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

ORELLANA, ROSA B.; BOSCH, GUILLERMO L.; CORTI, MARIELA A.

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Lugar: Paris; Año: 2018

0004-6361

Aims. We plan to identify the members of Bochum7 association by performing simultaneous astrometric and spectrophotometricanalysis, and estimate its size and evolutionary stage.Methods. We used our own visual spectroscopic and UBV photometric data of 30? 30? region centered in =8h44m47.2s, = - 4558055.500. This information enabled us to estimate the spectral classification and distance of allstars present in the region. The proper motion was analyzed with data of the UCAC4 and SPM4 catalogues. Thesewere employed to identify the members of this association. We added JHK data from 2MASS and IRAS catalogues tocheck for the presence of IR excess starsResults. We could discover that Bochum7 is an OB association with 27 stellar members (l = 265.12, b = 􀀀2) at thedistance of ´ 5700 pc. The proper motion of all of them is cos = 􀀀0:48 mas yr􀀀1, = 1:43 mas yr􀀀1 (UCAC4Catalogue), and cos = 􀀀0:49 mas yr􀀀1, = 1:93 mas yr􀀀1 (SPM 4 Catalogue). The heliocentric radial velocity ofthis association is 50 km s􀀀1 with confirmed binary system (ALS 1135) and three other binary star candidates. Bo 7is possibly formed by two open clusters, one younger of 1 106 years old associated with current star formation andthe other cluster with 3 106 years old or older. In the Bochum7 visual at the distance of ´ 3160 pc it is the Vela OB1association. We could study part of it finding that its proper motion is cos = 0:63 mas yr􀀀1, = 2:22 mas yr􀀀1(UCAC4 Catalogue), and cos = 􀀀0:50 mas yr􀀀1, = 1:10 mas yr􀀀1 (SPM 4 Catalogue), and it is something olderthan 15 106 years old probably without coeval star formation.