TITLE:   GCN CIRCULAR
NUMBER:  33851
SUBJECT: LIGO/Virgo/KAGRA S230518h: Swift/UVOT Upper Limits for MeerLICHT candidates: AT2023ixg and AT2023iyb
DATE:    23/05/22 15:52:54 GMT
FROM:    Alice Breeveld at MSSL-UCL <a.breeveld@ucl.ac.uk>

A. A. Breeveld (UCL-MSSL), N. P. M. Kuin (UCL-MSSL), S. R. Oates (U. of Birmingham),  P. Brown (TAMU), M. De Pasquale (U. Messina), C. Gronwall (PSU), N. Klingler (NASA-GSFC/UMBC/CRESST II), F. E. Marshall (NASA/GSFC), M. J. Page (UCL-MSSL), M. H. Siegel (PSU), A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), S. Campana (INAF-OAB), S.B. Cenko (NASA/GSFC), A. D’Aì (INAF-IASFPA), P. D’Avanzo (INAF-OAB), V. D’Elia (ASI-SSDC & INAF-OAR), S. Dichiara (PSU), P.A. Evans (U. Leicester), R.A.J. Eyles-Ferris (U. Leicester), D. Hartmann (Clemson University), J.A. Kennea (PSU), S. Laha (NASA/GSFC), A.Y. Lien (GSFC/UMBC), A. Melandri (INAF-OAB), J.A. Nousek (PSU), P. O’Brien (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), D. M. Palmer (LANL), S. Ronchini (PSU), T. Sbarrato (INAF-OAB), B. Sbarufatti (INAF-OAB), G. Tagliaferri (INAF-OAB), A. Tohuvavohu (U. Toronto) and E. Troja (U Tor Vergata, INAF) report on behalf of the Swift team:

We report Swift/UVOT observations of the candidates AT2023ixg and AT2023iyb (Johnston et al., Astronote 2023-121) found by the the MeerLICHT 0.65m wide-field telescope during the search for the EM counterpart of the LVC event S230518h (LIGO/VIRGO/KAGRA Collaboration GCN Circ. 33813).

Swift/UVOT observations of these MeerLICHT candidates began 73 hours after the LVK trigger (LIGO/VIRGO/KAGRA Collaboration, GCN Circ. 33813) in the UV filters. We do not detect either of the candidates in the UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the exposures are:

Target    Filter   T_start(s) T_stop(s)  Exp(s)   3sigUL

AT2023ixg   w1      267962     273767     164      18.4
            m2      267775     278324     1067     19.6
            w2      267587     278065     570      20.4

AT2023iyb   m2      265880     272062     507      19.9
            w2      265181     271869     1214     20.7

This circular is an official product of the Swift team.