Geometry Diagnostics of a Stellar Flare from Fluorescent X-rays

Abstract

We present evidence of Fe fluorescent emission in the Chandra HETGS spectrum of the single G-type giant HR 9024 during a large flare. In analogy to solar X-ray observations, we interpret the observed Fe K$\alpha$ line as being produced by illumination of the photosphere by ionizing coronal X-rays, in which case, for a given Fe photospheric abundance, its intensity depends on the height of the X-ray source. The HETGS observations, together with 3D Monte Carlo calculations to model the fluorescence emission, are used to obtain a direct geometric constraint on the scale height of the flaring coronal plasma. We compute the Fe fluorescent emission induced by the emission of a single flaring coronal loop which well reproduces the observed X-ray temporal and spectral properties according to a detailed hydrodynamic modeling. The predicted Fe fluorescent emission is in good agreement with the observed value within observational uncertainties, pointing to a scale height $\lesssim 0.3$\rstar. Comparison of the HR 9024 flare with that recently observed on II Peg by Swift indicates the latter is consistent with excitation by X-ray photoionization.

accepted for publication on the Astrophysical Journal Letters

References in corpus (24)

• Fluorescent iron lines as a probe of astrophysical black hole systems
• The Chandra High Energy Transmission Grating: Design, Fabrication, Ground Calibration and Five Years in Flight
• On the sizes of stellar X-ray coronae
• The Density of Coronal Plasma in Active Stellar Coronae
• Nonthermal Hard X-ray Emission and Iron Kalpha Emission from a Superflare on II Pegasi
• Iron Fluorescent Line Emission from Young Stellar Objects in the Orion Nebula
• Rotational modulation of X-ray emission in Orion Nebula young stars
• Modeling an X-ray Flare on Proxima Centauri: evidence of two flaring loop components and of two heating mechanisms at work
• The coronal structure of AB Dor determined from contemporaneous Doppler imaging and X-ray spectroscopy
• X-ray Doppler Imaging of 44i Boo with Chandra
• X-ray rotational modulation of a supersaturated star in IC 2391
• Three-dimensional photoionisation modelling of the hydrogen-deficient knots in the planetary nebula Abell 30
• Doppler Shifts and Broadening and the Structure of the X-ray Emission from Algol
• Inferring coronal structure from X-ray lightcurves and Doppler shifts: a Chandra study of AB Doradus
• X-ray Spectroscopy of the Contact Binary VW Cephei
• Detection of X-ray Resonance Scattering in Active Stellar Coronae
• Results from Droxo. I. The variability of fluorescent Fe 6.4 keV emission in the young star Elias 29: High-energy electrons in the star's accretion tubes?
• A survey for Fe 6.4 keV emission in young stellar objects in rho Oph: the strong fluorescence from Elias 29
• Detailed diagnostics of an X-ray flare in the single giant HR 9024
• On X-ray Optical Depth in the Coronae of Active Stars
• Flare X-ray observations of AB Dor: evidence for Stellar Coronal Opacity
• The nature of the fluorescent iron line in V 1486 Ori
• The Contribution of Particle Impact to the Production of Fe K Emission from Accreting Black Holes
• The Detectability of Neon Fluorescence and Measurement of the Solar Photospheric Neon Abundance

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