# Ruprecht 147: a paradigm of dissolving star cluster

## TL;DR

Using Gaia DR2 data, we studied Ruprecht 147 and found it is rapidly dissolving into the Milky Way, with prominent stellar tails and significant mass loss over time.

## Contribution

This paper provides a detailed dynamical analysis of Ruprecht 147, revealing its dissolving state and quantifying its mass loss using Gaia data and N-body simulation insights.

## Key findings

- Ruprecht 147 has prominent stellar tails indicating ongoing dissolution.
- The cluster's current mass is approximately 234 solar masses.
- The original mass of the cluster was around 50,000 solar masses.

## Abstract

We employed recent Gaia/DR2 data to investigate the dynamical status of the nearby (300 pc), old (2.5 Gyr) open cluster Ruprecht~147. We found prominent leading and trailing tails of stars along the cluster orbit, which demonstrates that Ruprecht~147 is losing stars at fast pace. Star counts indicate the cluster has a core radius of 33.3 arcmin, and a tidal radius of 137.5 arcmin. The cluster also possesses an extended corona, which cannot be reproduced by a simple King model. We computed the present-day cluster mass using its luminosity and mass function, and derived an estimate of 234$\pm$52 $M_{\odot}$. We also estimated the cluster original mass using available recipes extracted from N-body simulations obtaining a mass at birth of 50000$\pm$6500 $M_{\odot}$. Therefore dynamical mass loss, mostly caused by tidal interaction with the Milky Way, reduced the cluster mass by about 99\%. We then conclude that Ruprecht~147 is rapidly dissolving into the general Galactic disc.