Companion stars of type Ia supernovae and hypervelocity stars

Wang, Bo; Han, Zhanwen

doi:10.1051/0004-6361/200913326

Cited by 92 publications

(98 citation statements)

References 52 publications

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“…Identification of these remnant objects would help to support this scenario. The surviving companions from the model might also explain hypervelocity helium-rich stars like US 708 (e.g., Hirsch et al 2005) because of the short orbital periods at the moment of SN explosion (see also Justham et al 2009;Wang & Han 2009) 4 . Geier et al (2013) suggested that the CO WD + sdB system CD−30 11223 and the hypervelocity star US 708 might represent two different stages of an evolutionary sequence linked by an SN Ia explosion (the orbital velocity of the sdB at the moment of SN explosion will be about 600 km s −1 and thus close to the Galactic escape velocity).…”

Section: Discussionmentioning

confidence: 99%

Producing Type Iax supernovae from a specific class of helium-ignited WD explosions

Wang

Justham

Han

2013

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Context. It has recently been proposed that one subclass of Type Ia supernovae (SNe Ia) is sufficiently distinct and sufficiently common to be classified separately from the bulk of SNe Ia; the suggested class name is Type Iax supernovae (SNe Iax), after SN 2002cx. However, their progenitors are still uncertain. Aims. We study whether the population properties of this class might be understood if the events originate from a subset of subChandrasekhar mass explosions. In this potential progenitor population, a carbon-oxygen white dwarf (CO WD) accumulates a helium layer from a non-degenerate helium star; ignition of that helium layer then leads to ignition of the CO WD. Methods. We incorporated detailed binary evolution calculations for the progenitor systems into a binary population synthesis model to obtain rates and delay times for these events. Results. The predicted Galactic event rate of these explosions is ∼1.5 × 10 −3 yr −1 according to our standard model, in good agreement with the measured rates of SNe Iax. In addition, predicted delay times are ∼70 Myr−800 Myr, consistent with the fact that most of SNe Iax have been discovered in late-type galaxies. If the explosions are assumed to be double detonations -following current model expectations -then, based on the CO WD masses at explosion, we also estimate the distribution of resulting SN brightness (−13 > ∼ M bol > ∼ −19 mag), which can reproduce the empirical diversity of SNe Iax. Conclusions. We speculate on why binaries with non-degenerate donor stars might lead to SNe Iax if similar systems with degenerate donors do not. We suggest that the high mass of the helium layer necessary for ignition at the lower accretion rates typically delivered from non-degenerate donors might be necessary to produce SN 2002cx-like characteristics, perhaps even by changing the nature of the CO ignition.

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Section: Discussionmentioning

confidence: 99%

Producing Type Iax supernovae from a specific class of helium-ignited WD explosions

Wang

Justham

Han

2013

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“…Recently, Wang & Han (2009) and Justham et al (2009) have suggested a single degenerate SN Ia scenario to explain the formation of the helium sdO US 708. Accordingly, a white dwarf accretes matter from a helium star in a close binary system.…”

Section: Discussionmentioning

confidence: 99%

The Hyper-MUCHFUSS project: probing the Galactic halo with sdB stars

Tillich

Heber

Geier

et al. 2011

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Context. High-velocity stars in the Galactic halo, e.g. the so-called hyper-velocity stars (HVS), are important tracers of the properties of the dark matter halo, in particular its mass. Aims. A search for the fastest stars among hot subdwarfs (sdB) in the halo is carried out to identify HVS, unbound to the Galaxy, and bound population II stars, in order to derive a lower limit to the halo mass. Methods. Based on the SDSS DR6 spectral database we selected stars with high rest-frame velocities. These radial velocity (RV) measurements were verified at several telescopes to exclude RV variable stars. Out of 88 stars observed in the follow-up campaign, 39 stars were found to have constant RVs. For twelve of them we measured a proper motion significantly different from zero and obtained spectroscopic distances from quantitative spectral analysis to construct the full 6D phase space information for a kinematical study.Results. All but one programme sdB show halo characteristics, but can be distinguished as two kinematical groups, one (G1) with the low Galactic rotation typical of halo stars and a second one (G2) with rapid retrograde motion. We also investigate the possibility that the programme stars are not genuine halo stars but ejected from the Galactic disc or bulge. The G1 objects crossed the Galactic plane in the central bulge, whereas the G2 stars did so in the outer Galactic disc. J1211+1437 (G2) is an HVS candidate, as it is unbound to the Galaxy if the standard Galactic potential is adopted. Conclusions. We conclude that in the ejection scenario, G1 stars might have been formed via the slingshot mechanism that invokes acceleration by tidal interaction of a binary with the central supermassive black hole. The G2 stars, however, would originate in the outskirts of the Galactic disc and not in the central bulge. J1211+1437 is the first unbound subdwarf B star, for which we can rule out the slingshot mechanism. Alternatively, we may assume that the stars are old population II stars and so they have to be bound. Then the kinematics of J1211+1437 set a lower limit of 2 × 10 12 M to the mass of the Galactic dark matter halo.

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“…The WD + He stars channel can explain SNe Ia with short delay times ( < ∼ 10 8 yr) (Wang et al 2009a,b;Meng & Yang 2010b), therefore this channel may be related to the young SSSs. In addition, the WD + He star channel may be responsible for the origin of the hypervelocity stars (Wang & Han 2009). The system HD 49798/RXJ 0648.0-418 is confirmation of the existence of a rapidly rotating massive WD + He star system.…”

Section: Discussion and Summarymentioning

confidence: 99%

Helium-star evolutionary channel to super-Chandrasekhar mass type Ia supernovae

Liu

Chen

Wang

et al. 2010

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The recent discovery of several overluminous type Ia supernovae (SNe Ia) indicates that the explosive masses of white dwarfs may significantly exceed the canonical Chandrasekhar-mass limit. Rapid differential rotation may support these massive white dwarfs (WDs). Based on the single-degenerate scenario and assuming that the WDs would differentially rotate when the accretion ratė M > 3 × 10 −7 M yr −1 , we performed the numerical calculations for ∼1000 binary systems consisting of a He star and a CO WD with Eggleton's stellar evolution code. We present the initial parameters in the orbital period − helium star-mass plane (for WD masses of 1.0 M and 1.2 M , respectively), which lead to super-Chandrasekhar mass SNe Ia. Our results indicate that for an initially massive WD of 1.2 M , a large number of SNe Ia may result from super-Chandrasekhar mass WDs. The highest mass of the WD at the moment of the SNe Ia explosion is 1.81 M , but very massive (>1.85 M ) WDs cannot be formed. However, when the initial mass of WDs is 1.0 M , the explosive masses of SNe Ia are nearly uniform, which is consistent with the rareness of super-Chandrasekhar mass SNe Ia in observations.

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Companion stars of type Ia supernovae and hypervelocity stars

Cited by 92 publications

References 52 publications

Producing Type Iax supernovae from a specific class of helium-ignited WD explosions

Producing Type Iax supernovae from a specific class of helium-ignited WD explosions

The Hyper-MUCHFUSS project: probing the Galactic halo with sdB stars

Helium-star evolutionary channel to super-Chandrasekhar mass type Ia supernovae

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