Volume 376, Number 1, September II 2001
|Page(s)||144 - 153|
|Section||Galactic structure, stellar clusters, and populations|
|Published online||15 September 2001|
The young open cluster NGC 663 and its Be stars*
Wrocław University Observatory, Kopernika 11, 51-622 Wrocław, Poland
Corresponding author: A. Pigulski, firstname.lastname@example.org
Accepted: 14 June 2001
We present new Hα photometry of the young open cluster NGC 663. The Hα photometry is complete down to magnitude , corresponding to spectral type A5 for the cluster members. This allows detection of mild and strong Hα emission in all B-type stars in the cluster. In addition to the 22 Be stars known in the observed field of NGC 663, we discovered four new faint stars of this type. We find that Be stars in NGC 663 cover the whole range of the B spectral type. They are, however, most populous among stars with spectral types falling in the range between B0 and B3, where their fraction amounts to 31 ± 8% . Among B-type stars later than B3, Be stars are much less abundant: only 7 out of 101 observed stars, that is, 7 ± 3% , were detected. About 70% of the observed Be stars in NGC 663 show detectable variations of light. In the time interval covered by our observations, the ranges of the largest variations reach 0.4 mag in the IC band. By means of the isochrone fitting, we derived the cluster distance of 2.1 kpc, age of 20-25 Myr, and the mean colour excess = 0.54 mag, with a ~0.1 mag scatter due to differential reddening.
Key words: stars: emission-line, Be / open clusters and associations: individual: NGC 663
© ESO, 2001
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.