A search for OB stars in the field of the galactic OB association Bochum 7

TL;DR

This study identifies members of the Bochum7 OB association using astrometric and spectrophotometric data, estimating its distance, proper motion, and age, and confirming binary systems among its stars.

Contribution

It provides the first comprehensive astrometric and spectrophotometric analysis of Bochum7, identifying its stellar members and their properties, including binarity and age.

Findings

At least 27 stellar members identified.

Distance estimated at 5640 parsecs.

Young age of less than 3 million years.

Abstract

AIMS We plan to identify the members of the Bochum7 association by performing simultaneous astrometric and spectrophotometric analyses, and estimate its distance and evolutionary stage. METHODS. We used our own visual spectroscopic and UBV photometric data of a 30' x 30' region centered at R.A. = 8h44m47.2s, Decl = - 45d58m55.5s. This information enabled us to estimate the spectral classification and distance of all stars present in the region. The proper motion was analyzed with data of the UCAC5 catalog and was used to identify the members of this association. We added JHK data from 2MASS and IRAS catalogs to check for the presence of infrared (IR) excess stars. RESULTS. We found that Bochum7 is an OB association with at least 27 identified stellar members (l = 265.12d, b = -2.0d) at a distance of 5640 pc. Its proper motion is mu(alfa)cos(delta) = -4.92+-0.08 mas/yr, mu(delta) = 3.26+-0.08 mas/yr. We derived an average heliocentric radial velocity of 35 km/s and were able to confirm the binary nature of the (ALS 1135) system and detect four new binary star candidates. Analysis of data for massive Bo 7 star candidates points towards a young age (< 3x10^6 years old) for the association, although the presence of a previous episode of star formation remains to be analyzed.