2010/03/25 by D. J. James, David J. James, S. A. Barnes +15
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Cluster (spacecraft) #Differential rotation #Light curve #Open cluster #Proper motion #Rotation (mathematics) #Rotation period #Star (game theory) #Star cluster #Stars #Stellar, planetary, and galactic studies #astro-ph.GA #astro-ph.SR
paper · pdf · doi:10.1051/0004-6361/200913138
accepted for publication in Astronomy & Astrophysics
openalex publication_date 2010/03/25 · arxiv created 2010/04/01 · arxiv updated 2015/05/18 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
<i>Aims. <i/>Employing photometric rotation periods for solar-type stars in NGC 1039 [M 34], a young, nearby open cluster, we use its mass-dependent rotation period distribution to derive the cluster's age in a distance independent way, i.e., the so-called gyrochronology method.<i>Methods. <i/>We present an analysis of 55 new rotation periods, using light curves derived from differential photometry, for solar type stars in the open cluster NGC 1039 [M 34]. We also exploit the results of a recently-completed, standardized, homogeneous <i>BVI<i/>c CCD survey of the cluster, performed by the Indiana Group of the WIYN open cluster survey, in order to establish photometric cluster membership and assign colours to each photometric variable. We describe a methodology for establishing the gyrochronology age for an ensemble of solar-type stars. Empirical relations between rotation period, photometric colour and stellar age (gyrochronology) are used to determine the age of M 34. Based on its position in a colour-period diagram, each M 34 member is designated as being either a solid-body rotator (<i>interface or I-star<i/>), a differentially rotating star (<i>convective or C-star<i/>) or an object which is in some transitory state in between the two (<i>gap or g-star<i/>). Fitting the period and photometric colour of each I-sequence star in the cluster, we derive the cluster's mean gyrochronology age.<i>Results. <i/>Of the photometric variable stars in the cluster field, for which we derive a period, 47 out of 55 of them lie along the loci of the cluster main sequence in and space. We are further able to confirm kinematic membership of the cluster for half of the periodic variables [21/55], employing results from an on-going radial velocity survey of the cluster. For each cluster member identified as an I-sequence object in the colour-period diagram, we derive its individual gyrochronology age, where the mean gyro age of M 34 is found to be 193 <i>±<i/> 9 Myr.<i>Conclusions. <i/>Using differential photometry, members of a young open cluster can be easily identified in a colour–magnitude diagram from their periodic photometric variability alone. Such periodicity can be used to establish a period-colour distribution for the cluster, which for M 34, we have used to derive its gyrochronology age of 193 <i>±<i/> 9 Myr. Formally, our gyro age of M 34 is consistent (within the errors) with that derived using several <i>distance-dependent<i/>, photometric isochrone methods (<i>250<i/> <i>±<i/> <i>67<i/> Myr).