Cold giant planets evaporated by hot white dwarfs. (arXiv:1912.02345v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Schreiber_M/0/1/0/all/0/1">Matthias R. Schreiber</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gaensicke_B/0/1/0/all/0/1">Boris T. Gaensicke</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Toloza_O/0/1/0/all/0/1">Odette Toloza</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hernandez_M/0/1/0/all/0/1">Mercedes-S. Hernandez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lagos_F/0/1/0/all/0/1">Felipe Lagos</a>
Atmospheric escape from close-in Neptunes and hot Jupiters around sun-like
stars driven by extreme ultraviolet (EUV) irradiation plays an important role
in the evolution of exo-planets and in shaping their ensemble properties.
Intermediate and low mass stars are brightest at EUV wavelengths at the very
end of their lives, after they have expelled their envelopes and evolved into
hot white dwarfs. Yet the effect of the intense EUV irradiation of giant
planets orbiting young white dwarfs has not been assessed. We show that the
giant planets in the solar system will experience significant hydrodynamic
escape caused by the EUV irradiation from the white dwarf left behind by the
Sun. A fraction of the evaporated volatiles will be accreted by the solar white
dwarf, resulting in detectable photospheric absorption lines. As a large number
of the currently known extra-solar giant planets will survive the metamorphosis
of their host stars into white dwarfs, observational signatures of accretion
from evaporating planetary atmospheres are expected to be common. In fact, one
third of the known hot single white dwarfs show photospheric absorption lines
of volatile elements, which we argue are indicative of ongoing accretion from
evaporating planets. The fraction of volatile contaminated hot white dwarfs
strongly decreases as they cool. We show that accretion from evaporating
planetary atmospheres naturally explains this temperature dependence if more
than 50 per cent of hot white dwarfs still host giant planets.
Atmospheric escape from close-in Neptunes and hot Jupiters around sun-like
stars driven by extreme ultraviolet (EUV) irradiation plays an important role
in the evolution of exo-planets and in shaping their ensemble properties.
Intermediate and low mass stars are brightest at EUV wavelengths at the very
end of their lives, after they have expelled their envelopes and evolved into
hot white dwarfs. Yet the effect of the intense EUV irradiation of giant
planets orbiting young white dwarfs has not been assessed. We show that the
giant planets in the solar system will experience significant hydrodynamic
escape caused by the EUV irradiation from the white dwarf left behind by the
Sun. A fraction of the evaporated volatiles will be accreted by the solar white
dwarf, resulting in detectable photospheric absorption lines. As a large number
of the currently known extra-solar giant planets will survive the metamorphosis
of their host stars into white dwarfs, observational signatures of accretion
from evaporating planetary atmospheres are expected to be common. In fact, one
third of the known hot single white dwarfs show photospheric absorption lines
of volatile elements, which we argue are indicative of ongoing accretion from
evaporating planets. The fraction of volatile contaminated hot white dwarfs
strongly decreases as they cool. We show that accretion from evaporating
planetary atmospheres naturally explains this temperature dependence if more
than 50 per cent of hot white dwarfs still host giant planets.
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