GW190814 follow-up with the optical telescope MeerLICHT^⋆

¹ Inter-University Institute for Data Intensive Astronomy & Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
e-mail: DWTSIM002@myuct.ac.za
² Department of Astrophysics/IMAPP, Radboud University, PO Box 9010, 6500, GL Nijmegen, The Netherlands
³ South African Astronomical Observatory, PO Box 9, 7935 Observatory, South Africa
⁴ Leiden Observatory, Leiden University, PO Box 9513, 2300, RA Leiden, The Netherlands
⁵ IAU-Office For Astronomy for Development, PO Box 9, 7935 Observatory, South Africa
⁶ Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University, 1800 Sherman Ave, Evanston, IL 60201, USA

Received: 24 December 2020
Accepted: 1 March 2021

Abstract

Context. The Advanced LIGO and Virgo gravitational wave observatories detected a signal on 2019 August 14 during their third observing run, named GW190814. A large number of electromagnetic facilities conducted follow-up campaigns in the search for a possible counterpart to the gravitational wave event, which was made especially promising given the early source classification of a neutron star-black hole merger.

Aims. We present the results of the GW follow-up campaign taken with the wide-field optical telescope MeerLICHT, located at the South African Astronomical Observatory Sutherland site. We use our results to constrain possible kilonova models.

Methods. The MeerLICHT telescope observed more than 95% of the probability localisation each night for over a week in three optical bands (u, q, i) with our initial observations beginning almost two hours after the GW detection. We describe the search for new transients in MeerLICHT data and investigate how our limiting magnitudes can be used to constrain an AT2017gfo-like kilonova.

Results. A single new transient was found in our analysis of MeerLICHT data, which we exclude from being the electromagnetic counterpart to GW190814 owing to the existence of a spatially unresolved source at the coordinates of the transient in archival data. Using our limiting magnitudes, the confidence with which we can exclude the presence of an AT2017gfo-like kilonova at the distance of GW190814 was low (< 10⁻⁴).