Gamma-ray Burst 240828B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN Circular #37318
SVOM/ECLAIRs commissioning team: Herv=C3=A9 Le Provost, St=C3=A9phane Schan= ne, Fr=C3=A9d=C3=A9ric Chateau, Nicolas Dagoneau (CEA), Olivier Godet, Laur= ent Bouchet, Sebastien Guillot, Juliette Alaux (IRAP), Fr=C3=A9d=C3=A9ric P= iron (LUPM), Karine Mercier, Marie-Claire Charmeau, Stefano Crepaldi (CNES)= , Alexis Coleiro (APC)
SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang (I= HEP), St=C3=A9phane Basa (LAM), Jean-Luc Atteia (IRAP), Arnaud Claret (CEA)= , Zi-Gao Dai (USTC), Fr=C3=A9d=C3=A9ric Daigne (IAP), Jin-Song Deng (NAOC),= Andrea Goldwurm (APC), Diego G=C3=B6tz (CEA), Xu-Hui Han (NAOC), Cyril Lac= haud (APC), En-Wei Liang (GXU), Yu-Lei Qiu (NAOC), Susanna Vergani (Obs.Par= is), 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/ECLAIRs telescope triggered and lo= cated a very soft and weak X-ray transient at 2024-08-28T13:12:43 UT (Ttime= Tb), called GRB 240828B. The burst was detected by the Image Trigger (IMT) = with a signal to noise ratio of 7.1 in the 5-8 keV energy band on a single = time window of 81.92 s starting at TimeTb. Even if the source is weak, the = quality indicators of the reconstructed image are good.
The transient location is RA, Dec =3D 63.36, 16.71 (J2000). This is about 2= 7 degrees from the ECLAIRs optical axis. The statistical uncertainty on thi= s position is 12 arcminutes, to which we recommend to add 10 arcminutes of = systematic uncertainty. The field of view was free of the Earth.=20
SVOM did not slew to the burst since automated slewing is not yet enabled.
The Space Variable Objects Monitor (SVOM) is a China-France joint mission l= ed by the Chinese National Space Administration (CNSA, China), French Space= Agency (CNES, France) and the Chinese Academy of Sciences (CAS, China), wh= ich is dedicated to observing gamma-ray bursts and other transient phenomen= a in the energetic universe. ECLAIRs was developed jointly by APC, CEA, CNE= S and IRAP.
The SVOM point of contact for this burst is: s.schanne AT cea.fr
GCN Circular #37324
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the SVOM/ECLAIRs GRB 240828B. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021706
Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the SVOM/ECLAIRs event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration.
Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).
This circular is an official product of the Swift-XRT team.
GCN Circular #37334
K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti (INAF-OAB), C. Salvaggio (INAF-OAB), S. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the SVOM/ECLAIRs-detected burst GRB 240828B, collecting 2.9 ks of Photon Counting (PC) mode data between T0+13.5 ks and T0+25.0 ks.
Two uncatalogued X-ray sources are detected, of which one ("Source 1") is above the RASS 3-sigma upper limit at this position, and is therefore likely the GRB afterglow. Using 2142 s of PC mode data and 3 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 63.45995, +16.71561 which is equivalent to:
```
RA (J2000): 04h 13m 50.39s
Dec(J2000): +16d 42' 56.2"
```
with an uncertainty of 2.6 arcsec (radius, 90% confidence). This position is 5.5 arcmin from the SVOM/ECLAIRs position.
The light curve can be modelled with a power-law decay with a decay index of alpha=1.8 (+/-0.9).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.8 (+0.5, -0.4). The best-fitting absorption column is 6.2 (+3.7, -2.7) x 10^21 cm^-2, in excess of the Galactic value of 2.9 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.7 x 10^-11 (7.2 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     6.2 (+3.7, -2.7) x 10^21 cm^-2
Galactic foreground: 2.9 x 10^21 cm^-2
Excess significance: 1.9 sigma
Photon index:	     1.8 (+0.5, -0.4)
```
If the light curve continues to decay with a power-law decay index of 1.8, the count rate at T+24 hours will be 3.6 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.7 x 10^-13 (2.6 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00021706. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00021706.
This circular is an official product of the Swift-XRT team.
GCN Circular #37345
WeiKang Zheng and Alexei V. Filippenko (UCB),
SVOM JSWG: Jian-Yan Wei (NAOC, China), Bertrand Cordier (CEA, F),
Shuang-Nan Zhang (IHEP, CN), Stephane Basa (LAM, F), Jean-Luc Att=C3=A9ia
(IRAP, F), Arnaud Claret (CEA, F), Zi-Gao Dai (USTC, CN), Frederic Daigne
(IAP, F), Jin-Song Deng (NAOC, CN), Andrea Goldwurm (APC, F),
Diego G=C3=B6tz (CEA, F), Xu-Hui Han (NAOC, CN), Cyril Lachaud (APC, F),
En-Wei Liang (GXU, CN), Yu-Lei Qiu (NAOC, CN), Susanna Vergani
(Obs. Paris, F), Jing Wang (NAOC, CN), Chao Wu (NAOC, CN), Li-Ping Xin
(NAOC, CN), Bing Zhang (UNLV, CN)
report on behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, responded to GRB 240828B from the SVOM/ECLAIRs
(Le Provost et al., GCN 37318) by observing the Swift/XRT afterglow
position (Page et al., GCN 37334) starting at 11:05 UT, Aug 29th,
~21.88 hours after the trigger. A set of of 48x60s clear (roughly R)
filter images were obtained. Preliminary analysis do not reveal any
new optical counterpart candidate within the X-ray afterglow error
circles (Page et al., GCN 37334), neither in single image, nor in
the co-add images. We estimate the limiting magnitude of our coadd
image to be ~20.5 mag.
GCN Circular #37346
A. S. Moskvitin and O. I. Spiridonova (SAO RAS) report on behalf of the GRB follow-up team.
We observed the field of GRB 240828B (Le Provost et al., GCN 37318) with the SAO RAS 1-meter telescope Zeiss-1000 equipped with the CCD-photometer on August 29, 19:36:46 -- 20:00:01 UT (t_mid - T0 = 30.594 hours = 1.2748 days). We obtained several images in Rc band with a total exposure of 1040 seconds.
Within the XRT error circle (Page et al., GCN 37334) we didn't detect any source down to a limiting magnitude of R_lim = 21.0 as well as KAIT team (Zheng et al., GCN 37345).
The field was calibrated against nearby SDSS stars (magnitudes converted with Lupton 2005 equations) and not corrected for the Galaxy extinction.
GCN Circular #37347
SVOM/C-GFT team: Chao WU (NAOC), Zhe Kang (CHO)=EF=BC=8CLiping Xin(NAOC), X= uhui Han(NAOC),Pinpin Zhang (NAOC)=EF=BC=8CXiaomeng Lu (NAOC), Zhenwei Li (= CHO)=EF=BC=8CYou Lv (CHO)=EF=BC=8CRuosong Zhang (NAOC)=EF=BC=8CYujie Xiao(N= AOC)
SVOM JSWG: Jian-Yan Wei (NAOC, China), Bertrand Cordier (CEA, F), Shuang-N= an Zhang (IHEP, CN), Stephane Basa (LAM, F), Jean-Luc Att=C3=A9ia (IRAP, F= ), Arnaud Claret (CEA, F), Zi-Gao Dai (USTC, CN), Frederic Daigne (IAP, F)= , Jin-Song Deng (NAOC, CN), Andrea Goldwurm (APC, F), Diego G=C3=B6tz (CEA= , F), Xu-Hui Han (NAOC, CN), Cyril Lachaud (APC, F), En-Wei Liang (GXU, CN)= , Yu-Lei Qiu (NAOC, CN), Susanna Vergani (Obs.Paris, F), Jing Wang (NAOC, C= N), Chao Wu(NAOC, CN), Li-Ping Xin (NAOC,CN), Bing Zhang (UNLV, CN)
We observed the field of the SVOM/ECLAIRs-detected burst GRB 240828B (Le Pr= ovost et al., GCN 37318) starting at 16:14:47 UT, August 28, 2024, ~3.06 hr= after the burst trigger with C-GFT (Chinese Ground Follow-up Telescope in = SVOM mission) in System Test Mode (STM). C-GFT is located at Jilin (long.= =3D126.33 deg, lat.=3D 43.8243778 deg), Changchun Observatory, National Ast= ronomical Observatories, CAS. It has FOV of 1.28 deg x 1.28 deg with a 4k*4= k CMOS detector mounted on the primary focus of 1.2-meter-aperure telescope= .
A series of g ,r, and i band images were obtained. We obtained stacked imag= es of g: 249x10s, r: 232x 10s and i: 244x10s. No optical counterpart candid= ate was detected within the X-ray afterglow error circles (Page et al. GCN 37334) down to the limiting magnitude of mag_g=3D1= 9.7, mag_r=3D19.2, and mag_i=3D20.1 . It is consistent with the results reported by Zheng et al.(G= CN 37345) and Moskvitin et al. (GCN 37346).=20
The photometry was calibrated with nearby Pan-STARRS 1 catalogs.
We thank the observation assistant Chunlei Guo at Jilin observatory for the= ir excellent support.
GCN Circular #37348
SVOM/GWAC-F50A team=EF=BC=9AL.P.Xin(NAOC), Y.G.Yang(HNU), X.H.Han, X.M.Lu, = R.S.Zhang, Y.Xu, Y.J.Xiao, P.P.Zhang, H.B.Cai, Y.L.Qiu, H.L.Li,C.Wu, L.Lan,= W.J.Xie, J.Y.Wei(NAOC),J.Wang,X.G.Wang(GXU)
SVOM JSWG: Jian-Yan Wei (NAOC, China), Bertrand Cordier (CEA, F), Shuang-N= an Zhang (IHEP, CN), Stephane Basa (LAM, F), Jean-Luc Att=C3=A9ia (IRAP, F= ), Arnaud Claret (CEA, F), Zi-Gao Dai (USTC, CN), Frederic Daigne (IAP, F)= , Jin-Song Deng (NAOC, CN), Andrea Goldwurm (APC, F), Diego G=C3=B6tz (CE= A, F), Xu-Hui Han (NAOC, CN), Cyril Lachaud (APC, F), En-Wei Liang (GXU, CN= ), Yu-Lei Qiu (NAOC, CN), Susanna Vergani (Obs.Paris, F), Jing Wang (NAOC,= CN), Chao Wu(NAOC, CN), Li-Ping Xin (NAOC,CN), Bing Zhang (UNLV, CN)
We began to observe GRB 240828B (Le Provost et al., GCN 37318) detected by = SVOM/ECLAIRs, with GWAC-F50A telescope at Xinglong station,China,at 16:45:5= 0(UT), August 28,2024, about 3.55 hours after the burst. The weather was no= t good.
After stacking 20*100 seconds, no any new sources were detected in our stac= ked image within the X-ray afterglow error circles (Page et al. GCN 37334) = down to a limit magnitude of 18.5 mag in R band at the mid-time of 3.83 hou= rs post the burst, calibrated to several nearby USNO B1.0 stars.
We acknowledge the excellent support from observation assistant Yangtong Zh= eng and Winlong Dong.
GCN Circular #37350
B.-T. Wang, R.-Z. Li, F.-F. Song, J. Mao, K.-X. Lu and J.-M. Bai (YNAO, CAS= ) report:
We observed the field of GRB 240828B (SVOM/ECLAIRs, T0 at 2024-08-28T13:12:= 43, GCN 37318) using the GMG-2.4m telescope at the Lijiang Observatory. The= observation began at 2024-08-28T19:21:41.934, about 6.13 hours after the t= rigger.
No new reliable optical counterpart was detected within the 2.6-arcsec Swif= t/XRT error circle (GCN 37334), down to a 5-sigma limiting magnitude of sds= s-r =EF=BD=9E 21.7 mag, derived from calibration against the Pan-STARRS DR1= field stars.
We acknowledge the staff at the Lijiang Observatory for conducting the obse= rvation.
GCN Circular #37352
Benjamin Schneider (MIT), Geoffrey Mo (MIT), Robert Stein (Caltech), Viraj Karambelkar (Caltech), Nathan Lourie (MIT), Danielle Frostig (MIT), Tomas Ahumada (Caltech), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report:
We observed the field of the SVOM/ECLAIRs GRB 240828B (Le Provost et al, GCN 37318) in the near-infrared J-band with the Palomar 1-m telescope, equipped with the 1-square degree WINTER camera (Lourie et al. 2020).
Our observations began at 2024-08-29T09:00:15 UTC (~20 hours after the GRB trigger) and consisted of 30x120s exposures. The images were processed using the WINTER data reduction pipeline (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.10888436), with image subtraction performed relative to J-band images from the UKIRT Hemisphere survey (Dye et al., 2017).
In our stacked and subtracted images, we do not detect any new source within the Swift/XRT error circle (Page et al., GCN 37334) down to a 5-sigma depth of J ~ 19.2 mag (AB). The magnitude is not corrected for Galactic extinction.
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 #37359
D. Akl (AUS), S. Antier (OCA), M. Coughlin (UMN), P-A Duverne (APC), P. Hello (IJCLAB), C. Andrade (UMN), I. Tosta e Melo (UniCT-DFA), S. Karpov (FZU), D. Turpin (CEA-Saclay/Irfu), N. Guessoum (AUS), T. Pradier (Unistra/IPHC), R. Inasaridze, V. Aivazyan, N. Kochiashvili (AbAO), K. Noysena, M. Tanasan (NARIT), A. Kaeouch (OUCA) on behalf of the GRANDMA collaboration:
We performed observations with GRANDMA and its citizen science project Kilonova-catcher (KNC) on the field of GRB 240828B, detected by SVOM/ECLAIRs (GCN 37318), with the TRT-SRO, Abastumani-T70, and KNC-ASO telescopes.
The first observations started on 29-08-2024 at 10:24:08 (UTC), 0.88 days after the GRB trigger, and lasted for 0.65 days. The observations covered the B, V, R, and I filters.
We did not detect any optical counterpart at the Swift-XRT afterglow position (3 arcsec, centered around RA, Dec = 63.45995, 16.71561).
We also searched the SVOM/ECLAIRs localization position (25 arcmin, centered around RA, Dec = 63.36, 16.71) and did not detect any optical counterpart.
Our photometry results and upper limits can be found at: https://skyportal-icare.ijclab.in2p3.fr/public/sources/S24082808/
All the data has been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022).
Our results are consistent with Zheng et al. (GCN 37345), Moskvitin et al. (GCN 37346), Wu et al. (GCN 37347), Xin et al. (GCN 37348), Wang et al. (GCN 37350), and Schneider et al. (GCN 37352).
We use the SkyPortal application (skyportal.io) to monitor our observational campaign. We thank SVOM for the useful communication.
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 49, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/).
GCN Circular #37360
Guowang Du (SWIFAR, YNU), Helong Guo (SWIFAR, YNU), Jinghua Zhang (SWIFAR, YNU), Tao Wang (SWIFAR, YNU), Zhenfei Qin (SWIFAR, YNU), Yicheng Jin (SWIFAR, YNU), Yu Pan (SWIFAR, YNU), Xingzhu Zou (SWIFAR, YNU), Xinlei Chen (SWIFAR, YNU), Yehao Cheng (SWIFAR, YNU), Yuan Fang (SWIFAR, YNU), Brajesh Kumar (SWIFAR, YNU), Xuhui Han (NAOC), Pinpin Zhang (NAOC), Liping Xin (NAOC), Chao Wu (NAOC), Yuanpei Yang (SWIFAR, YNU), Xinzhong Er (SWIFAR, YNU), Xiangkun Liu (SWIFAR, YNU), Xiaowei Liu (SWIFAR, YNU) report on behalf of Mephisto Team:
The field of SVOM/ECLAIRs-detected burst GRB 240828B (Le Provost et al., GCN 37318) was observed with 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory. Simultaneous multi-band photometric observations were initiated at (UT) 19:25:20 Aug 28, (~6.21 hours after the burst notice). No new optical source was detected within the 2.6-arcsec Swift/XRT error circle (Page et al., GCN 37334). The 5-sigma limiting magnitudes in different bands are: u 20.75 (180 sec), v 20.97 (180 sec), g 20.54 (50 sec), r 20.83 (50 sec), i 20.44 (79 sec) and z 19.35 (79 sec). These are consistent with Zheng et al. (GCN 37345), Moskvitin et al. (GCN 37346), Wu et al. (GCN 37347), Xin et al. (GCN 37348), Wang et al. (GCN 37350), Schneider et al. (GCN 37352) and Akl et al. (GCN 37359).
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Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6m wide-field multi-channel telescope, the first of its type in the world, capable of imaging the same field of view in three optical bands simultaneously. It provides real-time, high-quality colors of stellar objects. The on-site telescope assemblage and commissioning were carried out in September 2022. The first light in all three channels was achieved on 2023 December 21.
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GCN Circular #37363
S. Belkin (HSE, IKI), R. Ya. Inasaridze (AbAO), A. Pozanenko (IKI), N. Pankov (HSE, IKI) report on behalf of GRB-IKI-FuN:
We observed the field of GRB 240828B (Le Provost, GCN 37318; Page et al., GCN 37334) with the 70-cm AS-32 telescope of Abastumani Observatory (AbAO) in the R-filter, starting on 2024-08-29 at 23:38:46 (UT). We did not detect the optical counterpart in the stacked image within the Swift-XRT error circle (Page et al., GCN 37334; ). Preliminary photometry is as follows:
Date UT_start t-T0 Filter Exp. OT err UL(3=CF=83) (mid, days) (s) 2024-08-29 23:38:46 1.46045 R 74=C3=9760 n/d n/d 22.0
The magnitudes were calibrated using nearby USNO-B1.0 stars.
```
RA DEC R2
04:13:38.682 +16:40:58.242 17.00
04:13:51.313 +16:42:50.073 16.7
```
GCN Circular #37365
R. Brivio, M. Ferro, P. D=E2=80=99Avanzo, M.G. Bernardini, S. Campana, S. C= ovino, D. Fugazza, E. Molinari, Y.-D. Hu (INAF-OAB) report on behalf of the= REM team:
We observed the field of the soft GRB 240828B detected by SVOM/ECLAIRs (Le = Provost et al., GCN 37318) with the REM 60cm robotic telescope located at t= he ESO observatory of La Silla (Chile). The observations were carried in th= e g, r, i, z, H bands, starting on 2024 August 31 at 06:19:52 UT (i.e. 2.71= days after the SVOM trigger), and lasting for about 1 hour.
From preliminary photometry we do not detect any optical/NIR counterpart at= the Swift-XRT position (Page et al., GCN 37334) down to the following 3sig= ma magnitude upper limits:
H > 15.7=20 (Vega; calibrated against the 2MASS catalogue)
r > 19.9 (AB; calibrated against the PanSTARRS catalogue)
at a mid-time of t - t0 =3D 2.73 days after the trigger.

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