pubhz0.bib
@comment{{This file has been generated by bib2bib 1.96}}
@comment{{Command line: bib2bib -c 'not journal:"Discussions"' -c 'not title:"Correction to"' -c 'abstract:"liquid" or abstract:"habitable"' -c $type="ARTICLE" -oc pubhz0.txt -ob pubhz0.bib leconte.link.bib}}
@article{2019ApJ...875...46Y,
author = {{Yang}, J. and {Leconte}, J. and {Wolf}, E.~T. and {Merlis}, T. and
{Koll}, D.~D.~B. and {Forget}, F. and {Abbot}, D.~S.},
title = {{Simulations of Water Vapor and Clouds on Rapidly Rotating and Tidally Locked Planets: A 3D Model Intercomparison}},
journal = {\apj},
keywords = {astrobiology, methods: numerical, planets and satellites: atmospheres, planets and satellites: general, radiative transfer },
year = 2019,
volume = 875,
eid = {46},
pages = {46},
abstract = {{Robustly modeling the inner edge of the habitable zone is essential for
determining the most promising potentially habitable exoplanets for
atmospheric characterization. Global climate models (GCMs) have become
the standard tool for calculating this boundary, but divergent results
have emerged among the various GCMs. In this study, we perform an
intercomparison of standard GCMs used in the field on a rapidly rotating
planet receiving a G-star spectral energy distribution and on a tidally
locked planet receiving an M-star spectral energy distribution.
Experiments both with and without clouds are examined. We find
relatively small difference (within 8 K) in global-mean surface
temperature simulation among the models in the G-star case with clouds.
In contrast, the global-mean surface temperature simulation in the
M-star case is highly divergent (20{\ndash}30 K). Moreover, even
differences in the simulated surface temperature when clouds are turned
off are significant. These differences are caused by differences in
cloud simulation and/or radiative transfer, as well as complex
interactions between atmospheric dynamics and these two processes. For
example we find that an increase in atmospheric absorption of shortwave
radiation can lead to higher relative humidity at high altitudes
globally and, therefore, a significant decrease in planetary radiation
emitted to space. This study emphasizes the importance of basing
conclusions about planetary climate on simulations from a variety of
GCMs and motivates the eventual comparison of GCM results with
terrestrial exoplanet observations to improve their performance.
}},
doi = {10.3847/1538-4357/ab09f1},
adsurl = {https://ui.adsabs.harvard.edu/abs/2019ApJ...875...46Y},
localpdf = {https://ui.adsabs.harvard.edu/abs/2019ApJ...875...46Y.pdf},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2018ExA....46...45T,
author = {{Turrini}, D. and {Miguel}, Y. and {Zingales}, T. and {Piccialli}, A. and
{Helled}, R. and {Vazan}, A. and {Oliva}, F. and {Sindoni}, G. and
{Pani{\'c}}, O. and {Leconte}, J. and {Min}, M. and {Pirani}, S. and
{Selsis}, F. and {Coudé du Foresto}, V. and {Mura}, A. and
{Wolkenberg}, P.},
title = {{The contribution of the ARIEL space mission to the study of planetary formation}},
journal = {Experimental Astronomy},
archiveprefix = {arXiv},
eprint = {1804.06179},
primaryclass = {astro-ph.EP},
keywords = {Atmospheric remote-sensing infrared exoplanet large-survey, ARIEL, Space missions, Exoplanets, Planetary formation, Astrochemistry},
year = 2018,
volume = 46,
pages = {45-65},
abstract = {{The study of extrasolar planets and of the Solar System provides
complementary pieces of the mosaic represented by the process of
planetary formation. Exoplanets are essential to fully grasp the huge
diversity of outcomes that planetary formation and the subsequent
evolution of the planetary systems can produce. The orbital and basic
physical data we currently possess for the bulk of the exoplanetary
population, however, do not provide enough information to break the
intrinsic degeneracy of their histories, as different evolutionary
tracks can result in the same final configurations. The lessons learned
from the Solar System indicate us that the solution to this problem lies
in the information contained in the composition of planets. The goal of
the Atmospheric Remote-Sensing Infrared Exoplanet Large-survey (ARIEL),
one of the three candidates as ESA M4 space mission, is to observe a
large and diversified population of transiting planets around a range of
host star types to collect information on their atmospheric composition.
ARIEL will focus on warm and hot planets to take advantage of their
well-mixed atmospheres, which should show minimal condensation and
sequestration of high-Z materials and thus reveal their bulk composition
across all main cosmochemical elements. In this work we will review the
most outstanding open questions concerning the way planets form and the
mechanisms that contribute to create habitable environments that the
compositional information gathered by ARIEL will allow to tackle.
}},
doi = {10.1007/s10686-017-9570-1},
adsurl = {https://ui.adsabs.harvard.edu/abs/2018ExA....46...45T},
localpdf = {https://ui.adsabs.harvard.edu/abs/2018ExA....46...45T.pdf},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2018A&A...612A..86T,
author = {{Turbet}, M. and {Bolmont}, E. and {Leconte}, J. and {Forget}, F. and
{Selsis}, F. and {Tobie}, G. and {Caldas}, A. and {Naar}, J. and
{Gillon}, M.},
title = {{Modeling climate diversity, tidal dynamics and the fate of volatiles on TRAPPIST-1 planets}},
journal = {\aap},
archiveprefix = {arXiv},
eprint = {1707.06927},
primaryclass = {astro-ph.EP},
keywords = {stars: individual: TRAPPIST-1, planets and satellites: terrestrial planets, planets and satellites: atmospheres, planets and satellites: dynamical evolution and stability, astrobiology},
year = 2018,
volume = 612,
eid = {A86},
pages = {A86},
abstract = {{TRAPPIST-1 planets are invaluable for the study of comparative planetary
science outside our solar system and possibly habitability. Both transit
timing variations (TTV) of the planets and the compact, resonant
architecture of the system suggest that TRAPPIST-1 planets could be
endowed with various volatiles today. First, we derived from N-body
simulations possible planetary evolution scenarios, and show that all
the planets are likely in synchronous rotation. We then used a versatile
3D global climate model (GCM) to explore the possible climates of cool
planets around cool stars, with a focus on the TRAPPIST-1 system. We
investigated the conditions required for cool planets to prevent
possible volatile species to be lost permanently by surface
condensation, irreversible burying or photochemical destruction. We also
explored the resilience of the same volatiles (when in condensed phase)
to a runaway greenhouse process. We find that background atmospheres
made of N$_{2}$, CO, or O$_{2}$ are rather resistant to
atmospheric collapse. However, even if TRAPPIST-1 planets were able to
sustain a thick background atmosphere by surviving early X/EUV radiation
and stellar wind atmospheric erosion, it is difficult for them to
accumulate significant greenhouse gases like CO$_{2}$,
CH$_{4}$, or NH$_{3}$. CO$_{2}$ can easily condense on
the permanent nightside, forming CO$_{2}$ ice glaciers that would
flow toward the substellar region. A complete CO$_{2}$ ice surface
cover is theoretically possible on TRAPPIST-1g and h only, but
CO$_{2}$ ices should be gravitationally unstable and get buried
beneath the water ice shell in geologically short timescales. Given
TRAPPIST-1 planets large EUV irradiation (at least 10$^{3}$
{\times} Titan's flux), CH$_{4}$ and NH$_{3}$ are
photodissociated rapidly and are thus hard to accumulate in the
atmosphere. Photochemical hazes could then sedimentate and form a
surface layer of tholins that would progressively thicken over the age
of the TRAPPIST-1 system. Regarding habitability, we confirm that few
bars of CO$_{2}$ would suffice to warm the surface of TRAPPIST-1f
and g above the melting point of water. We also show that TRAPPIST-1e is
a remarkable candidate for surface habitability. If the planet is today
synchronous and abundant in water, then it should very likely sustain
surface liquid water at least in the substellar region, whatever the
atmosphere considered.
}},
doi = {10.1051/0004-6361/201731620},
adsurl = {https://ui.adsabs.harvard.edu/abs/2018A%26A...612A..86T},
localpdf = {https://ui.adsabs.harvard.edu/abs/2018A_26A...612A..86T.pdf},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2018NatAs...2..214D,
author = {{de Wit}, J. and {Wakeford}, H.~R. and {Lewis}, N.~K. and {Delrez}, L. and
{Gillon}, M. and {Selsis}, F. and {Leconte}, J. and {Demory}, B.-O. and
{Bolmont}, E. and {Bourrier}, V. and {Burgasser}, A.~J. and
{Grimm}, S. and {Jehin}, E. and {Lederer}, S.~M. and {Owen}, J.~E. and
{Stamenkovi{\'c}}, V. and {Triaud}, A.~H.~M.~J.},
title = {{Atmospheric reconnaissance of the habitable-zone Earth-sized planets orbiting TRAPPIST-1}},
journal = {Nature Astronomy},
archiveprefix = {arXiv},
eprint = {1802.02250},
primaryclass = {astro-ph.EP},
year = 2018,
volume = 2,
pages = {214-219},
abstract = {{Seven temperate Earth-sized exoplanets readily amenable for atmospheric
studies transit the nearby ultracool dwarf star TRAPPIST-1 (refs
$^{1,2}$). Their atmospheric regime is unknown and could range
from extended primordial hydrogen-dominated to depleted
atmospheres$^{3-6}$. Hydrogen in particular is a powerful
greenhouse gas that may prevent the habitability of inner planets while
enabling the habitability of outer ones$^{6-8}$. An atmosphere
largely dominated by hydrogen, if cloud-free, should yield prominent
spectroscopic signatures in the near-infrared detectable during
transits. Observations of the innermost planets have ruled out such
signatures$^{9}$. However, the outermost planets are more likely
to have sustained such a Neptune-like atmosphere$^{10, 11}$. Here,
we report observations for the four planets within or near the system's
habitable zone, the circumstellar region where liquid water could exist
on a planetary surface$^{12-14}$. These planets do not exhibit
prominent spectroscopic signatures at near-infrared wavelengths either,
which rules out cloud-free hydrogen-dominated atmospheres for TRAPPIST-1
d, e and f, with significance of 8{$\sigma$}, 6{$\sigma$} and 4{$\sigma$},
respectively. Such an atmosphere is instead not excluded for planet g.
As high-altitude clouds and hazes are not expected in hydrogen-dominated
atmospheres around planets with such insolation$^{15, 16}$, these
observations further support their terrestrial and potentially habitable
nature.
}},
doi = {10.1038/s41550-017-0374-z},
adsurl = {https://ui.adsabs.harvard.edu/abs/2018NatAs...2..214D},
localpdf = {https://ui.adsabs.harvard.edu/abs/2018NatAs...2..214D.pdf},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2017E&PSL.476...11T,
author = {{Turbet}, M. and {Forget}, F. and {Leconte}, J. and {Charnay}, B. and
{Tobie}, G.},
title = {{CO$_{2}$ condensation is a serious limit to the deglaciation of Earth-like planets}},
journal = {Earth and Planetary Science Letters},
archiveprefix = {arXiv},
eprint = {1703.04624},
primaryclass = {astro-ph.EP},
keywords = {climate, snowball, exoplanet, CO$_{2}$ condensation, habitability, climate cycling},
year = 2017,
volume = 476,
pages = {11-21},
abstract = {{It is widely believed that the carbonate-silicate cycle is the main
agent, through volcanism, to trigger deglaciations by CO$_{2}$
greenhouse warming on Earth and on Earth-like planets when they get in a
frozen state. Here we use a 3D Global Climate Model to simulate the
ability of planets initially completely frozen to escape from glaciation
episodes by accumulating enough gaseous CO$_{2}$. The model
includes CO$_{2}$ condensation and sublimation processes and the
water cycle. We find that planets with Earth-like characteristics (size,
mass, obliquity, rotation rate, etc.) orbiting a Sun-like star may never
be able to escape from a glaciation era, if their orbital distance is
greater than {\sim}1.27 Astronomical Units (Flux $\lt$ 847
Wm$^{-2}$ or 62\% of the Solar constant), because CO$_{2}$
would condense at the poles - here the cold traps - forming permanent
CO$_{2}$ ice caps. This limits the amount of CO$_{2}$ in the
atmosphere and thus its greenhouse effect. Furthermore, our results
indicate that for (1) high rotation rates (P$_{rot}$ $\lt$ 24 h),
(2) low obliquity (obliquity $\lt$23.5{\deg}), (3) low background gas
partial pressures ($\lt$1 bar), and (4) high water ice albedo
(H$_{2}$O albedo $\gt$ 0.6), this critical limit could occur at a
significantly lower equivalent distance (or higher insolation). For each
possible configuration, we show that the amount of CO$_{2}$ that
can be trapped in the polar caps depends on the efficiency of
CO$_{2}$ ice to flow laterally as well as its gravitational
stability relative to subsurface water ice. We find that a frozen
Earth-like planet located at 1.30 AU of a Sun-like star could store as
much as 1.5, 4.5 and 15 bars of dry ice at the poles, for internal heat
fluxes of 100, 30 and 10 mW m$^{-2}$, respectively. But these
amounts are in fact lower limits. For planets with a significant water
ice cover, we show that CO$_{2}$ ice deposits should be
gravitationally unstable. They get buried beneath the water ice cover in
geologically short timescales of {\sim}10$^{4}$ yrs, mainly
controlled by the viscosity of water ice. CO$_{2}$ would be
permanently sequestered underneath the water ice cover, in the form of
CO$_{2}$ liquids, CO$_{2}$ clathrate hydrates and/or
dissolved in subglacial water reservoirs (if any). This would
considerably increase the amount of CO$_{2}$ trapped and further
reduce the probability of deglaciation.
}},
doi = {10.1016/j.epsl.2017.07.050},
adsurl = {https://ui.adsabs.harvard.edu/abs/2017E%26PSL.476...11T},
localpdf = {https://ui.adsabs.harvard.edu/abs/2017E_26PSL.476...11T.pdf},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2017AJ....154..121B,
author = {{Bourrier}, V. and {de Wit}, J. and {Bolmont}, E. and {Stamenkovi{\'c}}, V. and
{Wheatley}, P.~J. and {Burgasser}, A.~J. and {Delrez}, L. and
{Demory}, B.-O. and {Ehrenreich}, D. and {Gillon}, M. and {Jehin}, E. and
{Leconte}, J. and {Lederer}, S.~M. and {Lewis}, N. and {Triaud}, A.~H.~M.~J. and
{Van Grootel}, V.},
title = {{Temporal Evolution of the High-energy Irradiation and Water Content of TRAPPIST-1 Exoplanets}},
journal = {\aj},
archiveprefix = {arXiv},
eprint = {1708.09484},
primaryclass = {astro-ph.EP},
keywords = {planetary systems, planets and satellites: atmospheres, planets and satellites: terrestrial planets, stars: individual: TRAPPIST-1, stars: low-mass, ultraviolet: planetary systems},
year = 2017,
volume = 154,
eid = {121},
pages = {121},
abstract = {{The ultracool dwarf star TRAPPIST-1 hosts seven Earth-size transiting
planets, some of which could harbor liquid water on their surfaces.
Ultraviolet observations are essential to measuring their high-energy
irradiation and searching for photodissociated water escaping from their
putative atmospheres. Our new observations of the TRAPPIST-1 Ly{$\alpha$}
line during the transit of TRAPPIST-1c show an evolution of the star
an extended hydrogen exosphere. Based on the current knowledge of the
stellar irradiation, we investigated the likely history of water loss in
the system. Planets b to d might still be in a runaway phase, and
planets within the orbit of TRAPPIST-1g could have lost more than 20
Earth oceans after 8 Gyr of hydrodynamic escape. However, TRAPPIST-1e to
h might have lost less than three Earth oceans if hydrodynamic escape
stopped once they entered the habitable zone (HZ). We caution that these
estimates remain limited by the large uncertainty on the planet masses.
They likely represent upper limits on the actual water loss because our
assumptions maximize the X-rays to ultraviolet-driven escape, while
photodissociation in the upper atmospheres should be the limiting
process. Late-stage outgassing could also have contributed significant
amounts of water for the outer, more massive planets after they entered
the HZ. While our results suggest that the outer planets are the best
candidates to search for water with the JWST, they also highlight the
need for theoretical studies and complementary observations in all
wavelength domains to determine the nature of the TRAPPIST-1 planets and
their potential habitability.
}},
doi = {10.3847/1538-3881/aa859c},
adsurl = {https://ui.adsabs.harvard.edu/abs/2017AJ....154..121B},
localpdf = {https://ui.adsabs.harvard.edu/abs/2017AJ....154..121B.pdf},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2017Natur.542..456G,
author = {{Gillon}, M. and {Triaud}, A.~H.~M.~J. and {Demory}, B.-O. and
{Jehin}, E. and {Agol}, E. and {Deck}, K.~M. and {Lederer}, S.~M. and
{de Wit}, J. and {Burdanov}, A. and {Ingalls}, J.~G. and {Bolmont}, E. and
{Leconte}, J. and {Raymond}, S.~N. and {Selsis}, F. and {Turbet}, M. and
{Barkaoui}, K. and {Burgasser}, A. and {Burleigh}, M.~R. and
{Carey}, S.~J. and {Chaushev}, A. and {Copperwheat}, C.~M. and
{Delrez}, L. and {Fernandes}, C.~S. and {Holdsworth}, D.~L. and
{Kotze}, E.~J. and {Van Grootel}, V. and {Almleaky}, Y. and
{Benkhaldoun}, Z. and {Magain}, P. and {Queloz}, D.},
title = {{Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1}},
journal = {\nat},
archiveprefix = {arXiv},
eprint = {1703.01424},
primaryclass = {astro-ph.EP},
year = 2017,
volume = 542,
pages = {456-460},
abstract = {{One aim of modern astronomy is to detect temperate, Earth-like
exoplanets that are well suited for atmospheric characterization.
Recently, three Earth-sized planets were detected that transit (that is,
pass in front of) a star with a mass just eight per cent that of the
Sun, located 12 parsecs away. The transiting configuration of these
planets, combined with the Jupiter-like size of their host
star{\mdash}named TRAPPIST-1{\mdash}makes possible in-depth studies of
their atmospheric properties with present-day and future astronomical
facilities. Here we report the results of a photometric monitoring
campaign of that star from the ground and space. Our observations reveal
that at least seven planets with sizes and masses similar to those of
Earth revolve around TRAPPIST-1. The six inner planets form a
near-resonant chain, such that their orbital periods (1.51, 2.42, 4.04,
6.06, 9.1 and 12.35 days) are near-ratios of small integers. This
architecture suggests that the planets formed farther from the star and
migrated inwards. Moreover, the seven planets have equilibrium
temperatures low enough to make possible the presence of liquid water on
their surfaces.
}},
doi = {10.1038/nature21360},
adsurl = {https://ui.adsabs.harvard.edu/abs/2017Natur.542..456G},
localpdf = {https://ui.adsabs.harvard.edu/abs/2017Natur.542..456G.pdf},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2017MNRAS.464.3728B,
author = {{Bolmont}, E. and {Selsis}, F. and {Owen}, J.~E. and {Ribas}, I. and
{Raymond}, S.~N. and {Leconte}, J. and {Gillon}, M.},
title = {{Water loss from terrestrial planets orbiting ultracool dwarfs: implications for the planets of TRAPPIST-1}},
journal = {\mnras},
archiveprefix = {arXiv},
eprint = {1605.00616},
primaryclass = {astro-ph.EP},
keywords = {planets and satellites: atmospheres, planets and satellites: individual: TRAPPIST-1, planet star interactions, brown dwarfs, stars: low-mass},
year = 2017,
volume = 464,
pages = {3728-3741},
abstract = {{Ultracool dwarfs (UCD; T$_{eff}$ $\lt$ {\tilde}3000 K) cool to
settle on the main sequence after {\tilde}1 Gyr. For brown dwarfs, this
cooling never stops. Their habitable zones (HZ) thus sweeps inward at
least during the first Gyr of their lives. Assuming they possess water,
planets found in the HZ of UCDs have experienced a runaway greenhouse
phase too hot for liquid water prior to enter the HZ. It has been
proposed that such planets are desiccated by this hot early phase and
enter the HZ as dry worlds. Here, we model the water loss during this
pre-HZ hot phase taking into account recent upper limits on the XUV
emission of UCDs and using 1D radiation-hydrodynamic simulations. We
address the whole range of UCDs but also focus on the planets recently
found around the 0.08 M$_{&sun;}$ dwarf TRAPPIST-1. Despite
assumptions maximizing the FUV photolysis of water and the XUV-driven
escape of hydrogen, we find that planets can retain significant amount
of water in the HZ of UCDs, with a sweet spot in the 0.04-0.06
M$_{&sun;}$ range. We also studied the TRAPPIST-1 system using
observed constraints on the XUV flux. We find that TRAPPIST-1b and c may
have lost as much as 15 Earth oceans and planet d - which might be
inside the HZ - may have lost less than 1 Earth ocean. Depending on
their initial water contents, they could have enough water to remain
habitable. TRAPPIST-1 planets are key targets for atmospheric
characterization and could provide strong constraints on the water
erosion around UCDs.
}},
doi = {10.1093/mnras/stw2578},
adsurl = {https://ui.adsabs.harvard.edu/abs/2017MNRAS.464.3728B},
localpdf = {https://ui.adsabs.harvard.edu/abs/2017MNRAS.464.3728B.pdf},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2016A&A...596A.112T,
author = {{Turbet}, M. and {Leconte}, J. and {Selsis}, F. and {Bolmont}, E. and
{Forget}, F. and {Ribas}, I. and {Raymond}, S.~N. and {Anglada-Escudé}, G.
},
title = {{The habitability of Proxima Centauri b. II. Possible climates and observability}},
journal = {\aap},
archiveprefix = {arXiv},
eprint = {1608.06827},
primaryclass = {astro-ph.EP},
keywords = {stars: individual: Proxima Cen, planets and satellites: individual: Proxima Cen b, planets and satellites: atmospheres, planets and satellites: terrestrial planets, planets and satellites: detection, astrobiology},
year = 2016,
volume = 596,
eid = {A112},
pages = {A112},
abstract = {{Radial velocity monitoring has found the signature of a Msini =
1.3M$_{⊕}$ planet located within the habitable zone (HZ) of
Proxima Centauri. Despite a hotter past and an active host star, the
planet Proxima b could have retained enough volatiles to sustain surface
habitability. Here we use a 3D Global Climate Model (GCM) to simulate
the atmosphere and water cycle of Proxima b for its two likely rotation
modes (1:1 and 3:2 spin-orbit resonances), while varying the
unconstrained surface water inventory and atmospheric greenhouse effect.
Any low-obliquity, low-eccentricity planet within the HZ of its star
should be in one of the climate regimes discussed here. We find that a
broad range of atmospheric compositions allow surface liquid water. On a
tidally locked planet with sufficient surface water inventory, liquid
water is always present, at least in the substellar region. With a
non-synchronous rotation, this requires a minimum greenhouse warming (
10 mbar of CO$_{2}$ and 1 bar of N$_{2}$). If the planet is
dryer, 0.5 bar or 1.5 bars of CO$_{2}$ (for asynchronous or
synchronous rotation, respectively) suffice to prevent the trapping of
any arbitrary, small water inventory into polar or nightside ice caps.
We produce reflection and emission spectra and phase curves for the
simulated climates. We find that atmospheric characterization will be
possible via direct imaging with forthcoming large telescopes. The
angular separation of 7{$\lambda$}/D at 1 {$\mu$}m (with the E-ELT) and a
contrast of 10$^{-7}$ will enable high-resolution spectroscopy
and the search for molecular signatures, including H$_{2}$O,
O$_{2}$, and CO$_{2}$. The observation of thermal phase
curves can be attempted with the James Webb Space Telescope, thanks to a
contrast of 2 {\times} 10$^{-5}$ at 10 {$\mu$}m. Proxima b will also
be an exceptional target for future IR interferometers. Within a decade
it will be possible to image Proxima b and possibly determine whether
the surface of this exoplanet is habitable.
}},
doi = {10.1051/0004-6361/201629577},
adsurl = {https://ui.adsabs.harvard.edu/abs/2016A%26A...596A.112T},
localpdf = {https://ui.adsabs.harvard.edu/abs/2016A_26A...596A.112T.pdf},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2016A&A...596A.111R,
author = {{Ribas}, I. and {Bolmont}, E. and {Selsis}, F. and {Reiners}, A. and
{Leconte}, J. and {Raymond}, S.~N. and {Engle}, S.~G. and {Guinan}, E.~F. and
{Morin}, J. and {Turbet}, M. and {Forget}, F. and {Anglada-Escudé}, G.
},
title = {{The habitability of Proxima Centauri b. I. Irradiation, rotation and volatile inventory from formation to the present}},
journal = {\aap},
archiveprefix = {arXiv},
eprint = {1608.06813},
primaryclass = {astro-ph.EP},
keywords = {stars: individual: Proxima Cen, planets and satellites: individual: Proxima b, planets and satellites: atmospheres, X-rays: stars, planet-star interactions},
year = 2016,
volume = 596,
eid = {A111},
pages = {A111},
abstract = {{Proxima b is a planet with a minimum mass of 1.3M$_{⊕}$
orbiting within the habitable zone (HZ) of Proxima Centauri, a very
low-mass, active star and the Sun's closest neighbor. Here we
investigate a number of factors related to the potential habitability of
Proxima b and its ability to maintain liquid water on its surface. We
set the stage by estimating the current high-energy irradiance of the
planet and show that the planet currently receives 30 times more
extreme-UV radiation than Earth and 250 times more X-rays. We compute
the time evolution of the star's spectrum, which is essential for
modeling the flux received over Proxima b's lifetime. We also show that
Proxima b's obliquity is likely null and its spin is either synchronous
or in a 3:2 spin-orbit resonance, depending on the planet's eccentricity
and level of triaxiality. Next we consider the evolution of Proxima b's
water inventory. We use our spectral energy distribution to compute the
hydrogen loss from the planet with an improved energy-limited escape
formalism. Despite the high level of stellar activity we find that
Proxima b is likely to have lost less than an Earth ocean's worth of
hydrogen (EO$_{H}$) before it reached the HZ 100-200 Myr after its
formation. The largest uncertainty in our work is the initial water
budget, which is not constrained by planet formation models. We conclude
that Proxima b is a viable candidate habitable planet.
}},
doi = {10.1051/0004-6361/201629576},
adsurl = {https://ui.adsabs.harvard.edu/abs/2016A%26A...596A.111R},
localpdf = {https://ui.adsabs.harvard.edu/abs/2016A_26A...596A.111R.pdf},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2016ApJ...826..222Y,
author = {{Yang}, J. and {Leconte}, J. and {Wolf}, E.~T. and {Goldblatt}, C. and
{Feldl}, N. and {Merlis}, T. and {Wang}, Y. and {Koll}, D.~D.~B. and
{Ding}, F. and {Forget}, F. and {Abbot}, D.~S.},
title = {{Differences in Water Vapor Radiative Transfer among 1D Models Can Significantly Affect the Inner Edge of the Habitable Zone}},
journal = {\apj},
archiveprefix = {arXiv},
eprint = {1809.01397},
primaryclass = {astro-ph.EP},
keywords = {astrobiology, methods: numerical, planets and satellites: atmospheres, planets and satellites: general, planets and satellites: terrestrial planets, radiative transfer},
year = 2016,
volume = 826,
eid = {222},
pages = {222},
abstract = {{An accurate estimate of the inner edge of the habitable zone is critical
for determining which exoplanets are potentially habitable and for
designing future telescopes to observe them. Here, we explore
differences in estimating the inner edge among seven one-dimensional
radiative transfer models: two line-by-line codes (SMART and LBLRTM) as
well as five band codes (CAM3, CAM4\_Wolf, LMDG, SBDART, and AM2) that
are currently being used in global climate models. We compare radiative
fluxes and spectra in clear-sky conditions around G and M stars, with
fixed moist adiabatic profiles for surface temperatures from 250 to 360
K. We find that divergences among the models arise mainly from large
uncertainties in water vapor absorption in the window region (10 {$\mu$}m)
and in the region between 0.2 and 1.5 {$\mu$}m. Differences in outgoing
longwave radiation increase with surface temperature and reach 10-20 W
m$^{-2}$ differences in shortwave reach up to 60 W m$^{-2}$,
especially at the surface and in the troposphere, and are larger for an
M-dwarf spectrum than a solar spectrum. Differences between the two
line-by-line models are significant, although smaller than among the
band models. Our results imply that the uncertainty in estimating the
insolation threshold of the inner edge (the runaway greenhouse limit)
due only to clear-sky radiative transfer is {\ap}10\% of modern
Earth{\rsquo}s solar constant (I.e., {\ap}34 W m$^{-2}$ in global
mean) among band models and {\ap}3\% between the two line-by-line models.
These comparisons show that future work is needed that focuses on
improving water vapor absorption coefficients in both shortwave and
longwave, as well as on increasing the resolution of stellar spectra in
broadband models.
}},
doi = {10.3847/0004-637X/826/2/222},
adsurl = {https://ui.adsabs.harvard.edu/abs/2016ApJ...826..222Y},
localpdf = {https://ui.adsabs.harvard.edu/abs/2016ApJ...826..222Y.pdf},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2016A&A...591A.106B,
author = {{Bolmont}, E. and {Libert}, A.-S. and {Leconte}, J. and {Selsis}, F.
},
title = {{Habitability of planets on eccentric orbits: Limits of the mean flux approximation}},
journal = {\aap},
archiveprefix = {arXiv},
eprint = {1604.06091},
primaryclass = {astro-ph.EP},
keywords = {planets and satellites: atmospheres, planets and satellites: terrestrial planets, methods: numerical},
year = 2016,
volume = 591,
eid = {A106},
pages = {A106},
abstract = {{Unlike the Earth, which has a small orbital eccentricity, some
exoplanets discovered in the insolation habitable zone (HZ) have high
orbital eccentricities (e.g., up to an eccentricity of \~{}0.97 for HD
20782 b). This raises the question of whether these planets have surface
conditions favorable to liquid water. In order to assess the
habitability of an eccentric planet, the mean flux approximation is
often used. It states that a planet on an eccentric orbit is called
habitable if it receives on average a flux compatible with the presence
of surface liquid water. However, because the planets experience
important insolation variations over one orbit and even spend some time
outside the HZ for high eccentricities, the question of their
habitability might not be as straightforward. We performed a set of
simulations using the global climate model LMDZ to explore the limits of
the mean flux approximation when varying the luminosity of the host star
and the eccentricity of the planet. We computed the climate of tidally
locked ocean covered planets with orbital eccentricity from 0 to 0.9
receiving a mean flux equal to Earth's. These planets are found around
stars of luminosity ranging from 1 L$_{&sun;}$ to
10$^{-4}$L$_{&sun;}$. We use a definition of habitability
based on the presence of surface liquid water, and find that most of the
planets considered can sustain surface liquid water on the dayside with
an ice cap on the nightside. However, for high eccentricity and high
luminosity, planets cannot sustain surface liquid water during the whole
orbital period. They completely freeze at apoastron and when approaching
periastron an ocean appears around the substellar point. We conclude
that the higher the eccentricity and the higher the luminosity of the
star, the less reliable the mean flux approximation.
}},
doi = {10.1051/0004-6361/201628073},
adsurl = {https://ui.adsabs.harvard.edu/abs/2016A%26A...591A.106B},
localpdf = {https://ui.adsabs.harvard.edu/abs/2016A_26A...591A.106B.pdf},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2015A&A...583A.116B,
author = {{Bolmont}, E. and {Raymond}, S.~N. and {Leconte}, J. and {Hersant}, F. and
{Correia}, A.~C.~M.},
title = {{Mercury-T: A new code to study tidally evolving multi-planet systems. Applications to Kepler-62}},
journal = {\aap},
archiveprefix = {arXiv},
eprint = {1507.04751},
primaryclass = {astro-ph.EP},
keywords = {planets and satellites: dynamical evolution and stability, planets and satellites: terrestrial planets, planets and satellites: individual: Kepler 62, planet-star interactions},
year = 2015,
volume = 583,
eid = {A116},
pages = {A116},
abstract = {{A large proportion of observed planetary systems contain several planets
in a compact orbital configuration, and often harbor at least one
close-in object. These systems are then most likely tidally evolving. We
investigate how the effects of planet-planet interactions influence the
tidal evolution of planets. We introduce for that purpose a new
open-source addition to the MercuryN-body code, Mercury-T, which takes
into account tides, general relativity and the effect of
rotation-induced flattening in order to simulate the dynamical and tidal
evolution of multi-planet systems. It uses a standard equilibrium tidal
model, the constant time lag model. Besides, the evolution of the radius
of several host bodies has been implemented (brown dwarfs, M-dwarfs of
mass 0.1 M$_{&sun;}$, Sun-like stars, Jupiter). We validate the
new code by comparing its output for one-planet systems to the secular
equations results. We find that this code does respect the conservation
of total angular momentum. We applied this new tool to the planetary
system Kepler-62. We find that tides influence the stability of the
system in some cases. We also show that while the four inner planets of
the systems are likely to have slow rotation rates and small
obliquities, the fifth planet could have a fast rotation rate and a high
obliquity. This means that the two habitable zone planets of this
system, Kepler-62e ad f are likely to have very different climate
features, and this of course would influence their potential at hosting
surface liquid water.
The code is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr
(ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/583/A116
}},
doi = {10.1051/0004-6361/201525909},
adsurl = {https://ui.adsabs.harvard.edu/abs/2015A%26A...583A.116B},
localpdf = {https://ui.adsabs.harvard.edu/abs/2015A_26A...583A.116B.pdf},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2015Sci...347..632L,
author = {{Leconte}, J. and {Wu}, H. and {Menou}, K. and {Murray}, N.},
title = {{Asynchronous rotation of Earth-mass planets in the habitable zone of lower-mass stars}},
journal = {Science},
archiveprefix = {arXiv},
eprint = {1502.01952},
primaryclass = {astro-ph.EP},
year = 2015,
volume = 347,
pages = {632-635},
abstract = {{Planets in the habitable zone of lower-mass stars are often assumed to
be in a state of tidally synchronized rotation, which would considerably
affect their putative habitability. Although thermal tides cause Venus
to rotate retrogradely, simple scaling arguments tend to attribute this
peculiarity to the massive Venusian atmosphere. Using a global climate
model, we show that even a relatively thin atmosphere can drive
terrestrial planets{\rsquo} rotation away from synchronicity. We derive a
more realistic atmospheric tide model that predicts four asynchronous
equilibrium spin states, two being stable, when the amplitude of the
thermal tide exceeds a threshold that is met for habitable Earth-like
planets with a 1-bar atmosphere around stars more massive than \~{}0.5 to
0.7 solar mass. Thus, many recently discovered terrestrial planets could
exhibit asynchronous spin-orbit rotation, even with a thin atmosphere.
}},
doi = {10.1126/science.1258686},
adsurl = {https://ui.adsabs.harvard.edu/abs/2015Sci...347..632L},
localpdf = {https://ui.adsabs.harvard.edu/abs/2015Sci...347..632L.pdf},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2014RSPTA.37230084F,
author = {{Forget}, F. and {Leconte}, J.},
title = {{Possible climates on terrestrial exoplanets}},
journal = {Philosophical Transactions of the Royal Society of London Series A},
archiveprefix = {arXiv},
eprint = {1311.3101},
primaryclass = {astro-ph.EP},
year = 2014,
volume = 372,
pages = {20130084-20130084},
abstract = {{What kind of environment may exist on terrestrial planets around other
stars? In spite of the lack of direct observations, it may not be
premature to speculate on exoplanetary climates, for instance to
optimize future telescopic observations, or to assess the probability of
habitable worlds. To first order, climate primarily depends on 1) The
atmospheric composition and the volatile inventory; 2) The incident
stellar flux; 3) The tidal evolution of the planetary spin, which can
notably lock a planet with a permanent night side. The atmospheric
composition and mass depends on complex processes which are difficult to
model: origins of volatile, atmospheric escape, geochemistry,
photochemistry. We discuss physical constraints which can help us to
speculate on the possible type of atmosphere, depending on the planet
size, its final distance for its star and the star type. Assuming that
the atmosphere is known, the possible climates can be explored using
Global Climate Models analogous to the ones developed to simulate the
Earth as well as the other telluric atmospheres in the solar system. Our
experience with Mars, Titan and Venus suggests that realistic climate
simulators can be developed by combining components like a ``dynamical
core'', a radiative transfer solver, a parametrisation of subgrid-scale
turbulence and convection, a thermal ground model, and a volatile phase
change code. On this basis, we can aspire to build reliable climate
predictors for exoplanets. However, whatever the accuracy of the models,
predicting the actual climate regime on a specific planet will remain
challenging because climate systems are affected by strong positive
destabilizing feedbacks (such as runaway glaciations and runaway
greenhouse effect). They can drive planets with very similar forcing and
volatile inventory to completely different states.
}},
doi = {10.1098/rsta.2013.0084},
adsurl = {https://ui.adsabs.harvard.edu/abs/2014RSPTA.37230084F},
localpdf = {https://ui.adsabs.harvard.edu/abs/2014RSPTA.37230084F.pdf},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2013Natur.504..268L,
author = {{Leconte}, J. and {Forget}, F. and {Charnay}, B. and {Wordsworth}, R. and
{Pottier}, A.},
title = {{Increased insolation threshold for runaway greenhouse processes on Earth-like planets}},
journal = {\nat},
archiveprefix = {arXiv},
eprint = {1312.3337},
primaryclass = {astro-ph.EP},
year = 2013,
volume = 504,
pages = {268-271},
abstract = {{The increase in solar luminosity over geological timescales should warm
the Earth's climate, increasing water evaporation, which will in turn
enhance the atmospheric greenhouse effect. Above a certain critical
insolation, this destabilizing greenhouse feedback can `run away' until
the oceans have completely evaporated. Through increases in
stratospheric humidity, warming may also cause evaporative loss of the
oceans to space before the runaway greenhouse state occurs. The critical
insolation thresholds for these processes, however, remain uncertain
because they have so far been evaluated using one-dimensional models
that cannot account for the dynamical and cloud feedback effects that
are key stabilizing features of the Earth's climate. Here we use a
three-dimensional global climate model to show that the insolation
threshold for the runaway greenhouse state to occur is about 375 W
m$^{-2}$, which is significantly higher than previously thought.
Our model is specifically developed to quantify the climate response of
Earth-like planets to increased insolation in hot and extremely moist
atmospheres. In contrast with previous studies, we find that clouds have
a destabilizing feedback effect on the long-term warming. However,
subsident, unsaturated regions created by the Hadley circulation have a
stabilizing effect that is strong enough to shift the runaway greenhouse
limit to higher values of insolation than are inferred from
one-dimensional models. Furthermore, because of wavelength-dependent
radiative effects, the stratosphere remains sufficiently cold and dry to
hamper the escape of atmospheric water, even at large fluxes. This has
strong implications for the possibility of liquid water existing on
Venus early in its history, and extends the size of the habitable zone
around other stars.
}},
doi = {10.1038/nature12827},
adsurl = {https://ui.adsabs.harvard.edu/abs/2013Natur.504..268L},
localpdf = {https://ui.adsabs.harvard.edu/abs/2013Natur.504..268L.pdf},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2013A&A...554A..69L,
author = {{Leconte}, J. and {Forget}, F. and {Charnay}, B. and {Wordsworth}, R. and
{Selsis}, F. and {Millour}, E. and {Spiga}, A.},
title = {{3D climate modeling of close-in land planets: Circulation patterns, climate moist bistability, and habitability}},
journal = {\aap},
archiveprefix = {arXiv},
eprint = {1303.7079},
primaryclass = {astro-ph.EP},
keywords = {planets and satellites: general, planets and satellites: atmospheres, planets and satellites: physical evolution, planet-star interactions},
year = 2013,
volume = 554,
eid = {A69},
pages = {A69},
abstract = {{The inner edge of the classical habitable zone is often defined by the
critical flux needed to trigger the runaway greenhouse instability. This
1D notion of a critical flux, however, may not be all that relevant for
inhomogeneously irradiated planets, or when the water content is limited
(land planets). Based on results from our 3D global climate model, we
present general features of the climate and large-scale circulation on
close-in terrestrial planets. We find that the circulation pattern can
shift from super-rotation to stellar/anti stellar circulation when the
equatorial Rossby deformation radius significantly exceeds the planetary
radius, changing the redistribution properties of the atmosphere. Using
analytical and numerical arguments, we also demonstrate the presence of
systematic biases among mean surface temperatures and among temperature
profiles predicted from either 1D or 3D simulations. After including a
complete modeling of the water cycle, we further demonstrate that two
stable climate regimes can exist for land planets closer than the inner
edge of the classical habitable zone. One is the classical runaway state
where all the water is vaporized, and the other is a collapsed state
where water is captured in permanent cold traps. We identify this
``moist'' bistability as the result of a competition between the
greenhouse effect of water vapor and its condensation on the night side
or near the poles, highlighting the dynamical nature of the runaway
greenhouse effect. We also present synthetic spectra showing the
observable signature of these two states. Taking the example of two
prototype planets in this regime, namely Gl 581 c and HD 85512 b, we
argue that depending on the rate of water delivery and atmospheric
escape during the life of these planets, they could accumulate a
significant amount of water ice at their surface. If such a thick ice
cap is present, various physical mechanisms observed on Earth (e.g.,
gravity driven ice flows, geothermal flux) should come into play to
produce long-lived liquid water at the edge and/or bottom of the ice
cap. Consequently, the habitability of planets at smaller orbital
distance than the inner edge of the classical habitable zone cannot be
ruled out. Transiting planets in this regime represent promising targets
for upcoming exoplanet characterization observatories, such as EChO and
JWST.
}},
doi = {10.1051/0004-6361/201321042},
adsurl = {https://ui.adsabs.harvard.edu/abs/2013A%26A...554A..69L},
localpdf = {https://ui.adsabs.harvard.edu/abs/2013A_26A...554A..69L.pdf},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2013Icar..222...81F,
author = {{Forget}, F. and {Wordsworth}, R. and {Millour}, E. and {Madeleine}, J.-B. and
{Kerber}, L. and {Leconte}, J. and {Marcq}, E. and {Haberle}, R.~M.
},
title = {{3D modelling of the early martian climate under a denser CO$_{2}$ atmosphere: Temperatures and CO$_{2}$ ice clouds}},
journal = {\icarus},
archiveprefix = {arXiv},
eprint = {1210.4216},
primaryclass = {astro-ph.EP},
year = 2013,
volume = 222,
pages = {81-99},
abstract = {{On the basis of geological evidence, it is often stated that the early
martian climate was warm enough for liquid water to flow on the surface
thanks to the greenhouse effect of a thick atmosphere. We present 3D
global climate simulations of the early martian climate performed
assuming a faint young Sun and a CO$_{2}$ atmosphere with surface
pressure between 0.1 and 7 bars. The model includes a detailed radiative
transfer model using revised CO$_{2}$ gas collision induced
absorption properties, and a parameterisation of the CO$_{2}$ ice
cloud microphysical and radiative properties. A wide range of possible
climates is explored using various values of obliquities, orbital
parameters, cloud microphysic parameters, atmospheric dust loading, and
surface properties. Unlike on present day Mars, for pressures higher
than a fraction of a bar, surface temperatures vary with altitude
because of the adiabatic cooling and warming of the atmosphere when it
moves vertically. In most simulations, CO$_{2}$ ice clouds cover a
major part of the planet. Previous studies had suggested that they could
have warmed the planet thanks to their scattering greenhouse effect.
However, even assuming parameters that maximize this effect, it does not
exceed +15 K. Combined with the revised CO$_{2}$ spectroscopy and
the impact of surface CO$_{2}$ ice on the planetary albedo, we
find that a CO$_{2}$ atmosphere could not have raised the annual
mean temperature above 0 {\deg}C anywhere on the planet. The collapse of
the atmosphere into permanent CO$_{2}$ ice caps is predicted for
pressures higher than 3 bar, or conversely at pressure lower than 1 bar
if the obliquity is low enough. Summertime diurnal mean surface
temperatures above 0 {\deg}C (a condition which could have allowed rivers
and lakes to form) are predicted for obliquity larger than 40{\deg} at
high latitudes but not in locations where most valley networks or
layered sedimentary units are observed. In the absence of other warming
mechanisms, our climate model results are thus consistent with a cold
early Mars scenario in which nonclimatic mechanisms must occur to
explain the evidence for liquid water. In a companion paper by
Wordsworth et al. we simulate the hydrological cycle on such a planet
and discuss how this could have happened in more detail.
}},
doi = {10.1016/j.icarus.2012.10.019},
adsurl = {https://ui.adsabs.harvard.edu/abs/2013Icar..222...81F},
localpdf = {https://ui.adsabs.harvard.edu/abs/2013Icar..222...81F.pdf},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2011OLEB...41..539H,
author = {{Heller}, R. and {Barnes}, R. and {Leconte}, J.},
title = {{Habitability of Extrasolar Planets and Tidal Spin Evolution}},
journal = {Origins of Life and Evolution of the Biosphere},
archiveprefix = {arXiv},
eprint = {1108.4347},
primaryclass = {astro-ph.EP},
keywords = {Habitability, Orbital dynamics, Tidal processes, Habitable zone, Gl581d},
year = 2011,
volume = 41,
pages = {539-543},
abstract = {{Stellar radiation has conservatively been used as the key constraint to
planetary habitability. We review here the effects of tides, exerted by
the host star on the planet, on the evolution of the planetary spin.
Tides initially drive the rotation period and the orientation of the
rotation axis into an equilibrium state but do not necessarily lead to
synchronous rotation. As tides also circularize the orbit, eventually
the rotation period does equal the orbital period and one hemisphere
will be permanently irradiated by the star. Furthermore, the rotational
axis will become perpendicular to the orbit, i.e. the planetary surface
will not experience seasonal variations of the insolation. We illustrate
here how tides alter the spins of planets in the traditional habitable
zone. As an example, we show that, neglecting perturbations due to other
companions, the Super-Earth Gl581d performs two rotations per orbit and
that any primordial obliquity has been eroded.
}},
doi = {10.1007/s11084-011-9252-3},
adsurl = {https://ui.adsabs.harvard.edu/abs/2011OLEB...41..539H},
localpdf = {https://ui.adsabs.harvard.edu/abs/2011OLEB...41..539H.pdf},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2011A&A...535A..94B,
author = {{Bolmont}, E. and {Raymond}, S.~N. and {Leconte}, J.},
title = {{Tidal evolution of planets around brown dwarfs}},
journal = {\aap},
archiveprefix = {arXiv},
eprint = {1109.2906},
primaryclass = {astro-ph.EP},
keywords = {brown dwarfs, stars: rotation, planets and satellites: dynamical evolution and stability, planet-star interactions, astrobiology},
year = 2011,
volume = 535,
eid = {A94},
pages = {A94},
abstract = {{Context. The tidal evolution of planets orbiting brown dwarfs (BDs)
presents an interesting case study because BDs' terrestrial planet
forming region is located extremely close-in. In fact, the habitable
zones of BDs range from roughly 0.001 to 0.03 AU and for the lowest-mass
BDs are located interior to the Roche limit.
Aims: In contrast
with stars, BDs spin up as they age. Thus, the corotation distance moves
inward. This has important implications for the tidal evolution of
planets around BDs.
Methods: We used a standard equilibrium tidal
model to compute the orbital evolution of a large ensemble of planet-BD
systems. We tested the effect of numerous parameters such as the initial
semi-major axis and eccentricity, the rotation period of the BD, the
masses of both the BD and planet, and the tidal dissipation factors.
Results: We find that all planets that form at or beyond the
corotation distance and with initial eccentricities smaller than \~{}0.1
are repelled from the BD. Some planets initially interior to corotation
can survive if their inward tidal evolution is slower than the BD's spin
evolution, but most initially close-in planets fall onto the BD.
Conclusions: We find that the most important parameter for the tidal
evolution is the initial orbital distance with respect to the corotation
distance. Some planets can survive in the habitable zone for Gyr
timescales, although in many cases the habitable zone moves inward past
the planet's orbit in just tens to hundreds of Myr. Surviving planets
can have orbital periods of less than 10 days (as small as 10 h), so
they could be observable by transit.
}},
doi = {10.1051/0004-6361/201117734},
adsurl = {https://ui.adsabs.harvard.edu/abs/2011A%26A...535A..94B},
localpdf = {https://ui.adsabs.harvard.edu/abs/2011A_26A...535A..94B.pdf},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2011A&A...528A..27H,
author = {{Heller}, R. and {Leconte}, J. and {Barnes}, R.},
title = {{Tidal obliquity evolution of potentially habitable planets}},
journal = {\aap},
archiveprefix = {arXiv},
eprint = {1101.2156},
primaryclass = {astro-ph.EP},
keywords = {planets and satellites: dynamical evolution and stability, celestial mechanics, planet-star interactions, astrobiology, stars: low-mass, planets and satellites: tectonics},
year = 2011,
volume = 528,
eid = {A27},
pages = {A27},
abstract = {{Context. Stellar insolation has been used as the main constraint on a
planet's potential habitability. However, as more Earth-like planets are
discovered around low-mass stars (LMSs), a re-examination of the role of
tides on the habitability of exoplanets has begun. Those studies have
yet to consider the misalignment between a planet's rotational axis and
the orbital plane normal, i.e. the planetary obliquity.
Aims:
This paper considers the constraints on habitability arising from tidal
processes due to the planet's spin orientation and rate. Since tidal
processes are far from being understood we seek to understand
differences between commonly used tidal models.
Methods: We apply
two equilibrium tide theories - a constant-phase-lag model and a
constant-time-lag model - to compute the obliquity evolution of
terrestrial planets orbiting in the habitable zones around LMSs. The
time for the obliquity to decrease from an Earth-like obliquity of
23.5{\deg} to 5{\deg}, the ``tilt erosion time'', is compared to the
traditional insolation habitable zone (IHZ) in the parameter space
spanned by the semi-major axis a, the eccentricity e, and the stellar
mass M$_{s}$. We also compute tidal heating and equilibrium
rotation caused by obliquity tides as further constraints on
habitability. The Super-Earth Gl581 d and the planet candidate Gl581 g
are studied as examples for these tidal processes.
Results:
Earth-like obliquities of terrestrial planets in the IHZ around stars
with masses {\lsim} 0.25 M$_{&sun;}$ are eroded in less than 0.1
Gyr. Only terrestrial planets orbiting stars with masses {\gsim} 0.9
M$_{&sun;}$ experience tilt erosion times larger than 1 Gyr
throughout the IHZ. Tilt erosion times for terrestrial planets in highly
eccentric orbits inside the IHZ of solar-like stars can be {\lsim} 10
Gyr. Terrestrial planets in the IHZ of stars with masses {\lsim} 0.25
M$_{&sun;}$ undergo significant tidal heating due to obliquity
tides, whereas in the IHZ of stars with masses {\gsim} 0.5
M$_{&sun;}$ they require additional sources of heat to drive
tectonic activity. The predictions of the two tidal models diverge
significantly for e {\gsim} 0.3. In our two-body simulations, Gl581 d's
obliquity is eroded to 0{\deg} and its rotation period reached its
equilibrium state of half its orbital period in $\lt$ 0.1 Gyr. Tidal
surface heating on the putative Gl581 g is {\lsim} 150 mW/m$^{2}$
as long as its eccentricity is smaller than 0.3.
Conclusions:
Obliquity tides modify the concept of the habitable zone. Tilt erosion
of terrestrial planets orbiting LMSs should be included by atmospheric
modelers. Tidal heating needs to be considered by geologists.
}},
doi = {10.1051/0004-6361/201015809},
adsurl = {https://ui.adsabs.harvard.edu/abs/2011A%26A...528A..27H},
localpdf = {https://ui.adsabs.harvard.edu/abs/2011A_26A...528A..27H.pdf},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}