Abstract
Luminous blue variables (LBVs) are suprisingly isolated from the massive O-type stars that are their putative progenitors in single-star evolution, implicating LBVs as binary evolution products. Aadland et al. found that LBVs are, however, only marginally more dispersed than a photometrically selected sample of bright blue stars (BBS) in the Large Magellanic Cloud (LMC), leading them to suggest that LBV environments may not exclude a single-star origin. In both comparisons, LBVs have the same median separation, confirming that any incompleteness in the O-star sample does not fabricate LBV isolation. Instead, the relative difference arises because the photometric BBS sample is farmore dispersed than known O-type stars. Evidence suggests that the large BBS separation arises because it traces less massive (∼20 M), aging blue supergiants. Although photometric criteria used by A19 aimed to select only the most massive unevolved stars, visual-wavelength colour selection cannot avoid contamination because O and early B stars have almost the same intrinsic colour. Spectral types confirm that the BBS sample contains many B supergiants. Moreover, the observed BBS separation distribution matches that of spectroscopically confirmed early B supergiants, not O-type stars, and matches predictions for a roughly 10 Myr population, not a 3-4 Myr population. A broader implication for ages of stellar populations is that bright blue stars are not a good tracer of the youngest massive O-type stars. Bright blue stars in nearby galaxies (and unresolved blue light in distant galaxies) generally trace evolved blue supergiants akin to SN 1987A's progenitor.
Original language | English (US) |
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Pages (from-to) | 4378-4388 |
Number of pages | 11 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 489 |
Issue number | 3 |
DOIs | |
State | Published - Nov 1 2019 |
Keywords
- Binaries: General
- Blue stragglers
- Stars: Evolution
- Stars: Massive
- Stars: Wolf-Rayet
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science