TITLE:   GCN CIRCULAR
NUMBER:  21561
SUBJECT: LIGO/Virgo G298048: Subaru HSC z-band photometry of the possible optical counterpart
DATE:    17/08/18 14:27:26 GMT
FROM:    Nozomu Tominaga at Konan U  <tominaga@konan-u.ac.jp>

Yoshida, M., Tanaka, M., Terai, T., Nakata, F., Furusawa, H.,
Koshida, S. (NAOJ), Utsumi, Y., Kawabata K. S. (Hiroshima Univ.),
Tominaga, N. (Konan Univ.), Motohara, K., Ohsawa, R., Morokuma, T.,
Yasuda, N. (Univ. of Tokyo), Kawai, N. (Tokyo Tech) on behalf of
the J-GEM collaboration

As reported in Yoshida et al. 2017 (GCN 21549), we performed z-band imaging
observations for the gravitational wave event G298048 (GCN 21505; 21509; 21513)
with Hyper Suprime-Cam attached to the Subaru telescope on August 18 2017 UT. 
The survey fields include SSS17a (RA = 13:09:48.09 DECL. = -23:22:53.35, 
Coulter et al. 2017; GCN 21529) possibly associated with G298048. After photometric
calibration with Pan-STARRS1 catalog (Chambers et al. 2016) using HSC
pipeline (Bosch et al. 2017), we obtained psf magnitude of z = 17.3, which 
is consistent with the magnitudes reported by Chambers et al. (GCN 21553). 
We did not find a significant variability with > 0.1 mag during
our observations from 5:16 UT until 5:40 UT.