TITLE:   GCN CIRCULAR
NUMBER:  31884
SUBJECT: GRB 220408A: GRANDMA observations
DATE:    22/04/12 15:20:13 GMT
FROM:    Sarah Antier at OCA  <sarah.antier@oca.eu>

S. Beradze (AbAO), U. Bhardwaj (GRAPPA), T. Culino (ESILV), P. Hello
(IJCLAB), M. Masek (FZU), G. Raaijmakers (GRAPPA), Y. Rajabov (UBAI),
T. Sadibekova (AIM/CEA-UPS), F. Z. Guo (THU), X. F. Wang (THU/BJP), Y.
Zhu (NAOC), J. Zhang (NAOC), D. A. Kann (HETH/IAA-CSIC), K. Noysena
(TRT-SRO), C. Rinner (OUCA), Z. Benkhaldoun (OUCA), J. Zhu (BJP),
X. Song (BJP), S. Antier (OCA/Artemis), P. A. Duverne (IJCLAB), A. Simon
(Kyiv Univ), A. Baransky (Kyiv Univ) and V. Godunova (IC ICAMER)
report on behalf of GRANDMA collaboration:

The GRANDMA telescope network responded to the alert of GRB 220408A
(Caputo et al. GCNC 31848). The first observations started 0.63 h after
the SWIFT BAT trigger time.

We did not detect the optical afterglow within the first 24 h.
Upper limits are given in the AB system, at 3-sigma.


T-T0(hr)| MJD    | Observatory  | Exposure| Filter | Upp. Lim. (AB)
___________________________________________________________________________
0.63 |59677.26659|KNC-T19       |9*300 s  |  V        |   17.7
1.82 |59677.31602|SRO           |7*60 s   |  R        |   19.8
6.27 |59677.50176|Xinglong-2.16m|9*400 s  |  Rc       |   20.3
8.45 |59677.59259|BJP/ALi-50    |21*20 s  |  Clear |   21.4
14.89|59677.86076|MOSS          |45*60 s  |  Clear |   20.3
18.76|59678.02215|KNC-HAO       |23*180 s |  Lumen |   20.6

These upper limits are consistent with previous reports of detections by
UVOT (Caputo et al. GCNC 31848, Oates et al. GCNC 31855), KAIT (Zheng et al.
GCNC 31850), LCO (R. Strausbaugh et al. GCNC 31862), NOT (Zhu et al. GCNC
31864), RATIR (Watson et al. GCNC 31870), and LDT (B. O'Connor et al. GCNC
31875), and the upper limits provided by MASTER (Lipunov et al. GCNC 31849),
Xinglong-2.16m (Jiang et al. GCNC 31853), GIT (Kumar et al. GCNC 31857),
LOAO/SAO/DOAO (Paek et al. GCNC 31867), and 1.3m DFOT (Kumar et al. GCNC
31868).

The SRO, Xinglong-2.16m, and Ali-50 data have been calibrated with four 
stars
from the Pan-STARRS catalog, using the transformations by Lupton (2005) and
using Rc values for the Clear Al-50 observation. The MOSSm KNC-T19 and
KNC-HAO images have been calibrated using field stars from the 
PanSTARRS-DR1
catalog, measured with the MUPHOTEN pipeline (Duverne et al. 2021).

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/).