TITLE: GCN CIRCULAR NUMBER: 27621 SUBJECT: GRB 200410A: Liverpool Telescope First Hour Observations DATE: 20/04/22 11:40:04 GMT FROM: Iain Steele at Liverpool/JMU I.A. Steele, M. Shrestha, S. Kobayashi (Liverpool JMU), C. Mundell (Univ. Bath), A. Gomboc (Univ. Nova Gorica) report on behalf of a wider collaboration: We observed the field of Swift GRB 200410A (GCN 27518) with the 2.0m Liverpool Telescope, La Palma on 2020 Apr 10 starting at 02:28:38 UT using the IOO optical camera for a period of ~1 hour in the r’ and I’ bands. The target was well resolved from the two nearby stars. Data was calibrated with respect to APASS secondary standard stars in the images. We confirm the optical counterpart reported by Swift UVOT and Ondrejov (GCN 27520). At T=155 seconds after the BAT trigger time, we measure r’ = 18.2. Both the r’ and i’ band light curves subsequently show a power law decay in flux vs time with alpha = 0.7 over the first hour. ________________________________ Important Notice: the information in this email and any attachments is for the sole use of the intended recipient(s). If you are not an intended recipient, or a person responsible for delivering it to an intended recipient, you should delete it from your system immediately without disclosing its contents elsewhere and advise the sender by returning the email or by telephoning a number contained in the body of the email. No responsibility is accepted for loss or damage arising from viruses or changes made to this message after it was sent. The views contained in this email are those of the author and not necessarily those of Liverpool John Moores University.