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GCN Circular 32905

Subject
GRB 221027B: GRANDMA observations
Date
2022-11-03T14:53:01Z (2 years ago)
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/).
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