Measuring the masse of HD 52265b with asteroseismology

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Measuring the masse of HD 52265b with asteroseismology

Post by Led_Zep on 30th July 2013, 10:17 am

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Re: Measuring the masse of HD 52265b with asteroseismology

Post by Stalker on 30th July 2013, 10:25 am

Hum, spin-orbit alignement is not always good...

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Re: Measuring the masse of HD 52265b with asteroseismology

Post by Sirius_Alpha on 30th July 2013, 2:11 pm

My thoughts exactly. The temperature of HD 52265 is close to the Teff ~ 6250 K boundary between well aligned and misaligned hot Jupiter systems. It's not clear that this system should be aligned.

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Re: Measuring the masse of HD 52265b with asteroseismology

Post by Lazarus on 30th July 2013, 3:13 pm

Well the planet is not a hot Jupiter: orbital period is 119 days. (Nearly got confused about it being a multi-planet system because EPE has for whatever reason added the candidate systems in this paper as confirmed planets). So conclusions about alignment based on hot Jupiters, which constitute a distinct population and appear to have their own particular formation history, may not apply.

Not sure how many long-period Jovian planets have had the inclinations relative to the star determined: only ones I can recall are HD 80606b (wildly eccentric, misaligned) and the Kepler-30 planets (near-circular, well-aligned), plus the case of the superjovians at Upsilon Andromedae (presumably at least one of them must be misaligned).
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Re: Measuring the masse of HD 52265b with asteroseismology

Post by Led_Zep on 30th July 2013, 4:15 pm

http://www.space.com/22169-alien-planet-pulling-wobbly-star.html

I donít have any paper yet, but this comment :

The oscillations in brightness that the researchers investigated are linked to ripples in that star that are, in turn, based in part on its rate of rotation. The scientists calculated HD 52265's interior completes a revolution every 12 days, meaning it revolves some 2.3 times faster than the sun. "Knowing the rotation of stars is important to understand stellar activity cycles," said Laurent Gizon, an astrophysicist at the Max Planck Institute for Solar System Research in Germany and the study's lead author. "Magnetic fields in stars like the sun are maintained by rotation and convection." Discovering the manner in which the star HD 52265 rotates also provides clues about how the planet HD 52265b is oriented toward it, assuming the star's equator is lined up with the planet's, as is typically the case in Earth's solar system. When these data are combined with the information about the magnitude of the wobbles the planet exerts on its star, the mass of world is about 1.85 times the mass of Jupiter, the researchers calculated.
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Re: Measuring the masse of HD 52265b with asteroseismology

Post by Lazarus on 30th July 2013, 4:53 pm

Article in PNAS (for those with access behind the paywall)

Seismic constraints on rotation of Sun-like star and mass of exoplanet
Gizon et al.

http://www.pnas.org/content/early/2013/07/24/1303291110.abstract
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Re: Measuring the masse of HD 52265b with asteroseismology

Post by Led_Zep on 20th August 2013, 9:37 pm

http://arxiv.org/abs/1308.4352

Seismic constraints on rotation of Sun-like star and mass of exoplanet

Rotation is thought to drive cyclic magnetic activity in the Sun and Sun-like stars. Stellar dynamos, however, are poorly understood owing to the scarcity of observations of rotation and magnetic fields in stars. Here, inferences are drawn on the internal rotation of a distant Sun-like star by studying its global modes of oscillation. We report asteroseismic constraints imposed on the rotation rate and the inclination of the spin axis of the Sun-like star HD 52265, a principal target observed by the CoRoT satellite that is known to host a planetary companion. These seismic inferences are remarkably consistent with an independent spectroscopic observation (rotational line broadening) and with the observed rotation period of star spots. Furthermore, asteroseismology constrains the mass of exoplanet HD 52265b. Under the standard assumption that the stellar spin axis and the axis of the planetary orbit coincide, the minimum spectroscopic mass of the planet can be converted into a true mass of 1.85 (+0.52,-0.42) M_Jupiter, which implies that it is a planet, not a brown dwarf
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Re: Measuring the masse of HD 52265b with asteroseismology

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