High-energy spectra of LTT 1445A and GJ 486 reveal flares and activity

Abstract

The high-energy radiative output, from the X-ray to the ultraviolet, of exoplanet host stars drives photochemical reactions and mass loss in the upper regions of planetary atmospheres. In order to place constraints on the atmospheric properties of the three closest terrestrial exoplanets transiting M dwarfs, we observe the high-energy spectra of the host stars LTT1445A and GJ486 in the X-ray with XMM-Newton and Chandra and in the ultraviolet with HST/COS and STIS. We combine these observations with estimates of extreme ultraviolet flux, reconstructions of the Ly-a lines, and stellar models at optical and infrared wavelengths to produce panchromatic spectra from 1A--20um for each star. While LTT1445Ab, LTT1445Ac, and GJ486b do not possess primordial hydrogen-dominated atmospheres, we calculate that they are able to retain pure CO2 atmospheres if starting with 10, 15, and 50% of Earth's total CO2 budget, respectively, in the presence of their host stars' stellar wind. We use age-activity relationships to place lower limits of 2.2 and 6.6 Gyr on the ages of the host stars LTT1445A and GJ486. Despite both LTT1445A and GJ486 appearing inactive at optical wavelengths, we detect flares at ultraviolet and X-ray wavelengths for both stars. In particular, GJ486 exhibits two flares with absolute energies of 10^29.5 and 10^30.1 erg (equivalent durations of 4357+/-96 and 19724+/-169 s) occurring three hours apart, captured with HST/COS G130M. Based on the timing of the observations, we suggest that these high-energy flares are related and indicative of heightened flaring activity that lasts for a period of days, but our interpretations are limited by sparse time-sampling. Consistent high-energy monitoring is needed to determine the duration and extent of high-energy activity on individual M dwarfs, as well as the population as a whole.

arXiv comment21 pages, published in A&A

References in corpus (109)

• emcee: The MCMC Hammer
• The Gaia mission
• Gaia Data Release 3: Summary of the content and survey properties
• The Transiting Exoplanet Survey Satellite
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• MESA Isochrones and Stellar Tracks (MIST). I: Solar-Scaled Models
• dynesty: A Dynamic Nested Sampling Package for Estimating Bayesian Posteriors and Evidences
• A new extensive library of PHOENIX stellar atmospheres and synthetic spectra
• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
• The false positive rate of Kepler and the occurrence of planets
• Solar Chemical Abundances Determined with a CO5BOLD 3D Model Atmosphere
• Kepler planets: a tale of evaporation
• The evaporation valley in the Kepler planets
• A high accuracy computed water line list
• VOSA: Virtual Observatory SED Analyzer. An application to the Collinder 69 open cluster
• Extreme Water Loss and Abiotic O${}_2$ Buildup On Planets Throughout the Habitable Zones of M Dwarfs
• The Role of Core Mass in Controlling Evaporation: the Kepler Radius Distribution and the Kepler-36 Density Dichotomy
• The Effect of a Strong Stellar Flare on the Atmospheric Chemistry of an Earth-like Planet Orbiting an M dwarf
• Exoplanet Atmospheres
• Design Considerations for a Ground-based Transit Search for Habitable Planets Orbiting M dwarfs
• The MUSCLES Treasury Survey I: Motivation and Overview
• How Thermal Evolution and Mass Loss Sculpt Populations of Super-Earths and Sub-Neptunes: Application to the Kepler-11 System and Beyond
• Kepler Flares I. Active and Inactive M dwarfs
• The H$\alpha$ emission of nearby M dwarfs and its relation to stellar rotation
• Kepler Flares II: The Temporal Morphology of White-Light Flares on GJ 1243
• The stellar rotation--activity relationship in fully convective M dwarfs
• The rotation and Galactic kinematics of mid M dwarfs in the Solar Neighborhood
• The HARPS search for southern extra-solar planets. X. A m sin i = 11 Mearth planet around the nearby spotted M dwarf GJ 674
• Time-Resolved Properties and Global Trends in dMe Flares from Simultaneous Photometry and Spectra
• Photochemically-produced SO${}_2$ in the atmosphere of WASP-39b
• The MUSCLES Treasury Survey II: Intrinsic Lyman Alpha and Extreme Ultraviolet Spectra of K and M Dwarfs with Exoplanets
• Absence of a thick atmosphere on the terrestrial exoplanet LHS 3844b
• Thermal emission from the Earth-sized exoplanet TRAPPIST-1 b using JWST
• The MUSCLES Treasury Survey III: X-ray to Infrared Spectra of 11 M and K Stars Hosting Planets
• The cosmic shoreline: the evidence that escape determines which planets have atmospheres, and what this may mean for Proxima Centauri b
• A decreased probability of habitable planet formation around low-mass stars
• No thick carbon dioxide atmosphere on the rocky exoplanet TRAPPIST-1 c
• Atmospheric escape from the TRAPPIST-1 planets and implications for habitability
• Solar-type dynamo behaviour in fully convective stars without a tachocline
• The Intrinsic Extreme Ultraviolet Fluxes of F5 V to M5 V Stars
• Magnetic activity in the HARPS M-dwarf sample. The rotation-activity relationship for very low-mass stars through R'HK
• Abiotic O${}_2$ Levels on Planets around F, G, K, and M Stars: Possible False Positives for Life?
• High Stellar FUV/NUV Ratio and Oxygen Contents in the Atmospheres of Potentially Habitable Planets
• Effect of UV Radiation on the Spectral Fingerprints of Earth-like Planets Orbiting M dwarfs
• High Tide or Riptide on the Cosmic Shoreline? A Water-Rich Atmosphere or Stellar Contamination for the Warm Super-Earth GJ~486b from JWST Observations
• Atmospheric Reconnaissance of TRAPPIST-1 b with JWST/NIRISS: Evidence for Strong Stellar Contamination in the Transmission Spectra
• Habitable Evaporated Cores: Transforming Mini-Neptunes into Super-Earths in the Habitable Zones of M Dwarfs
• The MUSCLES Treasury Survey. V. FUV Flares on Active and Inactive M Dwarfs
• A JWST transmission spectrum of a nearby Earth-sized exoplanet
• K-H_2 Quasi-molecular absorption detected in the T-dwarf epsilon Indi Ba
• New Observational Constraints on the Winds of M Dwarf Stars
• SPIRou: the near-infrared spectropolarimeter/high-precision velocimeter for the Canada-France-Hawaii telescope
• The Space Weather of Proxima Centauri b
• The MUSCLES Treasury Survey IV: Scaling Relations for Ultraviolet, Ca II K, and Energetic Particle Fluxes from M Dwarfs
• Persistence of Flare-Driven Atmospheric Chemistry on Rocky Habitable Zone Worlds
• The Delivery of Water During Terrestrial Planet Formation
• Volatile Delivery to Planets from Water-rich Planetesimals around Low Mass Stars
• New rotation period measurements for M dwarfs in the southern hemisphere: an abundance of slowly rotating, fully convective stars
• The Threatening Environment of the TRAPPIST-1 Planets
• Carbon cycling and habitability of Earth-size stagnant lid planets
• Double Trouble: Two Transits of the Super-Earth GJ 1132 b Observed with JWST NIRSpec G395H
• The Structure of Stellar Coronae in Active Binary Systems
• Three Red Suns in the Sky: A Transiting, Terrestrial Planet in a Triple M Dwarf System at 6.9 Parsecs
• pyspeckit: A spectroscopic analysis and plotting package
• The CARMENES search for exoplanets around M dwarfs -- Photospheric parameters of target stars from high-resolution spectroscopy. II. Simultaneous multiwavelength range modeling of activity insensitive lines
• Semi-empirical Modeling of the Photosphere, Chromosphere, Transition Region, and Corona of the M-dwarf Host Star GJ 832
• The High-Energy Radiation Environment Around a 10 Gyr M Dwarf: Habitable at Last?
• Far-Ultraviolet Activity Levels of F, G, K, and M dwarf Exoplanet Host Stars
• The SPHINX M-dwarf Spectral Grid. I. Benchmarking New Model Atmospheres to Derive Fundamental M-Dwarf Properties
• A nearby transiting rocky exoplanet that is suitable for atmospheric investigation
• Discovery of an Extremely Short Duration Flare from Proxima Centauri Using Millimeter through FUV Observations
• A survey of stellar X-ray flares from the XMM-Newton serendipitous source catalogue: Hipparcos-Tycho cool stars
• EUV irradiation of exoplanet atmospheres occurs on Gyr timescales
• The Interaction of Venus-like, M-dwarf Planets with the Stellar Wind of Their Host Star
• Hydrogen dominated atmospheres on terrestrial mass planets: evidence, origin and evolution
• GJ 1252b: A Hot Terrestrial Super-Earth With No Atmosphere
• The Mega-MUSCLES Spectral Energy Distribution Of TRAPPIST-1
• Escape and fractionation of volatiles and noble gases from Mars-sized planetary embryos and growing protoplanets
• Fluctuations and Flares in the Ultraviolet Line Emission of Cool Stars: Implications for Exoplanet Transit Observations
• GJ 367b is a dark, hot, airless sub-Earth
• Catalog for the ESPRESSO blind radial velocity exoplanet survey
• The Sun as an X-ray Star: III. Flares
• A Second Planet Transiting LTT 1445A and a Determination of the Masses of Both Worlds
• Reconstructing the Extreme Ultraviolet Emission of Cool Dwarfs Using Differential Emission Measure Polynomials
• Development and construction of MAROON-X
• A detailed analysis of the Gl 486 planetary system
• The young Sun's XUV-activity as a constraint for lower CO${}_2$-limits in the Earth's Archean atmosphere
• AU Microscopii in the FUV: Observations in Quiescence, During Flares, and Implications for AU Mic b and c
• Galactic Kinematics and Observed Flare Rates of a Volume-Complete Sample of Mid-to-Late M-dwarfs: Constraints on the History of the Stellar Radiation Environment of Planets Orbiting Low-mass Stars
• A connection between the morphology of the X-ray emission and rotation for solar-type stars in open clusters
• Airy worlds or barren rocks? On the survivability of secondary atmospheres around the TRAPPIST-1 planets
• Effects of UV stellar spectral uncertainty on the chemistry of terrestrial atmospheres
• Extending Optical Flare Models to the UV: Results from Comparing of TESS and GALEX Flare Observations For M Dwarfs
• The K2-3 system revisited: testing photoevaporation and core-powered mass loss with three small planets spanning the radius valley
• Estimating the Ultraviolet Emission of M dwarfs with Exoplanets from Ca II and H$\alpha$
• Ground-based detection of G star superflares with NGTS
• Intrinsic Lyman alpha Profiles of High-Velocity G, K, and M Dwarfs
• How does the mass and activity history of the host star affect the population of low-mass planets?
• The impact of time-dependent stellar activity on exoplanet atmospheres
• Ground-based Optical Transmission Spectroscopy of the Nearby Terrestrial Exoplanet LTT 1445Ab
• High-Resolution Transmission Spectroscopy of the Terrestrial Exoplanet GJ 486b
• The Habitable Zone Planet Finder: A Proposed High Resolution NIR Spectrograph for the Hobby Eberly Telescope to Discover Low Mass Exoplanets around M Dwarfs
• Detection of a giant white-light flare on an L2.5 dwarf with the Next Generation Transit Survey
• The high-energy spectrum of the nearby planet-hosting inactive mid-M dwarf LHS 3844
• FUMES. II. Ly$\alpha$ Reconstructions of Young, Active M Dwarfs
• Coronal X-Ray Emission from Nearby, Low-Mass, Exoplanet Host Stars Observed by the MUSCLES and Mega-MUSCLES HST Treasury Survey Projects
• Beating stellar systematic error floors using transit-based densities
• The high energy spectrum of Proxima Centauri simultaneously observed at X-ray and FUV wavelengths
• X-ray Emission from the Exoplanet Hosting LTT 1445 Triple Star System

Cited by in corpus (9)

• The Thermal Emission Spectrum of the Nearby Rocky Exoplanet LTT 1445A b from JWST MIRI/LRS
• Population-level Hypothesis Testing with Rocky Planet Emission Data: A Tentative Trend in the Brightness Temperatures of M-Earths
• An HST Transmission Spectrum of the Closest M-Dwarf Transiting Rocky Planet LTT 1445Ab
• Searching for star-planet interactions in GJ 486 at radio wavelengths with the uGMRT
• Atmospheric collapse and re-inflation through impacts for terrestrial planets around M dwarfs
• Separating flare and secondary atmospheric signals with RADYN modeling of near-infrared JWST transmission spectroscopy observations of TRAPPIST-1
• Induction Heating in Super-Earths: A Thermochemical Perspective
• Inversion of Hydrogen-rich Atmosphere and Water Content for GJ 486b
• Upper Limits on Planet-Induced GHz Radio Emission from Inactive M Dwarfs