[vsnet-grb-info 23156] IceCube 190730A: No counterpart candidates or blazar activity in GOTO observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25255
SUBJECT: IceCube 190730A: No counterpart candidates or blazar activity in GOTO observations
DATE:    19/08/02 12:19:28 GMT
FROM:    Danny Steeghs at U.of Warwick/GOTO  <dsteeghs at gmail.com>

D.Steeghs(1), Y-L.Mong(2), G.Ramsay(5), L.Makrygianni(3),
M.Kennedy(8), D.Galloway(2), K.Ulaczyk(1), J.Lyman(1), K.Ackley(2),
A.Obradovic(2), M.Dyer(3), V.Dhillon(3), P.O'Brien(4), D.Pollacco(1),
E.Thrane(2), S.Poshyachinda(6), E.Palle(7), K.Wiersema(1),
R.Cutter(1), T. Marsh(1), R.West(1), B.Gompertz(1), E.Stanway(1),
A.Casey(2), M.Brown(2), E.Rol(2), J.Mullaney(3), S.Littlefair(3),
E.Daw(3), J.Maund(3), R.Starling(4), R.Eyles(4), S.Tooke(4),
U.Sawangwit(6), D.Mkrtichian(6), S.Awiphan(6), S.Aukkaravittayapun(6),
P.Irawati(6), R.Breton(8), D.Mata-Sanchez(8), T.Heikkila(9),
R.Kotak(9), L.Nuttall (10)
(1) Warwick University; (2) Monash University; (3) Univ. of Sheffield;
(4) University of Leicester; (5) Armagh Observatory & Planetarium;
(6) National Astronomical Research Institute of Thailand;
(7) Instituto de Astrofisica de Canarias; (8) Univ. of Manchester;
(9) University of Turku; (10) University of Portsmouth

report on behalf of the GOTO collaboration:


We carried out observations with the Gravitational-wave Optical
Transient Observer (GOTO), in response to the 190730A IceCube
neutrino event (GCN #25225, #25241).

We obtained a series of 3x60s exposures using our wide L-band filter
(400-700 nm) with four pointings covering the directional constraint
reported in GCN #25225.  Two sky passes have been completed so far,
starting on 2019 July 31 21:16 UT and 2019 Aug 1 21:15 UT.
Our mean 5-sigma detection limit was g=20.2 mag based on PS1
catalogue calibrators.

Images are processed immediately after acquisition using the GOTOphoto
pipeline. Difference imaging was performed on the median of each
triplet of exposures using recent survey observations of the same
pointings. Source candidates were initially filtered using a trained
classifier and cross-matched against a variety of catalogs, including
the MPC and PS1. Human candidate vetting was performed on those
candidates identified by the classifier. The region was also visually
inspected for any notable detections in case our classifier mis-scored
a detection. No viable optical counterpart candidates were identified.

We investigated the long-term behaviour of the FSRQ source PKS
1502+106 that was noted to be consistent with the directional
constraints. Our sky survey coverage of this sources shows no notable
signs of activity in recent months, including our recent epochs
following the neutrino event.  These findings are consistent with the
ZTF coverage noted in Stein et al. 2019, ATEL 12974. Additional
visits are planned, both scheduled and as part of the sky survey, to
monitor any changes.



=====
GOTO is operated at the La Palma observing facilities of the
University of Warwick on behalf of a consortium including the
University of Warwick, Monash University, Armagh Observatory, the
University of Leicester, the University of Sheffield, the National
Astronomical Research Institute of Thailand (NARIT), the University of
Portsmouth and the Instituto de Astrofisica de Canarias (IAC)
(https://goto-observatory.org)