GRB 240802A, EP240802a
GCN Circular 37178
Subject
EP240802a: Kinder optical, SWIFT-UVOT, and SWIFT-XRT upper limits 6 days after the WXT detection
Date
2024-08-14T12:51:11Z (a year ago)
From
Janet Chen at National Central University <janetstars@gmail.com>
Via
Web form
Y. J. Yang, A. Aryan, T.-W. Chen (all NCU), A. K. H. Kong (NTHU), S. Yang (HNAS), C.-C. Ngeow, C.-S. Lin, H.-Y. Hsiao, W.-J. Hou, C.-H. Lai, A. Sankar. K, M.-H. Lee, Y.-C. Pan, H.-C. Lin, J.-K. Guo (all NCU), S. J. Smartt (Oxford/QUB), H.-W. Lin (UMich), G. H. Sun, Z. N. Wang (both HNAS), J. Gillanders, H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz and M. Huber (both IfA, Hawaii) report:
We continued to observe the field of the fast X-ray transient EP240802a (Wang et al., GCN 37019, Aryan et al., GCN 37021, Leonini et al., GCN 37029, Wang et al., 37033, Zheng et al. 37094) using the 1m LOT at Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen & Yang et al., 2024arXiv240609270C). EP240802a showed a time coincidence with GRB 240802A (Waratkar et al., GCN 37018, Wang et al., GCN 37022, Frederiks et al., GCN 37079), which was first proposed by Aryan et al., (GCN 35021), and later confirmed by Svinkin et al., (GCN 37026) and Kozyrev et al., (GCN 37078). We triggered LOT again at 15:35 UTC on the 8th of August 2024 (MJD = 60530.650), 6.21 days after the EP trigger, with the hope of a supernova (SN) component emergence.
We utilized the astroalign (Beroiz et al., 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al., 2022, ApJ, 935, 167) packages to align and stack the individual frames. In the stacked frames, we did not find any evidence of a new and uncatalogued source within the 10" error circle of the Follow-up X-ray Telescope (FXT) onboard the Einstein Probe (EP) mission; hence, no emergence of an SN component 6.21 days post the Wide-field X-ray Telescope (WXT) trigger onboard EP.
Moreover, we utilized the Python-based package AutoPhOT (Brennan & Fraser, 2022, A&A, 667, A62) to perform the PSF photometry on our stacked frame. The details of the observations and the upper limit (in the AB system) are as follows:
Telescope | Filter | MJD (start) | t-t0 | Exposure | Magnitude | avg. Seeing | med. Airmass
LOT | r | 60530.650 | 6.21 days | 300 sec * 6 | >22.6 | 1".16 | 1.27
We also requested a Swift ToO observation, which was conducted on 2024-08-07 at 06:05:42 UTC, with a total exposure time of approximately 3536 seconds. No significant X-ray source was detected by XRT within the 10” error circle of EP FXT. Using the method described by Kraft et al. (1991), we estimated a 90% confidence level (CL) upper limit for the count rate at 0.00126 c/s. Assuming a photon index of 2 and NH =2.67×10^21 cm^-2 along the line of sight to the source position, WebPIMMS predicts an unabsorbed flux of 6.24×10^-14 ergs cm^-2 s^-1. No optical counterpart consistent with the EP FXT position was detected in the UVOT observation, with a total exposure of 1427 seconds using the w2 filter. An upper limit magnitude of >21.79 (AB system) was obtained.
The presented magnitudes are calibrated using the field stars from the Pan-STARRS1 catalogue and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V) = 0.56 mag in the direction of the transient (Schlafly & Finkbeiner 2011).
We thank the Swift team for scheduling the ToO observation.
GCN Circular 37094
Subject
EP240802a/GRB240802A: KAIT optical upper limit
Date
2024-08-07T19:47:10Z (a year ago)
From
Weikang Zheng at UC Berkeley <weikang@berkeley.edu>
Via
legacy email
WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and
Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, responded to the fast X-ray transient EP240802a
from the Einstein Probe (Wang et al. GCNC 37019) starting at 04:17
UT, Aug 3rd, ~0.74 days after the trigger. EP240802a was also found
to be coincidence with GRB 240802A (Waratkar et al., GCN 37018;
Aryan et al., GCN 37021; Kozyrev et al., GCN 37078). We obtained a
set of clear (roughly R) filter images, we do not detect any new
optical counterpart in the FXT errorbox (Wang et al. GCNC 37019),
neither in single image, nor in the co-add images. We measure the
limiting mag to be ~21.0 in 28x60s co-add image at a mid time of
~0.80 days after the trigger. Our result is consistent with the
upper limit reported from Aryan et al. (GCN 37021), Quadri et al.
(GCN 37023) and Leonini et al. (GCN 37029).
GCN Circular 37079
Subject
Konus-Wind detection of GRB 240802A (EP240802a)
Date
2024-08-06T17:04:23Z (a year ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
Via
legacy email
D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin,
A. Tsvetkova, M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:
The long GRB 240802A (AstroSat CZTI detection: Waratkar et al., GCN 37018;
SVOM/GRM observation: Wang et al., GCN 37022;
IPN triangulation: Svinkin et al., GCN 37026; Kozyrev et al., GCN 37078),
associated with the fast X-ray transient EP240802a (Wang et al., GCN 37019;
Aryan et al., GCN 37021; Svinkin et al., GCN 37026; Kozyrev et al., GCN 37078),
triggered Konus-Wind (KW) at T0=38048.482 s UT (10:34:08.482).
The burst light curve shows a multi-peaked emission pulse,
which starts at ~T0-13 s and has the total duration of ~47 s.
Two main peaks in the light curve are located around ~T0 and ~T0+29 s,
respectively.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB240802_T38048/
As observed by Konus-Wind, the burst had the total fluence
of 1.63(-0.14,+0.15)x10^-5 erg/cm^2 and a 2.944-s peak energy flux,
measured from T0+0.032 s, of 8.21(-2.63,+3.09)x10^-6 erg/cm^2/s
(both in the 20 keV - 10 MeV energy range).
Due to telemetry errors in the KW triggered-mode spectra, the spectral analysis
was performed using the 3-channel waiting-mode count rates.
Modeling the time-integrated spectrum (measured from T0-13.161 s to T0+33.943 s)
by a power law with exponential cutoff (CPL) function dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
yields alpha = -1.38(-0.11, + 0.12) and Ep = 226(-36,+51) keV.
A CPL fit to the spectrum near the peak count rate (measured from T0-1.385 s to T0+1.559 s)
results in alpha = -1.02(-0.15,+0.17) and Ep = 273(-42,+55) keV.
All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.
GCN Circular 37078
Subject
Improved IPN triangulation of GRB 240802A / EP 240802a
Date
2024-08-06T16:49:43Z (a year ago)
From
Anna Ridnaia at Ioffe Institute <ridnaia@mail.ioffe.ru>
Via
Web form
A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin
on behalf of the HEND/Mars Odyssey team,
D. Svinkin, D. Frederiks, A. Ridnaia, A. Lysenko,
and T. Cline on behalf of the Konus-Wind team,
E. Burns, on behalf of the IPN,
E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
G. Waratkar, V. Jethwani, J.Joshi, V. Bhalerao, D. Bhattacharya, and S. Vadawale,
on behalf of the Astrosat-CZTI team,
and
W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr,
and A.S. Gardner on on behalf of the GRS-Odyssey GRB team,
report:
Using the Mars-Odyssey (HEND) data we have improved
the previous IPN error box (Svinkin et al., GCN 37026).
The coordinates of the updated 3 sigma error box are:
---------------------------------------------
RA(2000), deg Dec(2000), deg
---------------------------------------------
Center:
287.477 (19h 09m 54s) -1.718 ( -1d 43' 05")
Corners:
285.131 (19h 00m 31s) +2.050 ( +2d 03' 01")
285.257 (19h 01m 02s) +2.088 ( +2d 05' 15")
289.523 (19h 18m 05s) -5.648 ( -5d 38' 51")
289.393 (19h 17m 34s) -5.668 ( -5d 40' 03")
---------------------------------------------
The error box area is 1.11 sq. deg, and its maximum
dimension is 8.9 deg (the minimum one is 7.6 arcmin).
The Sun distance was 146 deg.
The IPN localization may be further improved.
The EP240802a localization is inside the improved box.
Updated triangulation map and HEALPix FITS files are posted at
http://www.ioffe.ru/LEA/GRBs/GRB240802_T38048/IPN/
The HEALPix triangulation map is the multi-order HEALPix in units of probability density.
The Konus-Wind time history and spectrum will be given
in a forthcoming GCN Circular.
GCN Circular 37033
Subject
EP240802a: correction of EP-WXT trigger time in GCN 37019
Date
2024-08-05T03:42:18Z (a year ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
Y. L. Wang (NAOC, CAS), A. Li (BNU), W. X. Wang, H. W. Pan (NAOC,CAS) on behalf of the Einstein Probe team
The trigger time of EP240802a given in GCN 37019 is incorrect. The correct time is 2024-08-02T10:32:52 (UTC). This correction has also been implemented in GCN 37019.
We apologize for the mistake.
GCN Circular 37029
Subject
EP240802a: Montarrenti Observatory optical upper limit
Date
2024-08-04T20:41:01Z (a year ago)
From
Simone Leonini at Montarrenti Observatory (Siena, Italy) <s.leonini@iol.it>
Via
Web form
S. Leonini, M. Conti, P. Rosi, L.M. Tinjaca Ramirez (Montarrenti Observatory, Siena, Italy, part of UAI/SSV-GRB section), M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy), K. Kalinowski (Aarhus University, Department of Physics and Astronomy) and B. De Simone (Universita' degli Studi Di Salerno) report:
we observed the field of the fast X-ray transient EP240802a (Einstein Probe, GCN 37019, Wang et al.) probably associated to GRB 240802A (GCN 37018, G. Waratkar et al.) with the automated and remoted 0.53m Ritchey-Chretien telescope at Montarrenti Observatory (Siena, Italy, IAU code C88).
The observations were started at 2024-08-03 22:38:41 UT (approximately 36 hours after the discovery of the X-ray transient) stacking 45x40s calibrated Rc-band CCD images.
We have not found any optical transient candidate within the error-box of the EP mission position with the following upper limit:
MJD Filter Limit Err
60526.4544 Rc > 20.47 +/-0.07
consistent with other follow-up observations (GCN 37021, A. Aryan et al.; GCN 37023, U. Quadri et al.)
Magnitude was calibrated with the nearby PanSTARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied.
GCN Circular 37026
Subject
IPN triangulation of GRB 240802A / EP 240802a
Date
2024-08-04T13:52:18Z (a year ago)
Edited On
2024-08-05T15:44:14Z (a year ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
Edited By
Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
Via
Web form
D. Svinkin, D. Frederiks, A. Ridnaia, A. Lysenko,
and T. Cline on behalf of the Konus-Wind team,
E. Burns, on behalf of the IPN,
E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
G. Waratkar, V. Jethwani, J.Joshi, V. Bhalerao, D. Bhattacharya, and S. Vadawale,
on behalf of the Astrosat-CZTI team, report:
The long-duration GRB 240802A
(AstroSat-CZTI detection: Waratkar et al., GCN 37018;
SVOM-GRM detection: Wang et al., GCN 37022)
was detected by Astrosat (CZTI), Konus-Wind, and INTEGRAL (SPI-ACS),
and SVOM (GRM) at about 38044 s UT (10:34:04).
We have triangulated it to a preliminary, 3 sigma error region
whose area is 394 sq. deg, and its maximum
dimension is 51 deg (the minimum one is 6.7 deg).
This localization may be improved.
The X-ray transient EP 240802a (Wang et al., GCN 37019) is inside the region
(at the distance of 0.7 deg from the center line of the Konus-SPI-ACS annulus and
0.4 deg from the center line of Konus-CZTI annulus),
supporting the association of the GRB and EP 240802a.
A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB240802_T38048/IPN/
The HEALPix triangulation map is the multi-order HEALPix in units of probability density.
The Konus-Wind time history and spectrum will be given
in a forthcoming GCN Circular.
GCN Circular 37022
Subject
GRB 240802A: SVOM/GRM observation
Date
2024-08-04T08:01:38Z (a year ago)
From
Chenwei Wang at IHEP <cwwang@ihep.ac.cn>
Via
Web form
SVOM/GRM team: Chen-Wei Wang, Yan-Ting Zhang, Wen-Hui Yu, Yong-Wei Dong, Jiang-Tao Liu, Shi-Jie Zheng, Jian-Chao Sun, Wen-Jun Tan, Jiang He, Min Gao, Hao-Xuan Guo, Yue Huang, 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, Shu-Min Zhao, Xiao-Yun Zhao, Chao Zheng (IHEP), Maria-Grazia Bernardini (LUPM/INAF-OAB), Laurent Bouchet (IRAP), David Corre (CEA), Patrick Maeght (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), JeanLuc Attéia (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:
During the commissioning phase, the SVOM/GRM was triggered in-flight by a long GRB 240802A at 2024-08-02T10:34:03.300 UT (T0), which also triggered INTEGRAL/SPI-ACS (TrigID 10829) and AstroSat (GCN 37018).
With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multiple pulses with a duration of about 60 s.
The GRM light curve can be found here:
https://www.bursthub.cn/admin/static/svgrb240802A.png
The SVOM/GRM on-ground localization of this burst is (J2000):
RA: 282.6 deg
DEC: 2.6 deg
Error: 21.4 deg (1 sigma, statistical only)
We caution that the calibration of SVOM/GRM is undergoing and this localization is subject to systematic errors. The localization may be improved in the refined analysis.
At the time of this burst ECLAIRs was not in operational mode.
We note that the time coincidence (GCN 37021) and localization coincidence between EP240802a (GCN 37019) and GRB 240802A suggest the association of these two events. Further follow-up observations are strongly encouraged.
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 37021
Subject
EP240802a: Time coincidence with GRB 240802A and optical upper limits with Kinder observations
Date
2024-08-03T17:49:08Z (a year ago)
From
Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941@gmail.com>
Via
Web form
A. Aryan, T.-W. Chen (both NCU), S. Yang (HNAS), A. K. H. Kong (NTHU), W.-J. Hou, H.-Y. Hsiao, Y. J. Yang, Y.-C. Pan, C.-C. Ngeow, C.-S. Lin, C.-H. Lai, A. Sankar. K, M.-H. Lee, H.-C. Lin, J.-K. Guo (all NCU), S. J. Smartt (Oxford/QUB), H.-W. Lin (UMich), G. H. Sun, Z. N. Wang (both HNAS), J. Gillanders, H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz and M. Huber (both IfA, Hawaii) report:
We observed the field of the fast X-ray transient EP240802a (Wang et al., GCN 37019) using the One-meter Telescope (LOT) at Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen & Yang et al., 2024arXiv240609270C). The first LOT epoch of observations started at 15:46 UTC on 3rd of August 2024 (MJD = 60525.657), 1.22 days after the EP trigger.
In particular, we highlight a time coincidence between EP240802a and GRB 240802A (Waratkar et al. GCN 37018). The EP transient was observed to start at 2024-08-02T10:27:22 (UTC) and lasted for more than 500 seconds. AstroSat CZTI detected a long burst GRB 240802A with a T90 of 39 (+3, -8) seconds, showing multiple emission peaks, with the strongest peak at 2024-08-02T10:34:04.5 (UTC). The durations of these two events overlap and could potentially be physically related. Waratkar et al. also mentioned that GRB 240802A was detected by INTEGRAL/SPI-ACS (Trigger 10829) and Konus/WIND (IPN notices). There is no positional information from INTEGRAL at the time of writing and we cannot confirm if they overlap spatially. However, given the time coincidence, we strongly encourage further follow-up investigations.
We use the Kinder pipeline (Yang et al. A&A 646, A22) to stack six reduced frames, and to subtract the stacked image with the Pan-STARRS1 template image. However, we do not detect any optical counterpart in the errorbox of 10 arcseconds around the FXT reported position of the EP240802a in the subtracted frames. The details of the observations and measured 3-sigma upper limit (in the AB system) are as follow:
Telescope | Filter | MJD (start) | t-t0 | Exposure | Magnitude | avg. Seeing | med. Airmass
LOT | r | 60525.657 | 1.22 days | 300 sec * 6 | > 21.32 | 1".6 | 1.26
The presented magnitudes are calibrated using the field stars from the Pan-STARRS1 catalog and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V) = 0.56 mag in the direction of the transient (Schlafly & Finkbeiner 2011).
GCN Circular 37019
Subject
EP240802a: EP-WXT detection and EP-FXT follow-up observation of a fast X-ray transient
Date
2024-08-03T15:13:22Z (a year ago)
Edited On
2024-08-04T23:04:13Z (a year ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Edited By
Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
Y. L. Wang (NAOC, CAS), A. Li (BNU), W. X. Wang, H. W. Pan, Z. X. Ling, C. C. Jin, Y. Liu, C. Zhang, H. Q. Cheng, W. Chen, C. Z. Cui, D. W. Fan, H. B. Hu, M. H. Huang, D. Y. Li, H. Y. Liu, M. J. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, X. Pan, H. Sun, Y. L. Wang, Q. Y. Wu, X. P. Xu, Y. F. Xu, H. N. Yang, W. Yuan, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), Y. Chen, S. M. Jia, W. W. Cui, D. W. Han, C. K. Li, L. M. Song, X. F. Zhao, J. Zhang, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team
We report on the detection of a fast X-ray transient, designated EP240802a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. A follow-up observation by the Follow-up X-ray Telescope (FXT) on board EP was triggered about 14 hours after the WXT detection, and an uncatalogued X-ray source is detected at R.A. = 287.8070 deg, DEC = -2.3125 deg (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. statistical and systematic).
The transient event was observed to start at 2024-08-02T10:32:52 (UTC). The WXT position of the source is R.A. = 287.802 deg, DEC = -2.354 deg (J2000) with an uncertainty of 1.9 arcmin in radius (90% C.L. statistical and systematic). The transient event lasts for more than 500 seconds. The lightcurve of the transient observed by the WXT exhibits three sequentially weakened peaks. The average 0.5-4 keV spectrum can be fitted with an absorbed power law with a photon index of 0.94(+0.59/-0.56) (with a freely fitted column density value of 2.5(+2.0/-1.8) x 10^21 cm^-2). The derived average unabsorbed 0.5-4 keV flux is 1.7(+0.4/-0.3) x 10^-9 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters.
The average FXT spectrum in 0.5-10 keV band can be fitted by an absorbed power law with a photon index of 1.89(+0.33/-0.31) (with a freely fitted column density value of 4.8(+1.4/-1.2) x 10^21 cm^-2), giving an average unabsorbed flux of 1.3(+0.2/-0.1) x 10^-12 erg/s/cm^2.
No previously known bright X-ray sources are found within the error circle around the source position. Further follow-up observations are encouraged to identify the nature of this X-ray transient.
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 37018
Subject
GRB 240802A: AstroSat CZTI detection of a long burst
Date
2024-08-03T15:02:08Z (a year ago)
From
Gaurav Waratkar at IIT Bombay <gauravwaratkar@iitb.ac.in>
Via
Web form
G. Waratkar (IITB), A. Dasgupta (BITS Pilani, Hyderabad), J. Joshi (IUCAA), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:
Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long-duration GRB 240802A which was also detected by INTEGRAL/SPI-ACS (Trigger 10829) and Konus/WIND (IPN notices).
The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2024-08-02 10:34:04.5 UTC. The measured peak count rate associated with the burst is 213 (+35, -29) counts/s above the background in the combined data of three quadrants (out of four), with a total of 2026 (+291, -328) counts. We caution that there is a 0.3 s readout dead time in CZT data during the burst which affects the calculated peak count rate and total counts. The local mean background count rate was 259 (+2, -2) counts/s. Using cumulative rates, we measure a T90 of 39 (+3, -8) s.
The source was clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2024-08-02 10:34:07.1 UTC. The measured peak count rate associated with the burst is 205 (+63, -71) counts/s above the background in the combined data of all quadrants, with a total of 4553 (+1494, -1658) counts. The local mean background count rate was 1332 (+9, -9) counts/s. We measure a T90 of 46 (+1, -2) s from the cumulative Veto light curve.
CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project.
CZTI GRB detections are reported regularly on the payload site at:
http://astrosat.iucaa.in/czti/?q=grb