J/AJ/158/165 RV observations & activity indicators for Kepler-538b (Mayo+, 2019)
An 11 Earth-mass, long-period sub-Neptune orbiting a Sun-like star.
Mayo A.W., Rajpaul V.M., Buchhave L.A., Dressing C.D., Mortier A., Zeng L.,
Fortenbach C.D., Aigrain S., Bonomo A.S., Collier Cameron A.,
Charbonneau D., Coffinet A., Cosentino R., Damasso M., Dumusque X.,
Fiorenzano A.F.M., Haywood R.D., Latham D.W., Lopez-Morales M.,
Malavolta L., Micela G., Molinari E., Pearce L., Pepe F., Phillips D.,
Piotto G., Poretti E., Rice K., Sozzetti A., Udry S.
<Astron. J., 158, 165-165 (2019)>
=2019AJ....158..165M 2019AJ....158..165M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, G-type ; Exoplanets ; Radial velocities
Keywords: planets and satellites: composition -
planets and satellites: detection -
planets and satellites: fundamental parameters -
planets and satellites: gaseous planets - methods: data analysis -
techniques: photometric - techniques: radial velocities
Abstract:
Although several thousands of exoplanets have now been detected and
characterized, observational biases have led to a paucity of long-period,
low-mass exoplanets with measured masses and a corresponding lag in our
understanding of such planets. In this paper we report the mass estimation
and characterization of the long-period exoplanet Kepler-538b. This planet
orbits a Sun-like star (V=11.27) with M*=0.892-0.035+0.051 M☉
and R*=0.8717-0.0061+0.0064 R☉. Kepler-538b is a
2.215-0.034+0.040 R⊕ sub-Neptune with a period of
P=81.73778±0.00013 days. It is the only known planet in the system.
We collected radial velocity (RV) observations with the High Resolution
Echelle Spectrometer (HIRES) on Keck I and High Accuracy Radial velocity
Planet Searcher in North hemisphere (HARPS-N) on the Telescopio Nazionale
Galileo (TNG). We characterized stellar activity by a Gaussian process
with a quasi-periodic kernel applied to our RV and cross-correlation
function FWHM observations. By simultaneously modeling Kepler photometry,
RV, and FWHM observations, we found a semi-amplitude of
K=1.68-0.38+0.39 m/s and a planet mass of
Mp=10.6-2.4+2.5 M⊕. Kepler-538b is the smallest planet
beyond P=50 days with an RV mass measurement. The planet likely consists
of a significant fraction of ices (dominated by water ice), in addition
to rocks/metals, and a small amount of gas. Sophisticated modeling
techniques such as those used in this paper, combined with future
spectrographs with ultra high-precision and stability will be vital for
yielding more mass measurements in this poorly understood exoplanet regime.
This in turn will improve our understanding of the relationship between
planet composition and insolation flux and how the rocky to gaseous
transition depends on planetary equilibrium temperature.
Description:
We downloaded RVs from 26 spectra collected with the High Resolution
Echelle Spectrometer (HIRES) instrument (Vogt et al. 1994SPIE.2198..362V 1994SPIE.2198..362V)
at the Keck I telescope from 2010 July 25 to 2014 July 11. These spectra
were originally collected as part of the Kepler Follow-up Observing
Program. The standard California Planet Search setup was used
(Howard et al. 2010ApJ...721.1467H 2010ApJ...721.1467H) and the C2 decker was utilized to
conduct sky subtraction. Exposure times averaged 1800 s. Finally, we
gathered 83 spectra with the High Accuracy Radial velocity Planet Searcher
in North hemisphere (HARPS-N) instrument (Cosentino et al.
2012SPIE.8446E..1VC, 2014SPIE.9147E..8CC) on the 3.6 m Telescopio Nazionale
Galileo (TNG) on La Palma. These observations were made from 2014 June 20
to 2015 November 7, all with exposure times of 30 minutes. They were
collected as part of the HARPS-N Collaboration's Guaranteed Time
Observations (GTO) program.
Objects:
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RA (ICRS) DE Designation(s) (Period)
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19 49 56.85 +49 37 24.4 Kepler-538b = KOI-365.01 (P=81.73778)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 70 109 RV observations and activity indicators,
determined from the data reduction software
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See also:
J/ApJ/736/19 : Kepler planetary candidates. II. (Borucki+, 2011)
J/other/Nat/486.375 : Stellar parameters of KOI stars (Buchhave+, 2012)
J/ApJS/210/19 : Kepler planetary candidates. IV. 22 months (Burke+, 2014)
J/ApJS/217/31 : Kepler planetary candidates. VI. 4yr Q1-Q16
(Mullally+, 2015)
J/ApJS/224/12 : Kepler planetary candidates. VII. 48-month
(Coughlin+, 2016)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 14 F14.6 d BJD Barycentric Julian Date
16- 24 F9.2 m/s RV [-37346.9/7.76] Radial velocity
26- 30 F5.2 m/s e_RV [1.14/12.94] Uncertainty in RV
32- 38 F7.5 km/s FWHM [6.63443/6.67355]? Full width at half maximum
40- 47 F8.5 km/s BIS [-0.08202/-0.0222]? Bisector span inverse slope
49- 55 F7.4 [-] log(RHK) [-5.078/-4.912]? Stellar activity index
log10(R'HK)
57- 62 F6.4 [-] e_log(RHK) [0.0093/0.2193]? Uncertainty in log(RHK)
64- 70 A7 --- Inst Instrument (HIRES or HARPS-N)
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History:
From electronic version of the journal
(End) Tiphaine Pouvreau [CDS] 08-Nov-2019