GRB 240824A
GCN Circular 37254
Subject
GRB 240824A: Swift detection of a burst
Date
2024-08-24T01:27:23Z (9 months ago)
From
David Palmer at LANL <palmer@lanl.gov>
Via
email
S. B. Cenko (GSFC), S. Dichiara (PSU), M. Ferro (INAF-OAB),
A. Y. Lien (U Tampa), D. M. Palmer (LANL), C. Salvaggio (INAF-OAB) and
A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift
Observatory Team:
At 01:03:25 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 240824A (trigger=1250282). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 213.203, +63.737 which is
RA(J2000) = 14h 12m 49s
Dec(J2000) = +63d 44' 13"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a complex
structure with a duration of about 40 sec. The peak count rate
was ~1200 counts/sec (15-350 keV), at ~1 sec after the trigger.
The XRT began observing the field at 01:05:39.6 UT, 134.2 seconds after
the BAT trigger. No source was detected in 734 s of promptly downlinked
data. We are waiting for the full dataset to detect and localise the
XRT counterpart.
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 139 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 25% of
the BAT error circle. The typical 3-sigma upper limit has been about 19.6 mag.
The 8'x8' region for the list of sources generated on-board covers 100% of the
BAT 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
0.014.
Although we do not see an X-ray or optical counterpart, the high
significance of the source detection in BAT (>9 sigma, confirmed
by re-imaging on the ground) gives us confidence that this is
an astrophysical source.
Burst Advocate for this burst is S. B. Cenko (brad.cenko AT nasa.gov).
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 37255
Subject
GRB 240824A: Skynet Optical Afterglow Discovery
Date
2024-08-24T02:59:28Z (9 months ago)
From
Dylan Dutton at UNC Chapel Hill <ddutton59@gmail.com>
Via
Web form
Dylan Dutton, Megan Dubay, Donovan Schlekat, Ruide Fu, Daniel Reichart, Joshua Haislip, Vladimir Kouprianov, James Davidson, Edward Murphy, and Carlos Salgado report on behalf of the Skynet Robotic Telescope Network at the University of North Carolina at Chapel Hill.
We observed the field of GRB 240824A with the RRRT telescope located in Virginia. The observation began at 01:49:13 UT on August 24 2024, roughly 46 minutes post-trigger by the Swift-BAT instrument.
We detected a bright object within the uncertainty radius of the Swift localization, at:
R.A. (J2000): 14:12:43.899
Dec. (J2000): 63:43:46.805
We report the discovery photometry below. The time of the exposure is the middle time.
Time Since GRB | Telescope | Filter | Exposure Duration | Mag | Mag Error
2780s | RRRT | V | 70s | 15.227 | 0.024
Our images have been calibrated using stars from the APASS catalog. Additional Skynet observations are ongoing.
GCN Circular 37256
Subject
GRB 240824A: KAIT optical upper limit
Date
2024-08-24T04:23:39Z (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 the Swift GRB 240824A (Cenko et al.,
GCN 37254) starting at 03:43:04 UT, ~2.67 hours after the burst.
Observations were performed in the clear (roughly R) filter in
twilight condition. A total of 5 x 60s images were obtained. We did
not detect the optical afterglow reported by Dutton et al. (GCN 37255)
in our coadd image, which we estimate the limiting magnitude be ~18.5
mag, indicating the afterglow reported by Dutton et al. (GCN 37255)
has likely faded.
GCN Circular 37258
Subject
GRB240824A: GRANDMA/TAROT-TCA Upper Limit
Date
2024-08-24T09:54:07Z (9 months ago)
From
Dalya Akl at American Uni. SHJ <dalyaakl.d@gmail.com>
Via
Web form
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), A. Klotz (CNRS-OMP-IRAP), M. Boer, S. Gervasoni, C. Limonta (OCA) on behalf of the GRANDMA collaboration:
We imaged the field of GRB 240824A, detected by SWIFT (GCN 37254), with the TAROT-TCA telescope at the Calern observatory. The observations started ~1 min after the GRB trigger (without filter) and finished 150 min later.
We did not detect any optical counterpart within the SWIFT localization error box (3 arcmin radius centered on RA, Dec = 213.203, 63.737 (deg)). We estimate an upper limit of 17.0 mag in Gaia G (5-sigma) up to 5 min post-T0, and an upper limit of 17.3 mag in Gaia G for each 30-minute epoch from 15 - 150 min post-T0.
The data has been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022).
We also performed force photometry at the location of the Skynet optical afterglow candidate (GCN 37255), at RA, Dec (deg)=213.183, 63.730, and did not detect any optical counterpart, utilizing various exposures, and estimated an upper limit of 17.3 mag in Gaia G (Vega mag, 5-sigma) from 1 min post-T0 to 150 min, consistent with Zheng et al. (GCN 37256). We can not conclude that the candidate found in Dutton et al. (GCN 37255) is a real source.
We use the SkyPortal application (skyportal.io) to monitor our observational campaign.
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).
GCN Circular 37259
Subject
GRB 240824A: Retraction of GCN 37255
Date
2024-08-24T12:36:31Z (9 months ago)
From
Dylan Dutton at UNC Chapel Hill <ddutton59@gmail.com>
Via
Web form
On August 24 2024 at 02:59:28 UT the Skynet team issued a circular (GCN 37255) reporting the detection of an optical afterglow associated with GRB 240824A.
Upon closer examination of the photometry, it is clear that the source we reported is actually RBI and not astrophysical in origin. This is consistent with the non-detections for the trigger (GCN 37258, 37257, 37256, and 37253).
We apologize for any confusion this error may have caused.
GCN Circular 37263
Subject
GRB 240824A: Swift/UVOT Upper Limits
Date
2024-08-24T17:11:31Z (9 months ago)
From
Paul Kuin at MSSL <npkuin@gmail.com>
Via
email
GRB 240824A: Swift/UVOT Upper Limits
N. P. M. Kuin (UCL-MSSL) and S. B. Cenko (GSFC)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 240824A
139 s after the BAT trigger (Cenko et al., GCN Circ. 37254).
No optical afterglow consistent with the BAT position 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 139 289 147 >19.8
u_FC 297 547 246 >19.2
white 139 1717 411 >20.6
v 628 1767 136 >18.7
b 553 1866 136 >19.5
u 297 1841 362 >19.5
w1 677 1817 136 >19.1
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.014 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 37269
Subject
GRB 240824A: Swift-XRT observations
Date
2024-08-25T09:55:54Z (9 months ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
A. Tohuvavohu (U. Toronto), D.N. Burrows (PSU), J. D. Gropp (PSU), A.P.
Beardmore (U. Leicester), J.P. Osborne (U. Leicester), E. Ambrosi
(INAF-IASFPA) , M. Capalbi (INAF-IASFPA), M. Perri (SSDC & INAF-OAR)
and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
We have analysed 10.4 ks of Photon Counting (PC) mode XRT data for the
Swift-BAT-detected burst GRB 240824A, collected between T0+-897 s and
T0+40.9 ks.
One uncatalogued X-ray source has been detected consistent with being
within 3 arcmin of the Swift-BAT position, however it is not above the
RASS limit or shows definitive signs of fading. Therefore, at the
present time we cannot identify it as the afterglow. Details of the
source are given below:
Source 4:
RA (J2000.0): 213.1710 = 14:12:41.05
Dec (J2000.0): +63.7283 = +63:43:41.7
Error: 5.4 arcsec (radius, 90% conf.)
Count-rate: (1.26 [+0.55, -0.44])e-3 ct s^-1
Distance: 59 arcsec from Swift-BAT position.
Flux: (3.0 [+1.3, -1.1])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)
Seven uncatalogued sources were also detected too far from the GRB
position to be likely afterglow candidates.
The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
https://www.swift.ac.uk/ToO_GRBs/01250282.
This circular is an official product of the Swift-XRT team.
GCN Circular 37271
Subject
GRB 240824A: SVOM/C-GFT optical upper limit
Date
2024-08-25T14:38:45Z (9 months ago)
From
Chao Wu at NAOC <wuchao.lamost@gmail.com>
Via
legacy email
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, China), Bertrand Cordier (CEA, F),
Shuang-Nan Zhang (IHEP, CN), Stephane Basa (LAM, F), Jean-Luc Attéia
(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 Götz (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)
We observed the field of the Swift GRB 240824A (Cenko et al., GCN
37254) starting at 11:02:55UT, August 24, 2024, ~10 hr after the burst
with C-GFT (Chinese Ground Follow-up Telescope in SVOM mission) in
System Test Mode (STM). 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 series of g ,r,and i band images were obtained. We obtained stacked
images of r: 245 x 10s,g: 255 x 10s and i:234 x 10s. No optical
afterglow was detected for the candidate reported by Evans (GCN 37269)
down to the limit magnitude of mag_g=20.6 , mag_r=20.5, and
mag_i=20.0.
The photometry was calibrated with UCAC4 catalogs.
We thank the observation assistant Bowen Li at Jilin observatory for
their excellent support.
GCN Circular 37272
Subject
GRB 240824A: Swift-BAT refined analysis
Date
2024-08-25T14:48:57Z (9 months ago)
From
Amy <yarleen@gmail.com>
Via
email
C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), S. B. Cenko (GSFC), R.
Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa),
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-240 to T+963 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 240824A (trigger #1250282)
(Cenko et al., GCN Circ. 37254). The BAT ground-calculated position is
RA, Dec = 213.176, 63.735 deg which is
RA(J2000) = 14h 12m 42.3s
Dec(J2000) = +63d 44' 06.7"
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment). The
partial coding was 72%.
The mask-weighted light curve shows a complex structure that starts at ~T-1
s and ends at ~T+43 s. The main peak occurs at ~T+1 s. T90 (15-350 keV) is
39.47 +- 3.44 sec (estimated error including systematics).
The time-averaged spectrum from T-0.66 to T+43.40 sec is best fit by a
simple power-law model. The power law index of the time-averaged spectrum
is 1.30 +- 0.14. The fluence in the 15-150 keV band is 1.3 +- 0.1 x 10^-6
erg/cm2. The 1-sec peak photon flux measured from T-0.02 sec in the 15-150
keV band is 0.7 +- 0.2 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/1250282
GCN Circular 37312
Subject
GRB 240824A: GIT optical upper limit
Date
2024-08-27T16:58:54Z (9 months ago)
From
vishwajeet.s@iitb.ac.in
Via
Web form
T. Mohan, R. Kumar, V. Swain, 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 the Swift GRB 240824A (Cenko et al., GCN 37254) with the 0.7m GROWTH-India Telescope (GIT). The observations started at 2024-08-24 16:57:29 UT, about 16 hours after the Swift BAT trigger. We obtained 6 images of 300s exposure time in r' filter. We did not detect any new source in our stacked image around the coordinates reported by Swift-XRT (Tohuvavohu et al., GCN 37269). The obtained upper limit follows as:
-------------------------------------------------------------------------------------------
| JD (mid) | t-t0 (days) | Filter | Exposure (s) | Limiting Magnitude (AB) |
| ----------------- | ----------- |------- | ------------------ | ----------------------- |
| 2460547.2170023 | 0.67 | r' | 6x300 | 21.4 |
-------------------------------------------------------------------------------------------
Our result is consistent with the upper limits reported by (SVOM/C-GFT team, GCN 37271; Swift/UVOT team, GCN 37263; Akl et al., GCN 37258; KAIT GRB team, GCN 37256). The magnitude are 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/.