EP240930a, GRB 240930B
GCN Circular 37737
Subject
EP240930a / GRB 240930B: CrAO ZTSH optical upper limit
Date
2024-10-08T18:43:37Z (a year ago)
From
Alexei Pozanenko at IKI, Moscow <grb.alex@gmail.com>
Via
legacy email
A. Vonova (IKI), V. Rumyantsev (CrAO), A. Pozanenko (IKI), N. Pankov (HSE,
IKI), and S. Belkin (IKI) report on behalf of the GRB-IKI-FuN collaboration:
We observed EP240930a, detected by EP-WXT (Tian et al., GCN 37648) and FXT
(Peng et al., GCN 37653), and triangulated by IPN (Kozyrev et al., GCN
37696), using the 2.6-meter ZTSh telescope of CrAO, equipped with a CCD
photometer and an R-filter. The observations started on 2024-10-01 (UT)
16:48:01.
We did not detect any new optical object within the FXT (Peng et al., GCN
37653) localization area in comparison with DSS2. The preliminary
photometry is as follows:
Date UT start t-T0 Exp. Filter OT Err. UL(3sigma)
(mid, days) (s)
2024-10-01 16:48:01 0.98182 46x120 R n/d n/d 23.6
This result is in agreement with previous reports (Kumar et al., GCN 37651;
Zheng et al., GCN 37656; Bochenek et al., GCN 37682; SVOM/C-GFT team, GCN
37720). The magnitudes were calibrated using nearby USNO-B1.0 stars (R2
magnitude). No correction has been made for Galactic extinction toward
EP240930a
GCN Circular 37720
Subject
GRB 240930B: SVOM/C-GFT optical upper limit
Date
2024-10-06T12:15:20Z (a year ago)
From
Chao Wu at NAOC <cwu@nao.cas.cn>
Via
Web form
SVOM/C-GFT team: Chao WU (NAOC), Zhe Kang (CHO), Liping Xin(NAOC), Xuhui Han(NAOC), Pinpin Zhang (NAOC), Xiaomeng Lu (NAOC), Zhenwei Li (CHO), You Lv (CHO), Ruosong Zhang (NAOC), Yujie Xiao(NAOC)
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)
We observed the field of GRB 240930B/EP240930a by Fermi/GBM (Fermi GBM Team, GCN 37640; Smith & Meegan, GCN 37660), EP/WXT (Tian et al., GCN 37648), Swift/BAT (DeLaunay et al., GCN 37654), GRBAlpha (Dafcikova et al., GCN 37658), CALET/GBM (Shimizu et al., GCN 37691), HEND/Mars Odyssey, Konus-Wind, INTEGRAL SPI-ACS (Kozyrev et al., GCN 37696), and SVOM/GRM (Wang et al., GCN 37714) starting at 2024-10-01T11:41:08 UT, ~ 18.39 hr after the burst trigger with C-GFT (Chinese Ground Follow-up Telescope in SVOM mission) in the commissionig phase. C-GFT is located at Jilin (long.=126.33 deg, lat.= 43.8243778 deg), Changchun Observatory, National Astronomical Observatories, CAS. It has FOV of 1.28 deg x 1.28 deg with a 4k*4k CMOS detector mounted on the primary focus of 1.2-meter-aperure telescope.
A set of 61x30s iamges were obtained in g, r, and i band. No any optical counterpart detected within the EP-FXT source error circle (Peng et al., GCN 37653) down to the limiting magnitude (3 sigma) of mag_g=20.58, mag_r=20.33, mag_i=20.01 for stacked image. It is consistent with the results reported by Zheng et al. (GCN 37656) and Bochenek & Perley (GCN 37682).
The photometry was calibrated with nearby stars in Pan-STARRS 1 .
We thank the observation assistant Guo Chunlei at Jilin observatory for their excellent support.
GCN Circular 37714
Subject
GRB 240930B / EP 240930a: SVOM/GRM observation
Date
2024-10-05T03:53:40Z (a year ago)
From
Chenwei Wang at IHEP <cwwang@ihep.ac.cn>
Via
Web form
SVOM/GRM team: Chen-Wei Wang, 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, 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), Jean-Luc 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 on-ground by GRB 240930B / EP 240930a at 2024-09-30T17:18:08 UT (T0), which was also observed by Fermi/GBM (Fermi GBM Team, GCN 37640; Smith & Meegan, GCN 37660), EP/WXT (X. Tian et al., GCN 37648), Swift/BAT (James DeLaunay et al., GCN 37654), GRBAlpha (M. Dafcikova et al., GCN 37658), CALET/GBM (Y. Shimizu et al., GCN 37691), HEND/Mars Odyssey, Konus-Wind and INTEGRAL SPI-ACS (A.S. Kozyrev et al. GCN 37696).
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 T90 of 68.4 +6.2/-6.1 s.
.
The GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb240930B.png
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 37696
Subject
IPN triangulation of GRB 240930B / EP 240930a
Date
2024-10-03T15:44:56Z (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,
A. Ridnaia, D. Frederiks, D. Svinkin, A. Lysenko,
and T. Cline on behalf of the Konus-Wind team,
A. Goldstein, M. S. Briggs, C. Wilson-Hodge,
and E. Burns on behalf of the Fermi GBM team,
E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu
on behalf of the Swift-BAT 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:
The long-duration GRB 240930B
(Fermi-GBM detection: Fermi GBM team, GCN 37640;
Smith & Meegan, GCN 37660;
Swift/BAT-GUANO detection: DeLaunay et al., GCN 37654;
GRBAlpha detection: Dafcikova et al., GCN 37658;
CALET/GBM detection: Shimizu et al., GCN 37691)
was detected by Fermi (GBM trigger 749409487),
Konus-Wind, INTEGRAL (SPI-ACS), Swift (BAT),
GRBAlpha, CALET (CGBM), and Mars-Odyssey (HEND)
at about 62282 s UT (17:18:02).
The burst was outside the coded field of view of the BAT.
We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
---------------------------------------------
RA(2000), deg Dec(2000), deg
---------------------------------------------
Center:
319.774 (21h 19m 06s) +41.359 (+41d 21' 33")
Corners:
314.492 (20h 57m 58s) +43.551 (+43d 33' 05")
314.622 (20h 58m 29s) +43.741 (+43d 44' 27")
324.617 (21h 38m 28s) +38.847 (+38d 50' 49")
324.470 (21h 37m 53s) +38.668 (+38d 40' 06")
---------------------------------------------
The error box area is 1.9 sq. deg, and its maximum
dimension is 9.0 deg (the minimum one is 13 arcmin).
The Sun distance was 118 deg.
This localization may be improved.
The IPN localization is consistent with, but reduces the area of,
the Fermi-GBM localization. The position of EP240930a (Tian et al., GCN 37648;
Peng et al., GCN 37653) is inside the IPN localization,
strengthening the association of GRB 240930B with the EP240930a.
A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB240930_T62287/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 37691
Subject
GRB 240930B: CALET Gamma-Ray Burst Monitor detection
Date
2024-10-03T11:34:40Z (a year ago)
From
Yuta Kawakubo at Aoyama Gakuin University <kawakubo@phys.aoyama.ac.jp>
Via
Web form
Y. Shimizu (Kanagawa U), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU),
K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii,
Y. Akaike, K. Kobayashi (Waseda U), T. Tamura (Kanagawa U),
N. Cannady (GSFC/UMBC), M. L. Cherry (LSU), S. Ricciarini (U of Florence),
P. S. Marrocchesi (U of Siena),
and the CALET collaboration:
The long GRB 240930B (Fermi GBM Final Real-time Localization: Fermi GBM team,
GCN Circ. 37640; EP-WXT detection of a fast X-ray transient: Tian et al.,
GCN Circ. 37648; Swift/BAT-GUANO localization skymap of a burst: DeLaunay et al.,
GCN Circ. 37654; GRBAlpha detection, Dafcikova et al., GCN Circ. 37658;
Fermi GBM Observation: Smith et al., GCN Circ. 37660)
triggered the CALET Gamma-ray Burst Monitor (CGBM) at 17:18:02.638 UTC
on 30 September 2024
(https://cgbm.calet.jp/cgbm_trigger/flight/1411751821/).
The burst signal was seen by all CGBM detectors. Because of a problem with the ground
alert processing script, the GCN notice was not distributed automatically for this event.
The burst light curve shows a multi-peaked structure that starts
at T-1.5 sec, peaks at T+3.5 sec, and ends at T+74.0 sec.
The T90 and T50 durations measured by the SGM data are 67.2 s +/- 3.1 sec
and 34.7 s +/- 0.4 sec (40-1000 keV), respectively.
The ground-processed light curve is available at
https://cgbm.calet.jp/cgbm_trigger/ground/1411751821/
The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at Waseda University.
GCN Circular 37682
Subject
EP240930a: Liverpool Telescope observations
Date
2024-10-02T13:52:57Z (a year ago)
From
A. Bochenek at Liverpool John Moores University <a.m.bochenek@2023.ljmu.ac.uk>
Via
Web form
A. Bochenek, D. A. Perley (LJMU) report:
We observed the field of the X-ray transient EP240930a (Tian et al. GCN 37648) possibly associated with GRB240930a (Fermi GBM team, GCN 37633) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 5x120s exposures with the SDSS-r filter starting at 2024-10-01 20:37:49 UT, approximately 27.3 hours after the EP trigger.
The images were stacked and a reference image of the field from Pan-STARRS was subtracted using PSF matching with the help of PSFEx. No uncatalogued optical source was detected within the 90% confidence 10 arcsec EP/FXT error-circle. The 3-sigma limiting magnitude on the subtracted image is r > 22.16 mag.
GCN Circular 37660
Subject
GRB 240930B: Fermi GBM Observation
Date
2024-10-01T19:59:50Z (a year ago)
From
Jacob Smith at Fermi-GBM Team <jrs0118@uah.edu>
Via
Web form
J. Smith (UAH) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:
At 17:18:02 UT on 30 Sep 2024, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 240930B (trigger 749409487 / 240930721),
and was detected by Einstein Probe Wide-field X-ray Telescope (EP-WXT) (X. Tian et al. 2024, GCN 37648),
Einstein Probe Follow-up X-ray Telescope (EP-FXT) (H. L. Peng et al. 2024, GCN 37653),
and Swift-BAT (J. DeLaunay et al. 2024, GCN 37654).
The Fermi GBM on-ground location is consistent with the EP-WXT, EP-FXT, and Swift-BAT localizations.
The angle from the Fermi LAT boresight is 113 degrees.
The GBM light curve single emission episode with a duration (T90)
of about 64.3 s (50-300 keV). The time-averaged spectrum
from T0-9.7 to T0+74.2 s is best fit by
a Band function
with Epeak = 86 +/- 10 keV, alpha = -0.70 +/- 0.14,
and beta = -2.03 +/- 0.06.
The event fluence (10-1000 keV) in this time interval is
(1.7 +/- 0.06)E-05 erg/cm^2. The 1.024-s peak photon flux measured
starting from T0+3.3 s in the 10-1000 keV band is 9.2 +/- 0.4 ph/s/cm^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 37658
Subject
GRB 240930B: GRBAlpha detection
Date
2024-10-01T18:55:31Z (a year ago)
From
Marianna Dafčíková at Masaryk University <500025@mail.muni.cz>
Via
Web form
M. Dafcikova, J. Ripa, M. Kolar (Masaryk U.), A. Pal (Konkoly Observatory), 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.
The long-duration GRB 240930B (Fermi/GBM detection: GCN 37640; INTEGRAL/SPI-ACS peak detection at 2024-09-30 ~17:18:02 UTC) was observed by the GRBAlpha 1U CubeSat (Pal et al. 2023, A&A, 677, 40; https://ui.adsabs.harvard.edu/abs/2023A%26A...677A..40P/abstract).
The detection was confirmed at the peak time 2024-09-30 17:18:05.2 UTC. The T90 duration measured by GRBAlpha is 20.0 s and the overall significance during T90 reaches 6.1 sigma.
The light curve obtained by GRBAlpha is available here: https://grbalpha.konkoly.hu/static/share/GRB240930B_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 37656
Subject
EP240930a : KAIT optical upper limit
Date
2024-10-01T18:06:52Z (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 EP240930a (Tian et al., GCN 37648)
starting at 05:04 UT, Oct 1st, ~11.8 hours after the trigger. A
set of 30x60s images were obtained in the clear (roughly R) filters.
Preliminary analysis do not reveal any new optical counterpart
candidate within the EP-FXT source error circle (Peng et al., GCN
37653) neither in single image, nor in the co-add images. The typical
limiting magnitude of our single clear image is about 19.5 mag, and
about 20.5 mag in the co-add image.
GCN Circular 37654
Subject
GRB 240930B: Swift/BAT-GUANO localization skymap of a burst
Date
2024-10-01T16:55:28Z (a year ago)
From
Jimmy DeLaunay at Penn State <delauj2@gmail.com>
Via
Web form
James DeLaunay (PSU), Aaron Tohuvavohu (U Toronto), Samuele Ronchini (PSU), Gayathri Raman (PSU), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC) report:
Swift/BAT did not localize GRB 240930B onboard (T0: 2024-09-30 17:18:02.12 UTC, Fermi trig 749409487, possibly associated with EP240930a GCN 37648)
The GECAM notice, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1).
Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground.
The BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), performed on the temporal window [T0-20 s, T0+20 s], detects the burst with a sqrt(TS) of 18.7 in a 4.096 s analysis time bin, starting at T0 + 1.024 s.
With a DeltaLLHOut of 0.4, NITRATES results are able to constrain the position of this burst to most likely be outside the coded field of view.
See Section 9.1 and Figures 10 and 17 in the NITRATES paper for brief descriptions and interpretation of sqrt(TS), DeltaLLHPeak, and DeltaLLHOut.
Using the NITRATES analysis, parameter estimation was performed to obtain the localization of this burst in the form of a HEALPIX Multi-Order Coverage (MOC) skymap. This localization accounts for both statistical and systematic errors. More details in the creation and calibration of these maps will soon be published (DeLaunay et al. 2024. in prep)
The 90% credible area is 2,566 deg2 and the 50% credible area is 491 deg2. The integrated probability inside the coded field of view is ~0%.
The localization of EP240930a is consistent with GRB 240930B and is fully within the 50% contour.
A plot of the probability skymap can be viewed here, https://guano.swift.psu.edu/trigger_report?id=749409516/#:~:text=Probability%20Skymap
The probability skymap file can be downloaded from the link here, https://guano.swift.psu.edu/files/749409516/0_n_PROBMAP
Instructions on how to read and manipulate this map can be found here, https://guano.swift.psu.edu/documentation
More details about this burst can be found on the trigger report page here https://guano.swift.psu.edu/trigger_report?id=749409516
GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches.
A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/
GCN Circular 37653
Subject
EP240930a: EP-FXT follow-up observation update
Date
2024-10-01T13:14:13Z (a year ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
H. L. Peng (NNU), X. Tian (GXU), X. Mao, C. C. Jin, H. Y. Liu, Y. Liu, Z. X. Ling, C. Zhang, H. Q. Cheng, W. Chen, C. Z. Cui, D. W. Fan, H. B. Hu, J. W., Hu, M. H. Huang, D. Y. Li, M. J. Liu, Z. Z. Lv, T. Y. Lian, H. W. Pan, X. Pan, H. Sun, W. X. Wang, Y. L. Wang, 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), Y F. Liang (PMO, 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
Following the detection of the fast X-ray transient EP240930a (Tian et al., GCN 37648), we performed an observation of EP240930a with the Follow-up X-ray Telescope (FXT) on board Einstein Probe. The observation began at 2024-10-01T07:06:01 (UTC), about 14 hours after the EP-WXT detection, with an exposure time of 2801 seconds. An uncatalogued source was detected within the WXT positional uncertainty of EP240930a, at R.A. = 319.9331 deg and DEC = 41.3002 deg with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). The spectrum can be fitted with an absorbed power-law model with NH fixed at the Galactic value of 3.29E21 cm^-2 and a photon index of 2.1(-0.4, +0.4). The derived average unabsorbed flux in 0.5-10 keV is 7.6(-1.3, +1.7)E-13 erg/s/cm^2 (90% C.L.). We consider this FXT source to be the afterglow of the X-ray transient EP240930a, which is likely associated with the Fermi GRB 240930B (Fermi GBM team, GCN 37640) as proposed in the last circular (Tian et al., GCN 37648).
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 37651
Subject
EP240930a: GOTO optical upper limits
Date
2024-10-01T08:13:03Z (a year ago)
From
Amit Kumar at Royal Holloway - U. of London/U. of Warwick, UK <amitkundu515@gmail.com>
Via
Web form
A. Kumar, B. P. Gompertz, G. Ramsay, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, F. Jimenez-Ibarra, D. O'Neill, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, E. Palle and D. Pollacco report on behalf of the GOTO collaboration:
We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022; Dyer et al 2024) covering the EP-WXT detected fast X-ray transient (Tian et al. GCN 37648). The WXT localisation was covered by GOTO North on 2024-09-30 from 20:09:58 to 23:19:50 UT (2.869 to 6.033 hours post trigger) during its triggered response to GRB 240930B (Fermi GBM Team, GCN 37640). The observations consisted of 4x90s exposures in the GOTO L-band (400-700 nm), distributed across 4 epochs.
Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using recent survey observations of the same pointings. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogs. Human vetting was carried out in real-time on any candidates that passed the above checks.
No candidate optical counterpart is detected in the WXT localisation region down to a 5-sigma L-band limit of 19.8–20.9 (AB) across 4 epochs. The first observation, at 2.869 hours post-trigger, reaches a 5-sigma depth of 20.9 mag.
Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction.
GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC).
GCN Circular 37649
Subject
EP EP240930a: Global MASTER-Net observations report
Date
2024-10-01T05:09:25Z (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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the EP240930a ( EP Team et al., GCN 37648) errorbox 124 sec after trigger time at 2024-09-30 17:19:54 UT, with upper limit up to 17.3 mag. Observations started at twilight. The observations began at zenith distance = 79 deg. The sun altitude is -9.2 deg.
MASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the EP240930a errorbox 18062 sec after trigger time at 2024-09-30 22:18:52 UT, with upper limit up to 17.9 mag. The observations began at zenith distance = 49 deg. The sun altitude is -46.5 deg.
MASTER-OAFA robotic telescope located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP240930a errorbox 22682 sec after trigger time at 2024-09-30 23:35:52 UT, with upper limit up to 18.5 mag. Observations started at twilight. The observations began at zenith distance = 76 deg. The sun altitude is -13.5 deg.
The galactic latitude b = -6 deg., longitude l = 86 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2621049
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
134 | 2024-09-30 17:19:54 | MASTER-SAAO | (21h 28m 34.64s , +41d 45m 10.7s) | C | 20 | 14.2 |
450 | 2024-09-30 17:24:49 | MASTER-SAAO | (21h 24m 51.90s , +40d 43m 27.1s) | C | 60 | 15.6 |
1353 | 2024-09-30 17:39:52 | MASTER-SAAO | (21h 24m 48.78s , +40d 44m 02.1s) | C | 60 | 15.9 |
2319 | 2024-09-30 17:55:58 | MASTER-SAAO | (21h 24m 53.52s , +40d 43m 57.4s) | C | 60 | 17.0 |
3037 | 2024-09-30 18:07:56 | MASTER-SAAO | (21h 15m 20.45s , +40d 45m 07.5s) | C | 60 | 16.8 |
3528 | 2024-09-30 18:16:08 | MASTER-SAAO | (21h 12m 49.64s , +42d 39m 27.0s) | C | 60 | 16.3 |
4004 | 2024-09-30 18:24:03 | MASTER-SAAO | (21h 15m 39.66s , +40d 44m 59.0s) | C | 60 | 17.3 |
4498 | 2024-09-30 18:32:18 | MASTER-SAAO | (21h 13m 09.04s , +42d 40m 26.5s) | C | 60 | 16.4 |
5013 | 2024-09-30 18:40:53 | MASTER-SAAO | (21h 15m 54.04s , +40d 46m 28.6s) | C | 60 | 15.0 |
8747 | 2024-09-30 19:43:07 | MASTER-SAAO | (21h 13m 45.17s , +42d 42m 31.1s) | C | 60 | 13.1 |
18092 | 2024-09-30 22:18:52 | MASTER-Kislovodsk | (21h 14m 58.41s , +41d 06m 20.4s) | C | 60 | 17.9 |
19062 | 2024-09-30 22:35:01 | MASTER-Kislovodsk | (21h 14m 52.88s , +41d 05m 43.9s) | C | 60 | 17.3 |
20018 | 2024-09-30 22:50:57 | MASTER-Kislovodsk | (21h 14m 49.62s , +41d 05m 27.4s) | C | 60 | 17.8 |
22713 | 2024-09-30 23:35:52 | MASTER-OAFA | (21h 23m 32.56s , +41d 29m 56.2s) | C | 60 | 17.2 |
22713 | 2024-09-30 23:35:52 | MASTER-OAFA | (21h 11m 35.12s , +41d 04m 48.7s) | C | 60 | 18.1 |
23647 | 2024-09-30 23:51:26 | MASTER-OAFA | (21h 23m 26.87s , +41d 30m 50.2s) | C | 60 | 17.6 |
23647 | 2024-09-30 23:51:27 | MASTER-OAFA | (21h 11m 29.45s , +41d 05m 42.8s) | C | 60 | 18.4 |
25312 | 2024-10-01 00:19:11 | MASTER-OAFA | (21h 23m 27.65s , +41d 32m 01.7s) | C | 60 | 17.6 |
25312 | 2024-10-01 00:19:12 | MASTER-OAFA | (21h 11m 30.93s , +41d 06m 53.3s) | C | 60 | 18.5 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 37648
Subject
EP240930a: EP-WXT detection of a fast X-ray transient
Date
2024-10-01T04:53:36Z (a year ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
X. Tian (GXU), H. L. Peng (NNU), X. Mao, C. C. Jin, H. Y. Liu, Y. Liu, Z. X. Ling, C. Zhang, H. Q. Cheng, W. Chen, C. Z. Cui, D. W. Fan, H. B. Hu, J. W., Hu, M. H. Huang, D. Y. Li, M. J. Liu, Z. Z. Lv, T. Y. Lian, H. W. Pan, X. Pan, H. Sun, W. X. Wang, Y. L. Wang, 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), Y F. Liang (PMO, 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 EP240930a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient started at 2024-09-30T17:17:50(UTC) and lasted for around 200 seconds. The WXT position of EP240930a is R.A.= 319.899 deg, DEC = 41.303 deg (J2000) with an uncertainty of 2.1 arcmin (radius, 90% C.L. statistical and systematic). The average 0.5-4 keV spectrum can be fitted with an absorbed power law with a photon index of 0.79(-0.25, +0.24) (with a column density fixed at the Galactic one of 3.29 x 10^21 cm^-2). The derived average unabsorbed 0.5-4 keV flux is 3.8(-0.5, +0.5) x 10^(-9) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters.
EP240930a may be associated with Fermi GRB 240930B (Fermi GBM team, GCN 37640) considering the similar trigger time and localization. No previously known bright X-ray sources are found within the error circle around the source position. A follow-up observation with the Follow-up X-ray Telescope (FXT) on board the EP is planned. 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 37641
Subject
Fermi GRB 240930B: Global MASTER-Net observations report
Date
2024-09-30T18:45:58Z (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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 240930B ( Fermi GBM team, GCN 37640) errorbox 118 sec after notice time and 151 sec after trigger time at 2024-09-30 17:20:33 UT, with upper limit up to 15.9 mag. Observations started at twilight. The observations began at zenith distance = 75 deg. The sun altitude is -9.4 deg.
The galactic latitude b = -3 deg., longitude l = 83 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2620328
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
166 | 2024-09-30 17:20:33 | MASTER-SAAO | (20h 49m 45.26s , +39d 39m 45.0s) | C | 30 | 14.2 |
211 | 2024-09-30 17:20:33 | MASTER-SAAO | (20h 49m 45.27s , +39d 39m 45.1s) | C | 120 | 15.2 | Coadd
220 | 2024-09-30 17:21:22 | MASTER-SAAO | (20h 49m 45.45s , +39d 39m 47.8s) | C | 40 | 13.9 |
284 | 2024-09-30 17:22:21 | MASTER-SAAO | (20h 49m 45.71s , +39d 39m 51.7s) | C | 50 | 15.1 |
358 | 2024-09-30 17:23:30 | MASTER-SAAO | (20h 49m 45.95s , +39d 39m 55.2s) | C | 60 | 15.4 |
604 | 2024-09-30 17:27:36 | MASTER-SAAO | (20h 54m 11.43s , +40d 26m 14.9s) | C | 60 | 14.0 |
664 | 2024-09-30 17:27:36 | MASTER-SAAO | (20h 54m 11.43s , +40d 26m 14.9s) | C | 180 | 15.3 | Coadd
684 | 2024-09-30 17:28:55 | MASTER-SAAO | (20h 54m 11.69s , +40d 26m 17.7s) | C | 60 | 14.6 |
763 | 2024-09-30 17:30:14 | MASTER-SAAO | (20h 54m 11.95s , +40d 26m 20.0s) | C | 60 | 14.7 |
842 | 2024-09-30 17:31:33 | MASTER-SAAO | (20h 54m 12.22s , +40d 26m 22.3s) | C | 60 | 15.3 |
1181 | 2024-09-30 17:37:12 | MASTER-SAAO | (20h 44m 39.54s , +40d 45m 14.1s) | C | 60 | 15.8 |
1260 | 2024-09-30 17:38:32 | MASTER-SAAO | (20h 55m 17.13s , +40d 46m 14.7s) | C | 60 | 15.9 |
1578 | 2024-09-30 17:43:50 | MASTER-SAAO | (20h 49m 30.74s , +38d 51m 18.7s) | C | 60 | 15.3 |
1658 | 2024-09-30 17:45:09 | MASTER-SAAO | (20h 59m 44.68s , +38d 52m 04.7s) | C | 60 | 15.1 |
1737 | 2024-09-30 17:46:29 | MASTER-SAAO | (20h 41m 17.74s , +42d 41m 20.3s) | C | 60 | 14.8 |
1816 | 2024-09-30 17:47:48 | MASTER-SAAO | (20h 51m 56.45s , +42d 39m 51.8s) | C | 60 | 15.2 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 37640
Subject
GRB 240930B: Fermi GBM Final Real-time Localization
Date
2024-09-30T17:28:37Z (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 17:18:02 UT on 30 Sep 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240930B (trigger 749409487.116994 / 240930721).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 313.7, Dec = 40.8 (J2000 degrees, equivalent to J2000 20h 54m, 40d 47'), with a statistical uncertainty of 1.8 degrees.
The angle from the Fermi LAT boresight is 110.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240930721/quicklook/glg_skymap_all_bn240930721.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/bn240930721/quicklook/glg_healpix_all_bn240930721.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240930721/quicklook/glg_lc_medres34_bn240930721.gif