Open AccessAn L ′‐band survey for circumstellar discs around low‐mass stars in the young σ Orionis cluster
Author(s) -
Oliveira J. M.,
Jeffries R. D.,
Van Loon J. Th.
Publication year - 2004
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2004.07315.x
Subject(s) - physics , astrophysics , cluster (spacecraft) , stars , diagram , low mass , open cluster , myr , astronomy , statistics , computer science , gene , programming language , biochemistry , mathematics , chemistry , genome
We present new K ‐ and L ′‐band imaging of a representative sample of members of the young 3–5 Myr old σ Orionis cluster. We identified objects with ( K − L ′) excess by analysing colour–colour diagrams and comparing the observations with empirical main‐sequence colours. The derived disc frequency depends on the method used: (54 ± 15) per cent if measured directly from the JHKL ′ colour–colour diagram, or (46 ± 14) per cent if excesses are computed with respect to predicted photospheric colours (according to the object spectral types, 2σ excess detections). We compare the ( K − L ′) excess with other indicators and show that this is a robust and reliable disc indicator. We also compare the derived disc frequency with similarly aged clusters and discuss possible implications for disc lifetimes. The computed age of the σ Ori cluster is very important; a cluster age of 3 Myr would support the overall disc lifetime of 6 Myr proposed in the literature, while an age >4 Myr would point to a slower disc destruction rate.