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GCN Circular 36266

LIGO/Virgo/KAGRA S240422ed: SAGUARO upper limits from CSS
2024-04-24T01:03:00Z (3 months ago)
Griffin Hosseinzadeh <>
Griffin Hosseinzadeh (UA), Manisha Shrestha (UA), Charles D. Kilpatrick (NU), Jillian C. Rastinejad (NU), Jeniveve Pearson (UA), Jennifer E. Andrews (Gemini), David J. Sand (UA), K. Azalee Bostroem (UA), Philip N. Daly (UA), Wen-fai Fong (NU), Michael J. Lundquist (Keck), Kerry Paterson (MPIA), Samuel D. Wyatt (GSFC), David Rankin (UA), Alexander R. Gibbs (UA), and D. Carson Fuls (UA) report:

We initiated observations of the localization region of S240422ed on 2024-04-23 03:22:01 UT using the 5 square degree imager mounted on the 1.5m Catalina Sky Survey (CSS) telescope on Mt. Lemmon, AZ. We observed 24 fields in the 95% confidence region of the initial Bayestar localization map (LVK Collaboration 2024, GCN 36236) that were accessible from southern Arizona, which cover approximately 23% of the cumulative probability according to the updated Bilby localization map (LVK Collaboration 2024, GCN 36240). We have reported our pointings to the Treasure Map (Wyatt et al. 2020; doi:10.5281/zenodo.1105274). The typical limiting magnitude of each CSS pointing was G~19.5 mag (calibrated to Gaia DR2).

We performed a real-time analysis of the observations. Following the methods outlined in Rastinejad et al. (2022), we crossmatch each candidate with the TNS (Gal-Yam 2021) and point source catalogs (Tachibana and Miller 2018; Jayasinghe et al. 2019; Flesch et al. 2021; Gaia Collaboration 2023), search public ZTF photometry (Bellm et al. 2019), and run ATLAS forced photometry (Shingles et al. 2021) at the position of the candidate to rule out transients unrelated to the GW event. We determine a most likely host galaxy using the probability of chance coincidence method (Bloom et al. 2002) and search for an associated spectroscopic or photometric redshift in public galaxy catalogs (White et al. 2011; Alam et al. 2015; Beck et al. 2016, 2021; Dalya et al. 2021; DESI Collaboration et al. 2023).

We do not find any credible candidates in our observations. Follow-up observations and further analysis are ongoing.

SAGUARO stands for Searches After Gravitational-waves Using ARizona's Observatories (Hosseinzadeh et al. 2024). It is a partnership between the University of Arizona and Northwestern University.

# References
| source       | citation               |
| ------------ | ---------------------- |
| gcn_circular | 36236                  |
| gcn_circular | 36240                  |
| doi          | 10.5281/zenodo.1105274 |

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