TITLE: GCN CIRCULAR NUMBER: 41197 SUBJECT: LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm DATE: 25/07/29 20:55:32 GMT FROM: xjh@andrew.cmu.edu
Xander J. Hall (CMU), Lei Hu (CMU), Tomás Cabrera (CMU), Antonella Palmese (CMU), Igor Andreoni (UNC), Keerthi Kunnumkai (CMU), Brendan O’Connor (CMU), on behalf of the Gravitational Wave MultiMessenger Astronomy DECam Survey (GW-MMADS) team
DECam observed the southern high probability area of the LVK gravitational wave candidate S250727dc (GCN 41179) using the wide-field Dark Energy Camera (DECam) on the 4m Blanco telescope, as part of the Gravitational Wave Multi-Messenger Astronomy DECam Survey (GW-MMADS; PI: Andreoni & Palmese). Observations started at 2025-07-29 09:39 UTC and cover the 90% probability area (GCN 41188).
We inspected the location of AT 2025smm, reported by Swift UVOT (GCN 41187), we find no sources in the ugri-bands. Here we report the following limiting magnitudes, not corrected for Galactic extinction:
| Filter | Mag (AB) | |--------|----------| | g | > 22.15 | | r | > 21.46 | | i | > 20.60 |
Further analysis is underway.
We thank the CTIO and NOIRLab staff for supporting these observations and the data calibration.
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