The corona of a fully convective star with a near-polar flare

Abstract

In 2020, the Transiting Exoplanet Survey Satellite (TESS) observed a rapidly rotating M7 dwarf, TIC 277539431, produce a flare at 81° latitude, the highest latitude flare located to date. This is in stark contrast to solar flares that occur much closer to the equator, typically below 30°. The mechanisms that allow flares at high latitudes to occur are poorly understood. We studied five Sectors of TESS monitoring, and obtained 36 ks of XMM-Newton observations to investigate the coronal and flaring activity of TIC 277539431. From the observations, we infer the optical flare frequency distribution, flare loop sizes and magnetic field strengths, the soft X-ray flux, luminosity and coronal temperatures, as well as the energy, loop size and field strength of a large flare in the XMM-Newton observations. We find that TIC 277539431's corona does not differ significantly from other low mass stars on the canonical saturated activity branch with respect to coronal temperatures and flaring activity, but shows lower luminosity in soft X-ray emission by about an order of magnitude, consistent with other late M dwarfs. The lack of X-ray flux, the high latitude flare, the star's viewing geometry, and the otherwise typical stellar corona taken together can be explained by the migration of flux emergence to the poles in rapid rotators like TIC 277539431 that drain the star's equatorial regions of magnetic flux, but preserve its ability to produce powerful flares.

11 pages, 5 figues. Accepted to Astronomy & Astrophysics on May 6, 2024

References in corpus (47)

• Array Programming with NumPy
• The Transiting Exoplanet Survey Satellite
• A terrestrial planet candidate in a temperate orbit around Proxima Centauri
• The active lives of stars: a complete description of rotation and XUV evolution of F, G, K, and M dwarfs
• Solar-type dynamo behaviour in fully convective stars without a tachocline
• On the Age of the TRAPPIST-1 System
• The Threatening Environment of the TRAPPIST-1 Planets
• Relation of X-ray activity and rotation in M dwarfs and predicted time-evolution of the X-ray luminosity
• Time-resolved spectroscopy and photometry of an M dwarf flare star YZ Canis Minoris with OISTER and TESS: Blue asymmetry in H$\alpha$ line during the non-white light flare
• Mapping the magnetic field of flare coronal loops
• Simultaneous Multi-Wavelength Observations of Magnetic Activity in Ultracool Dwarfs. II. Mixed Trends in VB10 and LSR1835+32 and the Possible Role of Rotation
• Flare Rates, Rotation Periods. and Spectroscopic Activity Indicators of a Volume-Complete Sample of Mid-to-Late M dwarfs within 15 Parsecs
• A Panchromatic View of Brown Dwarf Aurorae
• EvryFlare III: Temperature Evolution and Habitability Impacts of Dozens of Superflares Observed Simultaneously by Evryscope and TESS
• Flares in Open Clusters with K2. II. Pleiades, Hyades, Praesepe, Ruprecht 147, and M67
• Simultaneous optical and X-ray observations of a giant flare on the ultracool dwarf LP412-31
• Magnetic Reconnection During the Post-Impulsive Phase of a Long-Duration Solar Flare: Bi-Directional Outflows as a Cause of Microwave and X-ray Bursts
• The Occurrence Rate of Terrestrial Planets Orbiting Nearby Mid-to-late M Dwarfs from TESS Sectors 1-42
• Formation of starspots in self-consistent global dynamo models: Polar spots on cool stars
• A Chandra X-ray detection of the L dwarf binary Kelu-1: Simultaneous Chandra and Very Large Array observations
• Simultaneous Multiwavelength Observations of Magnetic Activity in Ultracool Dwarfs. IV. The Active, Young Binary NLTT 33370 AB (=2MASS J13142039+1320011)
• First eROSITA study of nearby M dwarfs and the rotation-activity relation in combination with TESS
• 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
• APO & SMARTS flare star campaign observations I. Blue wing asymmetries in chromospheric lines during mid M dwarf flares from simultaneous spectroscopic and photometric observation data
• Giant white-light flares on fully convective stars occur at high latitudes
• A Seven-Day Multi-Wavelength Flare Campaign on AU Mic I: High-Time Resolution Light Curves and the Thermal Empirical Neupert Effect
• Simultaneous Kepler/K2 and XMM-Netwon observations of superflares in the Pleiades
• X-Ray Flaring on the dMe Star, Ross 154
• The MUSCLES Extension for Atmospheric and Transmission Spectroscopy: UV and X-ray Host-star Observations for JWST ERS & GTO Targets
• Searching for flaring star-planet interactions in AU Mic TESS observations
• A Reanalysis of the Fundamental Parameters and Age of TRAPPIST-1
• Stellar Superflares Observed Simultaneously with Kepler and XMM-Newton
• $K2$ Ultracool Dwarfs Survey. VI. White light superflares observed on an L5 dwarf and flare rates of L dwarfs
• TESS observations of flares and quasi-periodic pulsations from low mass stars and potential impact on exoplanets
• EXTraS discovery of an X-ray superflare from an L dwarf
• The Great Flare of 2021 November 19 on AD Leo. Simultaneous XMM-Newton and TESS observations
• Validation of a Scaling Law for the Coronal Magnetic Field Strengths and Loop Lengths of Solar and Stellar Flares
• Doppler imaging an X-ray flare on the ultrafast rotator BO Mic - A contemporaneous multiwavelength study using XMM-Newton and VLT
• The influence of host star activity evolution on the population of super-Earths and mini-Neptunes
• Coronal X-Ray Emission from Nearby, Low-Mass, Exoplanet Host Stars Observed by the MUSCLES and Mega-MUSCLES HST Treasury Survey Projects
• The Mouse that Squeaked: A small flare from Proxima Cen observed in the millimeter, optical, and soft X-ray with Chandra and ALMA
• The corona of GJ 1151 in the context of star-planet interaction
• The high energy spectrum of Proxima Centauri simultaneously observed at X-ray and FUV wavelengths
• AstroSat observations of long-duration X-ray superflares on active M-dwarf binary EQ Peg
• First eROSITA-TESS results for M dwarfs: Mass dependence of the X-ray activity rotation relation and an assessment of sensitivity limits
• Doubling of minute-long Quasi-Periodic Pulsations from super-flares on a low mass star
• Transitions in magnetic behavior at the substellar boundary

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