HAZMAT. V. The Ultraviolet and X-ray Evolution of K Stars

Abstract

Knowing the high-energy radiation environment of a star over a planet's formation and evolutionary period is critical in determining if that planet is potentially habitable and if any biosignatures could be detected, as UV radiation can severely change or destroy a planet's atmosphere. Current efforts for finding a potentially habitable planet are focused on M stars, yet K stars may offer more habitable conditions due to decreased stellar activity and more distant and wider habitable zones (HZ). While M star activity evolution has been observed photometrically and spectroscopically, there has been no dedicated investigation of K-star UV evolution. We present the first comprehensive study of the near-UV, far-UV, and X-ray evolution of K stars. We used members of young moving groups and clusters ranging in age from 10 - 625 Myr combined with field stars and their archived GALEX UV and ROSAT X-ray data to determine how the UV and X-ray radiation evolve. We find that the UV and X-ray flux incident on a HZ planet is 5 - 50 times lower than that of HZ planets around early-M stars and 50 - 1000 times lower than those around late-M stars, due to both an intrinsic decrease in K dwarf stellar activity occurring earlier than for M dwarfs and the more distant location of the K dwarf HZ.

27 pages, 19 figures

References in corpus (19)

• The NumPy array: a structure for efficient numerical computation
• The Transiting Exoplanet Survey Satellite
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• Habitable Zones Around Main-Sequence Stars: Dependence on Planetary Mass
• Second ROSAT all-sky survey (2RXS) source catalogue
• The Stellar Populations of Praesepe and Coma Berenices
• How to Characterize Habitable Worlds and Signs of Life
• Tidal Locking of Habitable Exoplanets
• Abiotic Ozone and Oxygen in Atmospheres Similar to Prebiotic Earth
• A Stellar Census of the Tucana-Horologium Moving Group
• HAZMAT I: The Evolution of Far-UV and Near-UV Emission from Early M Stars
• Pale Orange Dots: The Impact of Organic Haze on the Habitability and Detectability of Earthlike Exoplanets
• All-sky Co-moving Recovery Of Nearby Young Members. (ACRONYM) II: The Beta Pictoris Moving Group
• BANYAN. IX. The Initial Mass Function and Planetary-Mass Object Space Density of the TW Hya Association
• Magma oceans and enhanced volcanism on TRAPPIST-1 planets due to induction heating
• About Exobiology: The Case for Dwarf K Stars
• An Improved Age-Activity Relationship for Cool Stars older than a Gigayear
• The Dynamics-Based Approach to Studying Terrestrial Exoplanets
• HAZMAT II: Ultraviolet Variability of Low-Mass Stars in the GALEX Archive

Cited by in corpus (19)

• HAZMAT VI: The Evolution of Extreme Ultraviolet Radiation Emitted from Early M Star
• Current Population Statistics Do Not Favor Photoevaporation over Core-Powered Mass Loss as the Dominant Cause of the Exoplanet Radius Gap
• The relative emission from chromospheres and coronae: dependence on spectral type and age
• H-alpha and Ca II Infrared Triplet Variations During a Transit of the 23 Myr Planet V1298 Tau c
• The K Dwarf Advantage for Biosignatures on Directly Imaged Exoplanets
• The MUSCLES Extension for Atmospheric and Transmission Spectroscopy: UV and X-ray Host-star Observations for JWST ERS & GTO Targets
• Stellar X-ray activity across the Hertzsprung-Russell diagram. I. Catalogs
• HAZMAT. VII. The Evolution of Ultraviolet Emission with Age and Rotation for Early M Dwarf Stars
• The KOBE experiment: K-dwarfs Orbited By habitable Exoplanets. Project goals, target selection and stellar characterization
• HAZMAT. VIII. A Spectroscopic Analysis of the Ultraviolet Evolution of K Stars: Additional Evidence for K Dwarf Rotational Stalling in the First Gigayear
• HAZMAT. IX. An Analysis of the UV and X-Ray Evolution of Low-Mass Stars in the Era of Gaia
• Wolf 503 b: Characterization of a Sub-Neptune Orbiting a Metal-Poor K Dwarf
• Lyman-$\alpha$ Observations of High Radial Velocity Low-Mass Stars Ross 1044 and Ross 825
• Narrow loophole for H2-dominated atmospheres on habitable rocky planets around M dwarfs
• Hyades Member K2-136c: The Smallest Planet in an Open Cluster with a Precisely Measured Mass
• The Factory and the Beehive. V. Chromospheric and Coronal Activity and Its Dependence on Rotation in Praesepe and the Hyades
• TOI-712: a system of adolescent mini-Neptunes extending to the habitable zone
• An Eclipsing Binary Comprising Two Active Red Stragglers of Identical Mass and Synchronized Rotation: A Post-Mass-Transfer System or Just Born That Way?
• Companion Mass Limits for 17 Binary Systems Obtained with Binary Differential Imaging and MagAO/Clio