A preliminary look at the empirical mass distribution of hot B subdwarf stars

Fontaine, G.; Brassard, P.; Charpinet, S.; Green, Elizabeth M.; Randall, S. K.; Grootel, Valérie Van

doi:10.1051/0004-6361/201118220

Cited by 112 publications

(120 citation statements)

References 46 publications

(53 reference statements)

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“…This implies that the RV amplitude cannot be derived with the accuracy one may otherwise expect from these data. When computing the mass function, while assuming a typical value for the mass of the sdB star of 0.47 M (Fontaine et al 2012), we find a lower limit of the companion's mass of 0.24 M , and a minimum distance between both components of 5 R .…”

Section: Spectroscopic Datamentioning

confidence: 89%

A subsynchronously rotating pulsating subdwarf B star in a short-period binary with a white dwarf companion

Baran

Telting

Németh

et al. 2015

A&A

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We present our analysis of KIC 7664467, an sdB pulsator that we have found to be residing in a 1.56-day binary system with a whitedwarf companion. This system was observed photometrically with the Kepler spacecraft and spectroscopically with ground-based telescopes. We analyzed the amplitude spectra detecting 61 periods, rotationally split multiplets, and an equally spaced sequence in period. These two features helped with the mode identification. We derived both the binary and rotation periods showing that this is another binary system with a subsynchronous sdB star. From our spectroscopy of the sdB star, we determined T eff = 27440 ± 120 K, log g = 5.38 ± 0.02 dex. The abundance pattern follows the general trend observed in sdB stars, where light metals are subsolar, while the Fe abundance is very close to the solar value. We found the N enrichment and low abundances of C and O that resemble the equilibrium abundances of the CNO cycle. We could also measure the Mg and Si abundances. Using the radial velocity amplitude K 1 = 57(3) km s −1 and the Doppler boosting-dominated photometric signal at the orbital period, we constrained the companion to be a compact object, almost certainly a white dwarf.

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Section: Spectroscopic Datamentioning

confidence: 89%

A subsynchronously rotating pulsating subdwarf B star in a short-period binary with a white dwarf companion

Baran

Telting

Németh

et al. 2015

A&A

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“…The sdB stars are essentially the naked He cores of red clump stars, with masses of M ; 0.47 M e (Fontaine et al 2012) and thin H envelopes of M H ∼ 10 −3 M e . They provide an opportunity to constrain much of the physics discussed in this paper, since magnetic fields that would be confined to the cores of clump stars could be visible at the surfaces of sdB stars.…”

Section: Implications For Other Asteroseismic Targetsmentioning

confidence: 99%

Asteroseismic Signatures of Evolving Internal Stellar Magnetic Fields

Cantiello

Fuller

Bildsten

2016

ApJ

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Recent asteroseismic analyses indicate the presence of strong (B  10 5 G) magnetic fields in the cores of many red giant stars. Here, we examine the implications of these results for the evolution of stellar magnetic fields, and we make predictions for future observations. Those stars with suppressed dipole modes indicative of strong core fields should exhibit moderate but detectable quadrupole mode suppression. The long magnetic diffusion times within stellar cores ensure that dynamo-generated fields are confined to mass coordinates within the main-sequence (MS) convective core, and the observed sharp increase in dipole mode suppression rates above 1.5 M e is likely explained by the larger convective core masses and faster rotation of these more massive stars. In clump stars, core fields of ∼10 5 G can suppress dipole modes, whose visibility should be equal to or less than the visibility of suppressed modes in ascending red giants. High dipole mode suppression rates in low-mass (M  2 M e ) clump stars would indicate that magnetic fields generated during the MS can withstand subsequent convective phases and survive into the compact remnant phase. Finally, we discuss implications for observed magnetic fields in white dwarfs and neutron stars, as well as the effects of magnetic fields in various types of pulsating stars.

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“…We add to our sample the fast-rotating sdB SB 290 (Geier et al 2013a). We also add the 10 stars identified as single with only one set of atmospheric parameters in table 1 of Fontaine et al (2012). Our full sample of 48 sdBs is summarized in Table B1.…”

Section: A Sample Of Apparently Isolated Hot Subdwarfsmentioning

confidence: 99%

Hydrogen in hot subdwarfs formed by double helium white dwarf mergers

Hall

Jeffery

2016

Mon. Not. R. Astron. Soc.

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Isolated hot subdwarfs might be formed by the merging of two helium-core white dwarfs. Before merging, helium-core white dwarfs have hydrogen-rich envelopes and some of this hydrogen may survive the merger. We calculate the mass of hydrogen that is present at the start of such mergers and, with the assumption that hydrogen is mixed throughout the disrupted white dwarf in the merger process, estimate how much can survive. We find a hydrogen mass of up to about 2 × 10 −3 M in merger remnants. We make model merger remnants that include the hydrogen mass appropriate to their total mass and compare their atmospheric parameters with a sample of apparently isolated hot subdwarfs, hydrogen-rich sdBs. The majority of these stars can be explained as the remnants of double helium white dwarf mergers.

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A preliminary look at the empirical mass distribution of hot B subdwarf stars

Cited by 112 publications

References 46 publications

A subsynchronously rotating pulsating subdwarf B star in a short-period binary with a white dwarf companion

A subsynchronously rotating pulsating subdwarf B star in a short-period binary with a white dwarf companion

Asteroseismic Signatures of Evolving Internal Stellar Magnetic Fields

Hydrogen in hot subdwarfs formed by double helium white dwarf mergers

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