J/A+A/615/A78 Spectral models for binary products (Goetberg+, 2018)
Spectral models for binary products: Unifying Subdwarfs and Wolf-Rayet stars as
a sequence of stripped-envelope stars.
Goetberg Y., de Mink S.E., Groh J.H., Kupfer T., Crowther P.A.,
Zapartas E., Renzo M.
<Astron. Astrophys. 615, A78 (2018)>
=2018A&A...615A..78G 2018A&A...615A..78G (SIMBAD/NED BibCode)
ADC_Keywords: Models ; Stars, atmospheres ; Stars, Wolf-Rayet ;
Stars, subdwarf ; Energy distributions
Keywords: binaries: close - stars: atmospheres - subdwarfs - stars: Wolf-Rayet -
galaxies: stellar content - ultraviolet: galaxies
Abstract:
Stars stripped of their hydrogen-rich envelope through interaction
with a binary companion are generally not considered when accounting
for ionizing radiation from stellar populations, despite the
expectation that stripped stars emit hard ionizing radiation, form
frequently, and live 10-100 times longer than single massive stars.
We compute the first grid of evolutionary and spectral models
specially made for stars stripped in binaries for a range of
progenitor masses (2-20M☉) and metallicities ranging from
solar to values representative for pop II stars. For stripped stars
with masses in the range 0.3-7M☉, we find consistently high
effective temperatures (20000-100000K, increasing with mass),
small radii (0.2-1R☉), and high bolometric luminosities,
comparable to that of their progenitor before stripping. The spectra
show a continuous sequence that naturally bridges subdwarf-type stars
at the low-mass end and Wolf-Rayet-like spectra at the high-mass end.
For intermediate masses we find hybrid spectral classes showing a
mixture of absorption and emission lines. These appear for stars with
mass-loss rates of 10-8-10-6M☉/yr, which have
semi-transparent atmospheres. At low metallicity, substantial
hydrogen-rich layers are left at the surface and we predict spectra
that resemble O-type stars instead. We obtain spectra
undistinguishable from subdwarfs for stripped stars with masses up to
1.7M☉, which questions whether the widely adopted canonical
value of 0.47M☉ is uniformly valid. Only a handful of stripped
stars of intermediate mass have currently been identified
observationally. Increasing this sample will provide necessary tests
for the physics of interaction, internal mixing, and stellar winds. We
use our model spectra to investigate the feasibility to detect
stripped stars next to an optically bright companion and recommend
systematic searches for their UV excess and possible emission lines,
most notably HeII λ4686 in the optical and HeII λ1640 in
the UV. Our models are publicly available for further investigations
or inclusion in spectral synthesis simulations.
Description:
We have modeled the spectra of stars stripped of their envelope
through mass transfer in binary systems using the non-LTE radiative
transfer code CMFGEN. These stripped stars span a mass range from 0.34
up to 7.9M☉. We present four metallicities; Z=0.014 (solar),
0.006, 0.002, and 0.0002. For each model we provide the spectral
energy distribution and the normalized spectrum. We also provide the
magnitudes for the following filters: GALEX/NUV, GALEX/FUV Swift/UVW1,
Swift/UVW2, Swift/UVM2, Johnson UBVRI, 2MASS/J, 2MASS/H, and 2MASS/Ks.
These magnitudes are presented in tables for each metallicity grid.
Each model is labelled in the following way: M1Xq0.8PXZXvinf1.5,
where X stands for initial mass (mass of the star before stripping),
initial period, and metallicity, in order.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
m0002.dat 258 23 Absolute magnitudes of the spectral models of
stripped stars in the grid grid_0002, Z=0.0002
grid_0002/* . 23 Individual spectra and SED for each model
m002.dat 258 23 Absolute magnitudes of the spectral models of
stripped stars in the grid grid_002, Z=0.002
grid_002/* . 23 Individual spectra and SED for each model
m006.dat 258 23 Absolute magnitudes of the spectral models of
stripped stars in the grid grid_006, Z=0.006
grid_006/* . 23 Individual spectra and SED for each model
m014.dat 258 23 Absolute magnitudes of the spectral models of
stripped stars in the grid grid_014, Z=0.014
grid_014/* . 23 Individual spectra and SED for each model
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Byte-by-byte Description of file (#): m0002.dat m002.dat m006.dat m014.dat
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Bytes Format Units Label Explanations
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1- 32 A32 --- Model Model name (1)
34- 49 F16.13 mag NUV NUV absolute magnitude of the spectral model
51- 66 F16.13 mag FUV FUV absolute magnitude of the spectral model
68- 83 F16.13 mag UVW1 UVW1 absolute magnitude of the spectral model
85-101 F17.13 mag UVW2 UVW2 absolute magnitude of the spectral model
103-119 F17.14 mag UVM2 UVM2 absolute magnitude of the spectral model
121-137 F17.14 mag U U absolute magnitude of the spectral model
139-154 F16.13 mag B B absolute magnitude of the spectral model
156-171 F16.13 mag V V absolute magnitude of the spectral model
173-189 F17.14 mag R R absolute magnitude of the spectral model
191-206 F16.13 mag I I absolute magnitude of the spectral model
208-223 F16.13 mag J J absolute magnitude of the spectral model
225-240 F16.13 mag H H absolute magnitude of the spectral model
242-258 F17.14 mag Ks Ks absolute magnitude of the spectral model
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Note (1): Model name is subdirectory grid_0002 for m0002.dat,
grid_002 for m002.dat, grid_006 for m006.dat and grid_014 for m014.dat.
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Acknowledgements:
Ylva Gotberg, y.l.l.gotberg(at)uva.nl
(End) Patricia Vannier [CDS] 26-Mar-2018