TITLE: GCN CIRCULAR NUMBER: 42021 SUBJECT: LIGO/Virgo/KAGRA S250927ck: Updated Sky localization DATE: 25/09/28 21:09:53 GMT FROM: John Veitch at U of Glasgow john.veitch@ligo.org
The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report:
We have conducted further analysis of the LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S250927ck (GCN Circular 42015). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,0, distributed via GCN and SCiMMA notices, is available for retrieval from the GraceDB event page:
https://gracedb.ligo.org/superevents/S250927ck
For the Bilby.multiorder.fits,0 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(05h14m, -49d19m, 6.23d, 3.44d, 38.55d) Marginalized over the whole sky, the a posteriori luminosity distance estimate is 3566 +/- 911 Mpc (a posteriori mean +/- standard deviation).
For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/.
[1] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. PRD 108, 123040 (2023) doi:10.1103/PhysRevD.108.123040
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