Young Double Cluster Research Articles

CCD $uvby\beta$ photometry of young open clusters

We present CCD photometry for stars in the nuclei of the young double cluster h and χ Persei. We find that the reddening is highly variable through the h Per nucleus, increasing from west to east, with values ranging from in the western part to in the south-east. Towards χ Per the reddening is fairly constant, with . Both clusters share a common distance modulus of mag, and an age of years.

ITAL]UBVI[/ITAL] and Hα Photometry of the [CLC][ITAL]h[/ITAL][/CLC] and χ Persei Cluster

UBVI and Hα photometry is presented for 17319 stars in vicinity of the young double cluster h and χ Persei. Our photometry extends over a 37' × 1° field centered on the association. We construct reddening contours within the imaged field. We find that the two clusters share a common distance modulus of 11.75 ± 0.05 and ages of log age(yr) = 7.1 ± 0.1. From the V-Hα color, a measure of the Hα emission strength, we conduct a survey for emission line objects within the association. We detect a sample of 33 Be stars, eight of which are new detections. We present a scenario of evolutionary enhancement of the Be phenomenon to account for the peak in Be fraction toward the top of the main sequence in the population of h and χ Persei and similar young clusters.

WFPC2 observations of the double cluster NGC 1850 in the Large Magellanic Cloud

Hubble Space Telescope-Wide Field/Planetary Camera-2 (HST-WFPC2) optical and ultraviolet imaging observations of the young double cluster NGC 1850 in the Large Magellanic Cloud (LMC) are presented. The main cluster, NGC 1850A, is a globular-like cluster and has an age of 50 +/- 10 Myr, while the subcluster, NGC 1850B, which is more loosely distributed, is very young at 4.3 +/- 0.9 Myr. Its young age is confirmed by the detection of a pre-main-sequence population of stars associated to it. The two clusters have considerably different IMF slopes, with the main cluster having a flat slope (f(m) proportional to m(exp -1.4 +/- 0.2)) and the young cluster a much steeper one (f(m) proportional to m(exp -2.6 +/- -0.1)). The LMC field star population displays a broad range of ages, from approximately 0.5 Gyr up to more than 4 Gyr.