Kanata optical/near-infrared observations of a black hole X-ray binary V4641 Sgr
ATel #13437; F. Imazato, M. Sasada, T. Nakaoka, M. Uemura, H. Akitaya (Hiroshima University)
on 1 Feb 2020; 12:48 UT
Credential Certification: Makoto Uemura (uemuram@hiroshima-u.ac.jp)
Subjects: Infra-Red, Black Hole, Transient
Following the report on the new X-ray outburst (ATel: #13431), we performed the optical and near-infrared photometric observations of V4641 Sgr using the Hiroshima Optical and Near-InfraRed camera (HONIR; Akitaya et al. 2014, Proc. SPIE 9147, 91474O) installed to the Cassegrain focus of the 1.5-m Kanata telescope at the Higashi-Hiroshima Observatory. Observations were carried out on 2020 Jan 31 21:12:44 UT to 21:43:41 UT (MJD: 58879.884248 - 58879.905625).
Our preliminary analysis shows the following Vaga magnitudes (not applied reddening correction):
V=12.92+/-0.02
J=12.03+/-0.02
H=11.92+/-0.02
Ks=11.81+/-0.03
Compared with the previous report (MacDonald et al. 2014), V4641 Sgr is now significantly brighter than the quiescent ellipsoidal modulation level at the above four bands.
We will continue the optical and near-infrared observations of V4641 Sgr.
