Gaia Data Release 3

Ellipsoidal variables with possible black hole or neutron star secondaries^⋆

¹ School of Physics and Astronomy, Tel Aviv University, Tel Aviv 6997801, Israel
e-mail: roygomel6@gmail.com
² Department of Astronomy, University of Geneva, Chemin Pegasi 51, 1290 Versoix, Switzerland
³ Department of Astronomy, University of Geneva, Chemin d’Ecogia 16, 1290 Versoix, Switzerland
⁴ Warsaw University Astronomical Observatory Department of Physics, Al. Ujazdowskie 4, 00-478 Warszawa, Poland

Received: 24 March 2022
Accepted: 10 June 2022

Abstract

As part of Gaia Data Release 3, a large number of ellipsoidal variables were identified with supervised classification. The periodic variability of these ellipsoidals is presumably induced by tidal interaction with a companion in a close binary system. We present 6306 short-period probable ellipsoidal variables with relatively large-amplitude Gaia G-band photometric modulations that indicate a possible massive, undetected secondary. In case of a main-sequence primary, the more massive secondary is probably a compact object – either a black hole or a neutron star, and sometimes a white dwarf. The identification is based on the recently suggested robust modified minimum mass ratio (mMMR) that was derived from the observed ellipsoidal amplitude alone, without the use of the primary mass or radius. We also list a subset of 262 systems with an mMMR higher than unity, for which the probability of a compact secondary is higher. Follow-up observations are needed to verify the true nature of these variables.