{
  "body": "D. A. Coulter (UCSC), C. D. Kilpatrick (Northwestern), C. Rojas-Bravo (UCSC), R. J. Foley (UCSC), Y. Kong (LCO), B. O’Connor (GWU), A. L. Piro (Carnegie), and A. Rest (STScI), report on behalf of the 1M2H collaboration:\n\nWe conducted an optical search for candidate counterparts in the localization region of LVK gravitational wave event S230518h (GCN 33813) with the Swope 1-m telescope using the 29.8’ x 29.7’ field-of-view Direct camera.  The tiling was optimally determined using the latest localization map from the LVK and galaxy catalogs in Teglon (Coulter et al., in prep).  In total, Swope observed 9 fields within the 90th percentile localization region of S230518h at:\n\nMJD RA Dec Band Exptime Maglim(AB)\n60082.97419 07:22:15.898 -49:05:26.261 i 300.000 21.7621\n60082.98236 07:20:39.617 -84:47:34.465 i 285.000 21.3325\n60082.98727 07:20:03.166 -85:47:04.692 i 300.000 21.3605\n60082.99201 07:23:52.430 -84:17:49.351 i 285.000 21.5397\n60082.99720 07:42:22.186 -54:32:42.515 i 300.000 21.8507\n60083.00245 07:43:16.761 -70:24:46.161 i 300.000 21.1865\n60083.00728 07:50:34.461 -67:26:15.477 i 285.000 21.3315\n60083.01301 07:53:15.693 -75:52:02.414 i 315.000 21.1845\n60083.01791 07:54:53.802 -78:50:33.098 i 330.000 20.4372\n\nThese observations have been reported to the TreasureMap (Wyatt et al., 2020).\n\nSubtracting DECam and SkyMapper template images from the Swope images using photpipe (Rest et al., 2005), we identified the following candidate counterparts in our imaging:\n\nName MJD RA(deg) Dec(deg) Filter Mag Magerr 2D_Percentile\nSSS23a 60082.98236 108.74882083333331 -84.62690277777777 i 20.9 0.2 0.2479\nSSS23b 60082.98727 112.276725 -85.9142638888889 i 21.1 0.2 0.2435\nSSS23c 60083.01791 117.93889999999998 -78.77603055555555 i 20.1 0.2 0.1924\n\nWe have checked the Minor Planet Center and Transient Name Server, finding no previously reported solar system object or transient. We encourage follow-up observations of these sources.",
  "createdOn": 1684516100221,
  "bibcode": "2023GCN.33829....1C",
  "submitter": "David Coulter at UCSC <dcoulter@ucsc.edu>",
  "circularId": 33829,
  "subject": "LIGO/Virgo/KAGRA S230518h: Swope Search and Candidate Counterpart Identification",
  "eventId": "LIGO/Virgo/KAGRA S230518h"
}