GCN Circular 24950

The LIGO Scientific Collaboration and the Virgo Collaboration report:


We identified the compact binary merger candidate S190701ah during
real-time processing of data from LIGO Hanford Observatory (H1), LIGO
Livingston Observatory (L1), and Virgo Observatory (V1) at 2019-07-01
20:33:06.578 UTC (GPS time: 1246048404.578). The candidate was found
by the PyCBC Live [1], MBTAOnline [2], SPIIR [3], and GstLAL [4]
analysis pipelines.

S190701ah is an event of interest because its false alarm rate, as
estimated by the online analysis, is 1.9e-08 Hz, or about one in 1
year, 7 months. The event's properties can be found at this URL:

https://gracedb.ligo.org/superevents/S190701ah

The classification of the GW signal, in order of descending probability, is BBH (93%),
Terrestrial (7%), BNS (<1%), NSBH (<1%), or MassGap (<1%).

Assuming the candidate is astrophysical in origin, there is strong
evidence against the lighter compact object having a mass < 3 solar
masses (HasNS: <1%). Using the masses and spins inferred from the
signal, there is strong evidence against matter outside the final
compact object (HasRemnant: <1%).

One sky map is available at this time and can be retrieved from the
GraceDB event page:
 * bayestar.fits.gz, an updated localization generated by BAYESTAR
[5], distributed via GCN notice about 4 minutes after the candidate

For the bayestar.fits.gz sky map, the 90% credible region is well fit
by an ellipse with an area of 67 deg2 described by the following DS9
region (right ascension, declination, semi-major axis, semi-minor
axis, position angle of the semi-minor axis):
   icrs; ellipse(02h30m42s, -06d53m30s, 8d, 3d, 97d)
Marginalized over the whole sky, the a posteriori luminosity distance
estimate is 1045 +/- 234 Mpc (a posteriori mean +/- standard
deviation).


There is substantial scattered light noise in L1 for several seconds around the trigger time. This may affect the accuracy of the skymap, but is not expected to affect the significance of the candidate.

For further information about analysis methodology and the contents of
this alert, refer to the LIGO/Virgo Public Alerts User Guide
<https://emfollow.docs.ligo.org/userguide/>.

 [1] Nitz et al. PRD 98, 024050 (2018)
 [2] Adams et al. CQG 33, 175012 (2016)
 [3] Qi Chu, PhD Thesis, The University of Western Australia (2017)
 [4] Messick et al. PRD 95, 042001 (2017)���
 [5] Singer & Price PRD 93, 024013 (2016)