TITLE:   GCN CIRCULAR
NUMBER:  31883
SUBJECT: GRB 220403B: GRANDMA observations
DATE:    22/04/12 08:21:29 GMT
FROM:    Sarah Antier at OCA  <sarah.antier@oca.eu>

X. Song, J. Zhu (BJP), I. Tosta e Melo (INFN-LNS), J.-G. Ducoin (IAP),
N. Guessoum (AUS), W. Corradi (LNA), T. Culino (OCA), E. Gurbanov (ShAO),
E. Hesenov (ShAO), A. de Ugarte Postigo, S. Antier (OCA/Artemis), L. Wang,
A. Iskandar (XAO), X. F. Wang (TSU/BJP), X. Zeng (CTGU), D. Marchais (KNC),
P.A. Duverne, N. Leroy (IJCLAB), D. A. Kann (HETH/IAA-CSIC), A. Simon,
A. Baransky (Kyiv univ), V. Godunova (IC ICAMER),
report on behalf of GRANDMA collaboration:

The GRANDMA telescope network responded to the alert of GRB 220403B
(Klingler et al., GCN 31820). The first observations started 8 min after
the BAT trigger time.

We clearly detect the afterglow within the first hour.
We also report our 3-sigma upper limits. Magnitudes are given in the
AB system.

T-T0 (hr)| MJD   | Obser.   |Exposure| Filter | Mag +/- err  | Upp.Lim. (AB)
___________________________________________________________________________
0.13 |59672.86832| ALi-50   | 5x20s  | Clear  | 18.4 +/- 0.1 | -
0.35 |59672.8775 | ALi-50   | 20x20s | SDSS g'| 19.7 +/- 0.1 | -
0.48 |59672.88298| ALi-50   | 20x20s | SDSS r'| 18.6 +/- 0.1 | -
17.67|59673.59939| SNOVA    | 15x300s| Clear  |       -      | 19.4
24.72|59673.89285| KNC-T-CAT| 240x32s| Blue   |       -      | 20.9
24.72|59673.89285| KNC-T-CAT| 240x32s| Green  |       -      | 20.9
24.72|59673.89285| KNC-T-CAT| 240x32s| Red    |       -      | 19.9

These detections and limits are consistent with the detections and limits
previously reported in Klingler et al. (GCN 31820), Jelinek et al.
(GCN 31821),Nicuesa Guelbenzu et al. (GCN 31822), Zhu et al. (GCN 31823),
Lipunov et al. (GCN 31825),  Rossi et al. (GCN, 31826), Grossan et al.
(GCN 31830), Pankov et al. (GCN 31837, 31844), Hu et al. (GCN 31841),
and Kumar et al. (GCN 31869).

The photometry of Ali-50 was performed using field stars from the
PanSTARRs-DR1 catalog for images with SDSS g' and r' filters, and from the
Gaia gmag catalog for images with no filters. The SNOVA and T-CAT data have
been processed using field stars from the PanSTARRS-DR1 catalog and 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/).