{
  "subject": "GRB 241001A: GRANDMA and Kilonova-Catcher optical afterglow detection and upper limits",
  "submittedHow": "web",
  "createdOn": 1727873264248,
  "circularId": 37679,
  "eventId": "GRB 241001A",
  "format": "text/plain",
  "bibcode": "2024GCN.37679....1T",
  "body": "D. Turpin (CEA-Saclay/Irfu), H. Lau Jun Xian (Tsinghua Univ.), O. Pyshna (Caltech), S. Agayeva, Z. Vidadi (Shamakhy Obs.), S. Antier (OCA), S. Karpov (FZU), M. Coughlin (UMN), C. Andrade (UMN), I. Tosta e Melo (UniCT-DFA), P. Hello, N. Leroy (IJCLAB), P-A Duverne (APC), T. Pradier (Unistra/IPHC), N. Guessoum (AUS), A. Klotz (IRAP/OMP), J.-G. Ducoin (CPPM), M. Freeberg (KNC) on behalf of the GRANDMA and Kilonova-Catcher collaborations:\n\nWe observed the field of GRB 241001A (Dagoneau et al., GCN 37655) with GRANDMA and its citizen science project Kilonova-catcher (KNC). Our observations were performed with the TAROT-Reunion (TRE), TAROT-Chile (TCH) and iTelescope T72 telescopes starting from TGRB+42.3 min to TGRB+12h.\n\nIn the stacked TRE images, we detect a faint optical counterpart consistent in position with the Swift XRT source 2 (Osborne et al., GCN 37670) and with the optical afterglow candidate reported by Izzo et al., GCN 37667, Palmerio et al., GCN 37677. We do not detect the optical transient in our following observation epochs showing a clear fading since our first TRE epoch and the LCO and VLT observation (Izzo et al., GCN 37667; Palmerio et al., GCN 37677).\n\nAll our observations and upper limits (5 sigma C.L.) can be found here:\n+------------+-----------+-------------+----------------+\n| Tmid-T0\t|Filter  | Mag (AB)    |  Instrument \t|\n+============+===========+=============+================+\n| 48.75 min  |  Clear    |18.9 +/- 0.2 | TRE          \t|\n| 3.18 h     |  Clear    |20.0 (U.L.)  | TRE           \t|\n| 11.43 h    |  Rc       |21.1 (U.L.)  | iT72          \t|\n| 13.45 h    |  Clear    |20.3 (U.L.)  | TCH           \t|\n+------------+-----------+-----------+------------------+\n\n\nImages obtained in Johnson Cousin filters were calibrated using the Gaia DR3 Synphot catalog, images taken by TAROT were calibrated using the SkyMapper DR4 Catalog.\n\nAll the data have been reduced by a single data processing pipeline STDPIPE (Karpov et al., 2022). We use the Skyportal application (skyportal.io) to monitor our observational campaign.\n\nGRANDMA 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/).\n",
  "submitter": "Damien Turpin at CEA-Saclay <dturpin-astro@hotmail.com>"
}