GCN Circular 41564
Subject
EP250827A: An optical rebrightening was detected by LCO.
Event
Date
2025-08-27T15:36:17Z (a month ago)
From
ankur ghosh at CAPP, University of Johannesburg <ghosh.ankur1994@gmail.com>
Via
Web form
Ankur Ghosh, Soebur Razzaque (CAPP, University of Johannesburg), Rahul Gupta (NASA GSFC), Alexander Moskvitin, Yulia Sotnikova (SAO RAS), Naveen Dukiya (ARIES) on behalf of a larger collaboration.
We observed the field of the EP 250827A triggered by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Hua et al., GCN 41553) in the r, V filter of the 1-meter Sinistro telescope at the Las Cumbres Observatory Global Telescope (LCOGT) node located at Siding Spring is near Coonabarabran, New South Wales, Australia . The 1-m Sinistro telescope is equipped with a 4K x 4K CCD (FOV: 26 x 26 arcmin, scale: 0.39 arcsec/pixel).
Observations began on August 27, 2025, starting 5.135 hours after the GRB trigger. Further observations are currently ongoing.
We clearly detect the optical transient (OT) reported by GCNs (Levan et al., GCN 41554; Li et al., GCN 41555; Lipunov et al., GCN 41558; Gritsevich et al., GCN 41559, An et al., GCN 41660) in our r band image. A brightening of ≈ 0.5 mag was observed within 1–5 hours after the burst, with An et al,. GCN 41660, reported a magnitude of 18.9 mag at ~1 hour post-burst.
|Date| |UTstart| |t-T0 (hours)| |Exp (sec)| |Filter| |Magnitude|
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2025-08-27 12:48:48.96 5.135 1 x 900 r r = 18.44 +/- 0.01
The field was calibrated against nearby APASS stars, with magnitudes converted using Lupton (2005) equations, and has not been corrected for Galactic extinction.