TITLE: GCN CIRCULAR NUMBER: 37607 SUBJECT: LIGO/Virgo/KAGRA S240925n: Updated Sky localization and Source Classification DATE: 24/09/25 07:41:06 GMT FROM: Colm Talbot at University of Chicago talbotcolm@gmail.com
The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report:
We have identified a problem in the calibration of the LIGO Hanford instrument at the time of S240925n (GCN Circular 37604). Previously published skymaps, i.e. bayestar.multiorder.fits,0 and bayestar.multiorder.fits,1, are both affected and should be disregarded.
Parameter estimation has been performed using Bilby [1] and a new sky map (using only LIGO Livingston and Virgo data), Bilby.offline0.multiorder.fits,0, distributed via GCN Notice, is available for retrieval from the GraceDB event page:
https://gracedb.ligo.org/superevents/S240925n
Assuming the candidate is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is <1%. [2] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [2] Both HasNS and HasRemnant consider the support of several neutron star equations of state for maximum neutron star mass. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is 7%.
For the Bilby.offline0.multiorder.fits,0 sky map, the 90% credible region is 1748 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 323 +/- 70 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 [2] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe
View this GCN Circular online at https://gcn.nasa.gov/circulars/37607. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...