Astronomy and Astrophysics, volume 440, 511-522 (2005/9-3)
NGC 146: a young open cluster with a Herbig Be star and intermediate mass pre-main sequence stars.
SUBRAMANIAM A., SAHU D.K., SAGAR R. and VIJITHA P.
Abstract (from CDS):
We present UBV CCD photometry and low-resolution spectra of stars in the field of the young open cluster NGC 146. UBV photometry of 434 stars were used to estimate the E(B-V) reddening of 0.55±0.04mag and BV photometry of 976 stars were used to estimate a distance modulus of (m-M)0=12.7±0.2mag, corresponding to a distance of 3470+335–305pc. We estimated 10-16Myr as the turn-off age for the upper main sequence of the cluster using isochrones and synthetic colour magnitude diagrams. We identified two B type stars with Hα in emission and located on the MS using slit-less spectra. A higher resolution spectrum of the brighter Be star indicated the presence of a number of emission lines, with some lines showing the signature of gas infall. This star was found to be located in the region of Herbig Ae/Be stars in the (J-H) vs. (H-K) colour-colour diagram. Thus, we identify this star as a Herbig Be star. On the other hand, 54 stars were found to show near infrared excess, of which 17 were found to be located in the region of Herbig Ae/Be stars and 18 stars were found to be located in the region of Be stars in the NIR colour-colour diagram. Thus NGC 146 is a young cluster with a large number of intermediate mass pre-main sequence stars. The turn-on age of the cluster is found to be ∼3Myr. Though NGC 146 shows an older turn off, the bulk of stars in this cluster seems to belong to the younger population of 3Myr.
Galaxy: open cluster and associations: individual: NGC 146 - stars: emission-line, Be - stars: Hertzsprung-Russell (HR) and C-M diagrams - stars: pre-main sequence