GCN Circular 36417
Subject
EP240506a: CrAO ZTSH optical upper limit
Date
2024-05-08T18:48:21Z (11 days ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
Via
legacy email
EP240506a: CrAO ZTSH optical upper limit
N. Pankov (HSE, IKI), A. Pozanenko (IKI), V. Rumyantsev (CrAO), S. Belkin (IKI) report on behalf of GRB-IKI-FuN collaboration:
We observed the EP240506a detected by EP-WXT (GCN 36405) with 2.6-meter ZTSh telescope of CrAO, equipped with CCD-photometer and the R-filter. The observations started on 2024-05-07 at 20:43 (UT), i.e. ~1.6 day after EP trigger. The series of 31x120s images were taken.
We do not detect any optical object within EP-WXT localization area. The preliminary photometry is following:
Date UT start MJD Exp. Filter OT Err. UL(3sigma)
(mid, days) (s)
2024-05-07 20:58:29 60437.88266 28x120 R n/d n/d 22.5
The result is in agreement with previous observations (Aryan et al., GCN 36408; Perez-Garcia et al., GCN 36412; Tinyanont et al., GCN 36413).
We also do not detect any optical source consistent with the location of WISEA J141556.28-164124.4 reported by Chang et al. (GCN 36414).
The variable star SDSS J141557.82-164317.2 mentioned in (Chang et al., GCN 36414) does not show any variability in comparison with USNO-B1.0 (R2=17.02) for which we measure the magnitude of R=16.92 +/- 0.10.
The magnitudes were calibrated using nearby USNO-B1.0 stars (R2 magnitude). No correction has been made for a Galactic extinction towards the EP240506a.