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GCN Circular 21056

Subject
LIGO/Virgo G268556: Refined localization from CBC parameter estimation
Date
2017-05-02T14:16:10Z (7 years ago)
From
Christopher Berry at U of Birmingham/LVC <cplb@star.sr.bham.ac.uk>
The LIGO Scientific Collaboration and Virgo Collaboration report:

We have completed a Bayesian parameter-estimation analysis of the GW
candidate G268556 (GCN 20364) under the assumption that the signal
arises from a compact binary coalescence (CBC) and using the latest
calibration of the GW strain data. The data are still found to be
consistent with a binary black hole merger.

A refined sky localization is now available and can be retrieved
from GraceDB (https://gracedb.ligo.org/events/G268556):

 * LALInference_f.fits.gz, produced using a coherent Bayesian
   analysis (Veitch et al. PRD 91, 042003) of the full GW signal
   including spin precession, and incorporating the potential
   effects of calibration errors. We regard this LALInference sky
   map as the most authoritative localization for this event.

The localization is similar in structure to previous ones (GCN
20364 and 20385), with two arcs tracing part of the annulus set by
the 3 ms delay in arrival time between the Hanford and Livingston
observatories. The differences compared to previous localizations
are primarily a consequence of the improved calibration of the data.
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