GCN Circular 40240
Subject
GRB 250424A: Kilonova-Catcher optical afterglow detection
Event
Date
2025-04-24T18:25:31Z (10 months ago)
From
Damien Turpin at CEA-Saclay <dturpin-astro@hotmail.com>
Via
Web form
D. Turpin (CEA-Saclay/Irfu), R. Hellot, P. Jaquiery, M. Freeberg (KNC), C. Andrade(UMN), S. Antier (OCA), M. Coughlin (UMN),S. Karpov (FZU), I. Tosta e Melo (UniCT-DFA), P. Hello (IJCLAB), P-A Duverne (APC), T. Pradier (Unistra/IPHC), N. Guessoum (AUS), M. Pillas (ULiege) on behalf of the GRANDMA/Kilonova-Catcher collaboration:
We observed the field of GRB 250424A (Cenko et al., GCN 40224) detected by Swift/BAT with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with the iT30 telescope at the Siding Spring Observatory, a Celestron C14 telescope at Beverly Begg Observatory (New Zealand) and a CDK17 telescope located at AITP San Pedro Chile Observatory starting from TGRB+1.3hr.
In our stacked frames, subtracted from the Legacy Survey DR10 template image, we detect the optical afterglow at the position reported by Swift/UVOT (Cenko et al., GCN 40224), REM (Brivio et al., GCN 40225), DDOTI (Becerra et al., GCN 40226), VLT/X-Shooter (Saccardi et al., GCN 40228), BlackGEM (de Wet et al., GCN 40229)and COLIBRI (Ducoin et al., GCN 40230).
We report some of our detections in the table below:
+---------------+-----------+-----------+----------------+------------+
| Tmid-TGRB (hr)| Exp (s) | Filter | Magnitude | Instrument |
+===============+===========+===========+================+============+
| 1.3 | 1 x 300s | r (AB) | 19.34 +/- 0.09 | CDK17-AITP |
| 4.0 | 20 x 120s | r (AB) | 19.74 +/- 0.07 | C14-BBO |
| 6.8 | 17 x 180s | Rc (Vega) | 19.95 +/- 0.09 | iT30 |
+---------------+-----------+-----------+----------------+------------+
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 Synphot catalog while the sloan images were calibrated using the SkyMapper DR4 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/).