J/AJ/163/41 K2-79 and K2-222 photometry and radial velocity (Nava+, 2022)
K2-79b and K2-222b; Mass Measurements of Two Small Exoplanets with Periods
beyond 10 days that Overlap with Periodic Magnetic Activity Signals.
Nava C., Lopez-Morales M., Mortier A., Zeng Li, Giles H.A.C., Bieryla A.,
Vanderburg A., Buchhave L.A., Poretti E., Saar S.H., Dumusque X.,
Latham D.W., Charbonneau D., Damasso M., Bonomo A.S., Lovis C.,
Collier Cameron A., Eastman J.D., Sozzetti A., Cosentino R., Pedani M.,
Pepe F., Molinari E., Sasselov D., Mayor M., Stalport M., Malavolta L.,
Rice K., Watson C.A., Martinez Fiorenzano A.F., Di Fabrizio L.
<Astron. J., 163, 41 (2022)>
=2022AJ....163...41N 2022AJ....163...41N
ADC_Keywords: Exoplanets; Stars, G-type; Spectra, optical; Photometry;
Radial velocities
Keywords: Exoplanet astronomy ; Stellar activity
Abstract:
We present mass and radius measurements of K2-79b and K2-222b, two
transiting exoplanets orbiting active G-type stars observed with
HARPS-N and K2. Their respective 10.99day and 15.39day orbital periods
fall near periods of signals induced by stellar magnetic activity. The
two signals might therefore interfere and lead to an inaccurate
estimate of exoplanet mass. We present a method to mitigate these
effects when radial velocity (RV) and activity-indicator observations
are available over multiple observing seasons and the orbital period
of the exoplanet is known. We perform correlation and periodogram
analyses on subsets composed of each target's two observing seasons,
in addition to the full data sets. For both targets, these analyses
reveal an optimal season with little to no interference at the orbital
period of the known exoplanet. We make a confident mass detection of
each exoplanet by confirming agreement between fits to the full RV set
and the optimal season. For K2-79b, we measure a mass of
11.8±3.6M⊕ and a radius of 4.09±0.17R⊕. For
K2-222b, we measure a mass of 8.0±1.8M⊕ and a radius of
2.35±0.08R⊕. According to model predictions, K2-79b is a
highly irradiated Uranus analog and K2-222b hosts significant amounts
of water ice. We also present a RV solution for a candidate second
companion orbiting K2-222 at 147.5days.
Description:
We analyzed 3161 and 3424 photometric K2 observations of K2-79 and
K2-222, respectively, collected in long-cadence (29.4minutes) mode.
K2-79 was observed between 2015 February 10 and 2015 April 20 and
K2-222 between 2016 January 6 and 2016 March 23.
We collected 79 spectra of K2-79 over four seasons between 2015
November 4 and 2019 December 29, and 63 spectra of K2-222 over three
seasons between 2016 August 14 and 2019 December 23. All spectra were
collected with HARPS-N, the high-precision spectrograph mounted on the
Telescopio Nationale de Galileo at the Observatorio del Roque de los
Muchachos in La Palma, Spain. The spectrograph covers wavelengths in
the range 383-690nm, with average resolving power R=115000
Objects:
--------------------------------------------------------
RA (ICRS) DE Designation(s) (Period)
--------------------------------------------------------
03 41 01.42 +13 31 09.7 K2-79 = K2-79 (P=23.8d)
01 05 50.95 +11 45 12.3 K2-222 = BD+10 125 (P=17.5d)
--------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 38 3161 K2-79 LC observations
table2.dat 38 3424 K2-222 LC observations
table3.dat 68 79 K2-79 HARPS-N RV and stellar activity indicator
table4.dat 68 63 K2-222 HARPS-N RV and stellar activity indicator
--------------------------------------------------------------------------------
See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
I/322 : UCAC4 Catalogue (Zacharias+, 2012)
J/A+A/526/A99 : Metal-poor solartype stars spectroscopy & masses (Sousa+, 2011)
J/A+A/529/A75 : Limb-darkening coefficients (Claret+, 2011)
J/ApJ/736/19 : Kepler planetary candidates. II. (Borucki+, 2011)
J/other/Nat/486.375 : Stellar parameters of KOI stars (Buchhave+, 2012)
J/ApJS/204/24 : Kepler planetary candidates. III. (Batalha+, 2013)
J/ApJS/211/24 : Rotation periods of Kepler MS stars (McQuillan+, 2014)
J/A+A/585/A135 : HD175607 RV, logRHK and Halpha index (Mortier+, 2016)
J/AJ/152/204 : HARPS-N radial velocities of HD 179070 (Lopez-Morales+, 2016)
J/ApJS/222/14 : Planetary candidates from 1st yr K2 mission (Vanderburg+, 2016)
J/ApJS/224/2 : K2 EPIC stellar properties for 138600 targets (Huber+, 2016)
J/ApJS/226/7 : Planet candidates discovered using K2's 1yr (Crossfield+, 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/AJ/155/21 : Planet candidates from K2 campaigns 5-8 (Petigura+, 2018)
J/AJ/155/107 : HARPS-N obs. of K2-141 planetary system (Malavolta+, 2018)
J/AJ/155/136 : Planets orbiting bright stars K2 campaigns 0-10 (Mayo+, 2018)
J/AJ/156/277 : Sixty validated planets K2 campaigns 5-8 (Livingston+, 2018)
J/ApJS/244/11 : Planet candidates and EBs in K2 campaigns 0-8 (Kruse+, 2019)
J/AJ/159/211 : Exoplanet parameters from Kepler and K2 (Cloutier+, 2020)
Byte-by-byte Description of file: table1.dat table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 F10.4 d BJD Observation time, BJD-2400000
12- 19 F8.6 --- flux Relative flux after removal of high-frequency
systematic signals
21- 28 F8.6 --- fflux Relative flux of flattened light curve after removal
of low-frequency signals (1)
30- 38 E9.3 --- e_fflux Uncertainties associated with fflux (1)
--------------------------------------------------------------------------------
Note (1): See also description of flattening and errors in Section 2.1
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.3 d BJD Observation time, BJD-2400000
11- 16 F6.2 m/s RVel Radial velocity
18- 22 F5.2 m/s e_RVel Radial velocity error
24- 28 F5.3 km/s FWHM Full-width half-maximum
30- 35 F6.3 % con Contrast
37- 44 F8.5 km/s BS Bisector inverse span
46- 52 F7.5 km/s e_BS Bisector inverse span error
54- 60 F7.5 --- SHK S-index
62- 68 F7.5 --- e_SHK Uncertainty in SHK
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 07-Apr-2022