Volume 440, Number 2, September III 2005
|Page(s)||511 - 522|
|Section||Galactic structure, stellar clusters, and populations|
|Published online||01 September 2005|
NGC 146: a young open cluster with a Herbig Be star and intermediate mass pre-main sequence stars
Indian Institute of Astrophysics, II Block Koramangala, Bangalore 560034, India e-mail: firstname.lastname@example.org
2 CREST Campus, Indian Institute of Astrophysics, Hosakote, Bangalore, India e-mail: email@example.com
3 Aryabhatta Research Institute of Observational Studies (ARIES), Manora peak, Nainital 263129, India e-mail: firstname.lastname@example.org
4 VSRTP Student, Mother Theresa University, Kodaikanal, India
Accepted: 11 May 2005
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 reddening of 0.55 ± 0.04 mag and BV photometry of 976 stars were used to estimate a distance modulus of = 12.7 ± 0.2 mag, corresponding to a distance of 3470 pc. We estimated 10–16 Myr 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 vs. 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 ~3 Myr. Though NGC 146 shows an older turn off, the bulk of stars in this cluster seems to belong to the younger population of 3 Myr.
Key words: Galaxy: open cluster and associations: individual: NGC 146 / stars: emission-line, Be / stars: Hertzsprung-Russell (HR) and C-M diagrams / stars: pre-main sequence
© ESO, 2005
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