GCN Circular 26150

Tom��s Ahumada (UMD), Shreya Anand (Caltech), Michael W. Coughlin (Caltech),
S. Bradley Cenko (NASA GSFC), Eric C. Bellm (UW), Leo P. Singer (NASA
GSFC), Mansi M. Kasliwal (Caltech) on behalf of the ZTF and GROWTH
collaborations

We observed the localization region of the short GRB 191031D (trigger
594249816/191031891) detected by the Swift XRT, BAT and the Gamma-Ray Burst
Monitor (GBM) on the Fermi satellite with the Palomar 48 inch telescope
equipped with the 47 square degree Zwicky Transient Facility (ZTF) camera.
These observations are part of the ZTF public survey and serendipitously
covered the GRB localization. We obtained a series of g-band images
beginning at 02:48:56.6 UT on 2019 Nov 01 (5.4 hours after the burst
trigger time). This corresponds to ~68% of the probability enclosed in the
GBM localization region and the totality of the Swift region.

The images were processed through the ZTF reduction and image subtraction
pipelines at IPAC to search for potential counterparts. No
high-significance transients were identified by our pipeline in the area
observed.

The median 5 sigma upper limit for an isolated point source in our images
was g > 20.8 mag for these observations.

ZTF is a project led by PI S. R. Kulkarni at Caltech (see ATEL #11266
<http://www.astronomerstelegram.org/?read=11266>), and includes IPAC; WIS,
Israel; OKC, Sweden; JSI/UMd, USA; UW, USA; DESY, Germany; NRC, Taiwan; UW
Milwaukee, USA and LANL USA. ZTF acknowledges the generous support of the
NSF under AST MSIP Grant No 1440341. Alert distribution service provided by
DIRAC@UW. Alert filtering is being undertaken by the GROWTH marshal system,
supported by NSF PIRE grant 1545949.