Testing Binary Population Synthesis Models with Hot Subdwarfs

ABSTRACT Some surviving companions of Type Ia supernovae (SNe Ia) from the white dwarf + main-sequence (WD+MS) channel may evolve to hot subdwarfs. In this paper, we perform stellar evolution calculations for the surviving companions of close WD+MS systems in the spin-up/spin-down model and the canonical non-rotating model. This enables us to map out the initial parameter spaces in the orbital period–secondary-mass plane in which the surviving companions can evolve to hot subdwarfs. Based on these results, we carry out a series of binary population synthesis calculations to obtain the Galactic birth rate of hot subdwarfs from the WD+MS channel, which is $2.3{-}6\times 10^{\rm -4}\, {\rm yr}^{\rm -1}$ for the spin-up/spin-down model and $0.7{-}3\times 10^{\rm -4}\, {\rm yr}^{\rm -1}$ for the canonical non-rotating model. We also show the distributions of some integral properties of the hot subdwarfs, for example the mass and space velocity, for different models. In addition, by comparing our results with observations of intermediate helium-rich (iHe-rich) hot subdwarfs, we find that the hot subdwarfs from the WD+MS channel may explain some observational features of the iHe-rich hot subdwarfs, especially those from the spin-up/spin-down model. Although we expect that the SN Ia channel will contribute only a small fraction of the iHe-rich hot subdwarf population, some of these may help to explain cases with unusual kinematics.

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Evolution of binary stars and its implications for evolutionary population synthesis

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310002504 ◽

2009 ◽

Vol 5 (S262) ◽

pp. 44-47

Author(s):

Z. Han ◽

X. Chen ◽

F. Zhang ◽

Ph. Podsiadlowski

Keyword(s):

Binary System ◽

Binary Stars ◽

Elliptical Galaxies ◽

Close Binary System ◽

Close Binary ◽

Population Synthesis ◽

Blue Stragglers ◽

Uv Excess ◽

Hot Subdwarfs ◽

Binary Evolution

AbstractMost stars are members of binaries, and the evolution of a star in a close binary system differs from that of an ioslated star due to the proximity of its companion star. The components in a binary system interact in many ways and binary evolution leads to the formation of many peculiar stars, including blue stragglers and hot subdwarfs. We will discuss binary evolution and the formation of blue stragglers and hot subdwarfs, and show that those hot objects are important in the study of evolutionary population synthesis (EPS), and conclude that binary interactions should be included in the study of EPS. Indeed, binary interactions make a stellar population younger (hotter), and the far-ultraviolet (UV) excess in elliptical galaxies is shown to be most likely resulted from binary interactions. This has major implications for understanding the evolution of the far-UV excess and elliptical galaxies in general. In particular, it implies that the far-UV excess is not a sign of age, as had been postulated prviously and predicts that it should not be strongly dependent on the metallicity of the population, but exists universally from dwarf ellipticals to giant ellipticals.

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POPULATION SYNTHESIS OF HOT SUBDWARFS: A PARAMETER STUDY

The Astrophysical Journal ◽

10.1088/0004-637x/746/2/186 ◽

2012 ◽

Vol 746 (2) ◽

pp. 186 ◽

Cited By ~ 18

Author(s):

Drew Clausen ◽

Richard A. Wade ◽

Ravi Kumar Kopparapu ◽

Richard O'Shaughnessy

Keyword(s):

Parameter Study ◽

Population Synthesis ◽

Hot Subdwarfs

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Stellar Population Synthesis in AGN Host Galaxies

EAS Publications Series ◽

10.1051/eas:2001016 ◽

2001 ◽

Vol 1 ◽

pp. 145-152

Author(s):

M. Joly ◽

C. Boisson ◽

J. Moultaka ◽

D. Pelat

Keyword(s):

Stellar Population ◽

Population Synthesis ◽

Host Galaxies ◽

Stellar Population Synthesis

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Planetary Nebulae in M31: Abundances, and comparison with bright Planetary Nebulae in the LMC

Symposium - International Astronomical Union ◽

10.1017/s007418090013178x ◽

1997 ◽

Vol 180 ◽

pp. 475-476

Author(s):

M. G. Richer ◽

G. Stasińska ◽

M. L. McCall

Keyword(s):

Planetary Nebula ◽

Luminosity Function ◽

Large Population ◽

Wavelength Region ◽

Planetary Nebulae ◽

Surprising Result ◽

Population Synthesis ◽

Abundance Distribution ◽

Wide Range ◽

The Mean

We have obtained spectra of 28 planetary nebulae in the bulge of M31 using the MOS spectrograph at the Canada-France-Hawaii Telescope. Typically, we observed the [O II] λ3727 to He I λ5876 wavelength region at a resolution of approximately 1.6 å/pixel. For 19 of the 21 planetary nebulae whose [OIII]λ5007 luminosities are within 1 mag of the peak of the planetary nebula luminosity function, our oxygen abundances are based upon a measured [OIII]λ4363 intensity, so they are based upon a measured electron temperature. The oxygen abundances cover a wide range, 7.85 dex < 12 + log(O/H) < 9.09 dex, but the mean abundance is surprisingly low, 12 + log(O/H)–8.64 ± 0.32 dex, i.e., roughly half the solar value (Anders & Grevesse 1989). The distribution of oxygen abundances is shown in Figure 1, where the ordinate indicates the number of planetary nebulae with abundances within ±0.1 dex of any point on the x-axis. The dashed line indicates the mean abundance, and the dotted lines indicate the ±1 σ points. The shape of this abundance distribution seems to indicate that the bulge of M31 does not contain a large population of bright, oxygen-rich planetary nebulae. This is a surprising result, for various population synthesis studies (e.g., Bica et al. 1990) have found a mean stellar metallicity approximately 0.2 dex above solar. This 0.5 dex discrepancy leads one to question whether the mean stellar metallicity is as high as the population synthesis results indicate or if such metal-rich stars produce bright planetary nebulae at all. This could be a clue concerning the mechanism responsible for the variation in the number of bright planetary nebulae observed per unit luminosity in different galaxies (e.g., Hui et al. 1993).

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PHL 417: a zirconium-rich pulsating hot subdwarf (V366 Aquarid) discovered in K2 data

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3123 ◽

2020 ◽

Vol 499 (3) ◽

pp. 3738-3748

Author(s):

R H Østensen ◽

C S Jeffery ◽

H Saio ◽

J J Hermes ◽

J H Telting ◽

...

Keyword(s):

Heavy Metal ◽

Helium Abundance ◽

The Sun ◽

The Third ◽

Short Period ◽

Standard Models ◽

Hot Subdwarfs ◽

Amplitude Mode ◽

Rare Group

ABSTRACT The Kepler spacecraft observed the hot subdwarf star PHL 417 during its extended K2 mission, and the high-precision photometric light curve reveals the presence of 17 pulsation modes with periods between 38 and 105 min. From follow-up ground-based spectroscopy, we find that the object has a relatively high temperature of 35 600 K, a surface gravity of $\log g / {\rm cm\, s^{-2}}\, =\, 5.75$ and a supersolar helium abundance. Remarkably, it also shows strong zirconium lines corresponding to an apparent +3.9 dex overabundance compared with the Sun. These properties clearly identify this object as the third member of the rare group of pulsating heavy-metal stars, the V366-Aquarii pulsators. These stars are intriguing in that the pulsations are inconsistent with the standard models for pulsations in hot subdwarfs, which predicts that they should display short-period pulsations rather than the observed longer periods. We perform a stability analysis of the pulsation modes based on data from two campaigns with K2. The highest amplitude mode is found to be stable with a period drift, $\dot{P}$, of less than 1.1 × 10−9 s s−1. This result rules out pulsations driven during the rapid stages of helium flash ignition.

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DISK MASS-TO-LIGHT RATIO DISTRIBUTION FROM STELLAR POPULATION SYNTHESIS: APPLICATION TO ROTATION CURVE DECOMPOSITION OF NGC 5278 (KPG 390 A)

The Astrophysical Journal ◽

10.1088/0004-637x/765/1/7 ◽

2013 ◽

Vol 765 (1) ◽

pp. 7 ◽

Cited By ~ 6

Author(s):

P. Repetto ◽

Eric E. Martínez-García ◽

M. Rosado ◽

R. Gabbasov

Keyword(s):

Rotation Curve ◽

Stellar Population ◽

Population Synthesis ◽

Ratio Distribution ◽

Disk Mass ◽

Stellar Population Synthesis

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The IMF-SFH connection in massive early-type galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316007808 ◽

2015 ◽

Vol 11 (S315) ◽

Author(s):

I. Ferreras ◽

C. Weidner ◽

A. Vazdekis ◽

F. La Barbera

Keyword(s):

Age Distribution ◽

Stellar Populations ◽

Mass Function ◽

Initial Mass Function ◽

Population Synthesis ◽

Early Type ◽

Massive Galaxies ◽

Stellar Initial Mass Function ◽

The Many ◽

The Imf

The stellar initial mass function (IMF) is one of the fundamental pillars in studies of stellar populations. It is the mass distribution of stars at birth, and it is traditionally assumed to be universal, adopting generic functions constrained by resolved (i.e. nearby) stellar populations (e.g., Salpeter 1955; Kroupa 2001; Chabrier 2003). However, for the vast majority of cases, stars are not resolved in galaxies. Therefore, the interpretation of the photo-spectroscopic observables is complicated by the many degeneracies present between the properties of the unresolved stellar populations, including IMF, age distribution, and chemical composition. The overall good match of the photometric and spectroscopic observations of galaxies with population synthesis models, adopting standard IMF choices, made this issue a relatively unimportant one for a number of years. However, improved models and observations have opened the door to constraints on the IMF in unresolved stellar populations via gravity-sensitive spectral features. At present, there is significant evidence of a non-universal IMF in early-type galaxies (ETGs), with a trend towards a dwarf-enriched distribution in the most massive systems (see, e.g., van Dokkum & Conroy 2010; Ferreras et al. 2013; La Barbera et al. 2013). Dynamical and strong-lensing constraints of the stellar M/L in similar systems give similar results, with heavier M/L in the most massive ETGs (see, e.g., Cappellari et al. 2012; Posacki et al. 2015). Although the interpretation of the results is still open to discussion (e.g., Smith 2014; La Barbera 2015), one should consider the consequences of such a bottom-heavy IMF in massive galaxies.

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