TITLE: GCN CIRCULAR NUMBER: 31041 SUBJECT: GRB 211023A: continued 1.3m DFOT Optical Observations and possible jet break DATE: 21/11/05 06:00:44 GMT FROM: Rahul Gupta at ARIES, India <rahulbhu.c157@gmail.com> Rahul Gupta, S. B. Pandey, Amit Ror, Amit Kumar, Dimple, Ankur Ghosh, Amar Aryan, Bhavya, and Kuntal Misra (ARIES) report: We further observed the bright GRB 211023A (Fermi GBM Team 2021, GCN 30958; Lesage et al. 2021, GCN 30965; N. Di Lalla et al. 2021, GCN 30961; Ursi et al. 2021, GCN 30969; and Ridnaia et al. 2021, GCN 31022) with 1.3m Devasthal Fast Optical Telescope (DFOT) located at Devasthal observatory of Aryabhatta Research Institute of Observational Sciences (ARIES), India, starting on 2021-10-29 at 19:19:13 UT, i.e., ~ 6.26 days after the Fermi trigger. We obtained 24 and 18 frames having an exposure time of 300 sec in the R and I filters, respectively. We detected the optical afterglow of GRB 211023A (Lipunov et al. 2021, GCN 30970; Zhirkov et al. 2021, GCN 30977; Kann et al. 2021, GCN 30982; Hu et al. 2021, GCN 30990; Belkin et al. 2021, GCN 31004, 31018, 31020; Vinko et al. 2021, GCN 31008; and Kumar et al. 2021, GCN 31023) in our stacked images of both the filters. The preliminary photometric estimate of the afterglow in the R filter is following : Date Start UT T-T0 (mid, days) Filter Exp time (sec) Magnitude =========================================================2021-10-29 19:19:13 ~6.28 R 300*24 22.58 +/- 0.33 Based on the preliminary photometry reported by using various ground-based optical telescopes (Kann et al. 2021, GCN 30982; Hu et al. 2021, GCN 30990; and Belkin et al. 2021, GCN 31004, 31018, 31020) and our first epoch observations using 1.3m DFOT (Kumar et al. 2021, GCN 31023), we measure the optical flux decay power-law index of the afterglow light curve (Galactic extinction corrected) of GRB 211023A equal to 1.49 +/- 0.04, consistent with those reported earlier (Belkin et al. 2021, GCN 31004, 31020; and Vinko et al. 2021, GCN 31008). However, we noticed that our second epoch observations are fainter than the extrapolation of the early temporal decay index of ~1.5, suggesting a possible break in the light curve. However, due to the unavailability of near-simultaneous X-ray afterglow observations, we could not confirm if this optical steeping is due to the jet break. Further deeper and multiwavelength observations with larger telescopes will be helpful to establish the possible jet break. The reported magnitude value is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the USNO-B1.0 catalog. This circular may be cited.