TITLE:   GCN CIRCULAR
NUMBER:  36941
SUBJECT: GRB240727A: Skynet Optical Afterglow Observations
DATE:    24/07/27 05:40:13 GMT
FROM:    maedubay@unc.edu

Megan Dubay, Donovan Schlekat, Dylan Dutton, Ruide Fu, Daniel Reichart, Joshua Haislip, Vladimir Kouprianov report on behalf of the Skynet Robotic Telescope Network at the University of North Carolina at Chapel Hill.

We observed the field of GRB 240727A with one of the PROMPT telescopes at the Cerro-Tololo Inter-American Observatory. We began observing the field at 03:52:11 UTC on July 27, 2024. The first detection occurred at 04:27:12 UTC on July 27, 2024, approximately 40 minutes after the trigger reported by Swift (Parsotan et al., GCN 36938).

We detect the optical afterglow, also reported by (Zheng and Filippenko, GCN 36939) and (Liu et al., GCN 36940).


The coordinates are:
R.A. (J2000): 15:45:45.02
Dec. (J2000): 08:37:12.95

We report the photometry below. 

ExpLen  | Filter | Mag    | Mag Error | MJD         
--------------------------------------------------
61.45   | R      | 18.653 | 0.218     | 60518.1880
184.35  | R      | 18.818 | 0.167     | 60518.1881
184.35  | V      | 19.067 | 0.280     | 60518.1914

Our images have been calibrated using stars from the APASS catalog.