GRB 240824B
GCN Circular 37260
Subject
GRB 240824B: Fermi GBM Final Real-time Localization
Date
2024-08-24T13:21:51Z (9 months 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 SHORT GRB
At 13:11:16 UT on 24 Aug 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240824B (trigger 746197881.698742 / 240824549).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 17.5, Dec = -23.3 (J2000 degrees, equivalent to J2000 01h 10m, -23d 18'), with a statistical uncertainty of 28.2 degrees.
The angle from the Fermi LAT boresight is 72.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240824549/quicklook/glg_skymap_all_bn240824549.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/bn240824549/quicklook/glg_healpix_all_bn240824549.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240824549/quicklook/glg_lc_medres34_bn240824549.gif
GCN Circular 37261
Subject
GRB 240824B: MAXI/GSC detection
Date
2024-08-24T15:49:41Z (9 months ago)
From
Motoko Serino at Aoyama Gakuin U. <serino@phys.aoyama.ac.jp>
Via
Web form
M. Nakajima (Nihon U.), M. Serino, S. Sugita (AGU),
H. Negoro, Y. Kudo, H. Shibui, K. Takagi, H. Takahashi, K. Tatano, H. Nishio (Nihon U.),
T. Mihara, T. Kawamuro, S. Yamada, S. Wang, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN),
T. Sakamoto, Y. Kawakubo, H. Hiramatsu, H. Nishikawa, Y. Kondo, A. Yoshida (AGU),
Y. Tsuboi, H. Sugai, N. Nagashima (Chuo U.),
M. Shidatsu, Y. Niida (Ehime U.),
I. Takahashi, M. Niwano, N. Higuchi, Y. Yatsu (Tokyo Tech),
S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, M. Kurihara (JAXA),
Y. Ueda, Y. Okada (Kyoto U.),
M. Yamauchi, Y. Otsuki, T. Hasegawa, M. Nishio (Miyazaki U.),
K. Yamaoka (Nagoya U.),
M. Sugizaki (Kanazawa U.),
W. Iwakiri (Chiba U.)
report on behalf of the MAXI team:
The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at
13:10:30 UT on 24 Aug 2024.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (17.672 deg, 2.083 deg) = (01 10 41, +02 04 58) (J2000)
with a statistical 90% C.L. elliptical error region
with long and short radii of 0.27 deg and 0.07 deg, respectively.
The roll angle of long axis from the north direction is 136.0 deg counterclockwise.
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
This position is within the error of GRB 240824B detected by Fermi GBM (GCN #37260).
The X-ray flux averaged over the scan was 45 +- 15 mCrab
(4.0-10.0keV, 1 sigma error).
There was no significant excess flux in the previous transit at 11:37 UT
and in the next transit at 14:43 UT with an upper limit of 20 mCrab for each.
GCN Circular 37266
Subject
GRB 240824B: Swift ToO observations
Date
2024-08-24T20:50:24Z (9 months 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 team:
Swift has initiated a ToO observation of the Swift/BAT GRB 240824B.
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021705
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 Swift/BAT 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 37267
Subject
GRB 240824B: Swift/BAT arcminute localization of a burst
Date
2024-08-24T21:21:35Z (9 months 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 240824B onboard (T0: 2024-08-24T13:11:16.7 UTC, Fermi Trigger 746197881, MAXI GCN 37261).
In a ground search of a 10 s event file, available due to a subthreshold trigger onboard. The GRB was detected at a S/N of 8.5 in a single 10 s image. The duration in the rates data is ~16 s.
The BAT position is
RA, Dec = 17.835, +2.620 deg which is
RA(J2000) = 01h 11m 20.4s
Dec(J2000) = +02d 37′ 12.0″
with an estimated uncertainty of 3 arcmin radius.
XRT and UVOT follow-up has been requested.
Results of follow-up observations will be reported in future circulars.
GCN Circular 37270
Subject
GRB 240824B: Swift-XRT afterglow detection
Date
2024-08-25T13:38:49Z (9 months ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
J.A. Kennea (PSU), D.N. Burrows (PSU), J.P. Osborne (U. Leicester),
K.L. Page (U. Leicester), M. Capalbi (INAF-IASFPA), M. Perri (SSDC &
INAF-OAR), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU) and P.A.
Evans (U. Leicester) reports on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the Swift/BAT, MAXI
and Fermi-GBM-detected burst GRB 240824B (GCN #37260, #37261, #37266,
#37267) collecting 4.1 ks of Photon Counting (PC) mode data between
T0+27.7 ks and T0+52.3 ks.
Two uncatalogued X-ray sources are detected consistent with being
within 296 arcsec of the Swift/BAT position, of which one ("Source 1")
is fading with 2.4 sigma significance and thus is believed to be the
GRB afterglow. Using 732 s of PC mode data and 1 UVOT image, we find an
enhanced XRT position (using the XRT-UVOT alignment and matching UVOT
field sources to the USNO-B1 catalogue): RA, Dec = 17.83675, +2.60999
which is equivalent to:
RA (J2000): 01h 11m 20.82s
Dec(J2000): +02d 36' 36.0"
with an uncertainty of 4.5 arcsec (radius, 90% confidence). This
position is 36 arcsec from the Swift/BAT position.
The light curve can be modelled with a power-law decay with a decay
index of alpha=3.1 (+0.5, -2.1).
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00021705.
The results of the full analysis of the XRT observations are available
at https://www.swift.ac.uk/ToO_GRBs/00021705.
This circular is an official product of the Swift-XRT team.
GCN Circular 37281
Subject
GRB 240824B: NOT optical upper limit
Date
2024-08-25T18:42:26Z (9 months ago)
From
Daniele B. Malesani at IMAPP / Radboud University <d.malesani@astro.ru.nl>
Via
Web form
D. B. Malesani (DAWN/NBI and Radboud Univ.), A. Martin-Carrillo (UCD), J. Terwel (NOT and TCD), report on behalf of a larger collaboration:
We observed the field of GRB 240824B (Fermi GBM team, GCN 37260; Nakajima et al., GCN 37261; DeLaunay et al., GCN 37267) using the Nordic Optical Telescope (NOT) located in the Canary Islands. Observations consisted of three r-band exposures for a total of 900 s, with a mid time 2024 Aug 25.053 UT (12.1 hr after the trigger). The seeing was unfortunately poor, with a delivered PSF of ~2".
In the stack of our images, no source is detected at a location consistent with the candidate X-ray afterglow error circle (Kennea et al., GCN 37270), down to a 3-sigma limiting magnitude r = 22 (AB, calibrated against nearby sources from the Pan-STARRS catalog).
GCN Circular 37284
Subject
GRB 240824B: Fermi GBM Observation
Date
2024-08-25T20:38:41Z (9 months ago)
From
Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov>
Via
Web form
V. Sharma (NASA GSFC/UMBC), and C. Meegan (UAH) report on behalf of the
Fermi Gamma-ray Burst Monitor Team:
At 13:11:16.70 UT on 24 August 2024, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 240824B (trigger 746197881/240824549), which was
also detected by MAXI/GSC detection (M. Nakajima et al., 2024, GCN 37261),
Swift-BAT (J. DeLaunay et al. 2024, GCN 37267), and Swift-XRT (A. Tohuvavohu
et al. 2024, GCN 37269 and J.A. Kennea et al. 2024, GCN 37270).
The Final Real-time Localization (Fermi GBM Team 2024, GCN 37260)
is consistent with the MAXI/GSC, and Swift.
The angle from the Fermi LAT boresight is 79 degrees.
The GBM light curve many short peaks with a duration (T90)
of about 1.5 s (50-300 keV). The time-averaged spectrum
from T0-0.96 to T0+0.90 s is best fit by a power law
function with an exponential high-energy cutoff.
The power law index is -0.83 +/- 0.38 and the cutoff energy,
parameterized as Epeak, is 339 +/- 200 keV.
The event fluence (10-1000 keV) in this time interval is
(4 +/- 1)E-07 erg/cm^2. The 64-ms peak photon flux measured
starting from T0-0.64 s in the 10-1000 keV band is 3 +/- 1 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 37286
Subject
GRB 240824B: KAIT optical upper limit
Date
2024-08-25T21:22:49Z (9 months 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 240824B (Fermi GBM team, GCN
37260; Nakajima et al., GCN 37261; DeLaunay et al., GCN 37267;
Sharma et al., GCN 37284) starting at 06:53 UT, Aug. 25, ~17.70
hours after the burst. A total of 180 x 60s images were obtained
in the clear (roughly R) filters. We did not detect any new optical
counterpart candidate within the Swift/XRT X-ray afterglow
(Source 1) error circle reported by Kennea et al. (GCN 37270) in
our coadd image, which we estimate the limiting magnitude to be
~21.0 mag at a mid time of 20.70 hours after the burst, consistent
with the upper limit report from Malesani et al. (GCN 37281).
GCN Circular 37305
Subject
GRB 240824B: Ondrejov D50 optical limit
Date
2024-08-26T21:44:19Z (9 months ago)
From
Martin Jelinek at Astro.Inst-AVCR,Ondrejov <martin.jelinek@asu.cas.cz>
Via
legacy email
Martin Jelinek, Jan Strobl, Alzbeta Malenakova, Rene Hudec and Cyril
Polasek (ASU CAS Ondrejov, CZ), report:
We observed the Swift-XRT localization (Kennea et al. GCN 37270) of the
Fermi/GBM (Fermi GBM Team GCN 37260, Sharma et al. GCN 37284), MAXI/GSC
(Nakajima et al. GCN 37261) and Swift/BAT (DeLaunay et al. GCN 37267)
detected GRB 240824A with the 50 cm robotic telescope (D50) of Ondrejov
observatory in Czech republic.
We obtained a set of 120 s Sloan-i' band exposures starting at 00:10 UT,
i.e. 10.985 h after the initial trigger. Consistently with Malesani et al.
(GCN 37281) and Zheng et al (GCN 37286), we do not detect any emission in
or near the Swift-XRT error box. The magnitude limit of our 2.15 h summed
integration with a mean time T-T0 12.067 h post burst is i' > 21.3 (AB).