TITLE:   GCN CIRCULAR
NUMBER:  31366
SUBJECT: GRB 220101A: OASDG optical observations
DATE:    22/01/02 11:29:48 GMT
FROM:    Luca Izzo at DARK/NBI  <luca.izzo@gmail.com>

A. Noschese, L. D’Avino (OASDG), A. Di Dato (INAF/Naples & OASDG), L. Izzo (DARK/NBI) report:

We observed the field of GRB 220101A (Tohuvavohu et al., GCN #31347; Arimoto et al., GCN #31350; Ursi et al., GCN #31354) with the 0.5m telescope of the Osservatorio Astronomico S. Di Giacomo located in Agerola, Italy ( https://osservatorio.astrocampania.it/ ). We obtained three sets of 7x180s images in the Rc filter and two sets of 7x180s images in the Ic filter under moderate weather conditions (average humidity ~87%). The afterglow is clearly detected in the stacked Ic images, being quite fainter in the Rc stacked images, at the position reported by Swift-UVOT (Kuin & Tohuvavohu, GCN #31351) and by optical telescopes (Fu et al., GCN #31353; Hentunen et al., GCN #31356; Perley et al., GCN #31357; de Ugarte Postigo et al., GCN #31358; Fynbo et al., GCN #31359; Vinko et al., GCN #31361; Tomasella et al., GCN #31363; Mao et al., GCN #31364). We report the following preliminary magnitudes (AB)

Filter   Tmid-T0(days)   Mag.      Delta Mag.
Rc       0.568                 19.10     0.09  
Ic        0.586                 18.13     0.07
Rc       0.604                 19.40     0.20
Ic        0.620                 18.16     0.09
Rc       0.638                 19.09     0.17

The calibration was performed using nearby stars in the Pan-STARRS PS1 catalog, using transformation equations to Rc and Ic magnitudes.

We want to mention that these observations were done exactly one year after the damage caused to the OASDG instrumentation by a lightning storm. The detection of a GRB at z=4.618 (Fu et al., GCN #31353; Fynbo et al., GCN #31359) during one of the first observing nights following last year's disaster represents a big result for our group.