An upper limit to the mass of a close companion candidate to {\sigma} Ori E

TL;DR

This study uses lucky imaging to constrain the properties of a potential close companion to {\sigma} Ori E, setting an upper mass limit and spectral type, which informs future observational efforts.

Contribution

It provides the first upper mass limit and spectral type estimate for the companion candidate to {\sigma} Ori E using z'-band lucky imaging.

Findings

Maximum companion mass constrained to 2.0+0.2-0.1 Msol.

Spectral type of the companion estimated as K2+/-1.

Results support further near-infrared adaptive-optics studies.

Abstract

The famous, very young, helium rich, magnetically-active, radio and X-ray emitter, short-period rotationally variable, spectroscopically peculiar star {\sigma} Ori E may have a close late-type stellar companion, which could explain flaring activity observed in some {\sigma} Ori E X-ray light curves. In 2009, Bouy et al. announced the detection of a faint companion candidate in the Ks band at 0.330 arcsec (130 AU) to the B2 Vp primary. Here, we carry out z'-band lucky imaging with AstraLux at the 2.2 m Calar Alto telescope in an attempt to constrain the properties of the companion candidate to {\sigma} Ori E. We impose a maximum mass of 2.0+0.2-0.1 Msol and an earliest spectral type of K2+/-1, which leaves the door open to a new, inexpensive, near-infrared, adaptive-optics study.