Kanata Optical and Near-infrared Observations of AT 2018cow
ATel #11868; Yamanaka, M., Nakaoka, T., Kawabata, M., Takagi, K., Kimura, H., and Kawabata, K. S. (Hiroshima Univ.)
on 19 Jul 2018; 03:11 UT
Credential Certification: Masayuki Yamanaka (masyamanaka@hiroshima-u.ac.jp)
Subjects: Infra-Red, Optical, Supernovae, Transient
We have performed the optical and near-infrared photometric observations of
AT 2018cow (ATEL #11727) using the Hiroshima One-shot Wide-field Polarimeter
(HOWPol; Kawabata et al. 2010), and the Hiroshima Optical and Near-InfraRed
camera (HONIR; Akitaya et al. 2014) attached to the 1.5-m Kanata
telescope at Higashi-Hiroshima Observatory since Jun 21.
The point-spread function (PSF) photometry were carried out using IRAF/DAOPHOT.
We measured the optical magnitudes as B=15.1, V=14.9, R=14.9, and I=15.0 mag
on Jul 21.7. We also measured the near-infrared magnitudes as J=15.6,
H=15.4, and Ks=14.9 on Jul 24.5.
The optical light curves show almost linearly decline until
Jul 1, and the short plateau stage between Jul 1 and 10. After that, the optical
luminosity rapidly fades, again. We measured the ~17.2, ~17.2, and
~16.8 magnitudes
in V, R, and I bands on Jul 10.5, respectively. The large decline rates of the
light curves are quite large comparing to the broad-lined Type Ic (Ic-BL) and
Type Ib/c supernovae.
