GCN Circular 36402
Subject
LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfr and AT2024hfs
Date
2024-05-06T18:33:01Z (2 years ago)
From
Ryan Foley at UC Santa Cruz <foley@ucsc.edu>
Via
Web form
A. L. Piro, J. D. Simon (Carnegie), A. Polin (Carnegie/Purdue), C. R. Burns (Carnegie), D. A. Coulter (STScI), M. R. Drout (Toronto), R. J. Foley, and C. Rojas-Bravo (UC Santa Cruz)
report on behalf of the Carnegie Gravitational wave ElectroMagnetic follow-up (CGEM) collaboration, the One-Meter Two-Hemisphere (1M2H) collaboration, and the Swope Supernova Survey:
As part of our ongoing search for optical counterparts to the candidate gravitational wave event S240422ed (GCN 36236, GCN 36240), we have obtained additional imaging with the 1.0m Swope telescope at Las Campanas Observatory of the sources AT2024hfr (GCN 36298, GCN 36328) and AT2024hfs (GCN 36298, GCN 36328).
Differential PSF photometry of the candidates and local sequence stars was obtained using DAOPHOT. The local sequence photometry was calibrated using the Refcat2 catalog, transformed to the Carnegie Supernova Project (CSP) natural system. The measured magnitudes are listed in the table below.
At the time of these observations, AT2024hfr was somewhat brighter in r-band than measured by DECam on 2024-04-23. AT2024hfs had a similar brightness in the most recent data as it did 2-3 nights earlier, but may be growing redder. We note that we have concluded that our originally-reported i-band magnitude for AT2024hfr on 2460426.590 (GCN 36328) measured an artifact in the image, and the source was not detected on that night.
+-----------+---------------+--------+--------------------+
| ID | JD | filter | magnitude | +-----------+---------------+--------+--------------------+
| AT2024hfr | 2460428.545 | r | 21.36 +/- 0.13 |
| AT2024hfr | 2460428.551 | i | 20.61 +/- 0.12 |
| AT2024hfs | 2460428.537 | r | 21.26 +/- 0.07 |
| AT2024hfs | 2460428.520 | i | 20.71 +/- 0.29 |
+-----------+---------------+--------+--------------------+
We thank Francesco di Mille and the rest of the LCO staff for making these observations possible.