A Gravitational Redshift Determination of the Mean Mass of White Dwarfs. Da Stars

Falcon, Ross E.; Winget, D. E.; Montgomery, M. H.; Williams, Kurtis A.

doi:10.1088/0004-637x/712/1/585

Cited by 110 publications

(140 citation statements)

References 70 publications

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“…We therefore adopt 0.8-0.9 M as a typical mass for the primary star, and, fortunately, the method is not too sensitive to that assumption, given the way f (M 1 , M 2 ) = M 3 2 sin 3 i/(M 1 + M 2 ) 2 depends on M 1 . Figure 3 presents the distribution of the secondary masses M 2 , which are peaked in the range 0.5-0.7 M (with one exception), as expected for white-dwarf companions originating from the thermally-pulsing asymptotic giant branch (Falcon et al 2010). To confirm the robustness of that conclusion, Fig.…”

Section: Massessupporting

confidence: 57%

Binary properties of CH and carbon-enhanced metal-poor stars

Jorissen

Eck

Winckel

et al. 2016

A&A

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The HERMES spectrograph installed on the 1.2-m Mercator telescope has been used to monitor the radial velocity of 13 lowmetallicity carbon stars, among which seven carbon-enhanced metal-poor (CEMP) stars and six CH stars (including HIP 53522, a new member of the family, as revealed by a detailed abundance study). All stars but one show clear evidence for binarity. New orbits are obtained for eight systems. The sample covers an extended range in orbital periods, extending from 3.4 d (for the dwarf carbon star HE 0024-2523) to about 54 yr (for the CH star HD 26, the longest known among barium, CH, and extrinsic S stars). Three systems exhibit low-amplitude velocity variations with periods close to 1 yr superimposed on a long-term trend. In the absence of an accurate photometric monitoring of these systems, it is not clear yet whether these variations are the signature of a very lowmass companion or of regular envelope pulsations. The period -eccentricity (P − e) diagram for the 40 low-metallicity carbon stars with orbits now available shows no difference between CH and CEMP-s stars (the latter corresponding to those CEMP stars enriched in s-process elements, as are CH stars). We suggest that they must be considered as one and the same family and that their different names only stem from historical reasons. Indeed, these two families have as well very similar mass-function distributions, corresponding to companions with masses in the range 0.5-0.7 M , indicative of white-dwarf companions, adopting 0.8-0.9 M for the primary component. This result confirms that CH and CEMP-s stars obey the same mass-transfer scenario as their highermetallicity analogues, barium stars. The P − e diagrams of barium, CH, and CEMP-s stars are indeed very similar. They reveal two different groups of systems: one with short orbital periods (P < 1000 d) and mostly circular or almost circular orbits, and another with longer period and eccentric (e > 0.1) orbits. These two groups either trace different evolutionary channels during the mass-transfer episode responsible for the chemical peculiarities of the Ba/CH/CEMP-s stars, or result from the operation of tidal circularisation in a more recent past, when the current giant star was ascending the first giant branch.

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Section: Massessupporting

confidence: 57%

Binary properties of CH and carbon-enhanced metal-poor stars

Jorissen

Eck

Winckel

et al. 2016

A&A

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“…However, current initial-final mass relations (Catalán et al 2008;Renedo et al 2010) imply that this would be a very small effect on the mean mass as a function of cooling age. Furthermore, the masses determined from parallax, photometric, and gravitational redshift observations do not show evidences of higher masses for convective objects (Koester et al 2009a;Tremblay et al 2010;Falcon et al 2010).…”

Section: Introductionmentioning

confidence: 81%

Spectroscopic analysis of DA white dwarfs with 3D model atmospheres

Tremblay

Ludwig

Steffen

et al. 2013

A&A

219

334

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We present the first grid of mean three-dimensional (3D) spectra for pure-hydrogen (DA) white dwarfs based on 3D model atmospheres. We use CO 5 BOLD radiation-hydrodynamics 3D simulations instead of the mixing-length theory for the treatment of convection. The simulations cover the effective temperature range of 6000 < T eff (K) < 15 000 and the surface gravity range of 7 < log g < 9 where the large majority of DAs with a convective atmosphere are located. We rely on horizontally averaged 3D structures (over constant Rosseland optical depth) to compute 3D spectra. It is demonstrated that our 3D spectra can be smoothly connected to their 1D counterparts at higher and lower T eff where the 3D effects are small. Analytical functions are provided in order to convert spectroscopically determined 1D effective temperatures and surface gravities to 3D atmospheric parameters. We apply our improved models to well studied spectroscopic data sets from the Sloan Digital Sky Survey and the White Dwarf Catalog. We confirm that the so-called high-log g problem is not present when employing 3D spectra and that the issue was caused by inaccuracies in the 1D mixing-length approach. The white dwarfs with a radiative and a convective atmosphere have derived mean masses that are the same within ∼0.01 M , in much better agreement with our understanding of stellar evolution. Furthermore, the 3D atmospheric parameters are in better agreement with independent T eff and log g values from photometric and parallax measurements.

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“…If consistent with the predicted Hyades radial velocity, the probability of contamination is very low (see Table 3). Due to the extreme broadening of the spectral lines, the spectroscopic measurement of the radial velocity of white dwarfs is extremely difficult to obtain, and only possible with the help of the narrow NLTE cores of H α (Greenstein et al 1977;Koester 1987;Falcon et al 2010). Since this measurement must be corrected for the gravitational redshift, typically ∼40 km s −1 , such a determination is only possible if we have a good knowledge of the mass.…”

Section: Discussionmentioning

confidence: 99%

Spectroscopic and photometric studies of white dwarfs in the Hyades

Tremblay

Schilbach

Röser

et al. 2012

A&A

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The Hyades cluster is known to harbour ten so-called classical white dwarf members. Numerous studies through the years have predicted that more than twice this amount of degenerate stars should be associated with the cluster. Using the PPMXL Catalog of proper motions and positions, a recent study proposed 17 new white dwarf candidates. We review the membership of these candidates by using published spectroscopic and photometric observations, as well as by simulating the contamination from field white dwarfs. In addition to the ten classical Hyades white dwarfs, we find six white dwarfs that may be of Hyades origin and three more objects that have an uncertain membership status due to their unknown or imprecise atmospheric parameters. Among those, two to three are expected as field stars contamination. Accurate radial velocity measurements will confirm or reject the candidates. One consequence is that the longstanding problem that no white dwarf older than ∼340 Myr appears to be associated with the cluster remains unsolved.

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A Gravitational Redshift Determination of the Mean Mass of White Dwarfs. Da Stars

Cited by 110 publications

References 70 publications

Binary properties of CH and carbon-enhanced metal-poor stars

Binary properties of CH and carbon-enhanced metal-poor stars

Spectroscopic analysis of DA white dwarfs with 3D model atmospheres

Spectroscopic and photometric studies of white dwarfs in the Hyades

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