The rotation period distribution of the rich Pleiades-age Southern open cluster NGC 2516. Existence of a representative zero-age main sequence distribution

TL;DR

This study measures the rotation periods of stars in the NGC 2516 cluster, compares them with the Pleiades, and finds that both clusters share similar rotational and activity distributions, indicating a common zero-age main sequence distribution.

Contribution

It provides the first detailed rotation period distribution for NGC 2516 and demonstrates its similarity to the Pleiades, establishing a representative zero-age main sequence rotational distribution.

Findings

NGC 2516 and Pleiades have nearly identical colour-period diagrams.

A new rotation-activity diagram for NGC 2516 is constructed.

Evidence of a common zero-age main sequence rotational distribution.

Abstract

We wish to measure the cool star rotation period distribution for the Pleiades-age rich open cluster NGC 2516 and use it to determine whether cluster-to-cluster variations exist in otherwise identical open clusters. We obtained 42 d-long time-series CCD photometry of NGC 2516 using the Yale 1 m telescope at CTIO and performed a number of related analyses, including PSF-based time-series photometry. Our data are complemented with additional information from several photometric datasets, literature radial velocities, and Gaia DR2 astrometry. All available data are used to construct an integrated membership list for NGC 2516, containing 844 stars in our 1deg FoV. We derived 308 rotation periods for late-F to mid-M cluster members from our photometry. We identified an additional 247 periodic M dwarf stars from a prior study as cluster members, and used these to construct a 555-star rotation period distribution for NGC 2516. We find a group of slowly rotating M dwarfs (10d<P<23d), forming a branch in the colour-period diagram which we call the 'extended slow rotator sequence'. This, and other features of the rotational distribution can also be found in the Pleiades, making the colour-period diagrams of the two clusters nearly indistinguishable. We demonstrate the existence of a representative ZAMS rotational distribution and provide a simple colour-independent way to represent it. We perform a detailed comparison of the NGC 2516 rotation period data with a number of recent rotational evolution models. Using X-ray data from the literature, we also construct the first rotation-activity diagram for solar-type stars in NGC 2516. The two clusters NGC 2516 and Pleiades can be considered twins in terms of stellar rotation and related properties, suggesting that otherwise identical open clusters also have intrinsically similar cool star rotation and activity distributions. (Abridged)