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GCN Circular 36423

LIGO/Virgo/KAGRA S240422ed: GMOS-S photometry of J-GEM24a
2024-05-10T23:58:55Z (17 days ago)
Tomas Ahumada Mena at Caltech <>
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Tomas Ahumada (Caltech), Mansi Kasliwal (Caltech), Lei Hu (CMU), Robert Stein (Caltech), report on behalf of a larger collaboration:

We used the Gemini Multi-Object Spectrographs (GMOS) mounted at the Gemini-South Observatory to obtain r- and z-band photometry of J-GEM24a (GCN 36333). The observations started on UT 2024-05-01 23:41:06 (~8.7 days after the Subaru observations) and consisted of 6x60 sec exposures in the r-band and 10x90 sec in the z-band. We reduce the data using the DRAGONS (Labrie et al. 2019) pipeline, calibrate against Pan-STARRS sources, and similar to GCN 36337, we do not detect the source up to a 5-sigma limit of 24.5 in the r-band and 23.9 in the z-band.

Additionally, we do not detect the source on the ZTF g- and i-bands images of the field. The g-band 5-sigma limit is 20.5 mag on UT 2024-04-23 03:59:27 (~1.75 hours before the Subaru observations), while the i-band 5-sigma limit is 20 AB mag on UT 2024-04-24 04:48:32 (~21 hours after the Subaru observations). 

This suggests two possibilities: either the source has faded significantly or the source is spurious. We encourage additional confirmation of the nature of the source by forced photometry at this location (RA:122.215846 deg, Dec: -24.516465 deg) by other surveys. 

Unfortunately, the position falls in a chip gap in the DECam images of the field, and WINTER did not cover the region.

We thank the Gemini staff for their kind cooperation. 
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