scholarly journals Search for Close-in Planets around Evolved Stars with Phase-curve variations and Radial Velocity Measurements

2015 ◽  
Vol 11 (A29A) ◽  
pp. 63-64
Author(s):  
Teruyuki Hirano ◽  
Bun'ei Sato ◽  
Kento Masuda ◽  
Othman Michel Benomar ◽  
Yoichi Takeda ◽  
...  
Keyword(s):  
Major Axis ◽  
Giant Planets ◽  
Phase Curve ◽  
Main Sequence Stars ◽  
Semi Major Axis ◽  
Evolved Stars ◽  
Tidal Interactions ◽  
Reflected Light ◽  
History Of ◽  
Global Fit

AbstractTidal interactions are a key process to understand the evolution history of close-in exoplanets. But tidals still have a large uncertainty in their prediction for the damping timescales of stellar obliquity and semi-major axis. We have worked on a search for transiting giant planets around evolved stars, for which few close-in planets were discovered. It has been reported that evolved stars lack close-in planets, which is often attributed to the tidal evolution and/or engulfment of close-in planets by the hosts. Meanwhile, Kepler has detected a certain fraction of transiting planet candidates around evolved stars. Confirming the planetary nature for these candidates is especially important since the comparison between the occurrence rates of close-in planets around main sequence stars and evolved stars provides a unique opportunity to discuss the final stage of close-in planets. With the aim of confirming KOI planet candidates around evolved stars, we measured precision radial velocities (RVs) for evolved stars with transiting planet candidates using Subaru/HDS. We also developed a new code which simultaneously models and fits the observed RVs and phase-curve variations in the Kepler data (e.g., transits, stellar ellipsoidal variations, and planet emission/reflected light). As a result of applying the global fit to KOI giants/subgiants, we confirmed two giant planets around evolved stars (Kepler-91 and KOI-1894), as well as revealed that KOI-977 is more likely a false positive.

Dynamics of Tidal Disruption Events: Statistical Properties

2020 ◽  
Author(s):  
Amir Weissbein ◽  
Re’em Sari
Keyword(s):  
Major Axis ◽  
Statistical Properties ◽  
Strong Interactions ◽  
Tidal Effects ◽  
Semi Major Axis ◽  
Tidal Disruption ◽  
Loss Cone ◽  
Tidal Interactions ◽  
Radius Of Influence ◽  
History Of

Abstract We study the correlations between the dynamical history of a star that eventually experience a tidal disruption events (TDE), and the properties of the TDE itself. As expected, we find that (i) in empty loss cone at the radius of influence, most TDEs are non-violent TDEs, i.e., the star’s periastron is only a bit smaller than the tidal radius. These stars had experienced strong tidal interactions with the SMBH, just slightly outside the tidal radius. (ii) in full loss cone at the radius of influence, most TDEs are violent, i.e., the star’s periastron is significantly smaller than the tidal radius. These stars did not previously encounter strong tidal effects. Nevertheless, we demonstrate that even in extremely empty or extremely full loss cone a finite fraction of order $\sim 10\%$ of the events are non-typical. This is due to two surprising effects: (i) In an empty LC, a logarithmic fraction of the events are associated with stars that entered the loss cone via strong scatterings. Those events are usually violent penetrating deep into the loss cone. (ii) In full loss cone, orbits with semi-major axis smaller than the radius of influence, where the loss cone is marginally empty, dominate the TDEs rate. As a result, constant fraction of TDEs involve stars in an empty loss cone orbits, which have typically experienced strong interactions with the SMBH in previous orbits.

scholarly journals SOPHIE velocimetry of Kepler transit candidates

2018 ◽  
Vol 615 ◽  
pp. A90 ◽  
Author(s):  
J. M. Almenara ◽  
R. F. Díaz ◽  
G. Hébrard ◽  
R. Mardling ◽  
C. Damiani ◽  
...  
Keyword(s):  
Planetary System ◽  
Major Axis ◽  
Giant Planets ◽  
Eccentric Orbit ◽  
Semi Major Axis ◽  
Hot Jupiters ◽  
Timing Data ◽  
Single Host ◽  
Velocity Information ◽  
The Masses

Kepler-419 is a planetary system discovered by the Kepler photometry which is known to harbour two massive giant planets: an inner 3 MJ transiting planet with a 69.8-day period, highly eccentric orbit, and an outer 7.5 MJ non-transiting planet predicted from the transit-timing variations (TTVs) of the inner planet b to have a 675-day period, moderately eccentric orbit. Here we present new radial velocity (RV) measurements secured over more than two years with the SOPHIE spectrograph, where both planets are clearly detected. The RV data is modelled together with the Kepler photometry using a photodynamical model. The inclusion of velocity information breaks the MR−3 degeneracy inherent in timing data alone, allowing us to measure the absolute stellar and planetary radii and masses. With uncertainties of 12 and 13% for the stellar and inner planet radii, and 35, 24, and 35% for the masses of the star, planet b, and planet c, respectively, these measurements are the most precise to date for a single host star system using this technique. The transiting planet mass is determined at better precision than the star mass. This shows that modelling the radial velocities and the light curve together in systems of dynamically interacting planets provides a way of characterising both the star and the planets without being limited by knowledge of the star. On the other hand, the period ratio and eccentricities place the Kepler-419 system in a sweet spot; had around twice as many transits been observed, the mass of the transiting planet could have been measured using its own TTVs. Finally, the origin of the Kepler-419 system is discussed. We show that the system is near a coplanar high-eccentricity secular fixed point, related to the alignment of the orbits, which has prevented the inner orbit from circularising. For most other relative apsidal orientations, planet b’s orbit would be circular with a semi-major axis of 0.03 au. This suggests a mechanism for forming hot Jupiters in multiplanetary systems without the need of high mutual inclinations.

scholarly journals Mapping the Distributions of Exoplanet Populations with NICI and GPI

2015 ◽  
Vol 10 (S314) ◽  
pp. 220-225
Author(s):  
Eric L. Nielsen ◽  
Michael C. Liu ◽  
Zahed Wahhaj ◽  
Beth A. Biller ◽  
Thomas L. Hayward ◽  
...  
Keyword(s):  
Low Frequency ◽  
Major Axis ◽  
Giant Planets ◽  
Direct Imaging ◽  
Semi Major Axis ◽  
Solar Systems ◽  
Test Models ◽  
Nearby Stars ◽  
Formation And Evolution ◽  
Band Contrast

AbstractWhile more and more long-period giant planets are discovered by direct imaging, the distribution of planets at these separations (≳5 AU) has remained largely uncertain, especially compared to planets in the inner regions of solar systems probed by RV and transit techniques. The low frequency, the detection challenges, and heterogeneous samples make determining the mass and orbit distributions of directly imaged planets at the end of a survey difficult. By utilizing Monte Carlo methods that incorporate the age, distance, and spectral type of each target, we can use all stars in the survey, not just those with detected planets, to learn about the underlying population. We have produced upper limits and direct measurements of the frequency of these planets with the most recent generation of direct imaging surveys. The Gemini NICI Planet-Finding Campaign observed 220 young, nearby stars at a median H-band contrast of 14.5 magnitudes at 1”, representing the largest, deepest search for exoplanets by the completion of the survey. The Gemini Planet Imager Exoplanet Survey is in the process of surveying 600 stars, pushing these contrasts to a few tenths of an arcsecond from the star. With the advent of large surveys (many hundreds of stars) using advanced planet-imagers we gain the ability to move beyond measuring the frequency of wide-separation giant planets and to simultaneously determine the distribution as a function of planet mass, semi-major axis, and stellar mass, and so directly test models of planet formation and evolution.

scholarly journals PLANETARY MIGRATION IN EVOLVING PLANETESIMAL DISKS

2003 ◽  
Vol 12 (08) ◽  
pp. 1399-1414 ◽  
Author(s):  
İ. SAFFET YEŞİLYURT ◽  
E. NİHAL ERCAN ◽  
A. DEL POPOLO
Keyword(s):  
Accretion Disks ◽  
Migration Rate ◽  
Major Axis ◽  
Solid Particles ◽  
Giant Planets ◽  
Semi Major Axis ◽  
Density Profiles ◽  
Disk Model ◽  
Characteristic Radius ◽  
Planetary Migration

In the current paper, we further improved the model for the migration of planets introduced and extended to time-dependent planetesimal accretion disks by Del Popolo. In the current study, the assumption of Del Popolo, that the surface density in planetesimals is proportional to that of gas, is relaxed. In order to obtain the evolution of planetesimal density, we use a method developed by Stepinski and Valageas which is able to simultaneously follow the evolution of gas and solid particles for up to 107 years. Then, the disk model is coupled to migration model introduced by Del Popolo in order to obtain the migration rate of the planet in the planetesimal. We find that the properties of solids known to exist in protoplanetary systems, together with reasonable density profiles for the disk, lead to a characteristic radius in the range 0.03–0.2 AU for the final semi-major axis of the giant planet.Hence our model can explain the properties of discovered extrasolar giant planets.

scholarly journals Planetary migration in gaseous protoplanetary disks

2007 ◽  
Vol 3 (S249) ◽  
pp. 331-346
Author(s):  
Frédéric S. Masset
Keyword(s):  
Major Axis ◽  
Giant Planets ◽  
Type I ◽  
Type Ii ◽  
Orbital Elements ◽  
Intermediate Mass ◽  
Semi Major Axis ◽  
Low Mass ◽  
Planetary Migration ◽  
Different Parts

AbstractTides come from the fact that different parts of a system do not fall in exactly the same way in a non-uniform gravity field. In the case of a protoplanetary disk perturbed by an orbiting, prograde protoplanet, the protoplanet tides raise a wake in the disk which causes the orbital elements of the planet to change over time. The most spectacular result of this process is a change in the protoplanet's semi-major axis, which can decrease by orders of magnitude on timescales shorter than the disk lifetime. This drift in the semi-major axis is called planetary migration. In a first part, we describe how the planet and disk exchange angular momentum and energy at the Lindblad and corotation resonances. Next we review the various types of planetary migration that have so far been contemplated: type I migration, which corresponds to low-mass planets (less than a few Earth masses) triggering a linear disk response; type II migration, which corresponds to massive planets (typically at least one Jupiter mass) that open up a gap in the disk; “runaway” or type III migration, which corresponds to sub-giant planets that orbit in massive disks; and stochastic or diffusive migration, which is the migration mode of low- or intermediate-mass planets embedded in turbulent disks. Lastly, we present some recent results in the field of planetary migration.

scholarly journals HD 83443: a system with two Saturns

2004 ◽  
Vol 202 ◽  
pp. 84-86 ◽  
Author(s):  
M. Mayor ◽  
D. Naef ◽  
F. Pepe ◽  
D. Queloz ◽  
N. C. Santos ◽  
...  
Keyword(s):  
Planetary System ◽  
Major Axis ◽  
Giant Planets ◽  
Outer Planet ◽  
Semi Major Axis ◽  
Dynamical Study ◽  
Low Mass ◽  
The Stability ◽  
Extrasolar Planetary System

We report the discovery of an extrasolar planetary system with two Saturnian planets around the star HD 83443. The new planetary system is unusual by more than one aspect, as it contains two very low–mass gaseous giant planets, both on very tight orbits. Among the planets detected so far, the inner planet has the smallest semi–major axis (0.038 AU) and period (2.985 days) whereas the outer planet is the lightest one with m2 sin i = 0.53 MSat. A preliminary dynamical study confirms the stability of the system.

scholarly journals Retention of protoplanetary cores near the snowline

2007 ◽  
Vol 3 (S249) ◽  
pp. 309-312 ◽  
Author(s):  
Xiaojia Zhang ◽  
Katherine Kretke ◽  
D. N. C. Lin
Keyword(s):  
Surface Density ◽  
Major Axis ◽  
Giant Planets ◽  
Type I ◽  
Density Jump ◽  
Semi Major Axis ◽  
Snow Line ◽  
Linear Formula ◽  
Dominant Process ◽  
D Model

AbstractSuppression of type I migration is essential for the retention of protoplanetary cores which are sufficiently massive to accrete gas in their nascent disks and evolve into gas giant planets. We explore here the possibility that special disk properties at the snow line may be the dominant process which stalled the type I migration. We simply use a 1-D model to calculate the torque with linear formula and find that, if the surface density jump near snowline is great enough, the migration can be efficiently slowed down or even halted. This mechanism offers an explanation to the observed peak, at 2–3 AU, in the extra solar planets' semi major axis distribution.

scholarly journals Properties of long gamma-ray bursts from massive compact binaries

2013 ◽  
Vol 371 (1992) ◽  
pp. 20120230
Author(s):  
Ross P. Church ◽  
Andrew J. Levan ◽  
Melvyn B. Davies ◽  
Chunglee Kim
Keyword(s):  
Black Hole ◽  
Gamma Ray ◽  
Accretion Rate ◽  
Major Axis ◽  
Gamma Ray Bursts ◽  
Close Binary ◽  
Peak Time ◽  
Semi Major Axis ◽  
Massive Black Hole ◽  
Tidal Interactions

We consider the implications of a model for long-duration gamma-ray bursts in which the progenitor is spun up in a close binary by tidal interactions with a massive black-hole companion. We investigate a sample of such binaries produced by a binary population synthesis, and show that the model predicts several common features in the accretion on to the newly formed black hole. In all cases, the accretion rate declines as approximately t −5/3 until a break at a time of order 10 4   s . The accretion rate declines steeply thereafter. Subsequently, there is flaring activity, with the flare peaking between 10 4 and 10 5  s, the peak time being correlated with the flare energy. We show that these times are set by the semi-major axis of the binary, and hence the process of tidal spin-up; furthermore, they are consistent with flares seen in the X-ray light curves of some long gamma-ray bursts.

scholarly journals Properties of the young gas giant planet β Pictoris b

2013 ◽  
Vol 8 (S299) ◽  
pp. 241-246
Author(s):  
Mickaël Bonnefoy ◽  
Anthony Boccaletti ◽  
Anne-Marie Lagrange ◽  
France Allard ◽  
Christoph Mordasini ◽  
...  
Keyword(s):  
Spectral Energy Distribution ◽  
Giant Planet ◽  
Major Axis ◽  
Spectral Energy ◽  
Atmospheric Models ◽  
Semi Major Axis ◽  
Orbital Parameters ◽  
Formation History ◽  
History Of ◽  
Gas Giant

AbstractThe young (12+8−4 Myr) and nearby (19.44±0.05 pc) star β Pictoris is considered one of the best laboratories for the study of early phases of planetary systems formation since the identification of an extended debris disk surrounding the star in 1984. In 2009, we imaged at 3.8 μm with NaCo at VLT a gas giant planet around β Pictoris, roughly along the disk mid-plane, with a semi-major axis between 8 and 14 AU. We present here the first images of the planet in the J (1.265 μm), H (1.66 μm), and M' (4.78 μm) bands obtained between 2011 and 2012. We used these data to build the 1-5 μm spectral energy distribution (SED) of the companion, and to consolidate previous semi-major axis (8-10 AU) estimates. We compared the SED to seven atmospheric models to derive Teff = 1700 ± 100 K. We used the temperature and the luminosity of β Pictoris b to estimate new masses for the companion. We compared these masses to independent constraints set by the orbital parameters and the radial velocities and use them to discuss the formation history of the object.

scholarly journals Migration of gap-opening planets in 3D stellar-irradiated accretion disks

2020 ◽  
Vol 642 ◽  
pp. A219
Author(s):  
O. Chrenko ◽  
D. Nesvorný
Keyword(s):  
Major Axis ◽  
Temperature Inversion ◽  
Central Star ◽  
Giant Planets ◽  
Type Ii ◽  
Semi Major Axis ◽  
Numerical Studies ◽  
Temperature Excess ◽  
Gap Opening ◽  
Outward Migration

Context. The origin of giant planets at moderate separations ≃1–10 au is still not fully understood because numerical studies of Type II migration in protoplanetary disks often predict a decay of the semi-major axis that is too fast. According to recent 2D simulations, inward migration of a gap-opening planet can be slowed down or even reversed if the outer gap edge becomes heated by irradiation from the central star, and puffed up. Aims. Here, we study how stellar irradiation reduces the disk-driven torque and affects migration in more realistic 3D disks. Methods. Using 3D hydrodynamic simulations with radiation transfer, we investigated the static torque acting on a single gap-opening planet embedded in a passively heated accretion disk. Results. Our simulations confirm that a temperature inversion is established at the irradiated outer gap edge and the local increase of the scale height reduces the magnitude of the negative outer Lindblad torque. However, the temperature excess is smaller than assumed in 2D simulations and the torque reduction only becomes prominent for specific parameters. For the viscosity α = 10−3, the total torque is reduced for planetary masses ranging from 0.1 to 0.7 Jupiter mass, with the strongest reduction being by a factor of − 0.17 (implying outward migration) for a Saturn-mass planet. For a Jupiter-mass planet, the torque reduction becomes stronger with increasing α (the torque is halved when α = 5 × 10−3). Conclusions. We conclude that planets that open moderately wide and deep gaps are subject to the largest torque modifications and their Type II migration can be stalled due to gap edge illumination. We then argue that the torque reduction can help to stabilize the orbits of giant planets forming at ≳ 1 au.

Sign in / Sign up

Export Citation Format

Share Document