TITLE:   GCN CIRCULAR
NUMBER:  24187
SUBJECT: LIGO/Virgo S190425z: Palomar Gattini-IR wide-field infrared follow-up
DATE:    19/04/25 16:07:13 GMT
FROM:    Mansi M. Kasliwal at Caltech/Carnegie  <mansikasliwal@gmail.com>

K. De (Caltech), S. M. Adams (Caltech), M. Coughlin (Caltech), M. M.
Kasliwal (Caltech), M. Hankins (Caltech), I. Andreoni (Caltech), S. Anand
(Caltech), L. Singer (NASA GSFC), , T. Ahumada (UMD),  A. Moore (ANU), J.
Soon (ANU), M. Ashley (UNSW), T. Travouillon (ANU)

report on behalf of the Palomar Gattini-IR team and the larger GROWTH
(Global Relay of Observatories Watching Transients Happen) collaboration

We report wide-field near-infrared follow-up observations of the
localization region of the BNS gravitational wave event S190425z (GCN
24168) by the Palomar Gattini-IR survey (Moore and Kasliwal 2019).
Gattini-IR is a newly commissioned near-IR camera with a field of view of
25 square degrees mounted on a robotic 30 cm telescope at Palomar
observatory.

Gattini-IR was already observing the GW localization region as part of
routine survey operations at the time of the trigger. We started customized
Target of Opportunity observations at UT 2019-04-25 09:12:09 (11 minutes
after initial notice time). The tiling was optimally determined and
triggered using the GROWTH Target of Opportunity marshal (Coughlin et al.
2019a, Kasliwal et al. 2019b). We imaged a total of 2401 square degrees,
covering 31% of the probability region of the event. Each field visit
consisted of a sequence of 8 dithers of 8 second exposures each on the
field, which were processed and stacked with the Palomar Gattini-IR data
reduction pipeline (De et al., in prep.). The typical limiting magnitude of
each stacked epoch (64 second exposure time) was between 15.5 - 16 AB mag
in J-band. Transient vetting is ongoing and any viable counterparts will be
announced.