J/AJ/152/160 HARPS-N radial velocities of KOI-70 (Buchhave+, 2016)
A 1.9 Earth radius rocky planet and the discovery of a non-transiting planet in
the Kepler-20 system.
Buchhave L.A., Dressing C.D., Dumusque X., Rice K., Vanderburg A.,
Mortier A., Lopez-Morales M., Lopez E., Lundkvist M.S., Kjeldsen H.,
Affer L., Bonomo A.S., Charbonneau D., Collier Cameron A., Cosentino R.,
Figueira P., Fiorenzano A.F.M., Harutyunyan A., Haywood R.D., Johnson J.A.,
Latham D.W., Lovis C., Malavolta L., Mayor M., Micela G., Molinari E.,
Motalebi F., Nascimbeni V., Pepe F., Phillips D.F., Piotto G., Pollacco D.,
Queloz D., Sasselov D., Segransan D., Sozzetti A., Udry S., Watson C.
<Astron. J., 152, 160-160 (2016)>
=2016AJ....152..160B 2016AJ....152..160B (SIMBAD/NED BibCode)
ADC_Keywords: Planets ; Stars, double and multiple ; Radial velocities
Keywords: planetary systems - planets and satellites: composition -
stars: individual - techniques: radial velocities
Abstract:
Kepler-20 is a solar-type star (V=12.5) hosting a compact system of
five transiting planets, all packed within the orbital distance of
Mercury in our own solar system. A transition from rocky to gaseous
planets with a planetary transition radius of ∼1.6R⊕ has
recently been proposed by several articles in the literature.
Kepler-20b (Rp∼1.9R⊕) has a size beyond this transition
radius; however, previous mass measurements were not sufficiently
precise to allow definite conclusions to be drawn regarding its
composition. We present new mass measurements of three of the planets
in the Kepler-20 system that are facilitated by 104 radial velocity
measurements from the HARPS-N spectrograph and 30 archival Keck/HIRES
observations, as well as an updated photometric analysis of the Kepler
data and an asteroseismic analysis of the host star
(M*=0.948±0.051M☉ and R*=0.964±0.018R☉).
Kepler-20b is a 1.868-0.034+0.066R⊕ planet in a 3.7day
period with a mass of 9.70-1.44+1.41M⊕, resulting in a
mean density of 8.2-1.3+1.5g/cm3, indicating a rocky composition
with an iron-to-silicate ratio consistent with that of the Earth. This
makes Kepler-20b the most massive planet with a rocky composition
found to date. Furthermore, we report the discovery of an additional
non-transiting planet with a minimum mass of
19.96-3.61+3.08M⊕ and an orbital period of ∼34days in the
gap between Kepler-20f (P∼11days) and Kepler-20d (P∼78days).
Description:
We obtained 125 observations of Kepler-20 (KOI-70, KIC 6850504, 2MASS
J19104752+4220194) with the HARPS-N spectrograph on the 3.58m
Telescopio Nazionale Galileo (TNG) located at Roque de Los Muchachos
Observatory, La Palma, Spain. HARPS-N is an updated version of the
original HARPS spectrograph on the 3.6m telescope at the European
Southern Observatory on La Silla, Chile. HARPS-N is an ultra-stable
fiber-fed high-resolution (R=115000) spectrograph with an optical
wavelength coverage from 383 to 693nm. We obtained 61 and 64
observations of Kepler-20 in the 2014 and 2015 observing seasons,
respectively (125 observations in total). We rejected 21 observations
obtained under poor observing conditions where the internal error
estimate exceeded 5m/s leaving a total of 104 observations.
Kepler-20 has a mV=12.5 and required 30 minute exposure times to
build up an adequate signal-to-noise ratio (S/N). The average S/N per
pixel of the observations at 550nm is 30, yielding an average internal
uncertainty estimate of 3.66m/s. The radial velocities and their
1σ errors are shows in Table1.
Objects:
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RA (ICRS) DE Designation(s) (Period)
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19 10 47.52 +42 20 19.3 Kepler-20 = KOI-70 (P=3.69611525)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 58 104 HARPS-N radial velocity measurements of Kepler-20
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See also:
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
J/ApJ/800/135 : HARPS-N radial velocities of KOI-69 (Dressing+, 2015)
J/ApJS/204/24 : Kepler planetary candidates. III. (Batalha+, 2013)
J/ApJ/749/15 : The Kepler-20 planetary system (Gautier+, 2012)
J/other/Nat/486.375 : Stellar parameters of KOI stars (Buchhave+, 2012)
J/ApJ/736/19 : Kepler planetary candidates. II. (Borucki+, 2011)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 12 F12.6 d BJD Barycentric Julian Date (BJD-2400000) (1)
14- 22 F9.2 m/s RV [-20944.6/-20904.6] Radial velocity
24- 27 F4.2 m/s e_RV [2.46/4.95] The 1σ error in RV
29- 35 F7.2 m/s FWHM [6843.03/6926.1] Full-Width at Half-Maximum
37- 41 F5.2 m/s e_FWHM [5.78/11.63] The 1σ error in FWHM
43- 47 F5.2 [-] logR'HK [-5.08/-4.76] Log Ca II chromospheric activity
index (Ca II log(R'HK))
49- 52 F4.2 [-] e_logR'HK [0.03/0.13] The 1σ error in log(R'HK)
54- 58 F5.2 --- S/N [23.6/41.5] Signal-to-Noise ratio at 550nm
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Note (1): Of the weighted midtime of exposure (UTC).
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History:
From electronic version of the journal
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 18-Jan-2017