The Mouse that Squeaked: A small flare from Proxima Cen observed in the millimeter, optical, and soft X-ray with Chandra and ALMA

Abstract

We present millimeter, optical, and soft X-ray observations of a stellar flare with an energy squarely in the regime of typical X1 solar flares. The flare was observed from Proxima Cen on 2019 May 6 as part of a larger multi-wavelength flare monitoring campaign and was captured by Chandra, LCOGT, du Pont, and ALMA. Millimeter emission appears to be a common occurrence in small stellar flares that had gone undetected until recently, making it difficult to interpret these events within the current multi-wavelength picture of the flaring process. The May 6 event is the smallest stellar millimeter flare detected to date. We compare the relationship between the soft X-ray and millimeter emission to that observed in solar flares. The X-ray and optical flare energies of 10${}^{30.3\pm 0.2}$ and 10${}^{28.9\pm 0.1}$ erg, respectively, the coronal temperature of T=11.0$\pm$2.1 MK, and the emission measure of 9.5$\pm$2.2 X 10${}^{49}$ cm${}^{-3}$ are consistent with M-X class solar flares. We find the soft X-ray and millimeter emission during quiescence are consistent with the Gudel-Benz Relation, but not during the flare. The millimeter luminosity is >100X higher than that of an equivalent X1 solar flare and lasts only seconds instead of minutes as seen for solar flares.

12 pages, 5 figures. Accepted to ApJ

References in corpus (21)

• A terrestrial planet candidate in a temperate orbit around Proxima Centauri
• A Re-appraisal of the Habitability of Planets Around M Dwarf Stars
• Confirmation of the Electron Cyclotron Maser Instability as the Dominant Source of Radio Emission from Very Low Mass Stars and Brown Dwarfs
• Acceleration and propagation of Solar Energetic Particles
• X-ray flares in Orion young stars. I. Flare characteristics
• Strong dipole magnetic fields in fast rotating fully convective stars
• Persistence of Flare-Driven Atmospheric Chemistry on Rocky Habitable Zone Worlds
• Relation of X-ray activity and rotation in M dwarfs and predicted time-evolution of the X-ray luminosity
• A Flare-Type IV Burst Event from Proxima Centauri and Implications for Space Weather
• Discovery of an Extremely Short Duration Flare from Proxima Centauri Using Millimeter through FUV Observations
• Monitoring the radio emission of Proxima Centauri
• Optical and X-ray observations of stellar flares on an active M dwarf AD Leonis with Seimei Telescope, SCAT, NICER and OISTER
• A Very Bright, Very Hot, and Very Long Flaring Event from the M Dwarf Binary System DG CVn
• A circular polarisation survey for radio stars with the Australian SKA Pathfinder
• ALMA Discovery of Dust Belts Around Proxima Centauri
• Detection of Galactic and Extragalactic Millimeter-Wavelength Transient Sources with SPT-3G
• Optical Transmission Spectroscopy of the Terrestrial Exoplanet LHS 3844b from 13 Ground-Based Transit Observations
• A coronal explosion on the flare star CN Leonis
• The Atacama Cosmology Telescope: Detection of mm-wave transient sources
• HAZMAT. VII. The Evolution of Ultraviolet Emission with Age and Rotation for Early M Dwarf Stars
• Interaction of Space Weather Phenomena With Mars Plasma Environment During Solar Minimum 23/24

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• The Proxima Centauri Campaign -- First Constraints On Millimeter Flare Rates from ALMA
• The corona of a fully convective star with a near-polar flare
• Time-resolved X-ray spectra of Proxima Centauri as seen by XMM-Newton
• Role of non-thermal processes in the quiescent and active millimeter spectrum of a young M dwarf