J/AJ/165/235 115 HARPS-N and ESPRESSO radial velocity for K2-136 (Mayo+, 2023)
Hyades Member K2-136c; The Smallest Planet in an Open Cluster with a Precisely
Measured Mass.
Mayo A.W., Dressing C.D., Vanderburg A., Fortenbach C.D., Lienhard F.,
Malavolta L., Mortier A., Nunez A., Richey-Yowell T., Turtelboom E.V.,
Bonomo A.S., Latham D.W., Lopez-Morales M., Shkolnik E., Sozzetti A.,
Agueros M.A., Borsato L., Charbonneau D., Cosentino R., Douglas S.T.,
Dumusque X., Ghedina A., Gibson R., Granata V., Harutyunyan A.,
Haywood R.D., Lacedelli G., Lorenzi V., Magazzu A.,
Martinez Fiorenzano A.F., Micela G., Molinari E., Montalto M.,
Nardiello D., Nascimbeni V., Pagano I., Piotto G., Pino L., Poretti E.,
Scandariato G., Udry S., Buchhave L.A.
<Astron. J., 165, 235 (2023)>
=2023AJ....165..235M 2023AJ....165..235M
ADC_Keywords: Stars, K-type; Spectra, optical; Radial velocities
Keywords: Exoplanets ; Exoplanet systems ; Exoplanet atmospheres ;
Exoplanet detection methods ; Radial velocity ; Transits ;
Astronomy data modeling ; Exoplanet evolution ; Extrasolar
gaseous planets
Abstract:
K2-136 is a late-K dwarf (0.742±0.039M☉) in the Hyades open
cluster with three known, transiting planets and an age of
650±70Myr. Analyzing K2 photometry, we found that planets K2-136b,
c, and d have periods of 8.0, 17.3, and 25.6days and radii of
1.014±0.050R⊕, 3.00±0.13R⊕, and
1.565±0.077R⊕, respectively. We collected 93 radial velocity
(RVel) measurements with the High-Accuracy Radial-velocity Planet
Searcher for the Northern hemisphere (HARPS-N) spectrograph
(Telescopio Nazionale Galileo) and 22 RVs with the Echelle
SPectrograph for Rocky Exoplanets and Stable Spectroscopic
Observations (ESPRESSO) spectrograph (Very Large Telescope). Analyzing
HARPS-N and ESPRESSO data jointly, we found that K2-136c induced a
semi-amplitude of 5.49±0.53m/s, corresponding to a mass of
18.1±1.9M⊕. We also placed 95% upper mass limits on K2-136b
and d of 4.3 and 3.0M⊕, respectively. Further, we analyzed
Hubble Space Telescope and XMM-Newton observations to establish the
planetary high-energy environment and investigate possible atmospheric
loss. K2-136c is now the smallest planet to have a measured mass in an
open cluster and one of the youngest planets ever with a mass
measurement. K2-136c has ∼75% the radius of Neptune but is similar in
mass, yielding a density of 3.69-0.56+0.67g/cm3 (∼2-3 times
denser than Neptune). Mass estimates for K2-136b (and possibly d) may
be feasible with more RV observations, and insights into all three
planets' atmospheres through transmission spectroscopy would be
challenging but potentially fruitful. This research and future mass
measurements of young planets are critical for investigating the
compositions and characteristics of small exoplanets at very early
stages of their lives and providing insights into how exoplanets
evolve with time.
Description:
We collected 93 RV observations using the High Accuracy Radial
velocity Planet Searcher for the Northern hemisphere (HARPS-N)
spectrograph on the Telescopio Nazionale Galileo (TNG). The spectra
had an average exposure time of 1776.5s, and the average
signal-to-noise ratio (S/N) on the order around 550nm was 51.1. The RV
standard deviation was 6.9 m/s.
We collected 22 RV observations using the ESPRESSO spectrograph on the
Very Large Telescope (VLT) between 2019 November 1 and 2020 February
27 (program 0104.C-0837(A), PI: Malavolta). The typical exposure time
for the spectra was 1800s, and the average S/N at order 111 (central
wavelength=551 nm) was 79.9. The RV standard deviation was 7.8m/s.
Object:
------------------------------------------------------------
RA (ICRS) DE Designation(s) (Period)
------------------------------------------------------------
04 29 38.99 +22 52 57.7 K2-136 = EPIC 247589423 (17.3d)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 81 115 Radial velocity observations and activity indicators
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See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
I/352 : Distances to 1.47 billion stars in Gaia EDR3 (Bailer-Jones+, 2021)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
J/A+A/331/81 : Hyades membership (Perryman+ 1998)
J/A+A/526/A99 : Metal-poor solar-type * spectroscopy & masses (Sousa+, 2011)
J/other/Nat/486.375 : Stellar parameters of KOI stars (Buchhave+, 2012)
J/ApJ/757/161 : Spectroscopy of 56 exoplanet host stars (Torres+, 2012)
J/A+A/557/A70 : Evolved planet hosts - stellar parameters (Mortier+, 2013)
J/A+A/555/A150 : Physical parameters cool solar-type stars (Tsantaki+, 2013)
J/A+A/566/A35 : Radial velocities of HD 41248 (Santos+, 2014)
J/ApJ/795/167 : Transit of PH3 b, c, d through January 2019 (Schmitt+, 2014)
J/ApJS/210/25 : Transit timing variation 15 planetary pairs. II. (Xie, 2014)
J/A+A/576/A94 : Northern bright planet host stars parameters (Sousa+, 2015)
J/ApJS/222/14 : Planetary candidates 1st yr K2 mission (Vanderburg+, 2016)
J/ApJ/825/19 : Mass-radius relationship planets with Rp<4 (Wolfgang+, 2016)
J/AJ/154/109 : California-Kepler Survey. III. Planet radii (Fulton+, 2017)
J/MNRAS/472/1618 : Kepler study of starspot lifetimes (Giles+, 2017)
J/ApJ/879/100 : K2 rotation per Hyades & Praesepe members (Douglas+, 2019)
J/AJ/158/165 : RV obs & activity indicators Kepler-538b (Mayo+, 2019)
J/ApJ/872/17 : HAZMAT. V. UV & Xray evol of Kstars (Richey-Yowell+, 2019)
J/A+A/624/A15 : Kepler-411 mid-transit times (Sun+, 2019)
J/AJ/160/192 : Photometry and RVs of K2-25b with HPF (Stefansson+, 2020)
J/A+A/650/A66 : DS Tuc A radial velocity curve (Benatti+, 2021)
J/A+A/653/A41 : L 98-59 (TOI-175) ESPRESSO observations (Demangeon+, 2021)
J/A+A/649/A6 : Gaia Catalogue of Nearby Stars (Gaia collaboration, 2021)
J/A+A/661/A23 : Exoplanet Xray irradiation &evaporation rate (Foster+, 2022)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 16 F16.8 d BJD [2.4e+06/2.5e+06] Barycentric Julian Date at TBD
18- 25 F8.2 m/s RVel [39480/39519] Radial velocity
27- 30 F4.2 m/s e_RVel [0.4/6] Error on RVel
32- 38 F7.2 m/s CCFBIS [6886/6997] Cross Correlation Function bisector
span inverse slope
40- 44 F5.2 m/s e_CCFBIS [0.9/12] Error on CCFBIS
46- 50 F5.2 m/s CCFFWHM [34.1/86.1] Cross Correlation Function full
width at half maximum
52- 56 F5.2 m/s e_CCFFWHM [0.9/12] Error on CCFFWHM
58- 64 F7.5 --- SHK [1.05/1.41] Mt. Wilson CaII HK activity index
66- 72 F7.5 --- e_SHK [0.0006/0.2] Error on SHK
74- 81 A8 --- Inst Instrument used; ESPRESSO or HARPS-N
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History:
From electronic version of the journal
(End) Prepared by Coralie Fix [CDS], 12-Jan-2024