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GCN Circular 40785

Subject
GRB 250615A: Kilonova-Catcher optical upper limits
Event
GRB 250615A
Date
2025-06-19T21:45:50Z (13 days ago)
From
Damien Turpin at CEA-Saclay <dturpin-astro@hotmail.com>
Via
Web form
D. Turpin (CEA-Saclay/Irfu), R. Hellot,  M. Freeberg (KNC), 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 250615A (Dichiara et al., GCN 40736Loading...
 
 ) detected by Swift/BAT with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with the TEC160FL telescope operated by M. Freeberg and a CDK17 telescope located at AITP San Pedro Chile Observatory operated by R. Hellot. Our observations started at TGRB+7.6hr. 

In our stacked frames, subtracted from the PanSTARRS DR2 template image, we do not detect any optical counterpart inside the Swift/XRT refined position (Goad et al., GCN 40739Loading...
 
 ).

We report our follow-up results in the table below:
+---------------+-------------+---------+---------------------+--------------+
| Tmid-TGRB (hr)| Exp (s)     | Filter  | Magnitude           | Instrument   |
+===============+=============+=========+=====================+==============+
| 7.9           | 6 x 300s    | r (AB)  | 20.1 (U.L., 5sigma) | TEC160FL     | 
| 8.1           | 11 x 300s   | g (AB)  | 20.8 (U.L., 5sigma) | CDK17-AITP   | 
| 8.5           | 6 x 300s    | g (AB)  | 20.4 (U.L., 5sigma) | TEC160FL     | 
| 9.0           | 6 x 300s    | i (AB)  | 19.2 (U.L., 5sigma) | TEC160FL     | 
| 9.6           | 11 x 300s   | r (AB)  | 20.2 (U.L., 5sigma) | CDK17-AITP   | 
+---------------+-------------+---------+---------------------+--------------+

All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the sloan images were calibrated using the PanSTARRS DR1 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/).