J/ApJ/808/194 Performance of exoplanet search space missions (Leger+, 2015)
Impact of ηEarth on the capabilities of affordable space missions
to detect biosignatures on extrasolar planets.
Leger A., Defrere D., Malbet F., Labadie L., Absil O.
<Astrophys. J., 808, 194 (2015)>
=2015ApJ...808..194L 2015ApJ...808..194L (SIMBAD/NED BibCode)
ADC_Keywords: Models ; Stars, distances ; Spectral types ; Magnitudes ; Planets
Keywords: astrobiology; instrumentation: high angular resolution;
instrumentation: interferometers; instrumentation: miscellaneous;
planets and satellites: terrestrial planets
Abstract:
We present an analytic model to estimate the capabilities of space
missions dedicated to the search for biosignatures in the atmosphere
of rocky planets located in the habitable zone of nearby stars.
Relations between performance and mission parameters, such as mirror
diameter, distance to targets, and radius of planets, are obtained.
Two types of instruments are considered: coronagraphs observing in the
visible, and nulling interferometers in the thermal infrared. Missions
considered are: single-pupil coronagraphs with a 2.4m primary mirror,
and formation-flying interferometers with 4x0.75m collecting mirrors.
The numbers of accessible planets are calculated as a function of
ηEarth. When Kepler gives its final estimation for ηEarth,
the model will permit a precise assessment of the potential of each
instrument. Based on current estimations, ηEarth=10% around FGK
stars and 50% around M stars, the coronagraph could study in
spectroscopy only ∼1.5 relevant planets, and the interferometer ∼14.0.
These numbers are obtained under the major hypothesis that the
exozodiacal light around the target stars is low enough for each
instrument. In both cases, a prior detection of planets is assumed and
a target list established. For the long-term future, building both
types of spectroscopic instruments, and using them on the same
targets, will be the optimal solution because they provide
complementary information. But as a first affordable space mission,
the interferometer looks the more promising in terms of biosignature
harvest.
Description:
The selected target list is specific to each instrument. Starting from
the list of the nearest stars, the first step is to select the
sub-sample that can be observed with each instrument. For both types
of coronagraphs, there is no M star, because the HZ around these stars
is seen at too small an angle, around 20 to 60mas for the nearest M
stars (Table 8), whereas the inner working angle (IWA) is 170mas for
the built-in coronagraph with Φ=2.4m, IWA=2.5λ/Φ, and
λ=0.8um; or 115mas for a 34m starshade. For the interferometer,
the target list comprises both M stars and solar-type (FGK) stars due
to adjustable baseline length.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 88 200 Integration times divided by c for FGK stars
table3.dat 89 100 Possible target list for a 2.4m coronagraph
table7.dat 89 100 Integration times divided by d for G stars
table8.dat 84 180 M stars for 1yr observations with a 4x0.75m
interferometer
table9.dat 89 200 FGK stars for 4yr observations with a 4x0.75m
interferometer
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See also:
I/311 : Hipparcos, the New Reduction (van Leeuwen, 2007)
J/ApJ/799/180 : Radii of KOI Earth- to Neptune-sized planets (Silburt+, 2015)
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/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/736/19 : Kepler planetary candidates. II. (Borucki+, 2011)
J/ApJ/716/1336 : Stability analysis of single-planet (Kopparapu+, 2010)
J/A+A/505/859 : M dwarfs radial velocities (Zechmeister+, 2009)
http://exep.jpl.nasa.gov/exnps/index.html : ExNPS report
http://wfirst.gsfc.nasa.gov/ : Wide-Field IR Survey Telescope webpage
http://www.esa.int/Our_Activities/Space_Engineering_Technology/Proba_Missions/
: Proba Missions home page
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- HIP [171/120005] Hipparcos identifier
8- 26 A19 --- Name Common identifier
28- 32 F5.2 pc Dist [1.2/15] Distance
34- 38 F5.2 mag Vmag [-1.5/10] Apparent V band magnitude
40- 46 F7.3 solLum LBol [0.004/235.4] Bolometric luminosity
48- 57 A10 --- SpT MK spectral type
59- 66 E8.2 --- rho Transmission at HZ angle
68- 75 E8.2 yr t/c Integration time divided by c (1)
77- 79 I3 --- i [1/200] Target rank
81- 88 E8.2 yr St/c Cumulative time divided by c (1)
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Note (1): Where c is a parameter of the model. Fitting to Lunine et al. (2009;
arXiv:0808.2754v3) yields c=2.81e8yr.
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- HIP [746/116771] Hipparcos identifier
8- 24 A17 --- Name Common identifier
26- 30 F5.2 pc Dist [1.2/26.2] Distance
32- 36 F5.2 mag Vmag [-1.5/6] Apparent V band magnitude
38- 43 F6.3 solLum LBol [0.09/61] Bolometric luminosity
45- 58 A14 --- SpT MK spectral type
60- 67 E8.2 --- rho Transmission at HZ angle
69- 76 E8.2 yr t [0.05/568] Required integration time
78- 80 I3 --- i [1/100] Target rank
82- 89 E8.2 yr St [0.05/17500] Cumulative time
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- HIP [171/113357] Hipparcos identifier
8- 22 A15 --- Name Common identifier
24- 28 F5.1 arcsec Sep [10/137]? Double star separation
30 A1 --- f_Sep [b] b: Indicates Sep is for the year 2030
32- 36 F5.2 pc Dist [1.2/18] Distance
38- 40 I3 mas HZ [12/984] Angular distance between mean HZ and
star
42- 46 F5.2 mag Vmag [-0.01/10] Apparent V band magnitude
48- 51 F4.2 solLum LBol [0.04/9.6] Bolometric luminosity
53- 62 A10 --- SpT MK spectral type
64- 67 I4 --- Teff [4898/6602] Effective temperature
69- 76 E8.2 yr t/d [1/8540] Integration time divided by d (1)
78- 80 I3 --- i [1/100] Target rank
82- 89 E8.2 yr St/d [1.4/430000] Cumulative time divided by d (1)
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Note (1): Where d is a parameter of the model. Fitting to Defrere et al.
(2010A&A...509A...9D 2010A&A...509A...9D) yields d=3.4e-5yr.
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Byte-by-byte Description of file: table8.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- HIP [428/118212] Hipparcos identifier
8- 21 A14 --- Name Common name
23- 27 F5.2 pc Dist [1.3/20] Distance
29- 33 F5.2 mag Vmag [5.5/11.7] Apparent V band magnitude
35- 42 E8.2 solLum LBol [0.0008/3.5] Bolometric luminosity
44- 48 F5.1 mas HZ [20/133] Angular distance between mean HZ and
star
50- 57 A8 --- SpT MK spectral type
59- 62 I4 K Teff [2425/6504] Effective temperature
64- 71 E8.2 yr t [0.001/66] Required integration time
73- 75 I3 --- i [1/180] Target rank
77- 84 E8.2 yr St [0.001/2360] Cumulative time
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Byte-by-byte Description of file: table9.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- HIP [169/120005] Hipparcos identifier
8- 21 A14 --- Name Common identifier
23- 27 F5.1 arcsec Sep [10/400]? Companion separation (1)
29- 33 F5.2 pc Dist [1/16] Distance
35- 37 I3 mas HZ [6/984] Angular distance between mean HZ and
star
39- 43 F5.2 mag Vmag [-0.01/12.2] Apparent V band magnitude
45- 49 F5.2 solLum LBol [0.01/12] Bolometric luminosity
51- 62 A12 --- SpT MK spectral type
64- 67 I4 K Teff [3335/7109] Effective temperature
69- 71 I3 --- i [1/200] Target rank
73- 80 E8.2 yr t [0.002/26.2] Required integration time
82- 89 E8.2 yr St [0.002/2370] Cumulative time
--------------------------------------------------------------------------------
Note (1): α Cen is triple system. The angular separation between A or B
to proxima Cen is 2030".
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 04-Dec-2015