GRB 240502C
GCN Circular 36376
Subject
GRB 240502C: Fermi GBM Final Localization
Date
2024-05-02T23:07:37Z (a year ago)
From
sumanbala2210@gmail.com
Via
Web form
The Fermi GBM team reports the detection of a likely SHORT GRB
"At 21:45:04.75 UT on 02 May 2024, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 240502C (trigger 736379109/240502906).
The on-ground calculated location, using the Fermi GBM trigger data,
is RA = 166.88, Dec = 66.30 (J2000 degrees, equivalent to J2000 11h 7m, +66d 17'),
with a statistical uncertainty of 8.19 degrees.
The angle from the Fermi LAT boresight is 23 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240502906/quicklook/glg_skymap_all_bn240502906.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/bn240502906/quicklook/glg_healpix_all_bn240502906.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240502906/quicklook/glg_lc_medres34_bn240502906.gif"
GCN Circular 36380
Subject
GRB 240502C: GOTO possible optical counterpart candidates
Date
2024-05-03T10:21:17Z (a year ago)
From
Ben Gompertz at U of Birmingham <b.gompertz@bham.ac.uk>
Via
email
B. P. Gompertz, K. Ackley; A. Kumar; G. Ramsay, B. Godson, T. Killestein, D. O'Neill, R. Starling, M. J. Dyer; J. Lyman, K. Ulaczyk, F. Jimenez-Ibarra, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, E. Pall'e and D. Pollacco report on behalf of the GOTO collaboration:
We report on observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022) in response to the Fermi GBM detected GRB 240502C (Fermi GBM Team, GCN 36376). Targeted observations were performed by GOTO-N, from 2024-05-02 UT 21:56:49.49 to 2024-05-03 UT 00:34:13.78 (respectively from 11.75 mins to 2.82 hours after trigger) distributed over three epochs. Each observation consisted of 4x90s exposures in the GOTO L-band (400-700 nm).
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 catalogues. Human vetting was carried out in real time on any candidates that passed the above checks.
We identify 3 candidate optical counterparts within the GBM 90% localisation region. We find no evidence of these sources prior to the GRB trigger time in previous GOTO observations, the ZTF observations provided by the Lasair broker (Smith et al. 2019), or the ATLAS forced photometry server (Shingles et al. 2021). We caution that none of these sources exhibit clear afterglow-like behaviour in the available epochs and the fields had not been covered by GOTO since 2024-04-21 prior to the GBM trigger. Hence, while a connection to GRB 240502C is not excluded by available imaging, further observations are required to ascertain their nature.
Name | RA(J2000) | Dec(J2000) | Epoch(MJD) | dt_trig(hrs) | Filter | Mag(AB) | Notes
GOTO24azq | 10:45:20.2 | +63:23:03.3 | 60432.915748 | 0.23 | L | 20.1 +/- 0.1 | Detected in three epochs with some evidence for variability, but low S/N.
GOTO24bao | 09:57:09.5 | +62:01:04.6 | 60432.979525 | 1.76 | L | 19.4 +/- 0.1 | Detected in the only observation covering the position. Consistent with a g=22.00 mag galaxy with a photo-z of 0.3554+/-0.2158 in the PS1-STRM catalogue (Beck et al. 2021).
GOTO24bar | 11:20:26.8 | +62:07:17.2 | 60432.963164 | 1.36 | L | 20.6 +/- 0.2 | Found in both available epochs. No clear evidence of fading. Consistent with a g = 20.87 mag galaxy with a photo-z of 0.1591+/-0.0317 in the PS1-STRM catalogue (Beck et al. 2021).
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 36395
Subject
GRB 240502C: Zeiss-1000 at Koshka observatory observations of GOTO optical counterpart candidates
Date
2024-05-05T09:17:11Z (a year ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
Via
legacy email
S. Belkin (IKI), A. Novichonok (Petrozavodsk State University, KIAM), A. Pozanenko (IKI), N. Pankov (HSE,IKI) report on behalf of GRB IKI FuN:
We observed possible optical counterpart candidates of the GRB 240502C (Fermi GBM Team, GCN 36376) reported by Gompertz et al. (GCN 36380) with the Zeiss-1000 telescope at Koshka observatory (INASAN) in R-filter on 2024-05-13. Preliminary photometry of stacked images is the following
Name Date UT start t-T0 Exp. Filter OT Err. UL(3sigma)
(mid, days) (s)
GOTO24bao 2024-05-03 20:58:29 1.65611 15x120 R 19.24(OT+Host) 0.08 21.3
GOTO24azq 2024-05-03 21:34:06 1.68084 15x120 R 20.20 0.17 21.4
GOTO24bar 2024-05-03 22:06:55 1.70363 15x120 R 19.05(OT+Host) 0.07 21.0
The photometry is based on nearby USNO-B1.0 stars.
Ref.stars
USNO-B1.0
RA DEC R2
10:45:21.4440000 +63:19:42.470400 15.27
10:45:02.1088800 +63:24:07.632000 17.00
10:45:19.0320000 +63:24:02.682000 15.74
Photometry of the GOTObar (OT+Host) is dimmer than the underlying host galaxy (R~18.7 using Lupton transformation), which might indicate that the source either faded away or wasn't related to the GRB 240502C.
The magnitude of the GOTO24bao (OT+Host) is brighter than the underlying host galaxy (R~20.0 using Lupton transformation), and after host subtraction is R~20.0. This value seems to be fainter than the one reported by Gompertz et al. (GCN 36380). Nevertheless, we cannot ascertain the nature of this candidate using currently available data.
GOTO24azq is clearly visible in the stacked image; however, it doesn't show GRB-like behaviour on a two-day time scale in comparison with the reported magnitude by Gompertz et al. (GCN 36380).
Further observations might be needed to confirm the connection of these candidates with the GRB 240502C.
GCN Circular 36497
Subject
GRB 240502C: Zeiss-1000 at Koshka observations of GOTO24bao optical counterpart candidate
Date
2024-05-16T16:13:56Z (a year ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
Via
legacy email
A. Volnova (IKI), A. Novichonok (Petrozavodsk State University, KIAM), A. Pozanenko (IKI), S. Belkin (IKI), N. Pankov (HSE) report on behalf of GRB IKI FuN:
We observed GOTO24bao (Gompertz et al., GCN 36380; Belkin et al., GCN 36395), a possible optical counterpart of the GRB 240502C (Fermi GBM Team, GCN 36376) with the Zeiss-1000 telescope of Koshka observatory in R-filter on 2024-05-05/06. The preliminary photometry of stacked images in all epochs is as follows
Date UT start t-T0 Exp. Filter OT Err. UL (3sigma)
(mid, days) (s)
2024-05-03 20:58:29 0.99542 15x120 R 19.02 0.06 21.1
2024-05-05 18:58:54 2.89875 8x300 R 18.73 0.04 21.3
2024-05-06 20:48:24 3.97479 8x300 R 18.98 0.04 21.8
Ref. stars
USNO-B1.0
RA DEC R2
09:57:18.15288 +62:02:45.8412 17.46
09:56:49.99872 +62:01:39.1620 14.74
09:57:14.13480 +61:59:47.1624 16.44
The magnitude of the (possible OT + host) on May 5 is somewhat but significant) brighter than in adjacent epochs, indicating the presence of variability of the OT. Till now we cannot confirm the association of the candidate GOTO24bao with an GRB 240502C afterglow.