Gaia-ESO Survey: massive stars in the Carina Nebula. A new census of OB stars

TL;DR

This paper presents the most comprehensive census of massive OB stars in the Carina Nebula, combining data from multiple surveys to analyze stellar populations, binary systems, and stellar properties.

Contribution

It provides an updated, extensive catalog of OB stars in Carina, including new binary detections and analysis of stellar rotation and runaway candidates.

Findings

Catalog of 316 OB stars in Carina Nebula.

Identification of 20 new spectroscopic binary systems.

Estimated binary fraction of 35% among O-type stars.

Abstract

The Gaia-ESO survey sample of massive OB stars in the Carina Nebula consists of 234 stars. The addition of brighter sources from the Galactic O-Star Spectroscopic Survey and additional sources from the literature allows us to create the most complete census of massive OB stars done so far in the region. It contains a total of 316 stars, being 18 of them in the background and four in the foreground. Of the 294 stellar systems in Car OB1, 74 are of O type, 214 are of non-supergiant B type and 6 are of WR or non-O supergiant (II to Ia) spectral class. We identify 20 spectroscopic binary systems with an O-star primary, of which 6 are reported for the first time, and another 18 with a B-star primary, of which 13 are new detections. The average observed double-lined binary fraction of O-type stars in the surveyed region is 0.35, which represents a lower limit. We find a good correlation between the spectroscopic n-qualifier and the projected rotational velocity of the stars. The fraction of candidate runaways among the stars with and without the n-qualifier is 4.4% and 2.4%, respectively, although non resolved double-lined binaries can be contaminating the fast rotators sample.