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GCN Circular 26753

Subject
LIGO/Virgo S200114f: Candidates from SAGUARO observations
Date
2020-01-14T23:38:22Z (4 years ago)
From
Michael J. Lundquist at University of Arizona <mlundquist@email.arizona.edu>
Michael J. Lundquist, David J. Sand (UA), Jillian Rastinejad, Kerry
Paterson (Northwestern), Jennifer Andrews (UA), Wen-fai Fong,
(Northwestern), Sam Wyatt, Eric Christensen, Alex Gibbs, Frank Shelly (UA),
report on behalf of the SAGUARO collaboration:

We initiated observations of 36 fields (each 5 deg^2, totalling 180 deg^2)
within the LVC localization region for the GW trigger S200114f (LVC Circ
26734) starting on 2020-01-14 at 4:15 UT (2.12 hours after the GW trigger)
with the 1.5m Catalina Sky Survey (CSS) telescope on Mt. Lemmon, AZ.  The
typical limiting magnitudes of single pointings are G~21 mag (calibrated to
Gaia DR2).

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

http://treasuremap.space/alerts?graceids=S200114f

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 strong
candidates that we believe to be associated with the GW event with S/N>5.
Due to the uncertain nature of the GW event however, we report 5
additional, less likely candidates below for completeness. These are
possibly variable stars or AGN. All magnitudes are based on our difference
imaging and have been calibrated to Gaia G band.

Name        | RA        | Dec        | AB Mag   | Mag Error | Notes

SAGUARO20a     07:13:08.744        14:00:07.313 20.19         0.11 (a),
(b), (c)

SAGUARO20b 06:59:34.961        22:36:29.456 19.94         0.10 (a)

SAGUARO20c 07:05:34.026        22:44:44.495 20.67         0.20 (a), (b)

SAGUARO20d     07:20:21.244        07:35:19.555 19.85         0.10 (a)

SAGUARO20e     07:04:10.181        16:27:38.455 19.29         0.07 (d)

(a) Possible Variable Star

(b) Coincident with faint PS1 source

(c) Faded by 0.78 mag over 30 min

(d) Nuclear; possible AGN

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