An Empirical Study of Contamination in Deep, Rapid, and Wide-field Optical Follow-up of Gravitational Wave Events

Journal Article (Journal Article)

We present an empirical study of contamination in wide-field optical follow-up searches of gravitational wave sources from Advanced LIGO/Virgo using dedicated observations with the Dark Energy Camera. Our search covered ∼56 deg2, with two visits per night, in the i and z bands, followed by an additional set of griz images three weeks later to serve as reference images for subtraction. We achieve 5σ point-source limiting magnitudes of i ≈ 23.5 and z ≈ 22.4 mag in the coadded single-epoch images. We conduct a search for transient objects that mimic the i - z color behavior of both red (i-z > 0.5 mag) and blue (i-z < 0 mag) kilonova emission, finding 11 and 10 contaminants, respectively. Independent of color, we identify 48 transients of interest. Additionally, we leverage the rapid cadence of our observations to search for sources with characteristic timescales of ≈1 day and ≈3 hr, finding no potential contaminants. We assess the efficiency of our search with injected point sources, finding that we are 90% (60%) efficient when searching for red (blue) kilonova-like sources to a limiting magnitude of i ≲ 22.5 mag. Using our efficiencies, we derive sky rates for kilonova contaminants of deg-2 and deg-2. The total contamination rate is deg-2. We compare our results to previous optical follow-up efforts and comment on the outlook for gravitational wave follow-up searches as additional detectors (e.g., KAGRA, LIGO India) come online in the next decade.

Full Text

Duke Authors

Cited Authors

  • Cowperthwaite, PS; Berger, E; Rest, A; Chornock, R; Scolnic, DM; Williams, PKG; Fong, W; Drout, MR; Foley, RJ; Margutti, R; Lunnan, R; Metzger, BD; Quataert, E

Published Date

  • May 1, 2018

Published In

Volume / Issue

  • 858 / 1

Electronic International Standard Serial Number (EISSN)

  • 1538-4357

International Standard Serial Number (ISSN)

  • 0004-637X

Digital Object Identifier (DOI)

  • 10.3847/1538-4357/aabad9

Citation Source

  • Scopus