GCN Circular 39554
Subject
GRB 250226A: GRANDMA Optical Observations
Event
Date
2025-03-03T04:48:59Z (8 months ago)
Edited On
2025-03-03T14:37:52Z (8 months ago)
From
Lydia Nyambane at UMN <nyamb021@umn.edu>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Lydia Nyambane at UMN <nyamb021@umn.edu>
Via
Web form
M. Tanasan (NARIT), L. Nyambane (UMN), H. Muenter (UMN), C. Andrade (UMN), Y. Rajabov (UBAI), F. Magnani (CPPM), M. Masek (FZU), S. Alshamsi (AUS), W. Corradi (LNA), T. Almeida (LNA), K. Noysena (NARIT), L. Fraga (LNA), N. Sasaki (LNA), A. Takey (NRIAG), Y. Hendy (NRIAG), M. Abdelkareem (NRIAG), E. Elhosseiny F. Navarete (NOIRLab/SOAR), S. Antier (OCA/IJCLAB), M. Coughlin (UMN), S. Karpov (FZU), P. Hello (IJCLAB), P-A. Duverne (APC), T. Pradier (Unistra/IPHC), N. Guessoum (AUS) on behalf of the GRANDMA and Kilonova-Catcher collaborations:
The GRANDMA collaboration imaged the field of a fast X-ray transient GRB 250226A discovered by Fermi GBM (Fermi GBM team, GCN circ. 39479) and EP WXT and FXT (Jiang et al., GCN circ. 39482; Jiang et al., GCN circ. 39513) and detected also by GECAM-B (Zhang et al., GCN circ. 39492) and INTEGRAL SPI-ACS and PICsIT (Thakur et al., GCN circ. 39518).
GRANDMA observations were performed at RA = 224.2651, DEC = 20.9756 with the OPD/60cm, TRT-SBO, KAO, Lisnyky/AZT-8 and AbAO-T70 telescopes starting ~0.4 days post T0 in the R and i' bands.
We detect the optical afterglow and report some of the observations at the following magnitudes:
| T-start (UTC) | Magnitude | UL (5sigma) | Filter | Telescope |
| 2025-02-26 17:19:21 | 21.5 +/- 0.2 | 21.5 | R (AB) | TRT-SBO |
| 2025-02-27 01:39:46 | 21.15+/-0.15 | 22.6 | i’ (AB) | KAO |
| 2025-02-27 05:28:50 | 22.0+/-0.25 | 21.8 | R (AB) | OPD/60cm |
Our findings were consistent with the MEPHISTO telescope (Zou et al., GCN 39511), the Xinglong Observatory ( Jiang et al., GCN 39515), and the Las Cumbres Observatory Global Telescope network (LCOGT) (Poidevin et al., GCN 39524).
All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained in Johnson Cousin filters were calibrated using the Gaia DR3 and PS1 catalog.
We use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023).
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 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/).