GCN Circular 36999
Subject
EP240801a: GMG observation
Date
2024-08-01T17:06:44Z (3 months ago)
From
Rui-Zhi Li at Yunnan Observatories, CAS <liruizhi@ynao.ac.cn>
Via
email
R.-Z. Li, B.-T. Wang, J. Mao, X.-L. Zhang and J.-M. Bai (YNAO, CAS) report:
We observed the field of EP240801a (Zhou et al., GCN 36997, T0 at 2024-08-01T09:06:03) using the GMG-2.4m telescope at the Lijiang Observatory. The observation began at 2024-08-01T16:19:22, about 7.22 hours after the trigger.
The optical counterpart of EP240801a, not visible in the Pan-STARRS1 r-band image, was marginally detected at the coordinates (J2000):
RA = 23h00m39.02s
DEC = +32d35m37.2s
, with a positional uncertainty of 0.5" or better. The position is consistent with TRT observation (GCN 36998).
The preliminary analysis results are shown as follows:
+---------------+------------+----------+--------------+--------------+
| Tmid-T0 [h] | Exp. [s] | Filter | Mag | 5-sigma UL |
+===============+============+==========+==============+==============+
| 7.39 | 1200 | R | 21.21 ± 0.12 | 21.9 |
+---------------+------------+----------+--------------+--------------+
The given magnitudes are derived based on calibration against Pan-STARRS1 field stars, and are not corrected for the expected Galactic foreground extinction, corresponding to a reddening of E(B-V) = 0.092 mag in the direction of the optical counterpart (Schlafly & Finkbeiner 2011).
We note that this optical counterpart has become fainter compared to the TRT observation (R = 20.32 ± 0.16 mag, GCN 36998).