GCN Circular 41961
Subject
GRB 250919A / EP250919a: further LCO optical observation
Event
Date
2025-09-24T11:30:34Z (15 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
D. Turpin (CEA/Irfu), A. Saccardi (CEA/Irfu), J. T. Palmerio (CEA/Irfu), Z. Q. Wang (GXU), Y. F. Liang (PMO), report on behalf of the SVOM mission team:
We re-observed the field of GRB 250919A / EP250919a (Fermi GBM Team, GCN 41874; Liang et al., GCN 41879; Wang et al., GCN 41882; Holzmann Airasca et al., GCN 41884; Waratkar et al., GCN 41888; Cheung et al., GCN 41891; Wang et al. GCN 41900; Frederiks et al. GCN 41905) with the LCO 1m telescope at Siding Spring Observatory equipped with the Sinistro instrument.
We obtained 3x200 s exposures in the SDSS r filter. The optical counterpart (Li et al., GCN 41877; Levan et al., GCN 41883; Oates et al., GCN 41886; Lipunov et al., GCN 41893; Ma et al. GCN 41894, Saccardi et al., GCN 41906) is still clearly detected in our subtracted image (using the Legacy Survey DR10 image template) with the following magnitude (calibrated against the SkyMApper DR4 catalogued stars, not corrected for Galactic extinction):
r = 20.67 +/- 0.08 (AB), at a mid-time of 4.47 days after the trigger.
Compared to our first epoch (Saccardi et al., GCN 41906), the afterglow is fading as a power law decay with alpha ~ 1.1 with no evidence of any late break so far.
Further observations are planned.
This project is funded by the SVOM collaboration.