The Puzzling Story of Flare Inactive Ultra Fast Rotating M dwarfs. I. Exploring their Magnetic Fields

Abstract

Stars which are rapidly rotating are expected to show high levels of activity according to the activity-rotation relation. However, previous TESS studies have found Ultra Fast Rotating (UFR) M dwarfs with periods less than one day displaying low levels of flaring activity. As a result, in this study, we utilise VLT/FORS2 spectropolarimetric data of ten M dwarf UFR stars between spectral types $\sim$M2 - M6 all with $P_{\mathrm{rot}}<$ 1, to detect the presence of a magnetic field. We divide our sample into rotation period bins of equal size, with one star having many more flares in the TESS lightcurve than the other. We also provide an analysis of the long-term variability within our sample using TESS lightcurves taken during Cycles 1 and 3 (up to three years apart). We identify 605 flares from our sample which have energies between 2.0$\times$10${}^{31}$ and 5.4$\times$10${}^{34}$ erg. Although we find no significance difference in the flare rate between the Cycles, two of our targets display changes in their lightcurve morphology, potentially caused by a difference in the spot distribution. Overall, we find five stars (50%) in our sample have a detectable magnetic field with strengths $\sim$1 - 2 kG. Of these five, four were the more flare active stars within the period bins with one being the less flare active star. It would appear the magnetic field strength may not be the answer to the lack of flaring activity and supersaturation or magnetic field configuration may play a role. However, it is clear the relationship between rotation and activity is more complex than a steady decrease over time.

arXiv comment11 Pages, 6 Figures and 3 Tables, accepted for publication in MNRAS

References in corpus (50)

• Gaia Data Release 2. Summary of the contents and survey properties
• The Transiting Exoplanet Survey Satellite
• Intrinsic Colors, Temperatures, and Bolometric Corrections of Pre-Main Sequence Stars
• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• The stellar activity-rotation relationship and the evolution of stellar dynamos
• The TESS Input Catalog and Candidate Target List
• The Transiting Exoplanet Survey Satellite: Simulations of planet detections and astrophysical false positives
• Measuring the rotation period distribution of field M-dwarfs with Kepler
• Design Considerations for a Ground-based Transit Search for Habitable Planets Orbiting M dwarfs
• Kepler Flares I. Active and Inactive M dwarfs
• Stellar Flares from the First Tess Data Release: Exploring a New Sample of M-dwarfs
• The Kepler Catalog of Stellar Flares
• Kepler Flares II: The Temporal Morphology of White-Light Flares on GJ 1243
• The rotation and Galactic kinematics of mid M dwarfs in the Solar Neighborhood
• Parallax Systematics and Photocenter Motions of Benchmark Eclipsing Binaries in Gaia EDR3
• Planetary nebulae seen with TESS: Discovery of new binary central star candidates from Cycle 1
• Magnetic field generation in fully convective rotating spheres
• Frequent flaring in the TRAPPIST-1 system - unsuited for life?
• Flare Statistics for Young Stars from a Convolutional Neural Network Analysis of $\text{TESS}$ Data
• BANYAN. V. A Systematic All-Sky Survey for New Very Late-Type Low-Mass Stars and Brown Dwarfs in Nearby Young Moving Groups
• An Empirical Correction for Activity Effects on the Temperatures, Radii, and Estimated Masses of Low-Mass Stars and Brown Dwarfs
• The Evolution of Flare Activity with Stellar Age
• Flare Rates, Rotation Periods. and Spectroscopic Activity Indicators of a Volume-Complete Sample of Mid-to-Late M dwarfs within 15 Parsecs
• The global and small-scale magnetic fields of fully convective, rapidly spinning M dwarf pair GJ65A and B
• Investigating coronal saturation and super-saturation in fast-rotating M-dwarf stars
• Flares in Open Clusters with K2. II. Pleiades, Hyades, Praesepe, Ruprecht 147, and M67
• Orbiting Clouds of Material at the Keplerian Co-Rotation Radius of Rapidly Rotating Low Mass WTTs in Upper Sco
• A Measurement of Radius Inflation in the Pleiades and its Relation to Rotation and Lithium Depletion
• Flaring activity of Proxima Centauri from TESS observations: quasi-periodic oscillations during flare decay and inferences on the habitability of Proxima b
• Investigating the Rotational Phase of Stellar Flares on M dwarfs Using K2 Short Cadence Data
• Probing the Origin of Stellar Flares on M dwarfs Using TESS Data Sectors 1-3
• Calibration of the Halpha Age-Activity relation for M dwarfs
• Complex Rotational Modulation of Rapidly Rotating M-Stars Observed with TESS
• 10 Years of Stellar Activity for GJ 1243
• Stellar magnetic field parameters from a Bayesian analysis of high-resolution spectropolarimetric observations
• EvryFlare II: Rotation Periods of the Cool Flare Stars in TESS Across Half the Southern Sky
• Searching for the weakest detectable magnetic fields in white dwarfs. Highly-sensitive measurements from first VLT and WHT surveys
• Binaries among low-mass stars in nearby young moving groups
• Activity of TRAPPIST-1 analogue stars observed with TESS
• The Age of the Carina Young Association and Potential Membership of HD 95086
• HAZMAT. VII. The Evolution of Ultraviolet Emission with Age and Rotation for Early M Dwarf Stars
• TESS observations of southern ultra fast rotating low mass stars
• Magnetic and Rotational Evolution of $\rho$ CrB from Asteroseismology with TESS
• Complex Modulation of Rapidly Rotating Young M Dwarfs: Adding Pieces to the Puzzle
• Stellar Activity Effects on Moist Habitable Terrestrial Atmospheres Around M dwarfs
• A search for strong magnetic fields in massive and very massive stars in the Magellanic Clouds
• Upper limits to the magnetic field in central stars of planetary nebulae
• A transition of dynamo modes in M dwarfs: narrowing down the spectral range where the transition occurs*
• The Puzzling Story of Flare Inactive Ultra Fast Rotating M dwarfs. II. Searching for radial velocity variations

Cited by in corpus (6)

• 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
• Minute-Cadence Observations of the LAMOST Fields with the TMTS: II. Catalogues of Short-Period Variable Stars from the First Two-Year Surveys
• The connection between starspots and superflares: a case study of two stars
• Enhancing the detection of low-energy M dwarf flares: Wavelet-based denoising of CHEOPS data
• CaII and H$\alpha$ flaring M dwarfs detected with multi-filter photometry
• HiPERCAM and TESS observations of the rapidly rotating M7V star LP 89--187