The Great Flare of 2021 November 19 on AD Leo. Simultaneous XMM-Newton and TESS observations

Abstract

We present a detailed analysis of a superflare on the active M dwarf star AD Leonis. The event presents a rare case of a stellar flare observed simultaneously in X-rays (with XMM-Newton) and in optical (with the Transiting Exoplanet Survey Satellite, TESS). The radiated energy both in the 0.2-12 keV X-ray band ($1.26\pm 0.01\cdot 10^{33}$ erg) and the bolometric value ($E_{F,bol}=5.57\pm 0.03\cdot 10^{33}$ erg) put this event at the lower end of the superflare class. The exceptional photon statistics deriving from the proximity of AD Leo has enabled measurements in the 1-8 AA GOES band for the peak flux (X1445 class) and integrated energy ($E_{F,GOES}=4.30\pm 0.05\cdot 10^{32}$ erg), making possible a direct comparison with data on flares from our Sun. From extrapolations of empirical relations for solar flares we estimate that a proton flux of at least $10^{5}c{m}^{-2}{s}^{-1}s{r}^{-1}$ accompanied the radiative output. With a time lag of 300s between the peak of the TESS white-light flare and the GOES band flare peak as well as a clear Neupert effect this event follows very closely the standard (solar) flare scenario. Time-resolved spectroscopy during the X-ray flare reveals, in addition to the time evolution of plasma temperature and emission measure, a temporary increase of electron density and elemental abundances, and a loop that extends in the corona by 13% of the stellar radius ($4\cdot 10^9$ cm). Independent estimates of the footprint area of the flare from TESS and XMM-Newton data suggest a high temperature of the optical flare (25000 K), but we consider more likely that the optical and X-ray flare areas represent physically distinct regions in the atmosphere of AD Leo.

Accepted for publication in A&A Letters

References in corpus (19)

• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• The Kepler Catalog of Stellar Flares
• Flare-productive active regions
• The active lives of stars: a complete description of rotation and XUV evolution of F, G, K, and M dwarfs
• Do Kepler superflare stars really include slowly-rotating Sun-like stars ? - Results using APO 3.5m telescope spectroscopic observations and Gaia-DR2 data -
• The CARMENES search for exoplanets around M dwarfs -- Planet occurrence rates from a subsample of 71 stars
• Persistence of Flare-Driven Atmospheric Chemistry on Rocky Habitable Zone Worlds
• A path towards understanding the rotation-activity relation of M dwarfs with K2 mission, X-ray and UV data
• Nonthermal Hard X-ray Emission and Iron Kalpha Emission from a Superflare on II Pegasi
• Relation of X-ray activity and rotation in M dwarfs and predicted time-evolution of the X-ray luminosity
• Influence of Stellar Flares on the Chemical Composition of Exoplanets and Spectra
• Hydrogen dominated atmospheres on terrestrial mass planets: evidence, origin and evolution
• Optical and X-ray observations of stellar flares on an active M dwarf AD Leonis with Seimei Telescope, SCAT, NICER and OISTER
• The GAPS Programme at TNG XXI -- A GIARPS case-study of known young planetary candidates: confirmation of HD 285507 b and refutation of AD Leo b
• X-ray Super-Flares From Pre-Main Sequence Stars: Flare Energetics And Frequency
• First eROSITA study of nearby M dwarfs and the rotation-activity relation in combination with TESS
• Rotation-activity relations and flares of M dwarfs with K2 long- and short-cadence data
• The Statistical Relationship between White-light Emission and Photospheric Magnetic Field Changes in Flares
• Flares and rotation of M dwarfs with habitable zones accessible to TESS planet detections

Cited by in corpus (14)

• 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
• A Seven-Day Multi-Wavelength Flare Campaign on AU Mic I: High-Time Resolution Light Curves and the Thermal Empirical Neupert Effect
• Monitoring the large-scale magnetic field of AD~Leo with SPIRou, ESPaDOnS and Narval. Toward a magnetic polarity reversal?
• Complete X-ray census of Mdwarfs in the solar Neighborhood I. GJ 745 AB: Coronal-hole Stars in the 10 pc Sample
• Simultaneous X-ray and optical variability of M dwarfs observed with eROSITA and TESS
• Analysis of Solar-like X-Class Flare on Wolf 359 Observed Simultaneously with TESS and XMM-Newton
• Effects of transient stellar emissions on planetary climates of tidally-locked exo-earths
• Starspots as the origin of ultrafast drifting radio bursts from an active M dwarf
• A Seven-Day Multi-Wavelength Flare Campaign on AU Mic III: Quiescent and Flaring Properties of the X-ray Spectra and Chromospheric lines
• The corona of a fully convective star with a near-polar flare
• The average X-ray spectrum of the volume-complete M-, F-, G-, and K-type star sample within 10 pc of the Sun
• Superflare on a rapidly-rotating solar-type star captured in X-rays
• The Sun as an X-ray star V.: A new method to retrieve coronal filling factors
• Role of non-thermal processes in the quiescent and active millimeter spectrum of a young M dwarf