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EP241026a, GRB 241026A

GCN Circular 38320

Subject
GRB 241026A: radio detection with the VLA
Date
2024-11-26T12:03:32Z (a year 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 23:07:34 UT on 2024 Oct 30 (T_mid = 4.05 days post-burst)
the Karl G. Jansky VLA observed the field of GRB 241026A
(Fermi GBM team, GCN 37894; Melandri et al., GCN 37896;
Li et al., GCN 37909; SVOM team, GCN 37921; Zhang et al.,
GCN 37924; Pal et al., GCN 37929) in three bands,
with central frequencies of 6, 10 and 15 GHz.

The standard 3C286 was used as bandpass and flux density
calibrator, while J1927+6117 was used as phase calibrator.

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

RA: 19:33:36.063 +- 0.001
Dec: +57:59:09.06 +- 0.01

consistent with the optical (Moskvitin et al., GCN 37899;
Watson et al., GCN 37900; Zheng et al., GCN 37903;
Shrestha et al., GCN 37913; Mohan et al., GCN 37918;
Moskvitin et al., GCN 37922; Wang et al., GCN 37928;
Moskvitin et al., GCN 37953; Rossi et al., GCN 37969;
Moskvitin et al., GCN 38028) and X-ray (Osborne et al.,
GCN 37904) 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]
================================================================
4.05	6	67	7	0.33x0.27	12
4.05	10	196	7	0.20x0.17	-0.7
4.05	15	330	7	0.14x0.12	24
================================================================

No source is detected with a >3sigma confidence at the
aforementioned position in previous radio surveys (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 38299

Subject
GRB 241026A: VIRT Optical Upper Limit
Date
2024-11-22T16:35:54Z (a year 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 GRB241026A (Fermi GBM Team, GCN 37894; Melandri et al., GCN 37896; Li et al., GCN 37909; Zhang et al., GCN 37921) with the 0.5m Virgin Island Robotic Telescope (VIRT) at the University of the Virgin Islands' Etelman Observatory on 2024-10-27 starting at 22:49:52.275 (T-mid ~T0+24 hrs). We performed a series of exposures in an R filter with a total exposure of 1100s. The weather conditions were partly cloudy during the hours of observation with an average airmass of 1.48. 

We do not detect any source within the enhanced XRT position (Osborne et al. GCN 37904). This non-detection is consistent with reported detections (Moskvitin et al. GCN 37899; Watson et al. GCN 37900; Zheng et al. GCN 37903; Shrestha et al. GCN 37913; Mohan et al. GCN 37918; Moskvitin et al. GCN 37922; Wang et al. GCN 37928; Moskvitin et al. GCN 37953; Rossi et al. GCN 37969; Moskvitin et al. GCN 38028; and Wang et al. GCN 38035;) and upper limits  (Lipunov et al. GCN 37898; Mo et al. GCN 37915 and Siegel et al. GCN 37947). We report the following 3-sigma upper limit:

T_mid                ||Exposure   ||Filter   ||Limit 
T+24  hrs            || 1100s     || R       || >20.5

The limit is estimated from comparison to nearby USNO B1 stars 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. This message can be cited.

GCN Circular 38028

Subject
GRB 241026A: SAO RAS optical observations
Date
2024-11-01T10:04:47Z (a year ago)
From
Moskvitin Alexander at SAO RAS <mosk@sao.ru>
Via
legacy email
A. S. Moskvitin, A. S. Vinokurov (SAO RAS), A. S. Pozanenko (IKI),
N. Pankov (IKI, HSE) report on behalf of the GRB follow-up team.

We observed the field of GRB 241026A (The Fermi GBM team, GCN 37894;
Melandri et al., GCN 37896, Li et al., GCN 37909; Zhang et al.,
GCN 37921; Zhang, Xiong and Wang GCN 37924; Pal et al., GCN 37929;
Barthelmy et al., GCN 37971) with the 6-m telescope of SAO RAS
equipped with the focal reducer Scorpio-I on October 30,
17:38:47--18:14:14 UT (t_mid-T0 = 3.8014 d).

The OT (Moskvitin et al., GCNs 37899, 37916, 37953; Watson et al.,
GCN 37900; Zheng & Filippenko GCN 37903; Shrestha et al., GCN 37913;
Mo et al., GCN 37915; Mohan et al., GCN 37918; Izzo et al., GCN 37925;
Wang et al., GCN 37928, Rossi et al., GCN 37969) is detected
in a stack image of  42 x 30 sec. The brightness of the OT is
R = 23.9 +/- 0.2, calibrated against nearby USNO-B1.0 stars
(R2 magnitudes) and not corrected for Galaxy extinction.

GCN Circular 37971

Subject
GRB 241026A: Swift-BAT refined analysis
Date
2024-10-30T13:52:37Z (a year ago)
From
Takanori Sakamoto at AGU <tsakamoto@phys.aoyama.ac.jp>
Via
legacy email
S. D. Barthelmy (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC),
A. Melandri (INAF-OAR), M. J. Moss (GSFC), D. M. Palmer (LANL),
T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU)
(i.e. the Swift-BAT team):
 Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 241026A (trigger #1262764)
(Melandri, et al., GCN Circ. 37896).  The BAT ground-calculated position is
RA, Dec = 293.425, 57.996 deg which is
   RA(J2000)  =  19h 33m 41.9s
   Dec(J2000) = +57d 59' 46.7"
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 17%.
 The mask-weighted light curve shows a single-pulse structure that starts at
T-2 s, peaks at T0 s, and ends at T+31 s.  T90 (15-350 keV) is 25.2 +- 5.6 sec
(estimated error including systematics).
 The time-averaged spectrum from T-1.34 to T+30.98 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.56 +- 0.12.  The fluence in the 15-150 keV band is 2.5 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T-0.29 sec in the 15-150 keV band
is 4.0 +- 0.5 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.
 The results of the batgrbproduct analysis are available at
https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1262764

GCN Circular 37969

Subject
GRB 241026A: LBT optical observations
Date
2024-10-30T13:30:41Z (a year 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.), L. Izzo (INAF/OAC), and V. D'Elia (ASI/SSDC & INAF-OAR) report on behalf of the CIBO collaboration: 

We observed the optical counterpart of GRB 241026A (Melandri et al., GCN 37896; Trigg, GCN 37917; Zhang et al., GCN 37921 and GCN 37924; Pal et al., GCN 37929) with the LBC camera mounted on LBT (Mt. Graham, AZ, USA) in the g’, r’, i’, and z’ bands (12 min exposure time per filter) with approximate midtime 03:35:00 UT on 2024-10-28, or 1.20 days after the burst. Observations were performed under an average seeing of ~1" but with a few passing cirrus.

The optical afterglow (Moskvitin et al., GCNs 37899, 37916, 37922; Watson et al., GCN 37900; Zheng & Filippenko GCN 37903; Shrestha et al., GCN 37913; Mo et al., GCN 37915; Mohan et al., GCN 37918; Izzo et al., GCN 37925; Wang et al., GCN 37928) is well detected in all bands. We measure a preliminary AB magnitude of  

r' = 21.4+-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, R. Ansaldi, D. Paris and E. Marini.

GCN Circular 37953

Subject
GRB 241026A: SAO RAS optical observations
Date
2024-10-30T02:07:18Z (a year 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 241026A (The Fermi GBM team, GCN 37894;
Melandri et al., GCN 37896, Li et al., GCN 37909; Zhang et al.,
GCN 37921; Zhang, Xiong and Wang GCN 37924; Pal et al., GCN 37929)
with the 1-m telescope of SAO RAS, Zeiss-1000/CCD-photometer
in Rc band on October 28/29 and 29/30 nights.

The OT (Moskvitin et al., GCNs 37899, 37916; Watson et al., GCN 37900;
Zheng & Filippenko GCN 37903; Shrestha et al., GCN 37913; Mo et al.,
GCN 37915; Mohan et al., GCN 37918; Izzo et al., GCN 37925;
Wang et al., GCN 37928) is not detected in the October 28/29 data,
but marginally detected in the October 29 stacked frame.
Preliminary results are as follows.

date   UT_start--UT_end    t_mid-T0  exp, s  R magnitude      R_lim
28/29  21:30:53--01:10:41  2.02657   500     n/d              21.6
29     17:42:02--18:36:46  2.81034   2490    22.95 +/- 0.24   23.3

The frames were calibrated against nearby USNO-B1 stars
(R2 magnitudes) and not corrected for MW extinction.

GCN Circular 37947

Subject
GRB 241026A: Swift/UVOT Upper Limits
Date
2024-10-29T21:43:50Z (a year ago)
From
Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>
Via
Web form
M. H. Siegel (PSU) and A. Melandri (INAF-OAR)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 241026A
118 s after the BAT trigger (Melandri et al., GCN Circ. 37896).
No optical afterglow consistent with the XRT position
(Osborne et al., GCN Circ. 37904) or the optical counterparts
(Moskvitin et al., GCN Circ. 37899; Watson, GCN. Circ. 37900; Shrestha
et al., GCN Circ. 37913) is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

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

white_FC           118          268          147         >19.9
u_FC               331          581          246         >19.8
white              118         1708          411         >21.0
v                  662         1759          136         >19.8
b                  586         1849          128         >20.6
u                  331         1832          363         >20.2
w1                 712         1808          117         >20.7
m2                 686         1783          117         >20.7
w2                 636         1734          136         >20.0

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.073 in the direction of the burst
(Schlegel et al. 1998).

GCN Circular 37929

Subject
GRB 241026A: the 100th GRB detected by GRBAlpha
Date
2024-10-28T15:05:42Z (a year ago)
From
Andras Pal at Konkoly Observatory <apal@szofi.net>
Via
Web form

A. Pal (Konkoly Observatory), M. Dafcikova, J. Ripa, M. Kolar, N. Werner (Masaryk U.), M. Ohno, H. Takahashi (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), N. Husarikova, F. Munz , M. Topinka, M. Duriskova, L. Szakszonova, J.-P. Breuer, F. Hroch (Masaryk U.), T. Urbanec, M. Kasal, A. Povalac (Brno U. of Technology), J. Hudec, J. Kapus, M. Frajt (Spacemanic s.r.o), R. Laszlo, M. Koleda (Needronix s.r.o), M. Smelko, P. Hanak, P. Lipovsky (Technical U. of Kosice), G. Galgoczi (Wigner Research Center/Eotvos U.), Y. Uchida, H. Poon, H. Matake (Hiroshima U.), N. Uchida (ISAS/JAXA), T. Bozoki (Eotvos U.), G. Dalya (Eotvos U.), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), G. Friss (Eotvos U.), Y. Fukazawa, K. Hirose (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), K. Kapas (Eotvos U.), L. L. Kiss (Konkoly Observatory), T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), J. Takatsy (Eotvos U.), K. Torigoe (Hiroshima U.), N. Kogiso, M. Yoneyama (Osaka Metropolitan U.), M. Moritaki (U. Tokyo), T. Kano (U. Michigan) -- the GRBAlpha collaboration.

We report a detection of GRB 241026A, the 100th GRB detected by GRBAlpha 1U CubeSat (Pal et al. 2023, A&A, 677, 40; https://ui.adsabs.harvard.edu/abs/2023A%26A...677A..40P/abstract). The event was also observed by Fermi/GBM (GCN 37894

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), Swift/BAT (GCN 37896), EP/WXT (GCN 37909), SVOM/GRM (GCN 379210), GECAM-B (GCN 37924), and INTEGRAL/SPI-ACS (peak detection at 2024-10-26 ~22:42:31 UTC).

The detection was confirmed at the peak time 2024-10-26 22:42:32.3 UTC. The T90 duration measured by GRBAlpha is 10.0 s and the overall significance during T90 reaches 6.9 sigma.

The light curve obtained by GRBAlpha is available here: https://grbalpha.konkoly.hu/static/share/GRB241026A_GCN.pdf

All GRBAlpha detections are listed at: https://monoceros.physics.muni.cz/hea/GRBAlpha/ GRBAlpha, launched on 2021 March 22, is a demonstration mission for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). The detector of GRBAlpha consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~50 keV to ~1000 keV. To increase the duty cycle and the downlink rate, the upgrade of the on-board data acquisition software stack is in progress. The ground segment is also supported by the radio amateur community and it takes advantage of the SatNOGS network for increased data downlink volume.

GCN Circular 37928

Subject
GRB 241026A: TNOT optical counterpart detection
Date
2024-10-28T14:55:01Z (a year ago)
Edited On
2024-10-28T16:35:30Z (a year ago)
From
Xiaofeng Wang at Tsinghua University <wang_xf@mail.tsinghua.edu.cn>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@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), A. Esamdin (XAO), S. Antier (OCA)，and W. X. Li (NAOC) report the optical detections of the afterglow of GRB 241026A/EP241026a with a redshift of 2.79 (Fermi GBM team, GCN 37894; A. Melandri et al., GCN 37896; Yan-Qiu Zhang et al., GCN 37921; D. Y. Li et al., GCN 37909; Shrestha et al., GCN 37913; Moskvitin et al., GCN 37916; Mohan et al., GCN 37918; Moskvitin et al., GCN 37922; Izzo et al., GCN 37925).

We obtained 120sx16 (~16.7 hrs after the GRB detection) r-band and 120sx20 (~17.9 hrs after the GRB detection) i-band images with the 0.8~m 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 = 21.01 +- 0.07 mag (MJD = 60611.14)
i = 20.85 +- 0.08 mag (MJD = 60611.19)

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 37925

Subject
GRB 241026A: LBT redshift confirmation
Date
2024-10-28T11:41:05Z (a year ago)
From
Daniele B. Malesani at IMAPP / Radboud University <d.malesani@astro.ru.nl>
Via
Web form
L. Izzo (INAF/OAC), O. Kuhn (LBTO), A. Rossi (INAF/OAS), D. B. Malesani (DAWN/NBI and Radboud Univ.), V. D'Elia (ASI/SSDC & INAF-OAR) and F. Cusano (INAF/OAS), report on behalf of a larger collaboration: 

We observed the optical counterpart (Moskvitin et al.,, GCN 37899) of GRB 241026A (Melandri et al., GCN 37896; Trigg, GCN 37917; Zhang et al., GCN 37921) using the Large Binocular Telescope (LBT) located on Mount Graham (AZ, USA). Observations were carried out with the MODS instrument, and consisted of two 600-s spectra taken in each of the red and blue channels, starting on 2024 October 27.204 UT (6.18 hr after the trigger).

Strong continuum is detected, showing a multitude of absorption lines, which we interpret as due to, among others, Si II 1526, Si II* 1533, C IV 1458,1550, Fe II 1600, Al II 1670, Si II 1808, Al III 1854, 1862, all at a common redshift of z = 2.791.

We thus confirm the redshift value measured by Moskvitin et al. (GCN 37916).

We acknowledge support from R. Ansaldi at LBTO.

GCN Circular 37924

Subject
GRB 241026A: GECAM detection
Date
2024-10-28T08:29:21Z (a year ago)
From
yqzhang_cl@163.com
Via
Web form
Yan-Qiu Zhang (IHEP), Shao-Lin Xiong (IHEP), Chen-Wei Wang (IHEP) report on behalf of the GECAM team:

GECAM-B was triggered both in-flight and on-ground by a long burst, GRB 241026A, at 2024-10-26T22:42:31.200 UTC (T0), which was also detected by Fermi/GBM (Fermi GBM team, GCN #37894), Swift/BAT (A. Melandri et al., GCN #37896), SVOM/GRM (Yan-Qiu Zhang et al., GCN #37921) and EP/WXT (D. Y. Li et al., GCN #37909).

According to the GECAM-B light curves in about 6-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of about 14.9（+4.8,-3.6）s.
The time-averaged spectrum from T0-0.32 to T0+14.61 s could be fit by a power law with a fluence of about 6.67 (+0.36,-0.35) E-06 erg/cm^2 in 10-1000 keV.

The GECAM light curve could be found here:
https://twikinew.ihep.ac.cn/pubgecam/Sandbox/GRB/GECAMB_GRB241026A.png

We note that these results are very preliminary. Refined analysis will be reported later.

Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two microsatellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS).

GCN Circular 37922

Subject
GRB 241026A: BTA and Zeiss-1000 optical observations
Date
2024-10-28T02:29:19Z (a year ago)
From
Moskvitin Alexander at SAO RAS <mosk@sao.ru>
Via
legacy email
A. S. Moskvitin, A. S. Vinokurov, O. I. Spiridonova (SAO RAS),
A. S. Pozanenko (IKI) report on behalf of the GRB follow-up team.

We observed the field of GRB 241026A (The Fermi GBM team, GCN 37894;
Melandri et al., GCN 37896, Li et al., GCN 37909) with the BTA,
6-m telescope of SAO RAS (equipped with the focal reducer Scorpio-I
and V, Rc filters) and also with the 1-m telescope of SAO RAS,
Zeiss-1000 (equipped with the CCD-photometer and Rc filter)
on October 27.

The OT (Moskvitin et al., GCNs 37899, 37916; Watson et al., GCN 37900;
Zheng & Filippenko GCN 37903; Shrestha et al., GCN 37913; Mo et al.,
GCN 37915; Mohan et al., GCN 37918) is clearly detected in our stacked
frames with the following brightness:

UT_start--UT_end   t_mid-T0  exp, s  R magnitude     R_lim  telescope
18:37:41--18:41:24 0.8313 d  4 x 20  21.24 +/- 0.09  23.7   BTA
18:47:40--19:31:31 0.8521 d  8 x 300 21.23 +/- 0.11  23.8   Zeiss-1000

The frames were calibrated against nearby USNO-B1 stars
(R2 magnitudes) and not corrected for MW extinction.

GCN Circular 37921

Subject
GRB 241026A: SVOM/GRM observation
Date
2024-10-28T01:58:49Z (a year ago)
From
yqzhang_cl@163.com
Via
Web form
SVOM/GRM team: Yan-Qiu Zhang, Chen-Wei Wang, Shi-Jie Zheng, Wen-Jun Tan, 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, 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,  Wen-Long 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)

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 a long GRB 241026A (SVOM trigger reference: sb 24102603) at 2024-10-26T22:42:32.000 UT (T0), which was also observed by Fermi/GBM (Fermi GBM team, GCN #37894), Swift/BAT (A. Melandri et al., GCN #37896) and EP/WXT (D. Y. Li et al., GCN #37909).

The real-time alert data and light curves of SVOM/GRM were downlinked to the ground through the VHF system with low latency. The light curve shows that this burst consists of multiple pulses with a T90 of 18.5 +4.0/-3.7 s.

The GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb241026A.png

This burst is located at about 69 degrees from the SVOM optical axis, and outside the ECLAIRs field of view.

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: Yan-Qiu Zhang (IHEP)(zhangyanqiu@ihep.ac.cn)

GCN Circular 37918

Subject
GRB 241026A: GROWTH-India Telescope optical observations
Date
2024-10-28T01:20:53Z (a year 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 241026A (Fermi GBM Team, GCN 37894

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; Melandri et al., GCN 37896, Evans et al., GCN 37897) with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2024-10-27 15:02:21 UT, i.e., 16.3 hours after the Fermi GBM trigger. We obtained multiple exposures of 360 seconds in the r' and i' filters. We detected the afterglow in our images at the positions given by Swift XRT (GCN 37904) and COLIBRI (GCN 37900) In our stacked images, we detected the optical afterglow in the r' filter at the enhanced Swift-XRT position (GCN 37904). The photometry results follow as:

MJD (mid)FilterTotal Exposure (s)Magnitude (AB)
60610.6474653r'10x36020.8 +/- 0.06
60610.7360417i'7x36020.5 +/- 0.06

Above optical afterglow is also observed by Moskvitin et al., (GCN 37899

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), Watson et al., (GCN 37900), Zheng et al., (GCN 37903), Shrestha et al., (GCN 37913), and a spectroscopic redshift has been identified by Moskvitin et al., (GCN 37916)

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 37917

Subject
GRB 241026A Fermi GBM Analysis
Date
2024-10-28T00:42:41Z (a year ago)
From
atrigg2@lsu.edu
Via
Web form
A. Trigg (LSU) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

"At 22:42:31.28 UT on 26 October 2024, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 241026A (trigger 751675356/241026946).
which was also detected by Swift BAT (D. M. Palmer et al. 2024, GCN 37896)
and Einstein Probe  (D.Y. Li et al. 2024, GCN 37909).
The Fermi GBM on-ground location is consistent with the Swift BAT position.

The angle from the Fermi LAT boresight is 43 degrees.

The GBM light curve consists of a single emission episode with a duration (T90)
of about 16 s (50-300 keV). The time-averaged spectrum
from T0+0.003 to T0+16.768 s is best fit by
a Comptonized function with a power law index -0.96 +/- 0.05 and a cutoff energy,
parameterized as Epeak, is 229 +/- 20.

The event fluence (10-1000 keV) in this time interval is
(6.6 +/- 0.3)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+0.70 s in the 10-1000 keV band is 7.1 +/- 0.3 ph/s/cm^2.

A Band function fits the spectrum equally well with
Epeak = 183 +/- 22 keV, alpha = -0.87 +/- 0.07 and beta = -2.17 +/- 0.2.

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 37916

Subject
GRB 241026A: BTA redshift identification of z = 2.79
Date
2024-10-28T00:41:39Z (a year ago)
From
Moskvitin Alexander at SAO RAS <mosk@sao.ru>
Via
legacy email
A. S. Moskvitin, A. S. Vinokurov (SAO RAS), A. S. Pozanenko (IKI)
report on behalf of the GRB follow-up team.

We observed the GRB 241026A afterglow (The Fermi GBM team,
GCN 37894; Melandri et al., GCN 37896; Moskvitin et al., GCN 37899;
Watson et al., GCN 37900; Zheng & Filippenko GCN 37903;
Shrestha et al., GCN 37913; Mo et al., GCN 37915) with the BTA,
6-m telescope of SAO RAS equipped with the Scorpio-I focal reducer
starting on October 27, 18:42:01--19:44:13 UT (t_mid - T0 = 20.51
hours).

In the 4 x 900 sec spectrum obtained with VPHG550G grism (3500--7500
AA, FWHM resolution ~ 10A) we do not observe the continuum lower than
4000A. We also found at least OI, CII, CVI, SiIV, SiII absorption
lines with a common redshift of z = 2.79, which we suggest as the
redshift of the source GRB 241026A.

GCN Circular 37915

Subject
GRB 241026A: J-band observations with WINTER
Date
2024-10-27T21:24:29Z (a year ago)
From
Geoffrey Mo at MIT <gmo@mit.edu>
Via
Web form

Geoffrey Mo (MIT), Tomas Ahumada (Caltech), Benjamin Schneider (MIT), Viraj Karambelkar (Caltech), Danielle Frostig (CfA), Robert Stein (Caltech), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report:

We observed the field of GRB 241026A (Fermi GBM Team, GCN 37894

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; Melandri et al., GCN 37896; Li et al., GCN 37909; D'Avanzo et al., GCN 37908) in the near-infrared J-band with the Palomar 1-m telescope, equipped with the 1-square degree WINTER camera (Lourie et al. 2020, Frostig et al. 2024).

Observations were triggered automatically and began at 2024-10-27T01:39:58 UTC (~3.0 hours after the GRB), consisting of 15 x 120 s exposures. The images were processed using the WINTER data reduction pipeline (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.13352565

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).

We do not detect a source at the optical and enhanced Swift/XRT counterpart location (Evans et al., GCN 37897

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; Lipunov et al., GCN 37898; Moskvitin et al., GCN 37899; Watson et al., GCN 37900; Zheng et al., GCN 37903; Osborne et al., GCN 37904; Shrestha et al., GCN 37913). We obtain the following 5-sigma upper limit: J ~ 18.2 mag (AB).

WINTER (Wide-field INfrared Transient ExploreR) is a partnership between MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF AAG, the David and Lucile Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research.

GCN Circular 37913

Subject
GRB 241026A: Las Cumbres optical detection
Date
2024-10-27T15:49:14Z (a year ago)
From
Manisha Shrestha at University of Arizona <mshrestha1@arizona.edu>
Via
Web form
M. Shrestha (Univ. of Arizona),  D. Sand (Univ. of Arizona), K. D. Alexander (Univ. of Arizona), J. Andrews (Gemini), J. Pearson (Univ. of Arizona), K. Bostroem (Univ. of Arizona), D. A. Howell (LCO/UCSB), C. McCully (LCO/UCSB), M. Newsome (LCO/UCSB), C. Pellegrino (UV), J. Farah (LCO/UCSB) report on behalf of a wider Global Supernova Project collaboration:
 
We observed the field of GRB 241026A (Fermi GBM Team, GCN 37894; Melandri et al., GCN 37896, Evans et al., GCN 37897) with the Las Cumbres Observatory 1-m telescope at McDonald Observatory, on 2024-10-27T02:19:34.4 UT (60610.09 MJD, ~3.6 hours after the trigger) using the Sinistro instrument in r band. We clearly detect the optical counterpart within the error region of Swift XRT with:

r = 19.82 +-0.05 mag

These values were calculated with respect to the PS1 catalog (Tian et al. 2017). Magnitudes are not corrected for galactic extinction. This value is in agreement with Watson et al., GCN 37900, and Zheng et al., GCN 37903

GCN Circular 37909

Subject
EP241026a (GRB 241026A): EP on-board trigger and follow-up observation
Date
2024-10-27T14:34:15Z (a year ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
D. Y. Li, T. Y. Lian, Y. L. Wang, S. X. Wen, W. Yuan (NAO, CAS) report on behalf of the Einstein Probe team:

We report on the detection of an X-ray transient detected by EP-WXT, EP241026a, which triggered the on-board processing unit (trigger ID: 01709112485). A preliminary analysis of the EP-WXT data shows that the transient began at 2024-10-26T22:41:28 (UTC), and lasted for around 150 seconds, with the peak flux of around 8 x 10^-9 erg/s/cm^2 in 0.5-4 keV. The averaged spectrum can be fitted with an absorbed powerlaw（NH fixed at the Galactic value 9.2 x 10^20 cm^-2）with a photon index of 0.8 +/- 0.3. The average unabsorbed flux is (1.6 +/- 0.3) x 10^-9 erg/s/cm2 in 0.5-4 keV. An EP-FXT follow-up observation was triggered about 8 hours later, which detected an uncatalogued X-ray source at R.A. = 293.4008 deg, DEC = 57.9857 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. We note that the trigger time and position of this X-ray transient are consistent with those of GRB 241026A (Fermi GBM team, GCN #37894, Melandri et al. GCN #37896). The averaged EP-FXT spectrum can be fitted with an absorbed powerlaw (NH fixed at the Galactic value), with a photon index of 1.81 +/- 0.08. The derived average unabsorbed flux is (6.4 +/- 0.3) x 10^-12 and (1.06 +/- 0.07) x 10^-11 erg/s/cm2 in 0.5-4 keV and 0.5-10 keV, respectively. All the errors of the parameters quoted are at the 90% C.L.

Please note that the temporal and spectral analyses presented above are preliminary. 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 37908

Subject
GRB 241026A: Swift-XRT refined Analysis
Date
2024-10-27T13:50:10Z (a year ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), E. Ambrosi 
(INAF-IASFPA) , J.A. Kennea (PSU), D.N. Burrows (PSU), M. A. Williams
(PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester) and
P.A. Evans report on behalf of the Swift-XRT team:

We have analysed 7.6 ks of XRT data for GRB 241026A, from 98 s to 45.9
ks after the  BAT trigger. The data comprise 54 s in Windowed Timing
(WT) mode (the first 9 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=2.5 (+0.5, -0.4). At T+226 s  the decay
flattens to an alpha of 0.21 (+0.11, -0.12) before breaking again at
T+7943 s to a final decay with index alpha=0.90 (+/-0.11).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.88 (+/-0.10). The
best-fitting absorption column is  1.43 (+0.32, -0.30) x 10^21 cm^-2,
in excess of the Galactic value of 8.9 x 10^20 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 3.7 x 10^-11 (4.6 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     1.43 (+0.32, -0.30) x 10^21 cm^-2
Galactic foreground: 8.9 x 10^20 cm^-2
Excess significance: 3.0 sigma
Photon index:	     1.88 (+/-0.10)

If the light curve continues to decay with a power-law decay index of
0.90, the count rate at T+24 hours will be 0.10 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.8 x
10^-12 (4.7 x 10^-12) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01262764.

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

GCN Circular 37904

Subject
GRB 241026A: Enhanced Swift-XRT position
Date
2024-10-27T07:18:22Z (a year ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 1669 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 241026A, 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 = 293.40058, +57.98610 which is equivalent
to:

RA (J2000): 19h 33m 36.14s
Dec (J2000): +57d 59' 10.0"

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 37903

Subject
GRB 241026A: KAIT optical observations
Date
2024-10-27T06:33:47Z (a year ago)
From
Weikang Zheng at UC Berkeley <weikang@berkeley.edu>
Via
legacy email
WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on

behalf of the KAIT GRB team:


The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located

at Lick Observatory, responded to GRB 241026A detected by Swift

(Melandri et al., GCN 37896) starting about 3.33 hours after

the bust under cloudy condition. Observations were performed

in the clear (roughly R) filter, and a total of 30x60s images

were obtained. We marginally detected the optical afterglow

(Moskvitin et al., GCN 37899; Watson et al., GCN 37900) in our

coadd image. We measured its brightness of 19.4 +/- 0.3 mag at

a mid time of 3.66 hours after the burst.

GCN Circular 37900

Subject
GRB 241026A: COLIBRÍ Detection of the Optical Counterpart
Date
2024-10-27T03:12:36Z (a year ago)
From
Alan Watson at UNAM <alan@astro.unam.mx>
Via
legacy email
Alan M. Watson (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), Francesco Magnani (CPPM), and Margarita Pereyra (UNAM) report:

We imaged the field of GRB 241026A detected by Fermi/GBM, Swift/BAT, and
Swift/XRT (Fermi GBM Team, GCN Circ. 37894; Melandri et al., GCN Circ.
37896) during the commissioning of the COLIBRÍ (SVOM/F-GFT) telescope at
the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in
Mexico.

We observed with the engineering test camera in a red filter that
approximates SDSS r. We observed from 2024-10-27 01:47 to 02:07 UTC (3.1 to
3.4 hours after the trigger) and obtained 960 seconds of exposure. The data
were reduced using custom software and then analyzed and calibrated against
the PS1 catalog using the STDWeb service (Karpov et al., 2022).

We detect the optical counterpart at RA =293.40029 and Dec = 57.98585
(J2000) with an AB magnitude of:

    r = 19.63 +/- 0.04

This magnitude is similar to that reported by Moskvitin (GCN Circ. 37899)
at about 28 minutes after the trigger.

Further observations are planned.

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

GCN Circular 37899

Subject
GRB 241026A: SAO RAS observations of possible optical afterglow
Date
2024-10-27T00:19:04Z (a year ago)
From
Moskvitin Alexander at SAO RAS <mosk@sao.ru>
Via
legacy email
A. S. Moskvitin, O. I. Spiridonova V. S. Shergin and V. V. Komarov
(SAO RAS) report on behalf of the GRB follow-up team.

We observed the field of the GRB 241026A (The Fermi GBM team,
GCN 37894; Melandri et al., GCN 37896) with 1-m telescope of SAO RAS
equipped with the CCD-photometer on October 26, 23:02:35--23:18:09 UT.
Observations started 20 minutes after the trigger.

Within the prompt enhanced Swift-XRT error circle (Evans, GCN 37897)
we detected a single uncatalogued source (possible GRB afterglow)
with the coordinates
R. A. (J2000) = 19:33:36.06,
Decl. (J2000) = +57:59:09.04 +/- 0".5
and brightness of R = 20.04 +/- 0.14 calibrated against nearby
USNO-B1 stars (R2 magnitudes) and not corrected for MW extinction.
Further observations are ongoing.

GCN Circular 37898

Subject
Fermi GRB 241026A: Global MASTER-Net observations report
Date
2024-10-27T00:15:44Z (a year 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-Tavrida robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB 241026A ( Fermi GBM team, GCN 37894) errorbox  4286 sec after notice time and 4328 sec after trigger time at 2024-10-26 23:54:39 UT, with upper limit up to  18.2 mag. The observations began at zenith distance = 73 deg. The sun  altitude  is -45.5 deg. 

The galactic latitude b = 12 deg., longitude l = 87 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2650323

We obtain a following upper limits.  

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

    4359 | 2024-10-26 23:54:39 |      MASTER-Tavrida | (20h 07m 36.82s , +52d 57m 11.3s) |   C |    60 | 18.0 |        
    4433 | 2024-10-26 23:55:54 |      MASTER-Tavrida | (20h 20m 49.18s , +52d 54m 37.7s) |   C |    60 | 18.2 |        
    4507 | 2024-10-26 23:57:07 |      MASTER-Tavrida | (20h 07m 40.76s , +52d 57m 13.9s) |   C |    60 | 18.1 |        
    4581 | 2024-10-26 23:58:22 |      MASTER-Tavrida | (20h 20m 46.46s , +52d 55m 30.2s) |   C |    60 | 18.1 |        
    4655 | 2024-10-26 23:59:36 |      MASTER-Tavrida | (20h 07m 35.14s , +52d 57m 18.3s) |   C |    60 | 18.0 |        
    4828 | 2024-10-27 00:02:29 |      MASTER-Tavrida | (19h 50m 33.53s , +52d 56m 55.0s) |   C |    60 | 17.8 |        
    4904 | 2024-10-27 00:03:45 |      MASTER-Tavrida | (20h 03m 42.29s , +52d 57m 18.0s) |   C |    60 | 17.9 |        
    4978 | 2024-10-27 00:04:59 |      MASTER-Tavrida | (19h 50m 30.27s , +52d 56m 43.4s) |   C |    60 | 17.8 |        
    5052 | 2024-10-27 00:06:13 |      MASTER-Tavrida | (20h 03m 46.20s , +52d 57m 34.6s) |   C |    60 | 17.9 |        
    5127 | 2024-10-27 00:07:28 |      MASTER-Tavrida | (19h 50m 27.44s , +52d 57m 29.3s) |   C |    60 | 17.7 |        
    5298 | 2024-10-27 00:10:19 |      MASTER-Tavrida | (20h 06m 14.97s , +51d 37m 50.6s) |   C |    60 | 17.8 |        
Filter C is a clear (unfiltred) band. 


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

GCN Circular 37897

Subject
GRB 241026A: Prompt enhanced Swift-XRT position
Date
2024-10-26T23:25:35Z (a year ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:

Using  promptly downlinked XRT event data for GRB 241026A, we find an
enhanced XRT position of the afterglow: RA, Dec: 293.39949, 57.98563
which is equivalent to:
   RA (J2000)  = 19 33 35.88
   Dec (J2000) = +57 59 08.3
with an uncertainty of 1.9 arcseconds (radius, 90% confidence).
Analysis of the promptly available data is online at
http://www.swift.ac.uk/sper/1262764.

Position enhancement is is described by Goad et al. (2007, A&A, 476,
1401) and Evans et al. (2009, MNRAS, 397, 1177).

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

GCN Circular 37896

Subject
GRB 241026A: Swift detection of a burst
Date
2024-10-26T22:56:05Z (a year ago)
From
David Palmer at LANL <palmer@lanl.gov>
Via
email
A. Melandri (INAF-OAR), V. D'Elia (SSDC & INAF-OAR),
D. M. Palmer (LANL), T. Sakamoto (AGU) and B. Sbarufatti (INAF-OAB)
report on behalf of the Neil Gehrels Swift Observatory Team:

At 22:42:32 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 241026A (trigger=1262764).  Swift slewed immediately to the burst.
The BAT on-board calculated location is 
RA, Dec 293.423, +57.980 which is 
   RA(J2000) = 19h 33m 42s
   Dec(J2000) = +57d 58' 49"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single-peak
structure with a duration of about 30 sec.  The peak count rate
was ~3600 counts/sec (15-350 keV), at ~0 sec after the trigger.

The XRT began observing the field at 22:44:26.4 UT, 114.5 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 293.39935, 57.98544 which is equivalent
to:
   RA(J2000)  = 19h 33m 35.84s
   Dec(J2000) = +57d 59' 07.6"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 49 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at https://www.swift.ac.uk/sper.  We
cannot determine whether the source is fading at the present time. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (8.92 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 4.4
(+3.14/-2.68) x 10^21 cm^-2 (90% confidence).

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 117 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. Data from the 2.7'x2.7' sub-image are
not available at this time. The 8'x8' region for the list of sources generated
on-board covers 100% of the XRT error circle. The list of sources is typically
complete to about 18 mag. No correction has been made for the expected
extinction corresponding to E(B-V) of 0.073.

Burst Advocate for this burst is A. Melandri (andrea.melandri 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/)

GCN Circular 37894

Subject
GRB 241026A: Fermi GBM Final Real-time Localization
Date
2024-10-26T22:53:03Z (a year 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 22:42:31 UT on 26 Oct 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 241026A (trigger 751675356.28385 / 241026946).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 300.3, Dec = 52.9 (J2000 degrees, equivalent to J2000 20h 01m, 52d 53'), with a statistical uncertainty of 1.6 degrees.

The angle from the Fermi LAT boresight is 41.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn241026946/quicklook/glg_skymap_all_bn241026946.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/bn241026946/quicklook/glg_healpix_all_bn241026946.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn241026946/quicklook/glg_lc_medres34_bn241026946.gif
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