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GCN Circular 41310

Subject
GRB 250809A: LCOGT Optical Upper Limits
Event
GRB 250809A
Date
2025-08-10T00:29:39Z (22 days ago)
From
Robert Strausbaugh at Eastern Illinois University <rstrausbaugh@eiu.edu>
Via
email
R. Strausbaugh (Eastern Illinois University), A. Cucchiara (NASA) report on behalf of a larger collaboration:

We observed the Swift GRB 250809A field (Parsotan et al., GCN 41303)  with the LCOGT 1-meter Sinistro instrument at the Cerro Tololo Interamerican Observatory, Chile site, on August 9, from 23:10 to 23:42 UT (corresponding to 6.28 to 6.85 hours after the GRB trigger time) with the Bessel R and I filters.

We performed a series of 3x300s exposures in I-band and R-band.  We do not detect an uncatalogued source within the Prompt Swift XRT error region (Evans et al., GCN 41304) in either band.

The following 3-sigma upper limits are calculated using the USNO-B1.0 catalog as reference:

R > 20.6
I > 20.3

These magnitudes are not corrected for galactic extinction.
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