# TrES-4b spin-orbit alignment and hints of TrES-4 c?

## TrES-4b spin-orbit alignment and hints of TrES-4 c?

Spin-Orbit Alignment of the TrES-4 Transiting Planetary System and Possible Additional Radial Velocity Variation
http://arxiv.org/abs/1003.2268

Abstract wrote:We report new radial velocities of the TrES-4 transiting planetary system, including observations of a full transit, with the High Dispersion Spectrograph of the Subaru 8.2m telescope. Modeling of the Rossiter-McLaughlin effect indicates that TrES-4b has closely aligned orbital and stellar spin axes, with $\lambda = 6.3^{\circ} \pm 4.7^{\circ}$. The close spin-orbit alignment angle of TrES-4b seems to argue against a migration history involving planet-planet scattering or Kozai cycles, although there are two nearby faint stars that could be binary companion candidates. Comparison of our out-of-transit data from 4 different runs suggest that the star exhibits radial velocity variability of $\sim$20 ms^-1 in excess of a single Keplerian orbit. Although the cause of the excess radial velocity variability is unknown, we discuss various possibilities including systematic measurement errors, starspots or other intrinsic motions, and additional companions besides the transiting planet.

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Sirius_Alpha

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## Re: TrES-4b spin-orbit alignment and hints of TrES-4 c?

A nice, up to date page with measured RM effects.

http://www.hs.uni-hamburg.de/EN/Ins/Per/Heller/index.html

Perhaps it would be a good idea to have a "sticky" topic or even a "Resources" section in "Extrasolar Visions" with a list of links for exoplanet resources.

exoplanet
Planetesimal

Number of posts : 124
Location : here
Registration date : 2008-06-16

## Re: TrES-4b spin-orbit alignment and hints of TrES-4 c?

That's not a bad idea at all.

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Caps Lock: Cruise control for 'Cool'!

Sirius_Alpha

Number of posts : 3435
Location : Earth
Registration date : 2008-04-06

## Re: TrES-4b spin-orbit alignment and hints of TrES-4 c?

http://arxiv.org/abs/1501.06403

The GAPS Programme with HARPS-N@TNG VI: The Curious Case of TrES-4b

We revisit the TrES-4 system parameters based on high-precision HARPS-N radial-velocity measurements and new photometric light curves. A combined spectroscopic and photometric analysis allows us to determine a spectroscopic orbit with an amplitude K=51±3 m s−1. The derived mass of TrES-4b is found to be Mp=0.49±0.04MJup, significantly lower than previously reported. Combined with the large radius (Rp=1.84+0.08−0.09RJup) inferred from our analysis, TrES-4b becomes the second-lowest density transiting hot Jupiter known. We discuss several scenarios to explain the puzzling discrepancy in the mass of TrES-4b in the context of the exotic class of highly inflated transiting giant planets

Led_Zep
Jovian

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