Two new double-lined spectroscopic binary white dwarfs

Kilic, Mukremin; Bédard, Antoine; Bergeron, P.; Kosakowski, Alekzander

doi:10.1093/mnras/staa466

Cited by 18 publications

(15 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This is not surprising as low-mass white dwarfs are over-represented in magnitude-limited surveys due to their larger radii and luminosities. A caveat here is that our mass estimates for low-mass white dwarfs may be erroneous since they were based on the assumption of a single star, and that low-mass white dwarfs are usually found in binary systems (Marsh et al 1995;Kilic et al 2020). Hence, further observations would be useful for constraining the binary nature of these systems and the mass distribution below 0.5 M .…”

Section: The Da Mass Distributionmentioning

confidence: 98%

The 100 pc White Dwarf Sample in the SDSS Footprint

Kilic,

Bergeron,

Kosakowski

et al. 2020

Preprint

Self Cite

View full text Add to dashboard Cite

We present follow-up spectroscopy of 711 white dwarfs within 100 pc, and present a detailed model atmosphere analysis of the 100 pc white dwarf sample in the SDSS footprint. Our spectroscopic followup is complete for 83% of the white dwarfs hotter than 6000 K, where the atmospheric composition can be constrained reliably. We identify 1508 DA white dwarfs with pure hydrogen atmospheres. The DA mass distribution has an extremely narrow peak at 0.59 M , and reveals a shoulder from relatively massive white dwarfs with M = 0.7-0.9 M . Comparing this distribution with binary population synthesis models, we find that the contribution from single stars that form through mergers cannot explain the over-abundance of massive white dwarfs. In addition, the mass distribution of cool DAs shows a near absence of M > 1 M white dwarfs. The pile-up of 0.7-0.9 M and the disappearance of M > 1 M white dwarfs is consistent with the effects of core crystallization. Even though the evolutionary models predict the location of the pile-up correctly, the delay from the latent heat of crystallization by itself is insufficient to create a significant pile-up, and additional cooling delays from related effects like phase separation are necessary. We also discuss the population of infrared-faint (ultracool) white dwarfs, and demonstrate for the first time the existence of a well defined sequence in color and magnitude. Curiously, this sequence is connected to a region in the color-magnitude diagrams where the number of helium-dominated atmosphere white dwarfs is low. This suggests that the infrared-faint white dwarfs likely have mixed H/He atmospheres.

show abstract

Section: The Da Mass Distributionmentioning

confidence: 98%

The 100 pc White Dwarf Sample in the SDSS Footprint

Kilic,

Bergeron,

Kosakowski

et al. 2020

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…We use de-reddened GALEX FUV and NUV (Martin et al 2005), SkyMapper ugriz (Onken et al 2019), and VISTA Hemisphere Survey Y JK s photometry (McMahon et al 2021). Since the observed flux can be expressed as a combination of the individual contributions of the two components, the free parameters usually involved in this fitting process are the four atmospheric parameters T eff,1 , log g 1 , T eff,2 , log g 2 , plus the distance D (see Bédard et al 2017;Kilic et al 2020, for details). In the present case, the distance is known from the Gaia parallax, and the surface gravities can be obtained from our mass estimates together with the mass-radius relation of Althaus et al (2013).…”

Section: Binary Parametersmentioning

confidence: 99%

The Discovery of Two LISA Sources within 0.5 kpc

Kilic,

Brown,

Bedard

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

We report the discovery of the brightest detached binary white dwarfs with periods less than an hour, which provide two new gravitational wave verification binaries for the Laser Interferometer Space Antenna (LISA). The first one, SMSS J033816.16−813929.9 (hereafter J0338), is a 30.6 min orbital period, g = 17.2 mag detached double white dwarf binary with a Gaia parallax measurement that places it at a distance of 533 pc. The observed radial velocity and photometric variability provide precise constraints on the system parameters. J0338 contains a 0.230 ± 0.015 M white dwarf with a 0.38 +0.05 −0.03 M companion at an inclination of 69 ± 9 • . The second system, SDSS J063449.92+380352.2 (hereafter J0634), is a 26.5 min orbital period, g = 17.0 mag detached double white dwarf binary at a distance of 435 pc. J0634 contains a 0.452 +0.070 −0.062 M white dwarf with a 0.209 +0.034 −0.021 M companion at an inclination of 37 ± 7 • . The more massive white dwarf in J0634 is hotter than its companion, even though tidal dissipation is predicted to be relatively inefficient at such periods. This suggests that the more massive white dwarf formed last. J0338 and J0634 will be detected by LISA with a signal-to-noise ratio of 5 and 19, respectively, after four years. We identified these two systems based on their overluminosity and u-band photometry. Follow-up of u-band selected Gaia targets will likely yield additional LISA verification binaries.

show abstract

“…We use the same procedures as in Kilic et al (2020) to measure radial velocities for our targets. Briefly, we use a quadratic polynomial plus two Lorentzians (one for each line) to fit the H𝛼 line cores.…”

Section: Radial Velocity Measurementsmentioning

confidence: 99%

“…Trigonometric parallax measurements provide an opportunity to find SB2 white dwarfs through their over-luminosity. Bédard et al (2017) used a sample of 219 white dwarfs with parallax measurements to identify more than a dozen over-luminous white dwarfs, and Kilic et al (2020) confirmed binarity in at least nine out of 13 of these systems, including four SB2 white dwarfs. Similarly, Hollands et al (2018) analyzed the nearly complete Gaia 20 pc white dwarf sample of 139 stars, and identified several over-luminous binary candidates, including L 870-2.…”

Section: Introductionmentioning

confidence: 96%

Hidden in Plain Sight: A Double-lined White Dwarf Binary 26 pc Away and a Distant Cousin

Kilic,

Bedard,

Bergeron

2021

Preprint

Self Cite

View full text Add to dashboard Cite

We present high-resolution spectroscopy of two nearby white dwarfs with inconsistent spectroscopic and parallax distances. The first one, PG 1632+177, is a 13th magnitude white dwarf only 25.6 pc away. Previous spectroscopic observations failed to detect any radial velocity changes in this star. Here, we show that PG 1632+177 is a 2.05 d period double-lined spectroscopic binary (SB2) containing a low-mass He-core white dwarf with a more-massive, likely CO-core white dwarf companion. After L 870-2, PG 1632+177 becomes the second closest SB2 white dwarf currently known. Our second target, WD 1534+503, is also an SB2 system with an orbital period of 0.71 d. For each system, we constrain the atmospheric parameters of both components through a composite model-atmosphere analysis. We also present a new set of NLTE synthetic spectra appropriate for modeling high-resolution observations of cool white dwarfs, and show that NLTE effects in the core of the H𝛼 line increase with decreasing effective temperature. We discuss the orbital period and mass distribution of SB2 and eclipsing double white dwarfs with orbital constraints, and demonstrate that the observed population is consistent with the predicted period distribution from the binary population synthesis models. The latter predict more massive CO + CO white dwarf binaries at short (< 1 d) periods, as well as binaries with several day orbital periods; such systems are still waiting to be discovered in large numbers.

show abstract

Two new double-lined spectroscopic binary white dwarfs

Cited by 18 publications

References 40 publications

The 100 pc White Dwarf Sample in the SDSS Footprint

The 100 pc White Dwarf Sample in the SDSS Footprint

The Discovery of Two LISA Sources within 0.5 kpc

Hidden in Plain Sight: A Double-lined White Dwarf Binary 26 pc Away and a Distant Cousin

Contact Info

Product

Resources

About