Orbital Evolution of Compact White Dwarf Binaries

Kaplan, D. L.; Bildsten, Lars; Steinfadt, Justin D. R.

doi:10.1088/0004-637x/758/1/64

Cited by 55 publications

(58 citation statements)

References 67 publications

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“…Marsh (2011) and Kaplan, Bildsten & Steinfadt (2012) present recent compilations from searches for binary WDs. In the current century, the first large survey to search systematically for such WD pairs was SPY (Geier et al 2007, Napiwotzki et al 2004, Nelemans et al 2005.…”

Section: Binary Wdsmentioning

confidence: 99%

Observational Clues to the Progenitors of Type Ia Supernovae

Maoz

Mannucci

Nelemans

2014

Annu. Rev. Astron. Astrophys.

940

894

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Type-Ia supernovae (SNe Ia) are important distance indicators, element factories, cosmic-ray accelerators, kinetic-energy sources in galaxy evolution, and endpoints of stellar binary evolution. It has long been clear that a SN Ia must be the runaway thermonuclear explosion of a degenerate carbon-oxygen stellar core, most likely a white dwarf (WD). However, the specific progenitor systems of SNe Ia, and the processes that lead to their ignition, have not been identified. Two broad classes of progenitor binary systems have long been considered: single-degenerate (SD), in which a WD gains mass from a non-degenerate star; and doubledegenerate (DD), involving the merger of two WDs. New theoretical work has enriched these possibilities with some interesting updates and variants. We review the significant recent observational progress in addressing the progenitor problem. We consider clues that have emerged from the observed properties of the various proposed progenitor populations, from studies of their sites -pre-and post-explosion, from analysis of the explosions themselves, and from the measurement of event rates. The recent nearby and well-studied event, SN 2011fe, has been particularly revealing. The observational results are not yet conclusive, and sometimes prone to competing theoretical interpretations. Nevertheless, it appears that DD progenitors, long considered the underdog option, could be behind some, if not all, SNe Ia. We point to some directions that may lead to future progress.

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Section: Binary Wdsmentioning

confidence: 99%

Observational Clues to the Progenitors of Type Ia Supernovae

Maoz

Mannucci

Nelemans

2014

Annu. Rev. Astron. Astrophys.

940

894

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“…When mass transfer begins, detailed evolutionary and mass transfer calculations (Marsh et al 2004;D'Antona et al 2006;Kaplan et al 2012) will determine whether the objects remain separate (typically resulting in an AM CVn binary) or merge (as a R CrB star or possibly a Type Ia supernova; Iben & Tutukov 1984;Webbink 1984). Essential to determining the fates of these systems (and hence making predictions for lowfrequency gravitational radiation and other end products) is an accurate knowledge of their present properties: their masses determine the in-spiral time and their radii and degrees of degeneracy help determine the stability of mass transfer (Deloye et al 2005;D'Antona et al 2006;Kaplan et al 2012). This is particularly interesting for the ELM WDs, as they are predicted to possess stably burning H envelopes (with ∼10 −3 -10 −2 M of hydrogen) that keep them bright for Gyr (Serenelli et al 2002;Panei et al 2007) and increase their radii compared with "cold," fully degenerate WDs by a factor of two or more.…”

Section: Introductionmentioning

confidence: 99%

Properties of an Eclipsing Double White Dwarf Binary NLTT 11748

Kaplan

Marsh

Walker

et al. 2013

ApJ

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We present high-quality ULTRACAM photometry of the eclipsing detached double white dwarf binary NLTT 11748. This system consists of a carbon/oxygen white dwarf and an extremely low mass (<0.2 M ) helium-core white dwarf in a 5.6 hr orbit. To date, such extremely low-mass white dwarfs, which can have thin, stably burning outer layers, have been modeled via poorly constrained atmosphere and cooling calculations where uncertainties in the detailed structure can strongly influence the eventual fates of these systems when mass transfer begins. With precise (individual precision ≈1%), high-cadence (≈2 s), multicolor photometry of multiple primary and secondary eclipses spanning >1.5 yr, we constrain the masses and radii of both objects in the NLTT 11748 system to a statistical uncertainty of a few percent. However, we find that overall uncertainty in the thickness of the envelope of the secondary carbon/oxygen white dwarf leads to a larger (≈13%) systematic uncertainty in the primary He WD's mass. Over the full range of possible envelope thicknesses, we find that our primary mass (0.136-0.162 M ) and surface gravity (log(g) = 6.32-6.38; radii are 0.0423-0.0433 R ) constraints do not agree with previous spectroscopic determinations. We use precise eclipse timing to detect the Rømer delay at 7σ significance, providing an additional weak constraint on the masses and limiting the eccentricity to e cos ω = (−4 ± 5) × 10 −5 . Finally, we use multicolor data to constrain the secondary's effective temperature (7600±120 K) and cooling age (1.6-1.7 Gyr).

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“…Therefore, the mass transferred will vary from nearly pure H to nearly pure He. Kaplan et al (2012) suggest that the pronounced absence of heavy metals in the X-ray spectra of HM Cnc (Strohmayer 2008) points to an ELM origin that lived a long time before mass-transfer initiation.…”

Section: Nature Of the Secondarymentioning

confidence: 93%

“…We speculate, however, that there might be another explanation for the low metallicity. In a recent investigation of the role of extremely lowmass (ELM, M < 0.2 M ) helium WDs for the orbital evolution of compact WD binaries, the effects of gravitational settling of metals were emphasized (Kaplan et al 2012). It is argued that the long (∼Gyr) life of the ELM WDs prior to Roche-lobe overflow may allow for complete sedimentation of heavier metals from the outermost layers.…”

Section: Nature Of the Secondarymentioning

confidence: 99%

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

Gehron¹,

Nagel²,

Rauch³

et al. 2014

A&A

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Context. AM Canum Venaticorum stars are close, interacting binary systems with a white dwarf primary surrounded by a heliumdominated accretion disk. Because of the short orbital periods, the unseen secondary must be compact, too. Different evolutionary scenarios for the formation of these systems resulting in different kinds of secondaries are possible. Aims. Quantitative spectral analyses of accretion-disk spectra can reveal the nature of the secondary. We investigate a particular AM CVn system, discovered recently by the Palomar Transient Factory, PTF 09hpk. It is the only known AM CVn star exhibiting unambiguously both outbursts and superoutbursts. We characterize the accretion disk in quiescence and determine abundances of trace elements. Methods. We calculated line-blanketed nonlocal thermodynamic equilibrium (non-LTE) models and computed accretion-disk spectra by self-consistent solution of radiative transfer and vertical structure equations. These are compared to optical spectra taken during quiescence. Results. In quiescence, the disk has a uniform effective temperature of 6000 K. An optically thin boundary layer causes the observed He ii λ 4686 Å emission feature. The disk around the massive white dwarf primary (1.2 M ) is dominated by helium and is strongly hydrogen-deficient (<−5 dex relative to the solar value). For heavy elements (C, N, O, Mg, Si, Fe), we find moderate to strong subsolar abundances, with depletions down to −2.5 dex for iron. The N/O ratio is >10. Conclusions. According to the high N/O ratio, the secondary of PTF 09hpk is either a helium white dwarf or a helium star. The low metallicity points to a halo origin of the system or it might be the consequence of heavy-metal sedimentation if the secondary is an old, low-mass helium white dwarf.

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Orbital Evolution of Compact White Dwarf Binaries

Cited by 55 publications

References 67 publications

Observational Clues to the Progenitors of Type Ia Supernovae

Observational Clues to the Progenitors of Type Ia Supernovae

Properties of an Eclipsing Double White Dwarf Binary NLTT 11748

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

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