J/AJ/155/107 HARPS-N observations of K2-141 planetary system (Malavolta+, 2018)
An ultra-short period rocky super-Earth with a secondary eclipse and
a Neptune-like companion around K2-141.
Malavolta L., Mayo A.W., Louden T., Rajpaul V.M., Bonomo A.S.,
Buchhave L.A., Kreidberg L., Kristiansen M.H., Lopez-Morales M.,
Mortier A., Vanderburg A., Coffinet A., Ehrenreich D., Lovis C., Bouchy F.,
Charbonneau D., Ciardi D.R., Cameron A.C., Cosentino R., Crossfield I.J.M.,
Damasso M., Dressing C.D., Dumusque X., Everett M.E., Figueira P.,
Fiorenzano A.F.M., Gonzales E.J., Haywood R.D., Harutyunyan A., Hirsch L.,
Howell S.B., Johnson J.A., Latham D.W., Lopez E., Mayor M.,
Micela G., Molinari E., Nascimbeni V., Pepe F., Phillips D.F., Piotto G.,
Rice K., Sasselov D., Segransan D., Sozzetti A., Udry S., Watson C.
<Astron. J., 155, 107 (2018)>
=2018AJ....155..107M 2018AJ....155..107M (SIMBAD/NED BibCode)
ADC_Keywords: Exoplanets ; Radial velocities ; Stars, double and multiple
Keywords: planetary systems - planets and satellites: composition -
planets and satellites: individual (K2-141b, K2-141c) -
planets and satellites: interiors - stars: individual (K2-141) -
techniques: photometric - techniques: radial velocities
Abstract:
Ultra-short period (USP) planets are a class of low-mass planets with
periods shorter than one day. Their origin is still unknown, with
photo-evaporation of mini-Neptunes and in situ formation being the
most credited hypotheses. Formation scenarios differ radically in the
predicted composition of USP planets, and it is therefore extremely
important to increase the still limited sample of USP planets with
precise and accurate mass and density measurements. We report here the
characterization of a USP planet with a period of 0.28 days around K2-141
(EPIC 246393474), and the validation of an outer planet with a period
of 7.7 days in a grazing transit configuration. We derived the radii
of the planets from the K2 light curve and used high-precision radial
velocities gathered with the HARPS-N spectrograph for mass measurements.
For K2-141b, we thus inferred a radius of 1.51±0.05 R⊕ and a
mass of 5.08±0.41 M⊕, consistent with a rocky composition
and lack of a thick atmosphere. K2-141c is likely a Neptune-like planet,
although due to the grazing transits and the non-detection in the RV
data set, we were not able to put a strong constraint on its density.
We also report the detection of secondary eclipses and phase curve
variations for K2-141b. The phase variation can be modeled either by a
planet with a geometric albedo of 0.30±0.06 in the Kepler bandpass,
or by thermal emission from the surface of the planet at ∼3000 K. Only
follow-up observations at longer wavelengths will allow us to
distinguish between these two scenarios.
Description:
We collected 44 spectra using HARPS-N at the Telescopio Nazionale Galileo
(TNG), in La Palma (Cosentino et al. 2012SPIE.8446E..1VC), with the
goal of precisely determining the mass of the USP planet. To reach this
goal, we followed a twofold strategy: we gathered at least two points
each night (when weather allowed) in order to remove activity variations
by applying nightly offsets (e.g., Hatzes et al. 2011ApJ...743...75H 2011ApJ...743...75H;
Pepe et al. 2013Natur.503..377P 2013Natur.503..377P), and we observed the target for a
duration of a few stellar rotations to be able to use a Gaussian process
(GP) regression (e.g., Haywood et al. 2014MNRAS.443.2517H 2014MNRAS.443.2517H; Rajpaul et al.
2015MNRAS.452.2269R 2015MNRAS.452.2269R) to model the stellar activity signals directly.
Objects:
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RA (ICRS) DE Designation(s)
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23 23 39.97 -01 11 21.5 K2-141 = StKM 1-2122
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 81 42 HARPS-N Radial Velocity Measurements
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See also:
J/ApJ/787/47 : 106 Kepler ultra-short-period planets (Sanchis-Ojeda+, 2014)
J/ApJ/789/154 : Kepler-10 RV measurements by HARPS-N (Dumusque+, 2014)
J/A+A/584/A72 : A transiting rocky planet at 6.5pc from the Sun
(Motalebi+ 2015)
J/A+A/612/A95 : K2-141 b radial velocity and light curve (Barragan+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 14 F14.6 d BJD Barycentric Julian Date (TDB)
16- 24 F9.3 m/s RV [-3420.815/-3369.868] Radial velocity
26- 30 F5.3 m/s e_RV [1.126/5.545] Uncertainty in RV
32- 36 F5.2 m/s BIS [23.95/56.69] Bisector Inverse Span
38- 45 F8.6 km/s FWHM [6.8897/6.98785] Full-Width at Half-Maximum
47- 54 F8.6 [-] SHK [0.87323/1.005589] SHK index (in dex)
56- 63 F8.6 [-] e_SHK [0.007108/0.059868] Uncertainty in SHK (in dex)
65- 72 F8.6 [-] Ha [0.279721/0.295939] Hα index (in dex)
74- 81 F8.6 [-] e_Ha [0.000559/0.002062] Uncertainty in Ha (in dex)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 23-Oct-2018