The corona of HD 189733 and its X-ray activity

Abstract

Abridged. Here we report on the X-ray activity of the primary star, HD189733 A, using a new XMM-Newton observation and a comparison with the previous X-ray observations. The spectrum in the quiescent intervals is described by two temperatures at 0.2 keV and 0.7 keV, while during the flares a third component at 0.9 keV is detected. We obtain estimates of the electron density in the range $n_e=1.6-13\times 10^{10}$ cm${}^{-3}$ and thus the corona of HD189733 A appears denser than the solar one. {For the third time, we observe a large flare that occurred just after the eclipse of the planet. Together with the flares observed in 2009 and 2011, the events are restricted to a small planetary phase range of $\varphi =0.55-0.65$. Although we do not find conclusive evidence of a significant excess of flares after the secondary transits, we suggest that the planet might trigger such flares when it passes close to locally high magnetic field of the underlying star at particular combinations of stellar rotational phases and orbital planetary phases. For the most recent flares, a wavelet analysis of the light curve suggests a loop of length of four stellar radii at the location of the bright flare, and a local magnetic field of order of 40-100 G, in agreement with the global field measured in other studies. The loop size suggests an interaction of magnetic nature between planet and star, separated by only $\sim 8R_{\ast }$. We also detect the stellar companion (HD 189733 B, $\sim 12"$ from the primary star) in this XMM observation. Its very low X-ray luminosity ($L_X=3.4\times 10^{26}$ erg s${}^{-1}$) confirms the old age of this star and of the binary system. The high activity of the primary star is best explained by a transfer of angular momentum from the planet to the star.

Preprint format, 28 Pages, 10 Figures, accepted for publication on ApJ

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• A Model of the H$\alpha$ and Na Transmission Spectrum of HD 189733b
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• Giant white-light flares on fully convective stars occur at high latitudes
• MOVES III. Simultaneous X-ray and ultraviolet observations unveiling the variable environment of the hot Jupiter HD 189733b
• Effect of stellar flares on the upper atmospheres of HD 189733b and HD 209458b
• Lightning climatology of exoplanets and brown dwarfs guided by Solar System data
• Analysis of combined radial velocities and activity of BD+20 1790: evidence supporting the existence of a planetary companion
• Helium absorption in exoplanet atmospheres is connected to stellar coronal abundances
• Time-resolved UVES observations of a stellar flare on the planet host HD 189733 during primary transit
• The Rise of ROME. I. A Multiwavelength Analysis of the Star-Planet Interaction in the HD 189733 System
• X-ray variability of HD 189733 across eight years of XMM-Newton observations
• ROME (Radio Observations of Magnetized Exoplanets). II. HD 189733 Does Not Accrete Significant Material from its Exoplanet like a T Tauri Star from A Disk
• Computation of the transmitted and polarized scattered fluxes by the exoplanet HD 189733b in X-rays
• The high-energy environment of the heavy sub-Earth GJ 367 b indicates likely complete evaporation of its atmosphere
• Observational features of exoplanetary synchrotron radio bursts
• The X-ray activity of F stars with hot Jupiters: KELT-24 versus WASP-18
• X-ray Activity Variations and Coronal Abundances of the Star-Planet Interaction candidate HD 179949
• How stars and planets interact: a look through the high-energy window
• A circularly polarized low-frequency radio burst from the exoplanetary system HD 189733
• Hot Jupiters accreting onto their parent stars: effects on the stellar activity
• Tidal effects on stellar activity
• The impact of photospheric brightness field on exoplanetary transit timings and the TTV excess of HD 189733 b