TITLE: GCN CIRCULAR NUMBER: 32905 SUBJECT: GRB 221027B: GRANDMA observations DATE: 22/11/03 14:53:01 GMT FROM: Alexander Kann at IAA-CSIC kann@iaa.es
N. Kochiashvili (AbAO), Z. Vidadi (ShAO), D. A. Kann (Goethe Univ.), P. Gokuldass (Florida Tech.), S. Beradze (AbAO), Sh. Aghayeva (ShAO), R. Le Montagner (IJCLab), C. Rinner, Z. Benkhaldoun (OUCA), S. Antier (OCA/Artemis), J. Ali, A. Kaouech (OUCA/KNC), and Sergey Karpov (FZU) report on behalf of the GRANDMA collaboration:
The GRANDMA telescope network responded to the Swift-BAT alert of GRB 221027B (Lien et al., GCN 32867, Beardmore et al., GCN 32868, Perri et al., GCN 32870, Markwardt et al., GCN 32892). No optical afterglow consistent with the XRT position (Beardmore et al., GCN 32868) is detected by Swift in the initial UVOT exposures (Belles & Lien, GCN 32875).
The first observations started 23.8 hours after the BAT trigger time. The optical counterpart of the afterglow was not detected in our observations.
In the following table we report the preliminary photometry of our observations. Upper limits are reported at the 5-sigma limit, in the AB system.
T-T0 (hr)| MJD | Obser. |Exposure | Filter | Upp.Lim. ----------------------------------------------------------------- 23.7956 | 59880.79262 | KNC-HAO | 15 x 120 s | L | 20.5
HAO data have been calibrated with PS1 catalog. Values are not corrected for the Galactic extinction E(B-V) = 0.0262 mag (Schlafly & Finkbeiner 2011).
Our upper limits are in agreement with other non-detections from Swift UVOT (Belles & Lien, GCN 32875), BOOTES-1 (Hu et al., GCN 32869), MASTER (Lipunov et al., GCN 32871), BART-SBT and FRAM-ORM (Jelinek et al., GCN 32873), and COATLI (Becerra et al., GCN 32880).
GRANDMA is a worldwide coordinated 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/).