Evaporation of brown dwarfs in AGB envelopes

Harpaz, Amos; Soker, Noam

doi:10.1093/mnras/270.4.734

Cited by 34 publications

(51 citation statements)

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“…There are several good candidates for sub-stellar companions in CVs, but the extra light due to accretion makes it difficult to confirm their masses. 14, 15 3 Short period white dwarfs binaries with low mass companions that do not transfer mass are known as pre-CVs because the loss of orbital angular momentum by gravitational wave radiation (GWR) and other mechanisms will result in the shrinkage of the orbit, the initiation of mass transfer and the formation of a CV. 16 The timescale for WD0137-349 to become a CV through the loss of GWR is about 1.4Ga, at which time the orbit period will be 60 -80 minutes.…”

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confidence: 99%

Survival of a brown dwarf after engulfment by a red giant star

Maxted

Napiwotzki

Dobbie

et al. 2006

Nature

174

201

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Many sub-stellar companions (usually planets but also some brown dwarfs) have been identified orbiting solar-type stars. These stars can engulf their sub-stellar companions when they become red giants. This interaction may explain several outstanding problems in astrophysics 1-5 but is poorly understood, e.g., it is unclear under which conditions a low mass companion will evaporate, survive the interaction unchanged or gain mass. 1, 4, 5 Observational tests of models for this interaction have been hampered by a lack of positively identified remnants, i.e., white dwarf stars with close, sub-stellar companions. The companion to the prewhite dwarf AA Doradus may be a brown dwarf, but the uncertain history of this star and the extreme luminosity difference between the components make it difficult to interpret the observations or to put strong constraints on the models. 6, 7The magnetic white dwarf SDSS J121209.31+013627.7 may have a close brown dwarf companion 8 but little is known about this binary at present. Here we report the discovery of a brown dwarf in a short period orbit around a white dwarf. The properties of both stars in this binary can be directly observed and show that the brown dwarf was engulfed by a red giant but that this had little effect on it.

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mentioning

confidence: 99%

Survival of a brown dwarf after engulfment by a red giant star

Maxted

Napiwotzki

Dobbie

et al. 2006

Nature

174

201

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“…v տ v Ӎ 10 km s rot w nous to singly evolved AGB stars and requires the AGB to be spun up by a companion at least as massive as a brown dwarf (Harpaz & Soker 1994). …”

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confidence: 99%

Why Magnetic Fields Cannot Be the Main Agent Shaping Planetary Nebulae

Soker

2006

PUBL ASTRON SOC PAC

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ABSTRACT. An increasing amount of the literature reports the detection of magnetic fields in asymptotic giant branch (AGB) stars and in central stars of planetary nebulae (PNe). These detections lead to claims that the magnetic fields are the main agent shaping the PNe. In this paper, I examine the energy and angular momentum carried by magnetic fields expelled from AGB stars, as well as other physical phenomena that accompany the presence of large-scale fields, such as those claimed in the literature. I show that a single star cannot supply the energy and angular momentum if the magnetic fields have the large coherent structure required to shape the circumstellar wind. Therefore, the structure of nonspherical planetary nebulae cannot be attributed to dynamically important large-scale magnetic fields. I conclude that the observed magnetic fields around evolved stars can be understood with respect to locally enhanced magnetic loops, which can have a secondary role in the shaping of the PN. The primary role, I argue, rests with the presence of a companion.

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“…(1) In the above listed studies the contribution of the planet to the ejected mass was lower than half. The largest contribution of the planet mass is in the calculations of Harpaz & Soker (1994), where for four cases a planet of mass 0.01M ⊙ was destroyed inside an AGB envelope of mass 0.02M ⊙ . (2) The planet in these studied were destroyed near a hot core that still has a hydrogen burning in a shell.…”

Section: Real Planetary Nebula (Rpn) Formationmentioning

confidence: 99%

Planetary systems and real planetary nebulae from planet destruction near white dwarfs

Bear

Soker

2015

Monthly Notices of the Royal Astronomical Society

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We suggest that tidal destruction of Earth-like and icy planets near a white dwarf (WD) might lead to the formation of one or more low-mass − Earthlike and lighter − planets in tight orbits around the WD. The formation of the new WD planetary system starts with a tidal break-up of the parent planet to planetesimals near the tidal radius of about 1R ⊙ . Internal stress forces keep the planetesimal from further tidal break-up when their radius is less than about 100 km. We speculate that the planetesimals then bind together to form new subEarth daughter-planets at a few solar radii around the WD. More massive planets that contain hydrogen supply the WD with fresh nuclear fuel to reincarnate its stellar-giant phase. Some of the hydrogen will be inflated in a large envelope. The envelope blows a wind to form a nebula that is later (after the entire envelope is lost) ionized by the hot WD. We term this glowing ionized nebula that originated from a planet a real planetary nebula (RPN). This preliminary study of daughterplanets from a planet (DPP) and the RPN scenarios are of speculative nature. More detail studies must follow to establish whether the suggested scenarios can indeed take place.

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Evaporation of brown dwarfs in AGB envelopes

Cited by 34 publications

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Survival of a brown dwarf after engulfment by a red giant star

Survival of a brown dwarf after engulfment by a red giant star

Why Magnetic Fields Cannot Be the Main Agent Shaping Planetary Nebulae

Planetary systems and real planetary nebulae from planet destruction near white dwarfs

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