. Parsotan (GSFC) and
B. Sbarufatti (INAF-OAB) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 01:36:50 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 241025A (trigger=1262165).  Swift slewed immediately to the burst.
The BAT on-board calculated location is 
RA, Dec 333.330, +83.566 which is 
   RA(J2000) = 22h 13m 19s
   Dec(J2000) = +83d 33' 59"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex
structure with a duration of about 180 sec.  The peak count rate
was ~1800 counts/sec (15-350 keV), at ~2 sec after the trigger.

The XRT began observing the field at 01:38:46.2 UT, 115.7 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 333.6488, 83.5739 which is equivalent to:
   RA(J2000)  = 22h 14m 35.71s
   Dec(J2000) = +83d 34' 26.0"
with an uncertainty of 4.8 arcseconds (radius, 90% containment). This
location is 131 arcseconds from the BAT onboard position, within the
BAT error circle. No event data are yet available to determine the
column density using X-ray spectroscopy.

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 125 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	22:14:36.91 = 333.65379
  DEC(J2000) = +83:34:32.3  =  83.57565
with a 90%-confidence error radius of about 0.62 arc sec. This position is 6.6
arc sec. from the center of the XRT error circle. The estimated magnitude is
17.56 with a 1-sigma error of about  0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.249.

Burst Advocate for this burst is E. Ambrosi (elena.ambrosi AT inaf.it).
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)
Questions or comments?
Contact GCN directly.
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Get involved on GitHub.

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