Annapurni Subramaniam¹ , Blesson Mathew¹ and Sreeja S. Kartha^1,2
1 Indian Institute of Astrophysics, Bangalore 560 034, India
² Post-graduate Student, Physics Dept., M.G. University, Kottayam, India,500 007, India

Abstract. NGC 225 is believed to be a 120 Myr old open cluster located at tilda 650 pc. Eight stars with H emission are found to be located around the cluster, of which two are probable Herbig Be stars, indicating a very young age for the cluster. To explore whether the Herbig Be stars, which are pre- main sequence (PMS) stars are part of this cluster, we re-estimated the cluster parameters using optical (UBV)pg and 2MASS JHK photometry. We combined the above data to detect the presence of any possible PMS stars in the cluster region. Among the identified 28 proper motion members, 15 stars were found to have near-infrared (NIR) excess indicating that they are PMS stars. Also, most of the upper MS stars were found to show NIR excess suggesting that the brighter proper motion member stars have not yet reached the MS. PMS isochrones were used to estimate the age of stars with NIR excess and is found to be between 0.5-10 Myr. Thus, the cluster NGC 225 is a very young cluster, younger than 10 Myr and its age is not 120 Myr as previously believed. We propose that a recent star formation has resulted in the formation of NGC 225, two Herbig Be stars, stars with H emission, dust lanes and nebulosity in the vicinity of the cluster.

Keywords:open cluster, pre-main sequence star, Isochrone fitting

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