Am Canum Venaticorum Progenitors With Helium Star Donors and the Resultant Explosions

Brooks, Jared; Bildsten, Lars; Marchant, Pablo; Paxton, Bill

doi:10.1088/0004-637x/807/1/74

Cited by 52 publications

(72 citation statements)

References 42 publications

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“…The first is a 0.4 M He star donating onto a 0.8 M WD, and the second is the same donor model with a 1.0 M WD accretor. These correspond to panels 2 and 4 in figures 12 and 13 from Brooks et al (2015).…”

Section: The First Flash After Contactsupporting

confidence: 57%

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Electron Captures on as a Trigger for Helium Shell Detonations

Bauer

Schwab

Bildsten

2017

ApJ

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White dwarfs (WDs) that accrete helium at rates ∼ 10 −8 M yr −1 , such as those in close binaries with sdB stars, can accumulate large ( 0.1 M ) helium envelopes which are likely to detonate. We perform binary stellar evolution calculations of sdB+WD binary systems with MESA, incorporating the important reaction chain, including a recent measurement for the 14 C(α, γ) 18 O rate. In large accreted helium shells, the NCO reaction chain leads to ignitions at the dense base of the freshly accreted envelope, in contrast to 3α ignitions which occur away from the base of the shell. In addition, at these accretion rates, the shells accumulate on a timescale comparable to their thermal time, leading to an enhanced sensitivity of the outcome on the accretion rate history. Hence, time dependent accretion rates from binary stellar evolution are necessary to determine the helium layer mass at ignition. We model the observed sdB+WD system CD −30• 11223 and find that the inclusion of these effects predicts ignition of a 0.153 M helium shell, nearly a factor of two larger than previous predictions. A shell with this mass will ignite dynamically, a necessary condition for a helium shell detonation.

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Section: The First Flash After Contactsupporting

confidence: 57%

“…The latter case assumesṀ = 1.93 × 10 −8 M yr −1 , the time-average of the accretion rate from the binary evolution calculations of Brooks et al (2015). Both models here include the NCO reaction chain.…”

Section: The First Flash In CD −30mentioning

confidence: 99%

Electron Captures on as a Trigger for Helium Shell Detonations

Bauer

Schwab

Bildsten

2017

ApJ

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“…Note that WD+He star systems are also involved in the formation of some peculiar types of systems, such as AM CVn binaries (e.g. Nelemans et al 2001;Brooks et al 2015;Piersanti, Tornambé & Yungelson 2015) and double CO WDs (e.g. Ruiter et al 2013;Liu et al 2016).…”

Section: Introductionmentioning

confidence: 99%

He-accreting carbon–oxygen white dwarfs and Type Ia supernovae

Wang

Podsiadlowski

Han

2017

Monthly Notices of the Royal Astronomical Society

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He accretion onto carbon-oxygen white dwarfs (CO WDs) plays a fundamental role when studying the formation of type Ia supernovae (SNe Ia). Employing the MESA stellar evolution code, we calculated the long-term evolution of Heaccreting CO WDs. Previous studies usually supposed that a WD can grow in mass to the Chandrasekhar limit in the stable He burning region and finally produce a SN Ia. However, in this study we find that off-centre carbon ignition occurs in the stable He burning region if the accretion rate is above a critical value (∼2.05 × 10 −6 M ⊙ yr −1 ), resulting in accretion-induced collapse rather than a SN Ia. If the accretion rate is below the critical value, explosive carbon ignition will eventually happen in the centre producing a SN Ia. Taking into account the possibility of off-centre carbon ignition, we have re-determined the initial parameter space that produces SNe Ia in the He star donor channel, one of the promising channels to produce SNe Ia in young populations. Since this parameter space is smaller than was found in the previous study of Wang et al. (2009), the SN Ia rates are also correspondingly smaller. We also determined the chemical abundance profile of the He-accreting WDs at the moment of explosive carbon ignition, which can be used as initial input for SN Ia explosion models.

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“…Mass transfer starts at orbital periods ranging from 16 to 50 minutes. Subsequently, the semi-detached system evolves to shorter periods with typical mass-transfer rates of » -M 10 8  M yr −1 (e.g., Savonije et al 1986;Yungelson 2008;Piersanti et al 2014;Brooks et al 2015).…”

Section: Introductionmentioning

confidence: 99%

PTF1 J082340.04+081936.5: A Hot Subdwarf B Star with a Low-mass White Dwarf Companion in an 87-minute Orbit

Kupfer

Roestel

Brooks

et al. 2017

ApJ

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We present the discovery of the hot subdwarf B star (sdB) binary PTF1 J082340.04+081936.5. The system has an orbital period of P orb =87.49668(1) minutes (0.060761584(10) days), making it the second-most compact sdB binary known. The lightcurve shows ellipsoidal variations. Under the assumption that the sdB primary is synchronized with the orbit, we find a mass of M , we find that the sdB still burns helium at the time it will fill its Roche lobe if the orbital period was less than 106 minutes at the exit from the last common envelope (CE) phase. For longer CE exit periods, the sdB will have stopped burning helium and turned into a C/O white dwarf at the time of contact. Comparing the spectroscopically derived g log and T eff with our MESA models, we find that an sdB model with a hydrogen envelope mass of´- M 5 10 4 matches the measurements at a post-CE age of 94 Myr, corresponding to a post-CE orbital period of 109 minutes, which is close to the limit to start accretion while the sdB is still burning helium.

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Am Canum Venaticorum Progenitors With Helium Star Donors and the Resultant Explosions

Cited by 52 publications

References 42 publications

Electron Captures on as a Trigger for Helium Shell Detonations

Electron Captures on as a Trigger for Helium Shell Detonations

He-accreting carbon–oxygen white dwarfs and Type Ia supernovae

PTF1 J082340.04+081936.5: A Hot Subdwarf B Star with a Low-mass White Dwarf Companion in an 87-minute Orbit

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