Abstract
Abstract We present a catalog of unbound stellar pairs, within 100 pc of the Sun, that are undergoing close, hyperbolic, encounters. The data are drawn from the GAIA EDR3 catalog, and the limiting factors are errors in the radial distance and unknown velocities along the line of sight. Such stellar pairs have been suggested to be possible events associated with the migration of technological civilizations between stars. As such, this sample may represent a finite set of targets for a SETI search based on this hypothesis. Our catalog contains a total of 132 close passage events, featuring stars from across the entire main sequence, with 16 pairs featuring at least one main-sequence star of spectral type between K1 and F3. Many of these stars are also in binaries, so that we isolate eight single stars as the most likely candidates to search for an ongoing migration event—HD 87978, HD 92577, HD 50669, HD 44006, HD 80790, LSPM J2126+5338, LSPM J0646+1829 and HD 192486. Among host stars of known planets, the stars GJ 433 and HR 858 are the best candidates.
Highlights
We search for pairs of stars that have a finite probability of passing within 104 AU of one another – either in the recent past or near future. This threshold is chosen to be such that these events are sufficiently uncommon to justify the hypothesis in HZ21 that migration is limited to rare events
HD87978 is classified as G6IV and so should be starting to leave the main sequence, and is the perfect archetype of the rationale in HZ21 for a system in which a civilisation might be motivated to make an attempt at interstellar migration
HZ21 noted that the energy burden of transfer between stars is considerably eased during such encounters and postulated that most interstellar migration will occur during such episodes
Summary
The accelerating pace of discovery of planets around other stars, including the discovery of potentially habitable planets, has brought into clear focus the question of how frequently intelligent, technologically advanced, civilizations occur in the Galaxy. In this paper we seek to identify pairs of stars that meet the criterion of being in close physical proximity, but which are gravitationally unbound These may serve as a possible target list for a SETI search – one with the particular motivating hypothesis laid out in HZ21. We search for pairs of stars that have a finite probability of passing within 104 AU of one another – either in the recent past or near future This threshold is chosen to be such that these events are sufficiently uncommon (only ∼ 10−4 G stars will be involved in such an encounter at any one time) to justify the hypothesis in HZ21 that migration is limited to rare events.
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