Time series photometry and multi-wavelength characterisation of the young stellar cluster Mon R2

TL;DR

This study provides a comprehensive multi-wavelength analysis of the young stellar cluster Mon R2, including photometry, spectroscopy, and Gaia data, to characterize its members, their rotation, age, and disk presence.

Contribution

It offers new detailed measurements of stellar rotation, membership, and age in Mon R2 using multi-epoch photometry, spectroscopy, and Gaia data, enhancing understanding of young cluster properties.

Findings

Measured rotation periods for 136 stars.

Estimated cluster distance as 825 ± 51 pc.

Identified 11 brown dwarf members.

Abstract

Using the Las Cumbres Observatory Global Telescope Network (LCOGT), we have obtained multi-epoch photometry of the young cluster Mon R2. We have monitored over 6000 sources with $i$-band between 13 and 23 mag within a $ 26'x26'$ field of view. For each star, we collected $\sim1500$ photometric points covering a temporal window of 23 days. Based on these data, we have measured rotation-modulated of 136 stars and identified around 90 additional variables, including 14 eclipsing binary candidates. Moreover, we found 298 other variables with photometric high-scatter. In addition, we have obtained $r$-band and H${\alpha}$ narrow-band photometry of the cluster with LCOGT and low-resolution optical spectroscopy of 229 stars with GMOS-Gemini. We used the \textit{Gaia} data from the periodic stars and objects with H$\alpha$ or IR-excesses, which are mostly low-mass pre-main sequence stars ($<1$M$_{sun}$) in the cluster to estimate the distance ($825 \pm 51$ pc) and the mean proper motions ($\mu_{\alpha}cos(\delta)=-2.75$mas yr$^{-1}$ and $\mu_{\delta}=1.15$mas yr$^{-1}$) of its members. This allows us to use the \textit{Gaia} data to identify additional Mon R2 member candidates. We also used Pan-STARRS photometry from our LCOGT sources to construct a more precise H-R diagram, from which we estimate the mean age of the cluster and identify other possible members including eleven spectroscopy brown dwarf with M7 to M9 GMOS spectral types. Finally, we combined our membership lists with \textit{Spitzer} infrared photometry to investigate the incidence of stars with discs and the effect these have on stellar rotation.