J/ApJ/814/91 Comparative habitability of transiting exoplanets (Barnes+, 2015)
Comparative habitability of transiting exoplanets.
Barnes R., Meadows V.S., Evans N.
<Astrophys. J., 814, 91 (2015)>
=2015ApJ...814...91B 2015ApJ...814...91B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Planets ; Models
Keywords: planets and satellites: surfaces
Abstract:
Exoplanet habitability is traditionally assessed by comparing a
planet's semimajor axis to the location of its host star's "habitable
zone", the shell around a star for which Earth-like planets can
possess liquid surface water. The Kepler space telescope has
discovered numerous planet candidates near the habitable zone, and
many more are expected from missions such as K2, TESS, and PLATO.
These candidates often require significant follow-up observations for
validation, so prioritizing planets for habitability from transit data
has become an important aspect of the search for life in the universe.
We propose a method to compare transiting planets for their potential
to support life based on transit data, stellar properties and
previously reported limits on planetary emitted flux. For a planet in
radiative equilibrium, the emitted flux increases with eccentricity,
but decreases with albedo. As these parameters are often
unconstrained, there is an "eccentricity-albedo degeneracy" for the
habitability of transiting exoplanets. Our method mitigates this
degeneracy, includes a penalty for large-radius planets, uses
terrestrial mass-radius relationships, and, when available,
constraints on eccentricity to compute a number we call the
"habitability index for transiting exoplanets" that represents the
relative probability that an exoplanet could support liquid surface
water. We calculate it for Kepler objects of interest and find that
planets that receive between 60% and 90% of the Earth's incident
radiation, assuming circular orbits, are most likely to be habitable.
Finally, we make predictions for the upcoming TESS and James Webb
Space Telescope missions.
Description:
We consider the entire Kepler sample as of 2015 August 17, from the
NASA exoplanet archive, including confirmed and unconfirmed planets,
but no false positives. We cut this sample by requiring the
equilibrium temperature Teq to lie between 150 and 400K and Rp to be
less than 2.5R{earth}.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 160 269 Observed and derived parameters for potentially
habitable KOIs
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See also:
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
J/ApJS/222/14 : Planetary cand. from 1st yr K2 mission (Vanderburg+, 2016)
J/ApJ/809/77 : Transiting Exoplanet Survey Satellite (TESS) (Sullivan+, 2015)
J/ApJ/807/45 : Potential habitable planets around M dwarfs (Dressing+, 2015)
J/ApJS/210/20 : Small Kepler planets radial velocities (Marcy+, 2014)
J/A+A/567/A133 : Habitable zone code (Valle+, 2014)
J/ApJ/771/L45 : 3D climate models for exoplanet around M-star (Yang+, 2013)
J/ApJ/771/107 : Spectroscopy of faint KOI stars (Everett+, 2013)
J/ApJ/770/90 : Candidate planets in the habitable zones (Gaidos, 2013)
J/ApJS/204/24 : Kepler planetary candidates. III. (Batalha+, 2013)
J/A+A/549/A109 : HARPS XXXI. The M-dwarf sample (Bonfils+, 2013)
J/ApJ/736/L25 : Habitability of Kepler planetary cand. (Kaltenegger+, 2011)
J/ApJ/715/1050 : Predicted abundances for extrasolar planets. I. (Bond+, 2010)
http://exoplanetarchive.ipac.caltech.edu/ : NASA exoplanet archive
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Pl Planet identifier (KNNNNN.NN, K2-3d or
Kepler-NNa)
13- 17 F5.3 Rsun R* [0.1/2] Stellar radius
19- 22 I4 K Teff [2661/6640] Effective stellar temperature
24- 28 F5.3 [cm/s2] log(g)* [4/5.3] Log stellar surface gravity
30- 34 F5.3 Msun M* [0.09/1.4] Stellar mass
36- 40 F5.3 Lsun L* [0.001/4.5] Stellar luminosity
42- 48 F7.3 d Per [3.6/651.1] Orbital period
50- 56 F7.1 ppm Depth [52.5/37296] Transit depth
58- 63 F6.3 h Dur [0.8/34.2] Transit duration (D)
65- 69 F5.3 --- b [0/0.97] Impact parameter
71- 74 F4.2 Rgeo Rp [0.5/2.5] Planetary radius
76- 80 F5.2 Mgeo Mp [0.1/28.3] Planetary mass
82- 86 F5.2 [m/s2] log(g)p [4.3/44.4] Log planetary surface gravity
88- 92 F5.1 W/m2 Fmax [270.4/350] Runaway greenhouse flux
94- 99 F6.4 AU a [0.02/1.5] Semi-major axis
101-106 F6.3 h Dc [0.3/20.8] Transit duration if orbit is circular
108-112 F5.3 --- TDA [0.1/4] Transit Duration Anomaly (D/Dc)
114-119 F6.4 --- emin Minimum eccentricity
121-125 F5.3 --- emax Maximum eccentricity
127-132 F6.3 Earth Scir [0.1/21.5] Incident stellar radiation (1)
134-138 F5.3 --- H [0/0.93] "habitability index for transiting
exoplanets" (HITE)
140-144 F5.3 --- H' [0/0.96] HITE prime
146-150 F5.2 mag Jmag [9.4/14.7] Apparent J band magnitude
152-156 F5.2 mag Kmag [8.5/17.2] Apparent K band magnitude
158 I1 --- L [0/3]? Flux boundary (2)
160 I1 --- Nc [0/2] Number of adjacent planetary companions
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Note (1): If the orbit is circular, in Earth units.
Note (2): Limit as follows:
0 = max;
1 = min;
2 = both.
3 = Not explained in the paper (22 sources)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 24-Feb-2016