TITLE:   GCN CIRCULAR
NUMBER:  24353
SUBJECT: LIGO/Virgo S190426c: Swift rapid follow-up observations of S190425z and S190426c and URL for observation log for all future events
DATE:    19/04/30 13:44:57 GMT
FROM:    Aaron Tohuvavohu at PSU/Swift  <auc444@psu.edu>

A. Tohuvavohu (PSU), P.A. Evans (U. Leicester), J.A. Kennea (PSU),
S.B. Cenko (NASA/GSFC), S.D. Barthelmy (NASA/GSFC), A.P. Beardmore (U.
Leicester), A.A. Breeveld (UCL-MSSL), D.N. Burrows (PSU), S. Campana
(INAF-OAB), G. Cusumano (INAF-IASF PA),  A. D'Ai (INAF-IASFPA), P.
D'Avanzo (INAF-OAB), V.D'Elia(ASDC), S.W.K. Emery (UCL-MSSL),  P.
Giommi (ASI), C. Gronwall (PSU), D. Hartmann (U. Clemson), N. J.
Klingler (PSU), H.A. Krimm (CRESST/GSFC/USRA), N.P.M. Kuin (UCL-MSSL),
A.Y. Lien (GSFC/UMBC), D. Malesani (DARK/NBI), F.E. Marshall
(NASA/GSFC), A. Melandri (INAF-OAB), J.A. Nousek (PSU), S.R. Oates (U.
Warwick), P.T. O'Brien (U. Leicester), J.P. Osborne (U. Leicester), C.
Pagani (U. Leicester), K.L. Page (U.Leicester), D.M. Palmer (LANL), M.
Perri (ASDC), J.L. Racusin (NASA/GSFC), B. Sbarufatti (INAF-OAB/PSU),
M.H. Siegel (PSU), G. Tagliaferri (INAF-OAB), E. Troja
(NASA/GSFC/UMCP) report on behalf of the Swift team:

The Neil Gehrels Swift Observatory UVOT and XRT instruments began pointed
galaxy-targeted followup of the LIGO/Virgo detected S190425z (LVC GCN. 24168)
at 2019-04-25 12:53 UT (T0+274 min), delayed due to a commanding gap.
The observations continued until 2019-04-26 20:15 UT, when they were aborted
to begin followup of S190426c (LVC GCN. 24237).

The completed campaign comprised ~400 fields, covering several hundred
of the most massive galaxies in the localization volume.

The Swift UVOT and XRT began pointed galaxy-targeted followup of the
LIGO/Virgo detected S190426c (LVC GCN. 24237) at 2019-04-26 17:45:00
UT (T0+142 min) and continued until T0+~48 hours.

The completed campaign comprised ~800 fields, covering >30% of the
galaxy-convolved localization region of the 'LALInference1' skymap.

The GW rapid followup observations have a nominal 80 s duration, and
are performed primarily with the u filter and with XRT in PC mode. The
average limiting magnitude achieved is ~18.6 in u, and  ~5 x 10^-12
erg s^-1 cm^-2 in soft X-rays (0.3-10 keV).

Analysis of the data is ongoing, and candidate counterparts will be
reported as found.

A list of observed fields, times, and associated target IDs can be found at
the following URL for these triggers and for all future GW followup:
http://www.swift.ac.uk/LVC/

We remind the community that all Swift data are public, and encourage their use.

This circular is an official product of the Swift team.