GCN Circular 26473

Michael J. Lundquist, David J. Sand (UA),  Wen-fai Fong, Jillian
Rastinejad, Kerry Paterson (Northwestern), Jennifer Andrews (UA), Sam Wyatt
(UA), Eric Christensen, Alex Gibbs, Frank Shelly, report on behalf of the
SAGUARO collaboration:

We initiated observations of 24 fields (each 5 deg^2, totalling 120 deg^2)
within the LVC localization region for the GW trigger S191216ap (LVC Circ
26454) starting on 2019-12-17 at 1:25 UT (3.9 hours after the GW trigger)
with the 1.5m Catalina Sky Survey (CSS) telescope on Mt. Lemmon, AZ.

Below are the field centers observed.

RA   Dec

321.5850 1.10417

321.3495 3.3125

321.3495 5.52081

321.1110 7.72917

321.1110 9.93747

320.8695 12.1458

323.1060 12.1458

320.3775 14.3541

322.6410 14.3541

320.1255 16.5625

322.4055 16.5625

321.9225 18.7708

319.6155 18.7708

321.4290 20.9792

319.0905 20.9792

320.9205 23.1875

318.5520 23.1875

320.1330 25.3958

317.7180 25.3958

319.3155 27.6042

316.8495 27.6042

318.4605 29.8125

317.5710 32.0208

316.6425 34.2291

Overall image quality was poor. We perform real-time processing and image
subtraction (described in Lundquist et al. 2019, ApJL, 881, 2). After
discarding known moving objects, stellar sources and known transients
(cross-correlating with the Transient Name Server and the ZTF alert
stream), we find no significant candidates with S/N>5, although a more
detailed analysis is ongoing.

We have posted our pointings to the Treasure Map, and encourage others to
do the same:

http://treasuremap.space/alerts?graceids=S191216ap

SAGUARO is supported by the National Science Foundation under Award Nos.
AST-1909358 and AST-1908972.