Improved CoRoT-7 parameters - Deceased radius for b

View previous topic View next topic Go down

Improved CoRoT-7 parameters - Deceased radius for b

Post by Sirius_Alpha on 18th May 2010, 8:24 pm

Improved stellar parameters of CoRoT-7
http://arxiv.org/abs/1005.3208

Abstract wrote:Accurate parameters of the host stars of exoplanets are important for the interpretation of the new planet systems that continue to emerge. The CoRoT satellite recently discovered a transiting rocky planet with a density similar to the inner planets in our solar system, a so-called Super Earth. This planet is orbiting a relatively faint G9V star called CoRoT-7, and we wish to refine its physical properties, which are important for the interpretation of the properties of the planet system. We used spectra from HARPS@ESO-3.6m and UVES@VLT-8.2m. From the analysis of Fe-1 and Fe-2 lines we determine Teff, log g and microturbulence. We use the Balmer lines to constrain Teff and pressure sensitive Mg-1b and Ca lines to constrain log g. From the analysis we find Teff=5250+-60K, log g = 4.47+-0.05, [M/H]=+0.12+-0.06, and vsini = 1.1 km/s. We compared the L/M ratio with isochrones to constrain the evolutionary status. Using the age estimate of 1.2-2.3 Gyr based on stellar activity, we determine the mass and radius 0.91+-0.03 Msun and 0.82+-0.04 Rsun. With these updated constraints we fitted the CoRoT transit light curve for CoRoT-7b. We revise the planet radius to be slightly smaller, R = 1.58+-0.10 Rearth, and the density becomes higher, rho = 7.2+-1.8 g/cm3. The host star CoRoT-7 is a slowly rotating, metal rich, unevolved type G9V star. The star is relatively faint (V=11.7) and its fundamental parameters can only be determined through indirect methods. Our methods rely on detailed spectral analyses that depend on the adopted model atmospheres. From the analysis of spectra of stars with well-known parameters with similar parameters to CoRoT-7 (the Sun and alpha Cen B) we demonstrate that our methods are robust within the claimed uncertainties. Therefore our methods can be reliably used in subsequent analyses of similar exoplanet host stars.

_________________
Caps Lock: Cruise control for 'Cool'!
avatar
Sirius_Alpha
Admin
Admin

Number of posts : 3468
Location : Earth
Registration date : 2008-04-06

View user profile http://solar-flux.forumandco.com/

Back to top Go down

Re: Improved CoRoT-7 parameters - Deceased radius for b

Post by ciceron on 19th May 2010, 3:41 pm

Now , that's pretty heavy. Chromium has about that density (7.15) but if the upper density of the error margin is accurate , we are talking of copper (8.96) . As there must be some mix-up of elements , I suspect a masive iron ball (7.87). That's a mean piece of rock. As the star is still very young , I don't see it being the remaining core of some migrated giant.

Maybe a captured object from another star? I don't see how that object could have formed in that system.

Btw : I hope the radius has been Decreased...if the radius have deceased , then we are in trouble Wink


Last edited by ciceron on 19th May 2010, 3:42 pm; edited 1 time in total (Reason for editing : Inserting pun.)

_________________
---
Caution. This post contains broken english inside. Handle with care.

ciceron
Planetary Embryo
Planetary Embryo

Number of posts : 83
Age : 47
Location : Spain
Registration date : 2008-04-08

View user profile http://el-francotirador-mvv.blogspot.com/

Back to top Go down

Re: Improved CoRoT-7 parameters - Deceased radius for b

Post by Edasich on 19th May 2010, 4:00 pm

Maybe mostly made of iron?
avatar
Edasich
dM star
dM star

Number of posts : 1510
Location : Tau Ceti g - Mid Latitudes
Registration date : 2008-06-02

View user profile

Back to top Go down

Re: Improved CoRoT-7 parameters - Deceased radius for b

Post by ciceron on 19th May 2010, 4:07 pm

So masive a piece of iron should have a mean magnetic field. It could polarize the star's ligth , am i wrong ?

_________________
---
Caution. This post contains broken english inside. Handle with care.

ciceron
Planetary Embryo
Planetary Embryo

Number of posts : 83
Age : 47
Location : Spain
Registration date : 2008-04-08

View user profile http://el-francotirador-mvv.blogspot.com/

Back to top Go down

Re: Improved CoRoT-7 parameters - Deceased radius for b

Post by AVBursch on 19th May 2010, 5:40 pm

Massive terrestrial planets have a substantial amount of gravitational compression. For example, Earth has a higher density then Mercury in spite of lower iron content. Earth's uncompressed density is 4.4 g/cm^3, but gravitational compression increases it to 5.515 g/cm^3.

COROT-7b, being 4.8 times the mass of Earth, would have much greater gravitational compression. Taking into account the effect of gravitational compression, COROT-7b's uncompressed density would be around 3.7 g/cm^3. COROT-7b's composition would be more akin to Mars than with Earth or Venus.

AVBursch
Meteor
Meteor

Number of posts : 18
Registration date : 2009-05-01

View user profile

Back to top Go down

Re: Improved CoRoT-7 parameters - Deceased radius for b

Post by Lazarus on 19th May 2010, 6:03 pm

Mass of CoRoT-7b is revised upwards as well, to 5.20.8 M.
avatar
Lazarus
dG star
dG star

Number of posts : 2819
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: Improved CoRoT-7 parameters - Deceased radius for b

Post by Sponsored content


Sponsored content


Back to top Go down

View previous topic View next topic Back to top


 
Permissions in this forum:
You cannot reply to topics in this forum