Letter to the Editor

Infrared outbursts as potential tracers of common-envelope events in high-mass X-ray binary formation

¹ Institute for Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Potsdam, Germany
e-mail: lida@astro.physik.uni-potsdam.de
² Astronomical Observatory, University of Warsaw, Aleje Ujazdowskie 4, 00478 Warsaw, Poland
³ Université de Strasbourg, CNRS, Observatoire astronomique de Strasbourg, UMR 7550, 67000 Strasbourg, France
⁴ Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106, USA

Received: 28 February 2018
Accepted: 12 May 2018

Abstract

Context. Classic massive binary evolutionary scenarios predict that a transitional common-envelope (CE) phase could be preceded as well as succeeded by the evolutionary stage when a binary consists of a compact object and a massive star, that is, a high-mass X-ray binary (HMXB). The observational manifestations of common envelope are poorly constrained. We speculate that its ejection might be observed in some cases as a transient event at mid-infrared (IR) wavelengths.

Aims. We estimate the expected numbers of CE ejection events and HMXBs per star formation unit rate, and compare these theoretical estimates with observations.

Methods. We compiled a list of 85 mid-IR transients of uncertain nature detected by the Spitzer Infrared Intensive Transients Survey and searched for their associations with X-ray, optical, and UV sources.

Results. Confirming our theoretical estimates, we find that only one potential HMXB may be plausibly associated with an IR-transient and tentatively propose that X-ray source NGC 4490-X40 could be a precursor to the SPIRITS 16az event. Among other interesting sources, we suggest that the supernova remnant candidate [BWL2012] 063 might be associated with SPIRITS 16ajc. We also find that two SPIRITS events are likely associated with novae, and seven have potential optical counterparts.

Conclusions. The massive binary evolutionary scenarios that involve CE events do not contradict currently available observations of IR transients and HMXBs in star-forming galaxies.