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GCN Circular 35108

Subject
GRB 231118A: Continued Skynet Observations
Date
2023-11-18T21:49:27Z (7 months ago)
From
Dylan Dutton at UNC Chapel Hill <ddutton59@gmail.com>
Via
Web form
Dylan Dutton, Megan Dubay, Ruide Fu, Donovan Schlekat, Logan Selph, Daniel Reichart, Joshua Haislip, Vladimir Kouprianov, Daryl Janzen, Arie Verveer, and John Kennewell report on behalf of the Skynet Robotic Telescope Network at the University of North Carolina at Chapel Hill.

We continued to observe the afterglow of GRB 231118A located at RA=00:19:19.3583, Dec=-48:02:24.923 (GCN 35103, Dutton et al.) with our 0.4m robotic telecope located in Meckering, Australia. The observation began at 17:19:11 UTC on Nov 18 2023, approximately 3 minutes after the trigger, and continued for approximately 100 minutes, until 18:54:53 UTC. We obtained multiple expsoures in the B, V, R, and I filters.

During the first approximately 40 minutes of the observation, the afterglow faded very slowly, and irregularly, with an approximate temporal index between -0.2 and -0.1.

After 40 minutes, the afterglow faded much more quickly with an approximate temporal index between -2 and -1.5, which could be consistent with the non-detection from Global MASTER-Net (GCN 35107, Lipunov et al.).

Throughout the entire observation, the afterglow is very red, with an approximate spectral index between -2 and -1.5. This is likely due to source-frame dust.

We report the photometry of our most recent images below.

ExpLen  | Filter | Mag   | MagErr | Date         | UTC
-----------------------------------------------------------
110.95s | R      | 17.02 | 0.04   | Nov 18, 2023 | 18:52:55
89.47s  | I      | 16.65 | 0.07   | Nov 18, 2023 | 18:54:53

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