Coronal X-Ray Emission from Nearby, Low-Mass, Exoplanet Host Stars Observed by the MUSCLES and Mega-MUSCLES HST Treasury Survey Projects

Abstract

The high energy X-ray and ultraviolet (UV) radiation fields of exoplanet host stars play a crucial role in controlling the atmospheric conditions and the potential habitability of exoplanets. Major surveys of the X-ray/UV emissions from late-type (K and M spectral type) exoplanet hosts have been conducted by the MUSCLES and Mega-MUSCLES Hubble Space Telescope (HST) Treasury programs. These samples primarily consist of relatively old, ``inactive'', low mass stars. In this paper we present results from X-ray observations of the coronal emission from these stars obtained using the Chandra X-ray Observatory, the XMM-Newton Observatory, and the Neil Gehrels Swift Observatory. The stars effectively sample the coronal activity of low-mass stars at a wide range of masses and ages. The vast majority (21 of 23) of the stars are detected and their X-ray luminosities measured. Short-term flaring variability is detected for most of the fully-convective (M $\le$ 0.35 M${}_{\odot }$) stars but not for the more massive M dwarfs during these observations. Despite this difference, the mean X-ray luminosities for these two sets of M dwarfs are similar with more massive (0.35 M${}_{\odot }$ $\le$ M $\le$ 0.6 M${}_{\odot }$) M dwarfs at $\sim$5 $\times$ 10${}^{26}$ erg s${}^{-1}$ compared to $\sim$2 $\times$ 10${}^{26}$ erg s${}^{-1}$ for fully-convective stars older than 1 Gyr. Younger, fully-convective M dwarfs have X-ray luminosities between 3 and 6 $\times$ 10${}^{27}$ erg s${}^{-1}$.The coronal X-ray spectra have been characterized and provide important information that is vital for the modeling of the stellar EUV spectra.

arXiv comment39 pages, 15 figures. Accepted for publication in The Astronomical Journal

References in corpus (59)

• The Gaia mission
• Collisional Plasma Models with APEC/APED: Emission Line Diagnostics of Hydrogen-like and Helium-like Ions
• The stellar activity-rotation relationship and the evolution of stellar dynamos
• Evolution of the Solar Activity over Time and Effects on Planetary Atmospheres: I. High-energy Irradiances (1-1700 A)
• Spectroscopic parameters for 451 stars in the HARPS GTO planet search program. Stellar [Fe/H] and the frequency of exo-Neptunes
• The Cosmic Origins Spectrograph
• A ~ 7.5 Earth-Mass Planet Orbiting the Nearby Star, GJ 876
• Late-type stars members of young stellar kinematic groups - I. Single stars
• The MUSCLES Treasury Survey I: Motivation and Overview
• A dynamically-packed planetary system around GJ667C with three super-Earths in its habitable zone
• How to Constrain Your M dwarf II: the mass-luminosity-metallicity relation from 0.075 to 0.70$M_{\odot }$
• Stellar Activity Masquerading as Planets in the Habitable Zone of the M dwarf Gliese 581
• The stellar rotation--activity relationship in fully convective M dwarfs
• The rotation and Galactic kinematics of mid M dwarfs in the Solar Neighborhood
• The Ultraviolet Radiation Environment Around M dwarf Exoplanet Host Stars
• The MUSCLES Treasury Survey II: Intrinsic Lyman Alpha and Extreme Ultraviolet Spectra of K and M Dwarfs with Exoplanets
• The active lives of stars: a complete description of rotation and XUV evolution of F, G, K, and M dwarfs
• A rocky planet transiting a nearby low-mass star
• The MUSCLES Treasury Survey III: X-ray to Infrared Spectra of 11 M and K Stars Hosting Planets
• Near-infrared Metallicities, Radial Velocities and Spectral Types for 447 Nearby M Dwarfs
• The Sun in Time: Activity and Environment
• Rotation periods of late-type dwarf stars from time-series high-resolution spectroscopy of chromospheric indicators
• The CARMENES search for exoplanets around M dwarfs: Different roads to radii and masses of the target stars
• CARMENES input catalogue of M dwarfs. I. Low-resolution spectroscopy with CAFOS
• Frequent flaring in the TRAPPIST-1 system - unsuited for life?
• An Activity-Rotation Relationship and Kinematic Analysis of Nearby Mid-to-Late-type M Dwarfs
• The MUSCLES Treasury Survey. V. FUV Flares on Active and Inactive M Dwarfs
• Coronal properties of planet-bearing stars
• Strong XUV irradiation of the Earth-sized exoplanets orbiting the ultracool dwarf TRAPPIST-1
• A candidate super-Earth planet orbiting near the snow line of Barnard's star
• Revising the ages of planet-hosting stars
• The MUSCLES Treasury Survey IV: Scaling Relations for Ultraviolet, Ca II K, and Energetic Particle Fluxes from M Dwarfs
• Habitable-zone super-Earth candidate in a six-planet system around the K2.5V star HD 40307
• On the Age of the TRAPPIST-1 System
• New rotation period measurements for M dwarfs in the southern hemisphere: an abundance of slowly rotating, fully convective stars
• CARMENES input catalogue of M dwarfs IV. New rotation periods from photometric time series
• Time-resolved Ultraviolet Spectroscopy of the M-dwarf GJ 876 Exoplanetary System
• Magnetic fields in M dwarfs from the CARMENES survey
• Magnetic Activity Cycles in the Exoplanet Host Star epsilon Eridani
• Relation of X-ray activity and rotation in M dwarfs and predicted time-evolution of the X-ray luminosity
• The High-Energy Radiation Environment Around a 10 Gyr M Dwarf: Habitable at Last?
• The HARPS search for southern extra-solar planets. XXXIV. A planetary system around the nearby M dwarf GJ163, with a super-Earth possibly in the habitable zone
• Updated Parameters and a New Transmission Spectrum of HD 97658b
• Transit confirmation and improved stellar and planet parameters for the super-Earth HD 97658 b and its host star
• An X-ray activity cycle on the young solar-like star $\epsilon \mathrm{Eridani}$
• GJ1214: Rotation period, starspots, and uncertainty on the optical slope of the transmission spectrum
• Reconstructing the Extreme Ultraviolet Emission of Cool Dwarfs Using Differential Emission Measure Polynomials
• A comprehensive examination of the Eps Eri system -- Verification of a 4 micron narrow-band high-contrast imaging approach for planet searches
• The relative emission from chromospheres and coronae: dependence on spectral type and age
• The HADES RV Programme with HARPS-N@TNG VIII. Gl15A: A multiple wide planetary system sculpted by binary interaction
• The Rotation-Activity Correlations in K and M dwarfs. II. New constraints on the dynamo mechanisms in late-K and M dwarfs before and at the transition to complete convection
• X-Ray Flaring on the dMe Star, Ross 154
• The Mass-Activity relationships in M and K dwarfs. I. Stellar parameters of our sample of M and K dwarfs
• A Reanalysis of the Fundamental Parameters and Age of TRAPPIST-1
• Complexity of magnetic fields on red dwarfs
• Chemo-kinematic ages of eccentric-planet-hosting M dwarf stars
• Stellar activity analysis of Barnard's Star: Very slow rotation and evidence for long-term activity cycle
• Age-Rotation-Activity Relations for M Dwarf Stars Based on ASAS Photometric Data
• Spectroscopic Determination of Stellar Parameters and Oxygen Abundances for Hyades/Field G-K Dwarfs

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