The massive eclipsing system ALS 1135 and variable stars in the field of the distant OB association Bochum 7

TL;DR

This study precisely determined the physical parameters of the ALS 1135 binary system, estimated its age, and discovered 17 variable stars in its field, including pulsating stars potentially belonging to nearby OB associations.

Contribution

It presents new accurate measurements of the binary system ALS 1135 and identifies new variable stars, including pulsators, in the Bochum 7 field, offering an alternative age determination method.

Findings

Masses of binary components with better than 1% accuracy.

Discovery of 17 variable stars, including 7 pulsators.

Identification of potential pre-main sequence delta Scuti stars.

Abstract

Using photometric and spectroscopic observations of the double-lined early-type eclipsing binary system ALS 1135, a member of the distant OB association Bochum 7, we derived the new physical and orbital parameters of its components. The masses of both components were derived with an accuracy better than 1 per cent, their radii, with an accuracy better than 3 per cent. Since the primary's mass is equal to about 25 sun masses, its radius was subsequently used to derive the age of the system which is equal to 4.3+/-0.5 Myr. The result shows that this method represents a viable alternative to isochrone fitting. A photometric search of the field of ALS 1135 resulted in the discovery of 17 variable stars, including seven pulsating ones. One of them is an SPB star belonging to Vel OB1, the other six are delta Scuti stars. Of the six delta Scuti stars three might belong to Vel OB1, the other two are likely members of Bochum 7. Given the age of Bochum 7, these two stars are probably pre-main sequence pulsators. In addition, we provide UBVI_C photometry for about 600 stars in the observed field.