SIMBAD references

2009MNRAS.399..432N - Mon. Not. R. Astron. Soc., 399, 432-442 (2009/October-2)

Are pre-main-sequence stars older than we thought?


Abstract (from CDS):

We fit the colour-magnitude diagrams of stars between the zero-age main-sequence and terminal-age main sequence in young clusters and associations. The ages we derive are a factor of 1.5-2 longer than the commonly used ages for these regions, which are derived from the positions of pre-main-sequence stars in colour-magnitude diagrams. From an examination of the uncertainties in the main-sequence and pre-main-sequence models, we conclude that the longer age scale is probably the correct one, which implies that we must revise upwards the commonly used ages for young clusters and associations. Such a revision would explain the discrepancy between the observational lifetimes of protoplanetary discs and theoretical calculations of the time to form planets. It would also explain the absence of clusters with ages between 5 and 30Myr.

We use the τ2 statistic to fit the main-sequence data, but find that we must make significant modifications if we are to fit sequences which have vertical segments in the colour-magnitude diagram. We present this modification along with improvements to the methods of calculating the goodness-of-fit statistic and parameter uncertainties.

Software implementing the methods described in this paper is available from

Abstract Copyright: © 2009 The Author. Journal compilation © 2009 RAS

Journal keyword(s): methods: statistical - stars: early-type - stars: formation - stars: fundamental parameters - stars: pre-main-sequence - open clusters and associations: general

VizieR on-line data: <Available at CDS (J/MNRAS/399/432): table1.dat tables.dat>

Status at CDS : All or part of tables of objects could be ingested in SIMBAD with priority 2.

Simbad objects: 201

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