The enigmatic dance of the HD 189733A system: Does the planet accrete onto the star?
arxiv(2024)
摘要
Several studies suggest that the emission properties of a star can be
affected by its interaction with a nearby planet. However, the actual
observability of these effects remains a subject of debate. An example is the
HD189733A system, where some characteristics of its emissions have been
interpreted as indicative of ongoing interactions between the star and its
planet. Other studies attribute these characteristics to the coronal activity
of the star. In this work, we investigate whether the observed stellar X-ray
flare events, which appear to be in phase with the planetary period in the
HD189733A system, could be attributed to the accretion of the planetary wind
onto the stellar surface or resulted from an interaction between the planetary
and stellar winds. We developed a 3D MHD model that describes the system
HD189733A, including the central host star and its hot Jupiter, along with
their respective winds. The effects of gravity and the magnetic fields of both
star and planet are taken into account. In the cases examined in this study,
the accretion scenario is only viable when the stellar and planetary magnetic
field strengths are at 5 G and 1 G, respectively. In this case, the
Rayleigh-Taylor instabilities (RTIs) lead to the formation of an accretion
column connecting star and planet. Once formed the column remains stable for
the entire simulation. The accretion column yields an accretion rates of about
1e12 g/s and shows a mean density of about 1e7 cm^-3. In the other cases, the
accretion column does not form because the RTI is suppressed by the stronger
magnetic field intensities assumed for both the star and the planet. We
synthesized the emission resulting from the shocked planetary wind and, its
total X-ray emission ranges from 5e23 to 1e24 erg/s. In the case of accretion,
the emission originating from the hot spot cannot be distinguished from the
coronal activity.
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