Hot Stars With Cool Companions

TL;DR

This study conducts a spectroscopic survey of 400 nearby A- and B-type stars to identify stellar companions, revealing new candidates and analyzing their mass-ratio distribution to understand binary star formation.

Contribution

It provides the first large-scale spectroscopic census of companions to intermediate-mass stars, highlighting differences in formation mechanisms for close and wide binaries.

Findings

Found 18 new candidate companions.

Detected secondary spectral lines in 4 known binaries.

Discovered different mass-ratio distributions for close versus wide binaries.

Abstract

Young intermediate-mass stars have become high-priority targets for direct-imaging planet searches following the recent discoveries of planets orbiting e.g. HR 8799 and Beta Pictoris. Close stellar companions to these stars can affect the formation and orbital evolution of any planets, and so a census of the multiplicity properties of nearby intermediate mass stars is needed. Additionally, the multiplicity can help constrain the important binary star formation physics. We report initial results from a spectroscopic survey of 400 nearby A- and B-type stars. We search for companions by cross-correlating high resolution and high signal-to-noise ratio echelle spectra of the targets stars against model spectra for F- to M-type stars. We have so far found 18 new candidate companions, and have detected the spectral lines of the secondary in 4 known spectroscopic binary systems. We present the distribution of mass-ratios for close companions, and find that it differs from the distribution for wide ($a < 100$ AU) intermediate-mass binaries, which may indicate a different formation mechanism for the two populations.