# Upsilon Andromedae b polarimetry

## Upsilon Andromedae b polarimetry

Upsilon Andromedae b in polarized light: New constraints on the planet size, density and albedo
http://arxiv.org/abs/1109.3116

Polarimetry is a novel tool to detect and characterize exoplanets and their atmospheres. Polarized scattered light from the non-transiting hot Jupiter $\upsilon$~And~b is measured to further constrain its orbit, mass, density, and geometrical albedo. We obtained polarimetric measurements in the $UBV$ bands over the orbital period and deduce an average peak-to-peak amplitude of $(49 \pm 5)\times10^{-6}$ in both Stokes $q$ and $u$. From our data we evaluate the orbit inclination $i=111\degr\pm11\degr$, longitude of the ascending node $\Omega=236\degr\pm12\degr$ (or equivalently 56\degr), the effective size of the scattering atmosphere in the optical blue of $1.36\pm0.20$\,$R_{\rm J}$. These combined with spectroscopic measurements result in the planet mass $0.74\pm0.07$\,$M_{\rm J}$, mean density $0.36\pm0.08$\,g\,cm$^{-3}$, and surface gravity $\sim10^3$\,cm\,s$^{-2}$, which favor a close similarity of $\upsilon$~And~b to other inflated hot Jupiters. We also significantly improved the periastron epoch $T_{\rm p}={\rm JD}2,450,032.451$, interior conjunction epoch $T_{\rm t}={\rm JD}2,450,034.668$, and periastron longitude $\omega=279\degr\pm14\degr$. The latter indicates that the apsidal resonance known for planets c and d includes also planet b.
Obtained limits on the wavelength dependent geometrical albedo (average 0.35) indicate its similarity to Neptune with peak reflectivity in the blue. Combining all available measurements at various passbands, we construct a unified wavelength dependent albedo of an average hot Jupiter. It appears to be largely shaped by Rayleigh scattering in the blue and atomic and molecular absorption in the optical and near infrared. Our findings demonstrate the power of polarimetry for studying non-transiting exoplanets.

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Sirius_Alpha

Number of posts : 3655
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## Re: Upsilon Andromedae b polarimetry

Great tool. I did not expect to know density of ups and b due to lack of transit.I hope next systems will be gj 581,876 please.I have a question to you sirius is it possible to use polarimetry to longer period 20-100 days planet whether only close in non transiting?

Last edited by tommi59 on 15th September 2011, 4:00 am; edited 1 time in total

tommi59
Jovian

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## Re: Upsilon Andromedae b polarimetry

Excellent, going to have to try modelling this in Celestia with the astrometric orbits for c and d.

Lazarus
dF star

Number of posts : 2978
Registration date : 2008-06-12

## Re: Upsilon Andromedae b polarimetry

tommi59 wrote:I have a question to you sirius is it possible to use polarimetry to longer period 20-100 days planet whether only close in non transiting?

I don't know why it wouldn't be possible in principle. Of course the longer the period of the planet, the dimmer it will be and the harder it will be to pull off.

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Sirius_Alpha

Number of posts : 3655
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