The Monitor project: Rotation periods of low-mass stars in M50

TL;DR

This study measures rotation periods of low-mass stars in the 130-million-year-old open cluster M50, revealing mass-dependent rotation patterns and evidence of spot pattern evolution over a 10-month span.

Contribution

It provides the first extensive rotation period data for M50, demonstrating mass-dependent rotation behavior and spot evolution, comparable to other clusters of similar age.

Findings

Rotation periods for 812 stars were measured.

Rotation patterns are similar to those in other young clusters.

Clear evidence of spot pattern evolution over 10 months.

Abstract

We report on the results of a time-series photometric survey of M50 (NGC 2323), a ~130 Myr open cluster, carried out using the CTIO 4m Blanco telescope and Mosaic-II detector as part of the Monitor project. Rotation periods were derived for 812 candidate cluster members over the mass range 0.2 <~ M/Msol <~ 1.1. The rotation period distributions show a clear mass-dependent morphology, statistically indistinguishable from those in NGC 2516 and M35 taken from the literature. Due to the availability of data from three observing runs separated by ~10 and 1 month timescales, we are able to demonstrate clear evidence for evolution of the photometric amplitudes, and hence spot patterns, over the 10 month gap, although we are not able to constrain the timescales for these effects in detail due to limitations imposed by the large gaps in our sampling, preventing use of the phase information.