GCN Circular 40969
Subject
GRB 250702F: Kilonova-Catcher optical afterglow detection
Event
Date
2025-07-05T07:49:37Z (13 days ago)
From
Damien Turpin at CEA-Saclay <dturpin-astro@hotmail.com>
Via
Web form
E. Broens, M. Freeberg, R. Hellot (KNC), D. Turpin (CEA-Saclay/Irfu), C. Andrade(UMN), M. Pillas (ULiege), M. Tanasan (NARIT), S. Antier (OCA/IJCLAB) on behalf of the GRANDMA/Kilonova-Catcher collaboration:
We observed the field of GRB 250702F (Fermi GBM team, GCN 40892; Klingler et al., GCN 40894) with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with the T-BRO telescope operated by E. Broens and the CDK17 telescope located at AITP San Pedro Chile Observatory operated by R. Hellot, the iTelescope T72 and TEC180FL telescope operated by M. Freeberg and the 14SC telescope operated by M Odeh. Our observations started at TGRB+1.8hr.
In our stacked frames, subtracted from the PanSTARRS DR2 template image, we detect the optical counterpart reported by Swift/UVOT (Klingler et al., GCN 40894, Siegel et al., GCN 40933) and further confirmed by many other teams (Jelinek et al.,GCN 40895; Kumar et al., GCN 40896; Lipunov et al., GCN 40899; Martin-Carrillo et al., GCN 40900; de Ugarte Postigo et al., GCN 40901; Angulo et al., GCN 40907; Becerra et al., GCN 40911; Brivio et al., GCN 40913; An et al., GCN 40916; Dutton et al., GCN 40921; Odeh et al., GCN 40925; Moretti et al., GCN 40926; Ma et al., GCN 40936; Vinko et al., GCN 40939; Mohan et al., GCN 40946)
We report some of our first image follow-up results in the table below:
+---------------+-----------+------------+---------------+------------|
| Tmid-TGRB (hr)| Exp (s) | Filter | Magnitude | Instrument |
+===============+===========+============+===============+============+
| 1.9 | 5 x 180s | R (Vega) | 18.11 +/- 0.08 | T-BRO |
| 2.8 | 300s | sdssr (AB) | 18.45 +/- 0.07 | CDK17-AITP|
| 3.8 | 300s | sdssg (AB) | 19.01 +/- 0.08 | CDK17-AITP|
| 3.2 | 10 x 180s | R (Vega) | 18.56 +/- 0.06 | iT72 |
| 7.1 | 16 x 180s | sdssr (AB) | 19.54 +/- 0.15 | TEC180FL |
+---------------+-----------+------------+----------------+-----------+
All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the sloan filters were calibrated using the PanSTARRS DR1 catalog. Images obtained with the Johnson-cousins filters were calibrated using the GAIA DR3 synphot 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/).