TITLE:   GCN CIRCULAR
NUMBER:  38021
SUBJECT: GRB 241030A: Palomar 1-m telescope COSMOS optical observations
DATE:    24/11/01 00:07:33 GMT
FROM:    Benjamin Schneider at MIT <bschn@mit.edu>

Benjamin Schneider (MIT), Geoffrey Mo (MIT), Jill Juneau (MIT), Christopher Layden (MIT), Gustav Pettersson (MIT), Nathan Lourie (MIT), Robert Simcoe (MIT) report on behalf of a larger team:

We observed the field of GRB 241030A (Klingler et al., GCN 37956; Beardmore et al., GCN 37962; Wang et al., GCN 37972; Pillera et al., GCN 37979; Ridnaia et al., GCN 37982; Ambrosi et al., GCN 37988; Wu et al., GCN 37997) with the Palomar 1-m telescope, equipped with the large format COSMOS-8k Teledyne camera currently under testing.

Our observations began at 2024-10-31T02:05:52 UTC (~20.4 hours after the GRB trigger) and consisted of 20x30s exposures in the r’ band. In the stacked image, we clearly detect the optical counterpart of GRB 241030A (Klingler et al., GCN 37956; Watson et al., GCN 37957; Fernández-Rodríguez et al., GCN 37958; Zheng et al., GCN 37959; An et al., GCN 37960; Higuchi et al., GCN 37963; Qiu et al., GCN 37965; Lin et al., GCN 37966; Wu et al., GCN 37970; Breeveld & Klingler, GCN 37974; Méndez-Lapido et al., GCN 37993, Moskvitin et al, GCN 38016; Busmann et al., GCN 38019).

The preliminary magnitude derived for the source is

r’ = 20.2 +/- 0.1 mag (AB)

The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the magnitude is not corrected for Galactic extinction.