Stellar encounters in the solar neighbourhood and the special case of GJ~710

TL;DR

This study characterizes close stellar encounters near the Sun, focusing on GJ 710's predicted fly-by, and provides statistical insights into the frequency and dynamics of such events in the solar neighborhood.

Contribution

It offers a comprehensive analysis of stellar encounter rates, correcting for observational biases, and contextualizes the rare GJ 710 fly-by within the local stellar dynamics.

Findings

Encounter rate within 1 pc is approximately 10.6 per Myr.

GJ 710's fly-by is expected roughly once every 50 million years.

Corrected velocities account for gravitational redshift and convective blueshift.

Abstract

We present a comprehensive characterisation of close stellar encounters in the solar vicinity, with a particular focus on placing the predicted fly-by of GJ~710 in context. This star will come extremely close ($0.0621$\,pc or $\sim10^4$\,AU) to the Solar System in approximately 1.3\,Myr. Using a linear motion approximation, we identified past and future close stellar encounters within 1\,pc of the Solar System, using a complete sample of nearby stars. We assessed the completeness of our dataset and applied corrections to the radial velocities, accounting for gravitational redshift and convective blueshift. Such effects can bias the measured velocities and affect the derived encounter parameters. Furthermore, we computed close encounters for all the stars in the Solar System vicinity to build a statistically significant sample of such events. We accounted for binary systems and common proper motion pairs, applying corrections to account for incompleteness at the edges of our time window. We derived reliable statistics for close stellar encounters of stars within 25\,pc of the Sun. We report a rate of encounters within 1\,pc and within 0.47\,Myr of $10.6 \pm 4.5$ per Myr and star, implying an average of one encounter every $95^{+71}_{-28}$\,kyr. Additionally, from the resulting distribution, we can evaluate the relative frequency of the upcoming GJ~710 fly-by, which is found to be quite rare, at a rate of one per $\sim50$\,Myr. This work provides new insights into the dynamic environment of the solar neighbourhood by quantifying the rates and distributions of close stellar encounter events.