A comprehensive study of the rich open star cluster NGC 2099 based on deep $\vec{BVI}$ CCD observations

Abstract

Abstract. The CCD observations of the rich open star cluster NGC 2099 and its surrounding field region have been carried out up to a limiting magnitude of V ∼ 22 mag in B, V and I passbands for the first time. A total of ∼12 000 stars have been observed in the area of about 24 × 34 in the cluster region, as well as ∼2180 stars in the ∼12 × 12 area of the field region located ∼45 away from the cluster center. The cluster parameters determined by fitting the convective core overshoot isochrones in the V, (B − V ) and V, (V − I) diagrams are E(B − V ) = 0.30 ± 0.04 mag, distance = 1360 ± 100 pc, age = 400 Myr and metallicity Z = 0.008. A welldefined cluster main sequence spread over about 8 mag in range is observed for the first time. Its intrinsic spread amounting to ∼0.06 mag in colour is almost the same over the entire brightness and can be understood in terms of the presence of physical/optical binaries. The core and cluster radii determined from the radial stellar density profiles are 185 and 1000 respectively. Only about 22% of cluster members are present in the core region. The effects of mass segregation, most probably due to dynamical evolution, have been observed in the cluster. The mass function slope of the entire cluster is ∼−0.67 ± 0.12. It becomes closer to the Salpeter value of −1.35, if flattening in the cluster mass function due to presence of both binaries and a much more extended corona is considered.

Deep MMT Transit Survey of the Open Cluster M37. II. Variable Stars

“…Where available we took BV photometry for the sources from Kalirai et al (2001). We also transformed our ri photometry into I C using the I C photometry from Nilakshi & Sagar (2002) to define the transformation. Finally, we took K s photometry from the Two Micron All Sky Survey (2MASS; Skrutskie et al 2006) where available.…”

A study of spatial structure of galactic open star clusters

“…The clusters showing indication of well defined corona are planned for further extensive study using a large format CCD camera. In fact, Pandey et al (2001) and Nilakshi & Sagar (2002) have already carried out such a study for our sample clusters NGC 7654 and NGC 2099 respectively.…”

“…Differences in the structure of the corona have also been observed by Durgapal & Pandey (2001) in a sample of 4 clusters. They may be due to various reasons e.g., (i) the dynamical relaxation which causes mass segregation in the cluster (Nilakshi & Sagar 2002 and references therein), (ii) the external environment, as we know that the corona of the clusters are moulded by the Galactic tidal fields (Mathieu 1985).…”

CCD photometric search for peculiar stars in open clusters

“…A comprehensive study of this open cluster is given by Nilakshi & Sagar (2002). They included all relevant sources and data from the literature.…”

“…The Johnson UBV measurements of the literature as listed in Table 1 of Nilakshi & Sagar (2002) were averaged in order to derive mean photometric mean values within this system. The main sequence and the region of the red giants are clearly visible in Fig.…”