TITLE: GCN CIRCULAR NUMBER: 37049 SUBJECT: EP240801a: BTA BVRI photometry DATE: 24/08/05 17:22:19 GMT FROM: Moskvitin Alexander at SAO RAS mosk@sao.ru
A. Moskvitin, D. Oparin (SAO RAS), N. Pankov (HSE, IKI), A. Pozanenko (IKI) report:
We observed the field of the fast X-ray transient EP240801a (Zhou et al., GCN 36997) with the BTA 6-meter telescope of SAO RAS equipped with the focal reducer Scoprio-I on August, 3 (t_mid - T0 = 2.629 days) and August, 4 (t_mid - T0 = 3.485 days).
The OT (Fu et al., GCN 36998; Li et al., GCN 36999; Zheng et al., GCN 37000; Aryan et al., GCN 37002; An et al., GCN 37004; Perez-Fournon et al., GCN 37007; Malesani et al., GCN 37008; Zhu et al., GCN 37010; Moskvitin et al., GCNs 37012, 37017; Quirola-Vasquez et al., GCN 37013; Moretti et al., GCN 37014; Turpin et al., GCN 37015; Pankov et al., GCNs 37016, 37040) is clearly detected in stacked frames. Preliminary photometry of OT in the both epochs as is follows.
Filter, exp, t_start t_end (UTC) OT, mag s, (UT) (UT) B 620 2024-08-03T23:44:36 -- 2024-08-04T00:37:41 23.88 +/- 0.13 V 600 2024-08-03T23:50:17 -- 2024-08-04T00:33:45 23.13 +/- 0.09 Rc 510 2024-08-03T23:47:46 -- 2024-08-04T00:35:28 22.82 +/- 0.07 Ic 510 2024-08-03T23:52:56 -- 2024-08-04T00:30:14 22.05 +/- 0.10
V 900 2024-08-04T20:28:02 -- 2024-08-04T21:01:52 23.55 +/- 0.08 Rc 930 2024-08-04T20:23:36 -- 2024-08-04T21:03:41 22.91 +/- 0.06
The magnitudes were calibrated against nearby Pan-STARRS stars and not corrected for Galactic extinction.
We note significant reddening (V-Rc) between the two epochs.
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