TITLE:   GCN CIRCULAR
NUMBER:  34425
SUBJECT: GRB 230812B: GRANDMA further observations of ZTF23aaxeacr candidate afterglow
DATE:    23/08/14 21:28:38 GMT
FROM:    Aleksandra Pyshna at Astronomical Observatory of Taras Shevchenko National University of Kyiv, Kyiv, Ukraine <pyshnaya.sasha@gmail.com>

O. Pyshna (AO TSNU of Kyiv), Z. Vidadi (ShAO), S. Beradze (AbAO), Y.Rajabov (UBAI), D. Aql (American Uni. SHJ), S. Antier (OCA), M. Coughlin (UMN), J. Peloton,  P. Hello (IJCLAB), S. Karpov, M. Prouza, M. Mašek, M. Blazek (FZU), A. Klotz (IRAP),T. Pradier (Univ. Strasbourg), I. Tosta e Melo (UNICT), D. Turpin (CEA), A. Takey, E. G. Elhosseiny, A. Abulwfa, M. A. El-Sadek, M. Molham (NRIAG), R. Inasaridze, R. Natsvlishvili, N. Kochiashvili, V. Aivazyan (AbAO), A. Baransky, Y. Romanyuk, O. Sokoliuk, A. Simon, V. Vasylenko (Lisnyky) report on behalf of the GRANDMA collaboration:

GRANDMA observed the field of GRB 230812B (Lesage et al. GCN 34387; Scotton et al. GCN 34392; Page GCN 34394; Zheng
& Filippenko GCN 34395; Lipunov et al. GCN 34396; Ackley et al. GCN 34398; Xiong et al. GCN 34401; Casentini et al. 34402; Frederiks et al. 34403; Mao et al. 34404; Odeh et al. 34405; Moskvitin & Spiridonova 34406; Leonini et al. 34408; de Ugarte Postigo et al. 34409; de Ugarte Postigo et al. 34410; Belkin et al. 34412; Ruocco et al. 34413; Frederiks et al. 34414; Ruocco et al. 34415; Shrestha et al. 34416; Quadri et al. 34417; Adami et al. 34418; Moretti et al. 34419; Kumar et al. 34420; Belkin et al. 34421) 
in particular ZTF23aaxeacr candidate afterglow (16:36:31.483 +47:51:32.26) (Salgundi et al. GCN 34397) 


The first observation began about 22.56 hours from the trigger.


As time reference (T0), we choose: 2023-08-12T18:58:12 (60168.79041667 MJD) (Fermi GBM Team 34386)

In the following table we report a subset of the preliminary photometry
of our observations. Magnitudes and upper limits are reported
in the AB system.

ZTF23aaxeacr:

T-T0 (day) |MJD   |Obser.   |Exposure| Filter | Mag +/- err  |Upp.Lim. (AB)
--------------------------------------------------------------------------
0.940|60169.73055556    |Abastumani-T70|46X60s |sdssr|20.35+/-0.12|21.3 (5sig)
0.959|60169.75012731    |      KAO                   |10X180s|sdssg|20.53+/-0.05|21.7 (5sig)
0.988|60169.77848380    |      KAO                   |10X180s|sdssr|20.23+/-0.05|21.5 (5sig)
1.021|60169.81137731    |      KAO                   |20X150s|sdssi|20.17+/-0.03|22.3 (5sig)
1.115|60169.90562500    |  FRAM-CTA-N      |50X60s |  R  |      -     |>19.1 (Vega)


KAO data has been calibrated with respect to the PS1 catalog.
Abastumani-T70 data has been calibrated with respect to the PS1 catalog, with the Johnson cousin conversion into sloan r.
FRAM-CTA-N data has been calibrated with respect to the APASS catalog.

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/).