J/A+A/646/A30 Evolutionary sequences for ultra-massive CO-core (Althaus+, 2021)
The formation of ultra-massive carbon-oxygen core white dwarfs and their
evolutionary and pulsational properties.
Althaus L.G., Gil Pons P., Corsico A.H., Miller Bertolami M.,
De Geronimo F., Camisassa M.E., Torres S., Gutierrez J.,
Rebassa-Mansergas A.
<Astron. Astrophys. 646, A30 (2021)>
=2021A&A...646A..30A 2021A&A...646A..30A (SIMBAD/NED BibCode)
ADC_Keywords: Models, evolutionary ; Stars, white dwarf
Keywords: stars: evolution - stars: interiors - white dwarfs -
stars: oscillations
Abstract:
The existence of ultra-massive white dwarf stars, MWD≳1.05M☉,
has been reported in several studies. These white dwarfs are relevant
for the role they play in type Ia supernova explosions, the occurrence
of physical processes in the asymptotic giant-branch phase, the
existence of high-field magnetic white dwarfs, and the occurrence of
double-white-dwarf mergers.
We aim to explore the formation of ultra-massive, carbon-oxygen core
white dwarfs resulting from single stellar evolution. We also intend
to study their evolutionary and pulsational properties and compare
them with those of the ultra-massive white dwarfs with oxygen-neon
cores resulting from carbon burning in single progenitor stars, and
with binary merger predictions. The aim is to provide a theoretical
basis that can eventually help to discern the core composition of
ultra-massive white dwarfs and the circumstances of their formation.
We considered two single-star evolution scenarios for the formation of
ultra-massive carbon-oxygen core white dwarfs, which involve the
rotation of the degenerate core after core helium burning and reduced
mass-loss rates in massive asymptotic giant-branch stars. We find that
reducing standard mass-loss rates by a factor larger than 5-20 yields
the formation of carbon-oxygen cores more massive than 1.05M☉ as
a result of the slow growth of carbon-oxygen core mass during the
thermal pulses. We also performed a series of evolutionary tests of
solar-metallicity models with initial masses between 4 and 9.5M☉
and with different core rotation rates. We find that ultra-massive
carbon-oxygen core white dwarfs are formed even for the lowest
rotation rates we analyzed, and that the range of initial masses
leading to these white dwarfs widens as the rotation rate of the core
increases, whereas the initial mass range for the formation of
oxygen-neon core white dwarfs decreases significantly. Finally, we
compared our findings with the predictions from ultra-massive white
dwarfs resulting from the merger of two equal-mass carbon-oxygen core
white dwarfs, by assuming complete mixing between them and a
carbon-oxygen core for the merged remnant.
These two single-evolution scenarios produce ultra-massive white
dwarfs with different carbon-oxygen profiles and different helium
contents, thus leading to distinctive signatures in the period
spectrum and mode-trapping properties of pulsating hydrogen-rich white
dwarfs. The resulting ultra-massive carbon-oxygen core white dwarfs
evolve markedly slower than their oxygen-neon counterparts.
Our study strongly suggests the formation of ultra-massive white
dwarfs with carbon-oxygen cores from a single stellar evolution. We
find that both the evolutionary and pulsation properties of these
white dwarfs are markedly different from those of their oxygen-neon
core counterparts and from those white dwarfs with carbon-oxygen cores
that might result from double-degenerate mergers. This can eventually
be used to discern the core composition of ultra-massive white dwarfs
and their formation scenario.
Description:
Evolutionary sequences for ultra-massive carbon-oxygen core white
dwarfs of 1.15M☉ resulting from single progenitor evolution via
rotation and reduced mass-loss scenarios, as well as from WD merger.
It is also included the evolutionary sequence for an ultra-massive
oxygen-neon core white dwarf of the same stellar mass resulting from
off-center carbon burning in a single progenitor star.
In each case, it is tabulated:
Logarithm of surface luminosity in solar unit;
Logarithm of effective temperature (K);
Logarithm of age in 106yr (to get the WD cooling age,
the first tabulated age must be subtracted)
Stellar mass (in solar units)
Logarithm of surface gravity
Stellar radius (in solar radius)
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table.dat 67 1189 Evolutionary sequences
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 I1 --- Type [1/4] Type of evolutionary sequence (1)
3- 11 F9.6 [Lsun] logL Logarithm of surface luminosity
14- 21 F8.6 [K] logTeff Logarithm of effective temperature
23- 39 F17.15 [Myr] logAge Logarithm of age (2)
41- 47 F7.5 Msun Mass Stellar mass
49- 57 F9.7 [cm/s2] logg Logarithm of surface gravity
59- 67 F9.7 Rsun R Stellar radius
--------------------------------------------------------------------------------
Note (1): Models as follows:
1 = Evolutionary sequence for the CO-core WD resulting from the rotation
scenario in a single progenitor star
2 = Evolutionary sequence for the CO-core WD resulting from the reduced mass
loss scenario in a single progenitor star
3 = Evolutionary sequence for the CO-core WD resulting from merger
4 = Evolutionary sequence for the one-core WD resulting from off-center
C-burning in a single progenitor star
Note (2): to get the WD cooling age, the first tabulated age must be subtracted
--------------------------------------------------------------------------------
Acknowledgements:
Leandro G. Althaus, leandroalthaus(at)gmail.com
(End) Patricia Vannier [CDS] 07-Dec-2020