A precision study of two eclipsing white dwarf plus M dwarf binaries

Parsons, S. G.; Marsh, T. R.; Gänsicke, B. T.; Rebassa‐Mansergas, A.; Dhillon, V. S.; Littlefair, S. P.; Copperwheat, C. M.; Hickman, Richard; Burleigh, M. R.; Kerry, P.; Koester, D.; Gómez‐Morán, A. Nebot; Pyrzas, S.; Savoury, C. D. J.; Schreiber, M. R.; Schmidtobreick, L.; Schwope, A. D.; Steele, P. R.; Tappert, C.

doi:10.1111/j.1365-2966.2011.20251.x

Cited by 35 publications

(27 citation statements)

References 67 publications

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“…However, it is highly probable that the emission originates only from the heated hemisphere of the companion, and a more accurate estimate of the physical and binary parameters can be made by assuming the companion emission is uniformly spread across the inner hemisphere. This approach has been substantiated by observations of spectroscopic binaries where the secondary exhibits both heated emission and intrinsic absorption components (38).…”

Section: Methodsmentioning

confidence: 92%

“…If the white dwarf were instead accreting wind from the substellar companion, it would be an unexpected find; all known or suspected wind-accreting white dwarfs are in polars or detached binaries with stellar (M-type) companions (38). In the case that such material is optimally captured in a Bondi-Hoyle flow onto SDSS 1557, the required mass-loss from the companion can be expressed as (26):…”

Section: Methodsmentioning

confidence: 99%

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A circumbinary debris disk in a polluted white dwarf system

2017

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Planetary systems commonly survive the evolution of single stars, as evidenced by terrestrial-like planetesimal debris observed orbiting and polluting the surfaces of white dwarfs (1, 2). This letter reports the identification of a circumbinary dust disk surrounding a white dwarf with a substellar companion in a 2.27 hr orbit. The system bears the dual hallmarks of atmospheric metal pollution and infrared excess (3, 4), however the standard (flat and opaque) disk configuration is dynamically precluded by the binary. Instead, the detected reservoir of debris must lie well beyond the Roche limit in an optically thin configuration, where erosion by stellar irradiation is relatively rapid. This finding demonstrates that rocky planetesimal formation is robust around close binaries, even those with low mass ratios. 1The formation and evolution of planetary systems around close binary stars is a challengingproblem, yet provides insight into the growth of planetesimals within evolving protoplanetary disks and planet formation in general. The small but increasing number of transiting circumbinary planets detected with Kepler (5, 6) are providing the first tests of theoretical formation models. To date, it has been shown that in situ formation is unfavorable for most of these Neptune-to Jupiter-sized bodies due to the destructive, dynamical effects of the central binary on planetesimal agglomeration in the regions where the planets currently orbit (7,8,9). However, for a range of masses including small planets, recent models predict favorable conditions for planetesimal growth within the snow line, and thus promoting efficient terrestrial planet formation around binaries (10,11,12).Atmospheric pollution in white dwarf stars offers a unique and powerful window into the assembly and chemistry of terrestrial exoplanets. There are now more than three dozen planetary system remnants made evident based on thermal and line emission from circumstellar disks (2), and several hundred where photospheric metals indicate ongoing or recent accretion of planetary debris (13). The current paradigm of disrupted and accreted asteroids has been unequivocally confirmed by numerous studies, including the recent detection of complex and rapidly evolving photometric transits from debris fragments orbiting near the Roche limit of one star (14,15, 16). To date, all polluted white dwarfs with detailed analyses indicate the sources are rocky planetesimals comparable in both mass and composition to large Solar System asteroids (17, 18,1), and thus objects that formed within a snow line. These findings unambiguously demonstrate that large planetesimal formation in the terrestrial zone of stars is robust and common.Until now, over 90% of such dusty and polluted white dwarf systems have been discovered among single stars, with a small fraction belonging to sufficiently wide binaries (a ≫ 100 AU) where the evolution of each star -and any associated planetary system -proceeds as a singleton. The white dwarf SDSS J155720.77+091624.6 (hereafter SDSS 1557) ...

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Section: Methodsmentioning

confidence: 92%

Section: Methodsmentioning

confidence: 99%

A circumbinary debris disk in a polluted white dwarf system

2017

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“…For stars in a binary system with a white dwarf, the pollution of the white dwarf photosphere from the wind of the companion may leave a detectable trace in the white dwarf spectrum. Modelling of this process provides estimates of the wind outflow rates (Debes 2006;Parsons et al 2012). Most recently, the interaction of the escaping atmosphere of a planet with the stellar wind has provided a means of measuring the mass loss rate of the stellar wind (Bourrier et al 2016;Vidotto & Bourrier 2017;Kislyakova et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Slingshot prominences: nature’s wind gauges

Jardine

Cameron

2018

Monthly Notices of the Royal Astronomical Society

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Mass loss rates for the tenuous, hot winds of cool stars are extremely difficult to measure, yet they are a crucial ingredient in the stars' rotational evolution. We present a new method for measuring these mass loss rates in young, rapidly-rotating stars. These stars are known to support systems of "slingshot prominences" fed by hot wind material flowing up from the stellar surface into the summits of closed magnetic loop structures. The material gathers and cools near the co-rotation radius until its density becomes large enough that it is visible as a transient absorption feature in the hydrogen Balmer lines and strong resonance lines such as Ca II H & K. Here we present the key insight that the sonic point usually lies well below the condensation region. The flow at the wind base is therefore unaffected by the presence of an overlying prominence, so we can use the observed masses and recurrence times of the condensations to estimate the mass flux in the wind. These measurements extend the relationship between mass loss rate per unit surface area and X-ray flux to span 5 orders of magnitude. They demonstrate no evidence of the suspected weakening of stellar mass loss rates at high X-ray flux levels.

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“…Table 1 summarises the mass-loss rates inferred for dM stars, where the dM stars in close binary systems are marked with an asterisk. For the interacting stars where only massaccretion rates onto the white dwarf companions have been reported (Parsons et al 2012), these values are set as lower limits for the mass-loss rates of the dM stars. For example, Debes (2006) finds that dM mass-loss rates are about 15 to 100 times larger than white dwarf mass-accretion rates.…”

Section: Introductionmentioning

confidence: 99%

Exoplanets as probes of the winds of host stars: the case of the M dwarf GJ 436

Vidotto

Bourrier

2017

Monthly Notices of the Royal Astronomical Society

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Winds of cool dwarfs are difficult to observe, with only a few M dwarfs presenting observationally-derived mass-loss rates ( M), which span several orders of magnitude. Close-in exoplanets are conveniently positioned in the inner regions of stellar winds and can, thus, be used to probe the otherwise-unobservable local properties of their host-stars' winds. Here, we use local stellar wind characteristics observationally-derived in the studies of atmospheric evaporation of the warm-neptune GJ 436b to derive the global characteristics of the wind of its M-dwarf host. Using an isothermal wind model, we constrain the stellar wind temperature to be in the range [0.36,0.43] MK, with M = [0.5, 2.5] × 10 −15 M yr −1 . By computing the pressure balance between the stellar wind and the interstellar medium, we derive the size of the astrophere of GJ 436 to be around 25 au, significantly more compact than the heliosphere. We demonstrate in this paper that transmission spectroscopy, coupled to planetary atmospheric evaporation and stellar wind models, can be a useful tool for constraining the large-scale wind structure of planet-hosting stars. Extending our approach to future planetary systems discoveries will open new perspectives for the combined characterisation of planetary exospheres and winds of cool dwarf stars.

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A precision study of two eclipsing white dwarf plus M dwarf binaries

Cited by 35 publications

References 67 publications

A circumbinary debris disk in a polluted white dwarf system

A circumbinary debris disk in a polluted white dwarf system

Slingshot prominences: nature’s wind gauges

Exoplanets as probes of the winds of host stars: the case of the M dwarf GJ 436

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