Physical parameters of pre-main sequence stars in open clusters
Abstract
Aims: The aims are twofold: we search and analyse pre-main sequence (PMS) stars in Galactic young open clusters (YOCs) to determine the ages, masses, and spatial distribution of PMS members in YOCs, and to check and compare the performances of different model isochrones.
Methods: We compare UBVRI photometric observations to theoretical isochrones in the photometric diagrams. The comparison simultaneously provides membership assignments for both main sequence (MS) and PMS stars and estimates for the physical properties of the cluster candidate members: masses, ages, and spatial distribution inside the cluster.
Results: The photometric measurement of an average (U - V) excess, supposedly indicative of accretion disks, is considered prior to membership assignment. This photometric excess is correlated with cluster age, suggesting that disks able to show up in (U - V) excess vanish at ages around 5 Myr. We find that comparing photometry to models in the colour-magnitude (CM) diagram leads to better results for the masses than performing the comparison in the theoretical HR plane. The obtained cluster mass functions show a marginal steepening with cluster age. Significant variations in the mass function slopes are found with the models used in member selection. The clusters
Conclusions: The relations between the different cluster parameters show that the procedure applied to assign cluster membership and to measure physical parameters for the selected members is well founded.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- July 2011
- DOI:
- 10.1051/0004-6361/201116491
- arXiv:
- arXiv:1105.5906
- Bibcode:
- 2011A&A...531A.141D
- Keywords:
-
- stars: formation;
- stars: pre-main sequence;
- open clusters and associations: general;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 11 pages, 8 figures. Accepted for publication in Astronomy and Astrophysics (17.5.2011)