On the kinematics of a runaway Be star population
We explore the hypothesis that B-type emission-line stars (Be stars) have their origin in mass-transfer binaries by measuring the fraction of runaway Be stars. We assemble the largest-to-date catalogue of 632 Be stars with 6D kinematics, exploiting the precise astrometry of the Tycho-Gaia Astrometri...
| Main Authors: | , |
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| Format: | Journal article |
| Language: | English |
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Oxford University Press
2018
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| _version_ | 1826305866140221440 |
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| author | Boubert, D Evans, NW |
| author_facet | Boubert, D Evans, NW |
| author_sort | Boubert, D |
| collection | OXFORD |
| description | We explore the hypothesis that B-type emission-line stars (Be stars) have their origin in mass-transfer binaries by measuring the fraction of runaway Be stars. We assemble the largest-to-date catalogue of 632 Be stars with 6D kinematics, exploiting the precise astrometry of the Tycho-Gaia Astrometric Solution from the first Gaia data release. Using binary stellar evolution simulations, we make predictions for the runaway and equatorial rotation velocities of a runaway Be star population. Accounting for observational biases, we calculate that if all classical Be stars originated through mass transfer in binaries, then 17.5 per cent of the Be stars in our catalogue should be runaways. The remaining 82.5 per cent should be in binaries with subdwarfs, white dwarfs, or neutron stars, because those systems either remained bound post-supernova or avoided the supernova entirely. Using a Bayesian methodology, we compare the hypothesis that each Be star in our catalogue is a runaway to the null hypothesis that it is a member of the Milky Way disc. We find that 13.1 +2.6 −2.4 per cent of the Be stars in our catalogue are runaways and identify a subset of 40 high-probability runaways. We argue that deficiencies in our understanding of binary stellar evolution, as well as the degeneracy between velocity dispersion and number of runaway stars, can explain the slightly lower runaway fraction. We thus conclude that all Be stars could be explained by an origin in mass-transfer binaries. This conclusion is testable with the second Gaia data release (DR2). |
| first_indexed | 2024-03-07T06:39:21Z |
| format | Journal article |
| id | oxford-uuid:f8bb952f-8144-4d86-ae76-7864275b124f |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T06:39:21Z |
| publishDate | 2018 |
| publisher | Oxford University Press |
| record_format | dspace |
| spelling | oxford-uuid:f8bb952f-8144-4d86-ae76-7864275b124f2022-03-27T12:52:43ZOn the kinematics of a runaway Be star populationJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:f8bb952f-8144-4d86-ae76-7864275b124fEnglishSymplectic Elements at OxfordOxford University Press2018Boubert, DEvans, NWWe explore the hypothesis that B-type emission-line stars (Be stars) have their origin in mass-transfer binaries by measuring the fraction of runaway Be stars. We assemble the largest-to-date catalogue of 632 Be stars with 6D kinematics, exploiting the precise astrometry of the Tycho-Gaia Astrometric Solution from the first Gaia data release. Using binary stellar evolution simulations, we make predictions for the runaway and equatorial rotation velocities of a runaway Be star population. Accounting for observational biases, we calculate that if all classical Be stars originated through mass transfer in binaries, then 17.5 per cent of the Be stars in our catalogue should be runaways. The remaining 82.5 per cent should be in binaries with subdwarfs, white dwarfs, or neutron stars, because those systems either remained bound post-supernova or avoided the supernova entirely. Using a Bayesian methodology, we compare the hypothesis that each Be star in our catalogue is a runaway to the null hypothesis that it is a member of the Milky Way disc. We find that 13.1 +2.6 −2.4 per cent of the Be stars in our catalogue are runaways and identify a subset of 40 high-probability runaways. We argue that deficiencies in our understanding of binary stellar evolution, as well as the degeneracy between velocity dispersion and number of runaway stars, can explain the slightly lower runaway fraction. We thus conclude that all Be stars could be explained by an origin in mass-transfer binaries. This conclusion is testable with the second Gaia data release (DR2). |
| spellingShingle | Boubert, D Evans, NW On the kinematics of a runaway Be star population |
| title | On the kinematics of a runaway Be star population |
| title_full | On the kinematics of a runaway Be star population |
| title_fullStr | On the kinematics of a runaway Be star population |
| title_full_unstemmed | On the kinematics of a runaway Be star population |
| title_short | On the kinematics of a runaway Be star population |
| title_sort | on the kinematics of a runaway be star population |
| work_keys_str_mv | AT boubertd onthekinematicsofarunawaybestarpopulation AT evansnw onthekinematicsofarunawaybestarpopulation |