Why is the Main Sequence of NGC 2482 So Fat?

TL;DR

This study uses high-resolution spectra to analyze the stellar membership and main sequence width of NGC 2482, revealing that many stars appear broad due to foreground and background contamination rather than intrinsic cluster properties.

Contribution

The paper provides spectroscopic confirmation of cluster membership and clarifies that the main sequence broadening is mainly caused by non-member stars, improving understanding of cluster composition.

Findings

Confirmed radial velocity and metallicity of a giant star

Identified non-member stars based on radial velocity discrepancies

Attributed main sequence width mainly to foreground/background stars

Abstract

We present the results of high resolution spectra of seven stars in the field of NGC 2482, an open star cluster of age 447 Myr. We confirm the previously published values of the radial velocity and metallicity of one giant star. This gives us confidence that another giant star is a bona fide cluster member, and that three stars significantly above the main sequence in a color-magnitude diagram are not members, on the basis of discordant radial velocities. Another star ~1.7 mag above the main sequence may or may not be a member. Its [Fe/H] value is ~0.1 dex more positive than two giant stars studied, and its radial velocity is 3-4 km/s less than that of the two giant stars, which is a significant difference if the velocity dispersion of the cluster is less than +/-1 km/s. To a large extent the width of the main sequence seems to be due to the presence of foreground and background stars in the same general direction, stars that masquerade as main sequence stars in the cluster.