Estimating the masses of extra-solar planets

View previous topic View next topic Go down

Estimating the masses of extra-solar planets

Post by lodp on 10th June 2010, 8:21 pm

ABSTRACT
All extra-solar planet masses that have been derived spectroscopically are lower
limits since the inclination of the orbit to our line-of-sight is unknown except for tran-
siting systems. In theory, however, it is possible to determine the inclination angle, i,
between the rotation axis of a star and an observerís line-of-sight from measurements
of the projected equatorial velocity (v sin i), the stellar rotation period (Prot) and the
stellar radius (R). For stars which host planetary systems this allows the removal of
the sin i dependency of extra-solar planet masses derived from spectroscopic observa-
tions under the assumption that the planetary orbits lie perpendicular to the stellar
rotation axis.
We have carried out an extensive literature search and present a catalogue of v sin i,
Prot, and R estimates for stars hosting extra-solar planets. In addition, we have used
Hipparcos parallaxes and the Barnes-Evans relationship to further supplement the R
estimates obtained from the literature. Using this catalogue, we have obtained sin i
estimates using a Markov-chain Monte Carlo analysis. This technique allows proper 1-
 two-tailed confidence limits to be placed on the derived sin iís along with the transit
probability for each planet to be determined.
While we find that a small proportion of systems yield sin iís significantly greater
than 1, most likely due to poor Prot estimations, the large majority are acceptable.We
are further encouraged by the cases where we have data on transiting systems, as the
technique indicates inclinations of 90 and high transit probabilities. In total, we are
able to estimate the true masses of 133 extra-solar planets. Of these 133 extra-solar
planets, only 6 have revised masses that place them above the 13 MJ deuterium burn-
ing limit; 4 of those 6 extra-solar planet candidates were already suspected to lie above
the deuterium burning limit before correcting their masses for the sin i dependency.
Our work reveals a population of high-mass extra-solar planets with low eccentricities
and we speculate that these extra-solar planets may represent the signature of differ-
ent planetary formation mechanisms at work. Finally, we discuss future observations
that should improve the robustness of this technique.

http://arxiv.org/PS_cache/arxiv/pdf/1006/1006.2069v1.pdf

lodp
Asteroid
Asteroid

Number of posts : 57
Location : Leeds, UK
Registration date : 2009-08-11

View user profile http://www.lodp2.plus.com

Back to top Go down

Re: Estimating the masses of extra-solar planets

Post by Edasich on 11th June 2010, 5:38 am

According to those estimations we would lose HD 162020 b that would turn out either a M4 dwarf or a 67 Mj brown dwarf.

Nonetheless, apparently, we would gain three more planets previously ruled out as brown dwarfs or low-mass stars: HD 33636 b, HD 136118 b and HD 150706 b.

HD 4308 b turns out a 0.27 Mj planet rather a 14.1 Earth masses one and HD 69830 b,c and would become 0.066-0.069-0.103 Mj.

HD 81040 b, HD 141937 b could be low-mass brown dwarfs (around 17.6 Mj).

Edasich
dM star
dM star

Number of posts : 1495
Location : Tau Ceti g - Mid Latitudes
Registration date : 2008-06-02

View user profile

Back to top Go down

Re: Estimating the masses of extra-solar planets

Post by Lazarus on 11th June 2010, 1:48 pm

The key assumption is that the planets lie in the equatorial plane of the parent star. This may not be the case: the WASP results for hot Jupiter misalignments or the Upsilon Andromedae astrometric results show that it is not always the case that this assumption holds.

Lazarus
dG star
dG star

Number of posts : 2739
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: Estimating the masses of extra-solar planets

Post by Sirius_Alpha on 11th June 2010, 2:21 pm

As for HD 33636 b, HD 136118 b and HD 150706 b, I'd trust HST astrometry over the λ ≈ 0 assumption any day.

_________________
Caps Lock: Cruise control for 'Cool'!

Sirius_Alpha
Admin
Admin

Number of posts : 3375
Location : Earth
Registration date : 2008-04-06

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

Back to top Go down

Re: Estimating the masses of extra-solar planets

Post by Edasich on 12th June 2010, 4:38 am

Now I get why no update at EPE.

Edasich
dM star
dM star

Number of posts : 1495
Location : Tau Ceti g - Mid Latitudes
Registration date : 2008-06-02

View user profile

Back to top Go down

Re: Estimating the masses of extra-solar planets

Post by Sirius_Alpha on 21st June 2010, 8:27 pm

Along similar lines,

Rotation periods of exoplanet host stars
http://arxiv.org/abs/1006.4121

Abstract wrote:The stellar rotation periods of ten exoplanet host stars have been determined using newly analysed Ca II H & K flux records from Mount Wilson Observatory and Stromgren b, y photometric measurements from Tennessee State University's automatic photometric telescopes (APTs) at Fairborn Observatory. Five of the rotation periods have not previously been reported, with that of HD 130322 very strongly detected at Prot = 26.1 \pm 3.5 d. The rotation periods of five other stars have been updated using new data. We use the rotation periods to derive the line-of-sight inclinations of the stellar rotation axes, which may be used to probe theories of planet formation and evolution when combined with the planetary orbital inclination found from other methods. Finally, we estimate the masses of fourteen exoplanets under the assumption that the stellar rotation axis is aligned with the orbital axis. We calculate the mass of HD 92788 b (28 MJ) to be within the low-mass brown dwarf regime and suggest that this object warrants further investigation to confirm its true nature.

_________________
Caps Lock: Cruise control for 'Cool'!

Sirius_Alpha
Admin
Admin

Number of posts : 3375
Location : Earth
Registration date : 2008-04-06

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

Back to top Go down

Re: Estimating the masses of extra-solar planets

Post by Sponsored content Today at 10:00 am


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