Characterizing K2 Candidate Planetary Systems Orbiting Low-Mass Stars I: Classifying Low-mass Host Stars Observed During Campaigns 1-7

Abstract

We present near-infrared spectra for 144 candidate planetary systems identified during Campaigns 1-7 of the NASA K2 Mission. The goal of the survey was to characterize planets orbiting low-mass stars, but our IRTF/SpeX and Palomar/TripleSpec spectroscopic observations revealed that 49% of our targets were actually giant stars or hotter dwarfs reddened by interstellar extinction. For the 72 stars with spectra consistent with classification as cool dwarfs (spectral types K3 - M4), we refined their stellar properties by applying empirical relations based on stars with interferometric radius measurements. Although our revised temperatures are generally consistent with those reported in the Ecliptic Plane Input Catalog (EPIC), our revised stellar radii are typically 0.13 solar radii (39%) larger than the EPIC values, which were based on model isochrones that have been shown to underestimate the radii of cool dwarfs. Our improved stellar characterizations will enable more efficient prioritization of K2 targets for follow-up studies.

36 pages, 25 figures, 7 tables, in press at ApJ. Stellar parameters and spectra posted to ExoFOP-K2 (https://exofop.ipac.caltech.edu/k2/). Also see related paper by Martinez et al. titled "Stellar & Planetary Parameters for K2's Late Type Dwarf Systems from C1 to C5."

References in corpus (53)

• Validation of the new Hipparcos reduction
• Evolutionary tracks and isochrones for low- and intermediate-mass stars: from 0.15 to 7 M_sun, and from Z=0.0004 to 0.03
• The Eleventh and Twelfth Data Releases of the Sloan Digital Sky Survey: Final Data from SDSS-III
• Intrinsic Colors, Temperatures, and Bolometric Corrections of Pre-Main Sequence Stars
• The Dartmouth Stellar Evolution Database
• The K2 Mission: Characterization and Early results
• Evolution of asymptotic giant branch stars II. Optical to far-infrared isochrones with improved TP-AGB models
• Exploring the Milky Way stellar disk. A detailed elemental abundance study of 714 F and G dwarf stars in the Solar neighbourhood
• Planetary Candidates Observed by Kepler, III: Analysis of the First 16 Months of Data
• Characteristics of planetary candidates observed by Kepler, II: Analysis of the first four months of data
• A Method of Correcting Near-Infrared Spectra for Telluric Absorption
• The First Data Release (DR1) of the LAMOST general survey
• Kepler Input Catalog: Photometric Calibration and Stellar Classification
• The PPMXL catalog of positions and proper motions on the ICRS. Combining USNO-B1.0 and 2MASS
• Spectral Irradiance Calibration in the Infrared. XIV: the Absolute Calibration of 2MASS
• The Infrared Telescope Facility (IRTF) Spectral Library: Cool Stars
• How to Constrain Your M Dwarf: measuring effective temperature, bolometric luminosity, mass, and radius
• The Occurrence Rate of Small Planets around Small Stars
• Stellar Diameters and Temperatures II. Main Sequence K & M Stars
• New Grids of ATLAS9 Model Atmospheres
• The Solar Neighborhood XVII: Parallax Results from the CTIOPI 0.9m Program -- Twenty New Members of the RECONS 10 Parsec Sample
• Revised Stellar Properties of Kepler Targets for the Quarter 1-16 Transit Detection Run
• Evolution of asymptotic giant branch stars I. Updated synthetic TP-AGB models and their basic calibration
• The RAdial Velocity Experiment (RAVE): Fourth data release
• Metallicity and Temperature Indicators in M dwarf K band Spectra: Testing New & Updated Calibrations With Observations of 133 Solar Neighborhood M dwarfs
• Efficient identification of exoplanetary transit candidates from SuperWASP light curves
• Characteristics of Kepler Planetary Candidates Based on the First Data Set: The Majority are Found to be Neptune-Size and Smaller
• Galaxia: a code to generate a synthetic survey of the Milky Way
• The K2 Ecliptic Plane Input Catalog (EPIC) and Stellar Classifications of 138,600 Targets in Campaigns 1-8
• Planetary Candidates Observed by Kepler IV: Planet Sample From Q1-Q8 (22 Months)
• Near-infrared Metallicities, Radial Velocities and Spectral Types for 447 Nearby M Dwarfs
• Planetary Candidates from the First Year of the K2 Mission
• Spectro-Thermometry of M dwarfs and their candidate planets: too hot, too cool, or just right?
• 197 Candidates and 104 Validated Planets in K2's First Five Fields
• They are Small Worlds After All: Revised Properties of Kepler M Dwarf Stars and their Planets
• Prospecting in late-type dwarfs: a calibration of infrared and visible spectroscopic metallicities of late-K and M dwarfs spanning 1.5 dex
• Stellar and Planetary Properties of K2 Campaign 1 Candidates and Validation of 17 Planets, Including a Planet Receiving Earth-like Insolation
• The Radius Distribution of Planets Around Cool Stars
• The Solar Neighborhood XXXV: Distances to 1404 M Dwarf Systems Within 25 pc in the Southern Sky
• Characterizing the Cool Kepler Objects of Interest. New Effective Temperatures, Metallicities, Masses and Radii of Low-Mass Kepler Planet-Candidate Host Stars
• They might be giants: luminosity class, planet frequency, and planet-metallicity relation of the coolest Kepler target stars
• Local Stellar Kinematics from RAVE Data: I. Local Standard of Rest
• New planetary and EB candidates from Campaigns 1-6 of the K2 mission
• Transiting exoplanet candidates from K2 Campaigns 5 and 6
• An empirical calibration to estimate cool dwarf fundamental parameters from H-band spectra
• Prospecting in Ultracool Dwarfs: Measuring the Metallicities of Mid- and Late-M Dwarfs
• The Age, Stellar Content and Star Formation Timescale of the B59 Dense Core
• That's How We Roll: The NASA K2 Mission Science Products and Their Performance Metrics
• Candidate Planets in the Habitable Zones of Kepler Stars
• Accurate Low-Mass Stellar Models of KOI-126
• Characterizing the Cool KOIs. VI. H- and K-band Spectra of Kepler M Dwarf Planet-Candidate Hosts
• Ultra Short Period Planets in K2: SuPerPiG Results for Campaigns 0-5
• Trawling for transits in a sea of noise: A Search for Exoplanets by Analysis of WASP Optical Lightcurves and Follow-up (SEAWOLF)

Cited by in corpus (38)

• How to Constrain Your M dwarf II: the mass-luminosity-metallicity relation from 0.075 to 0.70$M_{\odot }$
• 275 Candidates and 149 Validated Planets Orbiting Bright Stars in K2 Campaigns 0-10
• The California-Kepler Survey. X. The Radius Gap as a Function of Stellar Mass, Metallicity, and Age
• Scaling K2. I. Revised Parameters for 222,088 K2 Stars and a K2 Planet Radius Valley at 1.9 $R_{\oplus }$
• A Catalog of Cool Dwarf Targets for the Transiting Exoplanet Survey Satellite
• The First Habitable Zone Earth-sized Planet from TESS. I: Validation of the TOI-700 System
• Characterizing K2 Candidate Planetary Systems Orbiting Low-Mass Stars II: Planetary Systems Observed During Campaigns 1-7
• Zodiacal Exoplanets in Time (ZEIT) VI: a three-planet system in the Hyades cluster including an Earth-sized planet
• Exoplanets around Low-mass Stars Unveiled by K2
• 60 Validated Planets from K2 Campaigns 5-8
• K2-136: A Hyades Binary Star with a Neptune-sized Planet
• Hubble WFC3 Spectroscopy of the Habitable-zone Super-Earth LHS 1140 b
• Detection of Hundreds of New Planet Candidates and Eclipsing Binaries in K2 Campaigns 0-8
• Precise Masses in the WASP-47 System
• A Compact Multi-Planet System With A Significantly Misaligned Ultra Short Period Planet
• The Breakthrough Listen Search for Intelligent Life: A 3.95-8.00 GHz Search for Radio Technosignatures in the Restricted Earth Transit Zone
• The K2-HERMES Survey. I. Planet Candidate Properties from K2 Campaigns 1-3
• Planet Candidates from K2 Campaigns 5-8 and Follow-Up Optical Spectroscopy
• Simulating the Exoplanet Yield of a Space-based MIR Interferometer Based on Kepler Statistics
• K2-264: A transiting multi-planet system in the Praesepe open cluster
• Eyes on K2-3: A system of three likely sub-Neptunes characterized with HARPS-N and HARPS
• Characterizing K2 Candidate Planetary Systems Orbiting Low-Mass Stars IV: Updated Properties for 86 Cool Dwarfs Observed During Campaigns 1-17
• The K2-OjOS Project: New and revisited planets and candidates in K2 campaigns 5, 16, & 18
• Stellar & Planetary Parameters for K2's Late Type Dwarf Systems from C1 to C5
• The Gold Standard: Accurate Stellar and Planetary Parameters for Eight Kepler M dwarf Systems Enabled by Parallaxes
• A TESS Dress Rehearsal: Planetary Candidates and Variables from K2 Campaign 17
• Exoplanet Populations and their Dependence on Host Star Properties
• K2-288Bb: A Small Temperate Planet in a Low-mass Binary System Discovered by Citizen Scientists
• The occurrence rate of exoplanets orbiting ultracool dwarfs as probed by K2
• The LHS 1678 System: Two Earth-Sized Transiting Planets and an Astrometric Companion Orbiting an M Dwarf Near the Convective Boundary at 20 pc
• Another super-dense sub-Neptune in K2-182 b and refined mass measurements for K2-199 b and c
• Characterizing K2 Candidate Planetary Systems Orbiting Low-Mass Stars III: A High Mass & Low Envelope Fraction for the Warm Neptune K2-55b
• Characterization of Low Mass K2 Planet Hosts Using Near-Infrared Spectroscopy
• Temperate super-Earths/mini-Neptunes around M/K dwarfs Consist of 2 Populations Distinguished by Their Atmospheres
• Search for Exoplanetary Transits in the Galactic Bulge
• Mass Derivation of planets K2-21b and K2-21c from Transit Timing Variations
• Disentangling Atmospheric Compositions of K2-18 b with Next Generation Facilities
• The M-dwarf Ultraviolet Spectroscopic Sample I. Determining Stellar Parameters for Field Stars