GCN Circular 25907
Subject
LIGO/Virgo S190930t: Upper limits on the two of the ZTF/GROWTH candidates
Event
Date
2019-10-01T19:16:47Z (6 years ago)
From
Tomoki Morokuma at U of Tokyo <tmorokuma@ioa.s.u-tokyo.ac.jp>
Morokuma, T. (U. Tokyo); Utsumi, Y. (Stanford/SLAC) on behalf of J-GEM
collaboration
We report optical follow-up imaging observations for the electromagnetic
counterpart candidates of the gravitational wave event S190930t (The
LIGO Scientific Collaboration and the Virgo Collaboration, GCN Circ.
25876) reported by Stein et al. (GCN Circ. 25899).
We took 12 contiguous frames of 0.5-second exposures 19-22 hours from
the possible neutron star and black hole merger for the regions around
ZTF19acbpqlh (AT2019rpn) and ATLAS19wyn (AT2019rpj) with Tomo-e Gozen
(Sako et al. 2018, SPIE, 10702, 107020J) on the 1.05-m Kiso Schmidt
telescope. No filters are used and the data are calibrated relative to
r-band data from Pan-STARRS DR2. We find no transients at the reported
locations down to depths in the AB system shown below.
| MJD | AT | depth (5 sigmas) |
| 58757.40871 | ZTF19acbpqlh (AT2019rpn) | 18.69 |
| 58757.51431 | ZTF19acbpqlh (AT2019rpn) | 17.66 |
| 58757.43221 | ATLAS19wyn (AT2019rpj) | 18.53 |
| 58757.52506 | ATLAS19wyn (AT2019rpj) | 18.04 |
We note that the ZTF/GROWTH reported magnitudes are 1.0-2.4 magnitudes
fainter than our detection limits above.