TY - JOUR
T1 - The isolation of luminous blue variables resembles aging B-type supergiants, not the most massive unevolved stars
AU - Smith, Nathan
N1 - Funding Information:
awards AST-1312221 and AST-1515559, and by the National Aeronautics and Space Administration (NASA) through HST grant AR-14316 from the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555. This research has made use of the SIMBAD data base, operated at CDS, Strasbourg, France.
Publisher Copyright:
© 2019 The Author(s).
PY - 2019/11/1
Y1 - 2019/11/1
N2 - 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.
AB - 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.
KW - Binaries: General
KW - Blue stragglers
KW - Stars: Evolution
KW - Stars: Massive
KW - Stars: Wolf-Rayet
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U2 - 10.1093/mnras/stz2277
DO - 10.1093/mnras/stz2277
M3 - Article
AN - SCOPUS:85075161829
VL - 489
SP - 4378
EP - 4388
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 3
ER -