Simultaneous Kepler/K2 and XMM-Netwon observations of superflares in the Pleiades

Abstract

Flares are powerful events ignited by a sudden release of magnetic energy. With the aim of studying flares in the 125-Myr-old stars in the Pleiades observed simultaneously in optical and X-ray light, we obtained new XMM-Newton observations of this cluster during the observations of Kepler K2 Campaign 4. Our objective is to characterize the most powerful flares observed in both bands and to constrain the energy released in the optical and X-ray, the geometry of the loops, and their time evolution. We aim to compare our results to existing studies of flares occurring in the Sun and stars at different ages. We selected bright X-ray/optical flares occurred in 12 known members of the Pleiades from their K2 and XMM-Newton light curves. The sample includes ten K-M stars, one F9 star, and one G8 star. Flare average properties were obtained from integrated analysis of the light curves during the flares. The time evolution of the plasma in the magnetic loops is constrained with time-resolved X-ray spectral analysis. Most of the flares studied in this work emitted more energy in optical than in X-rays, as in most solar flares, even if the Pleiades flares output a larger fraction of their total energy in X-rays than typical solar flares do. Additionally, the energy budget in the two bands is weakly correlated. We also found comparable flare duration in optical and X-rays and observed that rapidly rotating stars (e.g., with rotation period shorter than 0.5 days) preferentially host short flares. We estimated the slope of the cooling path of the flares in the log(EM)-versus-log(T) plane. The values we obtained are affected by large uncertainties, but their nominal values suggest that the flares analyzed in this paper are mainly due to single loops with no sustained heating occurring during the cooling phase. We also observed and analyzed oscillations with a period of 500 s during one of the flares.

Accepted for publication by Astronomy & Astrophysics. Some figures are included with low resolution. The abstract is shorter than that of the orginal paper

References in corpus (22)

• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• The K2 Mission: Characterization and Early results
• Kepler Flares I. Active and Inactive M dwarfs
• The Kepler Catalog of Stellar Flares
• Advances in Observing Various Coronal EUV Waves in the SDO Era and Their Seismological Applications (Invited Review)
• Magnetic Properties of Solar Active Regions that Govern Large Solar Flares and Eruptions
• Quasi-periodic pulsations in solar and stellar flares: an overview of recent results
• X-ray flares in Orion young stars. I. Flare characteristics
• Near and Mid-IR Photometry of the Pleiades, and a New List of Substellar Candidate Members
• Diagnostics of stellar flares from X-ray observations: from the decay to the rise phase
• A statistical analysis of X-ray variability in pre-main sequence objects of the Taurus Molecular Cloud
• The Seven Sisters DANCe. I. Empirical isochrones, Luminosity and Mass Functions of the Pleiades cluster
• Beyond the Kepler/K2 bright limit: variability in the seven brightest members of the Pleiades
• Unveiling the Cygnus OB2 stellar population with Chandra
• X-ray Flares in Orion Low Mass Stars
• The periodic variations of a white-light flare observed with ULTRACAM
• Plasma sloshing in pulse-heated solar and stellar coronal loops
• Kepler super-flare stars: what are they?
• Spectral properties of X-ray bright variable sources in the Taurus Molecular Cloud
• An XMM-Newton view of the young open cluster NGC 6231 III. Optically faint X-ray sources
• High Dispersion Spectroscopy of Solar-type Superflare Stars. III. Lithium Abundances
• XMM-Newton survey of two Upper Scorpius regions

Cited by in corpus (26)

• X-ray Super-Flares From Pre-Main Sequence Stars: Flare Energetics And Frequency
• A blueprint of state-of-the-art techniques for detecting quasi-periodic pulsations in solar and stellar flares
• Tuning the Exo-Space Weather Radio for Stellar Coronal Mass Ejections
• Giant white-light flares on fully convective stars occur at high latitudes
• 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
• Discovery of a Long-Duration Superflare on a Young Solar-Type Star EK Draconis with Nearly Similar Time Evolution for H$\alpha$ and White-Light Emissions
• Sun-as-a-star Analysis of H$\alpha$ Spectra of a Solar Flare Observed by SMART/SDDI: Time Evolution of Red Asymmetry and Line Broadening
• A comparative study of two X2.2 and X9.3 solar flares observed with HARPS-N: Reconciling Sun-as-a-star spectroscopy and high-spatial resolution solar observations in the context of the solar-stellar connection
• Stellar Superflares Observed Simultaneously with Kepler and XMM-Newton
• Oscillatory Reconnection of a 2D X-point in a hot coronal plasma
• Flares and rotation of M dwarfs with habitable zones accessible to TESS planet detections
• EXTraS discovery of an X-ray superflare from an L dwarf
• Reconstructing the XUV Spectra of Active Sun-like Stars Using Solar Scaling Relations with Magnetic Flux
• Oscillatory reconnection as a plasma diagnostic in the solar corona
• X-ray/H$\alpha$ scaling relationships in stellar flares
• Multi-wavelength quasi-periodic pulsations in a stellar superflare
• Simultaneous X-ray and optical variability of M dwarfs observed with eROSITA and TESS
• A Seven-Day Multi-Wavelength Flare Campaign on AU Mic III: Quiescent and Flaring Properties of the X-ray Spectra and Chromospheric lines
• The complex phenomena of YSOs revealed by their X-ray variability
• The corona of a fully convective star with a near-polar flare
• Simultaneous photometric and CARMENES spectroscopic monitoring of fast-rotating M dwarf GJ 3270. Discovery of a post-flare corotating feature
• X-Ray and Ultraviolet Flares on AT Microscopii Observed by AstroSat
• X-ray Super-Flares From Pre-Main Sequence Stars: Flare Modeling
• Superflare on a rapidly-rotating solar-type star captured in X-rays
• Coronal Mass Ejections and Exoplanets: A Numerical Perspective
• The independence of oscillatory reconnection periodicity from the initial pulse