A search for OB stars in the field of the galactic OB association Bochum 7. II. Proper motion and IR photometry

CORTI, M. A.; ORELLANA, R. B.; BOSCH, G. L.

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Año: 2018 vol. 616

0004-6361

Aims: We plan to identify the members of the Bochum 7 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´ × 30´ region centered at = 8h44m47.2s, = -45°58´55.5″. 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 UCAC 5 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 Bochum 7 is an OB association with at least 27 identified stellar members (l = 265°.12, b = - 2°) at a distance of ≃5640 pc. Its proper motion is μαcos δ = -4.92 ± 0.08 mas yr-1, μδ = 3.26 ± 0.08 mas yr-1. We derived an average heliocentric radial velocity of 35 km s-1 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 (≤ 3 × 106 years old) for the association, although the presence of a previous episode of star formation remains to be analyzed.