TITLE: GCN CIRCULAR NUMBER: 36259 SUBJECT: LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam upper limits on the Swift/XRT source S240422ed_X61 DATE: 24/04/23 18:11:21 GMT FROM: Igor Andreoni at JSI/UMD/NASA igor.andreoni@gmail.com

Lei Hu (CMU), Tomás Cabrera (CMU), Brendan O'Connor (CMU), Keerthi Kunnumkai (CMU), Igor Andreoni (UMD), Antonella Palmese (CMU) report on behalf of the GW-MMADS team:

During GW-MMADS DECam follow-up (Palmese et al., GCN 36245) of the LIGO/Virgo/KAGRA event S240422ed (GCN 36236, GCN 36240), we serendipitously observed the location of the Swift/XRT source 61 (here labelled S240422ed_X61) at coordinates RA, Dec = 120.3245d, -28.1765d (J2000; [1]).

In our difference imaging relative to archival DECam images, obtained using SFFT (Hu et al., 2021), we do not detect any optical transient or variable emission within a 20 arcsec radius. Upper limits are reported below.

filter | observation time UT | limiting magnitude (AB, 5 sigma) DECam-r | 2024-04-22T23:59:29 | 22.46 DECam-z | 2024-04-23T02:55:26 | 21.33

[1] https://gcn.gsfc.nasa.gov/other/S240422ed.counterpart

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