Non-LTE spectral analysis of the AM CVn system PTF 09hpk during quiescence

Gehron, K.; Nagel, T.; Rauch, T.; Werner, K.

doi:10.1051/0004-6361/201322180

Cited by 5 publications

(5 citation statements)

References 39 publications

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“…None of the systems show a halo orbit. In a small number of AM CVn stars, the extreme depletion of heavy elements have been taken as evidence that these stars were halo objects (GP Com: Marsh et al (1991); V396 Hya: Nagel et al (2009) and PTF1 J0719+4858: Gehron et al (2014). Our study has shown that these AM CVn stars are likely thin or thick disk objects and not halo objects.…”

Section: Galactic Distributionmentioning

confidence: 55%

Physical properties of AM CVn stars: New insights fromGaiaDR2

Ramsay

Green

Marsh

et al. 2018

A&A

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AM CVn binaries are hydrogen deficient compact binaries with an orbital period in the 5-65 min range and are predicted to be strong sources of persistent gravitational wave radiation. Using Gaia Data Release 2, we present the parallaxes and proper motions of 41 out of the 56 known systems. Compared to the parallax determined using the HST Fine Guidance Sensor we find that the archetype star, AM CVn, is significantly closer than previously thought. This resolves the high luminosity and mass accretion rate which models had difficulty in explaining. Using Pan-STARRS1 data we determine the absolute magnitude of the AM CVn stars. There is some evidence that donor stars have a higher mass and radius than expected for white dwarfs or that the donors are not white dwarfs. Using the distances to the known AM CVn stars we find strong evidence that a large population of AM CVn stars have still to be discovered. As this value sets the background to the gravitational wave signal of LISA this is of wide interest. We determine the mass transfer rate for 15 AM CVn stars and find that the majority have a rate significantly greater than expected from standard models. This is further evidence that the donor star has a greater size than expected.

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Section: Galactic Distributionmentioning

confidence: 55%

Physical properties of AM CVn stars: New insights fromGaiaDR2

Ramsay

Green

Marsh

et al. 2018

A&A

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“…Radial velocity measurements show that these lines originate from the white dwarf (Marsh 1999;Roelofs et al 2005;Kupfer et al 2015) and is likely boundary layer emission from the surface of the white dwarf (e.g. Green et al 2019a;Gehron et al 2014).…”

Section: The Average Spectra and Spectral Linesmentioning

confidence: 99%

Discovery and characterization of five new eclipsing AM CVn systems

Roestel

Kupfer

Green

et al. 2021

Monthly Notices of the Royal Astronomical Society

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AM CVn systems are ultra-compact, hydrogen-depleted and helium-rich, accreting binaries with degenerate or semi-degenerate donors. We report the discovery of five new eclipsing AM CVn systems with orbital periods of 61.5, 55.5, 53.3, 37.4, and 35.4 minutes. These systems were discovered by searching for deep eclipses in the Zwicky Transient Facility (ZTF) lightcurves of white dwarfs selected using Gaia parallaxes. We obtained phase-resolved spectroscopy to confirm that all systems are AM CVn binaries, and we obtained high-speed photometry to confirm the eclipse and characterize the systems. The spectra show double-peaked He-lines but also show metals, including K and Zn, elements that have never been detected in AM CVn systems before. By modelling the high-speed photometry, we measured the mass and radius of the donor star, potentially constraining the evolutionary channel that formed these AM CVn systems. We determined that the average mass of the accreting white dwarf is ≈0.8 M⊙, and that the white dwarfs in long-period systems are hotter than predicted by recently updated theoretical models. The donors have a high entropy and are a factor of ≈ 2 more massive compared to zero-entropy donors at the same orbital period. The large donor radius is most consistent with He-star progenitors, although the observed spectral features seem to contradict this. The discovery of 5 new eclipsing AM CVn systems is consistent with the known observed AM CVn space density and estimated ZTF recovery efficiency.

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“…In the latter case a red-giant like extended envelope forms and components, most probably, merge 1 . Thus, the existing interacting double-degenerates should start their evolution with Ṁ∼ 10 −6 M⊙ yr −1 and may evolve in a Hubble time to Ṁ∼ 10 −12 M⊙ yr −1 as it is theoretically inferred (Tutukov & Yungelson 1979;Nelemans et al 2001;Deloye et al 2007) and supported by the analysis of the spectra of several AM CVn stars (Krausz et al 2010;Gehron et al 2014).…”

Section: Introductionmentioning

confidence: 74%

He-accreting WDs: AM CVn stars with WD donors

Piersanti

Yungelson

Tornambé

2015

Mon. Not. R. Astron. Soc.

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We study the physical and evolutionary properties of the "WD family" of AM CVn stars by computing realistic models of Interacting Double-Degenerate systems. We evaluate selfconsistently both the mass transfer rate from the donor, as determined by gravitational wave emission and interaction with the binary companion, and the thermal response of the accretor to mass deposition. We find that, after the onset of mass transfer, all the considered systems undergo a strong non-dynamical He-flash. However, due to the compactness of these systems, the expanding accretors fill their Roche lobe very soon, thus preventing the efficient heating of the external layers of the accreted CO WDs. Moreover, due to the loss of matter from the systems, the orbital separations enlarge and mass transfer comes to a halt. The further evolution depends on the value ofṀ after the donors fill again their lobe. On one hand, if the accretion rate, as determined by the actual value of (M don , M acc ), is high enough, the accretors experience several He-flashes of decreasing strength and then quiescent Heburning sets in. Later on, since the mass transfer rate in IDD is a permanently decreasing function of time, accretors experience several recurrent strong flashes. On the other hand, for intermediate and low values ofṀ the accretors enter directly the strong flashes accretion regime. As expected, in all the considered systems the last He-flash is the strongest one, even if the physical conditions suitable for a dynamical event are never attained. When the mass accretion rate decreases below (2 − 3) × 10 −8 M ⊙ yr −1 , the compressional heating of the He-shell becomes less efficient than the neutrino cooling, so that all the accretors in the considered systems evolve into massive degenerate objects. Our results suggest that SN .Ia or type Ia Supernovae due to Edge-Lit Detonation in the WD family of AM CVn stars should be much more rare than previously expected.

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Non-LTE spectral analysis of the AM CVn system PTF 09hpk during quiescence

Cited by 5 publications

References 39 publications

Physical properties of AM CVn stars: New insights fromGaiaDR2

Physical properties of AM CVn stars: New insights fromGaiaDR2

Discovery and characterization of five new eclipsing AM CVn systems

He-accreting WDs: AM CVn stars with WD donors

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