GCN Circular 39577
Subject
LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
Date
2025-03-03T19:55:29Z (13 days ago)
From
noelklin@umbc.edu
Via
Web form
Noel Klingler (NASA-GSFC / UMBC / CRESST II), Sam Shilling (Lancaster U.), P.A. Evans (U. Leicester), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), S.B. Cenko (NASA/GSFC), R.A.J. Eyles-Ferris (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), A.A. Breeveld (UCL-MSSL), S. Campana (INAF-OAB), J.J. Delaunay (PSU), M. De Pasquale (University of Messina), S. Dichiara (PSU), P. D'Avanzo (INAF-OAB), A. D'Aì (INAF-IASFPA) , V. D'Elia (ASI-SSDC & INAF-OAR), C. Gronwall (PSU), D. Hartmann (Clemson University), N. Klingler (NASA-GSFC / UMBC / CRESST II), N.P.M. Kuin (UCL-MSSL), S. Laha (NASA/GSFC), S.R. Oates (U. Birmingham), J.P. Osborne (U. Leicester), P. O'Brien (U. Leicester), M.J. Page (UCL-MSSL), S. Ronchini (PSU), T. Sbarrato (INAF-OAB), B. Sbarufatti (INAF-OAB), M.H. Siegel (PSU), G. Tagliaferri (INAF-OAB), E. Troja (U Tor Vergata, INAF) report on behalf of the Swift team:
Swift/UVOT has carried out 1 observation of the combined LVK/Swift-BAT-GUANO error region for the GW trigger S250223dk (GCN 39443), centered on the most-probable location (RA,Dec = 85.4260, -47.5420 [J2000]; GCN 39485). UVOT collected 4.9 ks of data from 106 ks to 140 ks after the LVK trigger, using the White filter.
For the X-ray sources reported by Evans et al. (GCN 39485): X1, X5, and X6 are outside of the UVOT field of view. X2 is not detected, with a 3 sigma detection limit > 21.54 mag (AB). X3 is not detected, with a 3 sigma detection limit > 23.01 mag (AB). X7 is not detected, with a 3 sigma detection limit > 23.09 (AB). X4 is detected (20.14 +/- 0.03 mag, AB) but its position is coincident with a known source (classified as an AGN in the AllWISE catalog), WISEA J054219.27-473400.6.
No uncatalogued/transient sources are detected, with an average 3 sigma limit > 23.0 mag (AB) over the UVOT field of view.