Extrasolar Mechanics

Lithium, exoplanets and 16 Cygni

Lazarus — Wed, 18 Nov 2009 22:19:35 GMT

Don't think this one's been mentioned here, but it seems exoplanet host stars are lithium-poor. I've linked to systemic instead of the paper because the paper's behind the Nature paywall so I haven't read it. :-) So an obvious test would be a multiple star system where one of the stars is an exoplanet host. You'd assume that the stars should have similar compositions because they probably formed from the same nebula at roughly the same time. So let's take the 16 Cygni system which contains ...

Super-Earths in orbits close to Jovian planets

Sirius_Alpha — Wed, 18 Nov 2009 03:58:35 GMT

Seems that a super-Earth can migrate toward a gas giant's orbit and be caught into a 3:2 or greater-integer resonance. This would let a terrestrial planet to orbit a star fairly close to a gas giant. Moreover, this means that the presence of a gas giant planet in or near the habitable zone does not rule out the possibility of a habitable world in the same system. Do we expect to find the Super-Earths close to the gas giants? http://arxiv.org/abs/0911.3390 Abstract wrote:We have investigated ...

Are Late Heavy Bombardments rare?

Sirius_Alpha — Wed, 18 Nov 2009 03:59:47 GMT

How Common are Extrasolar, Late Heavy Bombardments? http://arxiv.org/abs/0911.3271 Abstract wrote:The habitability of planets is strongly affected by impacts from comets and asteroids. Indications from the ages of Moon rocks suggest that the inner Solar System experienced an increased rate of impacts roughly 3.8 Gya known as the Late Heavy Bombardment (LHB). Here we develop a model of how the Solar System would have appeared to a distant observer during its history based on the Nice model ...

Jupiter+Saturn analogue OGLE-2006-BLG-109L

Lazarus — Thu, 03 Jul 2008 11:16:23 GMT

Prospects for the habitability of OGLE-2006-BLG-109L

Apparently the two known jovian planets in the OGLE-2006-BLG-109L system would disrupt a habitable planet, unless the system contains yet another terrestrial-mass planet in an inner orbit.

Whether it would be possible to detect such worlds around such a dim and distant star is another matter of course...

HD 202206: Dynamical constraints on orbits

Sirius_Alpha — Wed, 11 Nov 2009 02:14:24 GMT

Dynamical stability analysis of the HD202206 system and constraints to the planetary orbits http://arxiv.org/abs/0911.1963 Abstract wrote:Long-term precise Doppler measurements with the CORALIE spectrograph revealed the presence of two massive companions to the solar-type star HD202206. Although the three-body fit of the system is unstable, it was shown that a 5:1 mean motion resonance exists close to the best fit, where the system is stable. We present here an extensive dynamical study ...

HD 45364: forming a 3:2 resonant system

Lazarus — Wed, 28 Oct 2009 17:56:26 GMT

The Dynamical Origin of the Multi-Planetary System HD45364

Considering the formation of the system and avoiding the capture into a 2:1 resonance, it is predicted that the eccentricities of the two planets around HD 45364 have significantly lower eccentricities than the previously-published orbits. Give it a few years for the orbits to evolve, and this can be tested.

Destroying inner planets around giant stars

Lazarus — Wed, 14 Oct 2009 21:11:48 GMT

A possible explanation for the lack of close-in planets around intermediate-mass subgiant and giant stars? Apparently, a combination of gas drag from the enhanced stellar wind and stronger tidal effects due to increased depth of the convection zone can cause significant inward migration and perhaps engulfment, without needing to have the star expand all the way to the planet's orbit. Maybe has interesting implications for the planet population around intermediate-mass stars. The Orbital ...

Long-range outward migration

Sirius_Alpha — Wed, 07 Oct 2009 00:59:32 GMT

Long range outward migration of giant planets, with application to Fomalhaut b http://arxiv.org/abs/0910.1004 Abstract wrote:Recent observations of exoplanets by direct imaging, reveal that giant planets orbit at a few dozens to more than a hundred of AU from their central star. The question of the origin of these planets challenges the standard theories of planet formation. We propose a new way of obtaining such far planets, by outward migration of a pair of planets formed in the 10 AU region. ...

Rarity of very long-period exoplanets around FGKM stars

Sirius_Alpha — Mon, 28 Sep 2009 00:08:45 GMT

A Uniform Analysis of 118 Stars with High-Contrast Imaging: Long Period Extrasolar Giant Planets are Rare around Sun-like Stars http://arxiv.org/abs/0909.4531 Abstract wrote:We expand on the results of Nielsen et al. (2008), using the null result for giant extrasolar planets around the 118 target stars from the VLT NACO H and Ks band planet search (Masciadri et al. 2005), the VLT and MMT Simultaneous Differential Imaging (SDI) survey (Biller et al. 2007), and the Gemini Deep Planet Survey ...

Hot Jupiter satellites

Lazarus — Mon, 07 Sep 2009 17:49:24 GMT

Interesting study of hot Jupiter satellites - apparently the tidal Q factor of 105 typically used for giant planets may be a significant underestimate, which may mean massive satellites around hot Jupiters can exist. The evaporation of such satellites suggests that for hot Jupiters with periods longer than 2.4�6.6 days (depending on efficiency of heat redistribution around the satellite), detectable Earth-size moons could perhaps exist.

Forming terrestrial planets around a pulsar

Lazarus — Fri, 07 Aug 2009 19:32:48 GMT

From the arXiv, a paper on the formation of the terrestrial planets in the PSR B1257+12 system (which is of course the system that contains the first confirmed extrasolar planet, the first confirmed extrasolar terrestrial-mass planets, the lowest mass extrasolar planet currently known, and was the first confirmed extrasolar multiplanet system, but despite all this has received little attention since its discovery... I'd guess fusion chauvinism). The Pulsar Planets: A Test Case of Terrestrial ...

Homogeneous comparison of planet candidates imaged directly until 2008

Michael Johne — Tue, 05 May 2009 09:29:33 GMT

Hi! http://arxiv.org/abs/0905.0439 We present a compilation of the planet candidates currently known from direct imaging. We have gathered available data from the literature and derive the luminosity of all candidates in a homogeneous way using a bolometric correction, the distances and the K band magnitudes of the objects. In a final step we find the masses of the candidates from a comparison of the luminosity or, if not available, an absolute brightness and several well known hot-start ...

Inclination resonances

Lazarus — Wed, 29 Jul 2009 20:17:29 GMT

arXiv: Planetary Migration and Eccentricity and Inclination Resonances in Extrasolar Planetary Systems

Capture into the 2:1 mean motion resonance can be associated with capture into a 4:2 inclination resonance, which can drive mutual inclinations up to tens of degrees. Some resonant exoplanetary systems may therefore be significantly non-coplanar.

trend in the periods of the planets being discovered

tesh90 — Tue, 09 Jun 2009 09:04:12 GMT

I have a lay question about the periods of planets discovered to date. [img]http://exoplanet.eu/graph_correl.php?Global_Language=en&catPlanet[]=1&catPlanet[]=7&catPlanet[]=8&obs1=plDiscover&obs2=plPeriod&scalex=lin&scaley=log&minx=&miny=&maxx=&maxy=&resol=600&grille=on[/img] [img]http://exoplanet.eu/graph_correl.php?Global_Language=en&catPlanet[]=1&catPlanet[]=7&catPlanet[]=8&obs1=plMass&obs2=plPeriod&scalex=lin&scaley=log&minx=&miny=&maxx=&maxy=&resol=600&grille=on[/img] If ...

M-dwarf habitable planets safer than thought?

Sirius_Alpha — Tue, 09 Jun 2009 00:12:21 GMT

M Star Astrosphere Size Fluctuations and Habitable Planet Descreening http://arxiv.org/abs/0906.1274 Abstract wrote:Stellar astrospheres--the plasma cocoons carved out of the interstellar medium by stellar winds--are continually influenced by their passage through the fluctuating interstellar medium (ISM). Inside dense interstellar regions, an astrosphere may be compressed to a size smaller than the liquid-water habitable zone distance. Habitable planets then enjoy no astrospheric buffering ...

More planets in 55 Cancri?

Lazarus — Tue, 26 Aug 2008 12:23:59 GMT

Here's a topic that doesn't seem to fit well with any of the forum descriptions, but would go nicely into an "Extrasolar systems" forum as in my proposal on the subject... Can more planets fit into the 55 Cancri system between planets f and d? If this is possible, the Packed Planetary Systems hypothesis says that more planets will exist. Results: you can get up to 2-3 planets in the gap. Beyond the orbit of planet d, there is a stable zone at 8.6-9 AU, but the main stability ...

M-dwarf metallicity, same correlation as FGK stars?

Sirius_Alpha — Tue, 21 Apr 2009 00:09:51 GMT

Looks like dM stars with planets are also metal-rich. On the Metal-Richness of M Dwarfs with Planets http://arxiv.org/abs/0904.3092 Abstract wrote:Knowledge of the metallicities of M dwarfs rests predominantly on the photometric calibration of Bonfils and collaborators, which predicts that M dwarfs in the solar neighborhood, including those with known planets, are systematically metal-poor compared to their higher-mass counterparts. We test this prediction using a volume-limited sample ...

Extrasolar planet population synthesis

Sirius_Alpha — Fri, 17 Apr 2009 00:18:03 GMT

Extremely interesting papers on ArXiv. The second one suggests that indeed, we're only knee-deep in the exoplanet lake, and predicts an explosion of newly detectable planets at precisions at the sub metre-per-second accuracy level. Definitely worth discussion! Extrasolar planet population synthesis I: Method, formation tracks and mass-distance distribution http://arxiv.org/abs/0904.2524 Extrasolar planet population synthesis II: Statistical comparison with observation http://arxiv.org/abs/0904.2542

Noncoplanarity and forming planets around Alpha Centauri

Lazarus — Fri, 10 Apr 2009 16:05:00 GMT

Planetesimal Accretion in Binary Systems: Role of the Companion's Orbital Inclination Seems that if the circumstellar disc has a small misalignment to the binary orbit, accretion becomes more favourable. This might allow for an expanded accretion zone around the Alpha Centauri stars sufficient to produce habitable planets, despite the negative conclusions of previous studies.

Stable planets in the habitable zone of Gliese 581

Lazarus — Fri, 10 Apr 2009 13:26:08 GMT

Additional planets in the habitable zone of Gliese 581?

Looks like there are stable regions between the orbits of planets c and d which could host a planet of around 2.5 Earth masses. This would place such a planet in the middle of the habitable zone.

Gliese 876 coplanarity confirmed.

Sirius_Alpha — Thu, 22 Jan 2009 01:05:37 GMT

The architecture of the GJ876 planetary system. Masses and orbital coplanarity for planets b and c http://arxiv.org/abs/0901.3144 Abstract wrote:We present a combined analysis of previously published high-precision radial velocities and astrometry for the GJ876 planetary system using a self-consistent model that accounts for the planet-planet interactions. Assuming the three planets so far identified in the system are coplanar, we find that including the astrometry in the analysis does not ...

Habitable planets in the HD 47186 system

Lazarus — Tue, 24 Mar 2009 20:35:20 GMT

Stability of additional planets in and around the habitable zone of the HD 47186 Planetary System HD 47186 is a non-packed (as far as is currently known) planetary system with a hot Neptune and a Saturn-mass planet in an outer orbit. The inner part of the habitable zone seems to be capable of hosting additional low-mass planets. In particular... It is possible that the two known planets in HD 47186 may have migrated to their present location. Previous studies (Raymond et al. 2006; ...

Detecting Transits of Planetary Companions to Giant Stars

Edasich — Fri, 27 Feb 2009 09:13:56 GMT

Since the transit detections are on a roll, I thought to post this one: Detecting Transits of Planetary Companions to Giant Stars Of the approximately 350 extrasolar planets currently known, of order 10% orbit evolved stars with radii R >~ 2.5 R_sun. These planets are of particular interest because they tend to orbit more massive hosts, and have been subjected to variable stellar insolation over their recent histories as their primaries evolved off the main sequence. Unfortunately, we ...

Local Linear Analysis of Interaction between a Planet and Viscous Disk and an Implication on Type I Planetary Migration

Michael Johne — Fri, 13 Feb 2009 08:04:12 GMT

Hi! http://de.arxiv.org/abs/0902.1887 We investigate the effect of the viscosity on disk-planet interaction and type I migration of planets. We have performed a linear calculation using shearing-sheet approximation and obtained the detailed, high resolution density structure around the planet embedded in a viscous disk with a wide range of viscous coefficients. We find that the density structure in the vicinity of the resonance is modified and the main contribution to the torque comes ...

Binarity of Transit Host Stars - Implications on Planetary Parameters

Michael Johne — Fri, 13 Feb 2009 07:54:15 GMT

Hi! http://de.arxiv.org/abs/0902.2179 Straight-forward derivation of planetary parameters can only be achieved in transiting planetary systems. However, planetary attributes such as radius and mass strongly depend on stellar host parameters. Discovering a transit host star to be multiple leads to a necessary revision of the derived stellar and planetary parameters. Based on our observations of 14 transiting exoplanet hosts, we derive parameters of the individual components of three ...

Warm Jupiters and terrestrial planets

Lazarus — Tue, 03 Feb 2009 19:21:41 GMT

Terrestrial planet formation in low eccentricity warm-Jupiter systems - not quite as difficult as might at first be imagined, apparently.

Tidal destruction of hot Jupiters?

Sirius_Alpha — Sat, 13 Sep 2008 16:01:49 GMT

This paper suggests that tidal evolution may destroy some Hot Jupiters. It points to the age of transiting planet stars as being younger. Planetary Transits and Tidal Evolution http://arxiv.org/abs/0809.1855 Abstract wrote:Transiting planets are generally close enough to their host stars that tides may govern their orbital and thermal evolution of these planets. We present calculations of the tidal evolution of recently discovered transiting planets and discuss their implications. The ...

HD 98800 and high inclination planets in multiple star systems

Lazarus — Fri, 26 Dec 2008 23:55:29 GMT

Apparently in a multiple stellar system the Kozai mechanism can be suppressed in certain cases, e.g. when the object is in a circumbinary orbit around an eccentric binary star. This applies to the HD 98800B system for which high-inclination orbits are apparently stable.

Verrier and Evans (arXiv): High Inclination Planets in Multistellar Systems

Dynamical Simulations of HD 69830 system

Sirius_Alpha — Tue, 16 Dec 2008 01:09:35 GMT

Dynamical Simulations of the Planetary System HD69830 http://arxiv.org/abs/0812.2475 Abstract wrote:HD 69830 exhibits radial velocity variations attributed to three planets as well as infrared emission attributed to a warm debris disk. Previous studies have developed models for the planet migration and mass growth (Alibert et al. 2006) and the replenishment of warm grains (Wyatt et al. 2007). We perform n-body integrations in order to explore the implications of these models for: 1) the excitation ...

Planets diving in Mira giants' photospheres

Edasich — Sat, 06 Dec 2008 14:48:32 GMT

A (relatively) old paper, from 2003, discussing about the possibility of exoplanets around Mira-type variable stars as an explanation of (part of) their variability. Mira Variables explained by a planetary companion interaction: A means to drop the pulsation paradigm? If you cannot download the paper, ask me. I have the fulltext. If I've read right, assuming orbital periods equal to host star's variability period, we could have jovian planets laying between 1 and 5.2 AUs. But host stars ...

Trojan planet formation

Lazarus — Mon, 20 Oct 2008 10:27:39 GMT

Standing on the shoulders of giants: Trojan Earths and vortex trapping in low mass self-gravitating protoplanetary disks of gas and solids

These simulations, which model both gas and dust self-consistently, form Earth-mass planets and super-Earths in the Trojan points of a gas giant, in contrast to earlier simulations where the mass of the Trojan planet only reached about 0.6 Earth masses.

Rapid super-earth formation in low mass disks

Sirius_Alpha — Mon, 01 Dec 2008 01:09:43 GMT

Rapid Formation of Icy Super-Earths and the Cores of Gas Giant Planets http://arxiv.org/abs/0811.4665 Abstract wrote:We describe a coagulation model that leads to the rapid formation of super-Earths and the cores of gas giant planets. Interaction of collision fragments with the gaseous disk is the crucial element of this model. The gas entrains small collision fragments, which rapidly settle to the disk midplane. Protoplanets accrete the fragments and grow to masses of at least 1 Earth mass ...

A horde of brown dwarf secondaries in cataclysmic binary systems?

Edasich — Fri, 28 Nov 2008 12:33:50 GMT

According to The Donor Stars of Cataclysmic Variables, yes. Here I see most of CV secondaries being much below stellar/substellar limit (even <<0.05 MSol). Am I wrong? Radii, as expected look a bit "bloated" (>>1.5 Rj) due to extreme heating and closeness to degenerate host. Others seem Jupiter-sized. An example: DI UMa has a 0.051 MSol companion with radius 0.105 RSol (i.e 1.05 Jupiter radii). I think. EG Cnc's secondary is even less massive (31 Mj) and Saturn-sized ...

Bad news for Alpha Centauri B

Lazarus — Thu, 06 Nov 2008 11:41:42 GMT

Previously, a study of planet formation around Alpha Centauri A concluded that planet formation in the habitable zone was unlikely, however the paper cautioned that the results couldn't be generalised to Alpha Centauri B. Here's the Alpha Centauri B study. Results: only the very innermost part of the habitable zone is favourable for planetary formation, unless the binary started out with different parameters.

Detecting planets from exozodial dust

Sirius_Alpha — Thu, 16 Oct 2008 00:28:16 GMT

The Detectability of Exo-Earths and Super-Earths Via Resonant Signatures in Exozodiacal Clouds http://arxiv.org/abs/0810.2702 Abstract wrote:Directly imaging extrasolar terrestrial planets necessarily means contending with the astrophysical noise of exozodiacal dust and the resonant structures created by these planets in exozodiacal clouds. Using a custom tailored hybrid symplectic integrator we have constructed 120 models of resonant structures created by exo-Earths and super-Earths on circular ...

Eccentric planet versus 2:1 resonance

Lazarus — Tue, 09 Sep 2008 11:52:50 GMT

Apparently several of the eccentric planets in the current lists of exoplanets may actually be systems with 2:1 resonant orbits in disguise. (Similar to the discovery of Gliese 876c) arXiv: How eccentric orbital solutions can hide planetary systems in 2:1 resonant orbits We find that a significant fraction of the published eccentric one-planet solutions might instead be multiple planet systems in near circular orbits, and that several planets with masses comparable to Earth could have ...

Double extrasolar planets

NuclearVacuum — Thu, 17 Jul 2008 22:11:04 GMT

I am very interested in double planets. I am curious if there is currently a way that a Jupiter-sized system of double extrasolar planets (or something of that nature) could be found with today's current methods. I can understand that a transit can be a good way, but what about Doppler? Another question, what if a transiting planet showed very strong evidence of being a double planet (maybe with the primary planet being the mass of Jupiter and the secondary being Neptune), what would it ...

"double orbit"?

Mezon — Wed, 04 Jun 2008 01:55:39 GMT

I was thinking,(hypothetically) removing interfering gravity from other nearby celestial bodies, lets say you had two celestial bodies, exact same mass,diameter, etc and they were somehow able to move in opposite directions(they are side-by-side and are moving in a 'Z' formation) at the same speed and acceleration(if there is any at all). Based on this, would gravity be able to not only pull them back, but cause them to orbit around each other so they are(relative to a viewer of the orbit) forming ...