Long-Period Giant Companions to Three Compact, Multiplanet Systems
Sean M. Mills, Andrew W. Howard, Lauren M. Weiss, Jason H. Steffen, Howard Isaacson, Benjamin J. Fulton, Erik A. Petigura, Molly R. Kosiarek, Lea A. Hirsch, John H. Boisvert
Understanding the relationship between long-period giant planets and multiple smaller short-period planets is critical for formulating a complete picture of planet formation. This work characterizes three such systems. We present Kepler-65, a system with an eccentric (e=0.28+/-0.07) giant planet companion discovered via radial velocities (RVs) exterior to a compact, multiply-transiting system of sub-Neptune planets. We also use precision RVs to improve mass and radius constraints on two other systems with similar architectures, Kepler-25 and Kepler-68. In Kepler-68 we propose a second exterior giant planet candidate. Finally, we consider the implications of these systems for planet formation models, particularly that the moderate eccentricity in Kepler-65's exterior giant planet did not disrupt its inner system.
Planets around binary stars and those in multiplanet systems may experience resonant eccentricity excitation and disruption due to perturbations from a distant stellar companion. This "evection resonance" occurs when the apsidal precession frequency of the planet, driven by the quadrupole associated with the inner binary or the other planets, matches the orbital frequency of the external companion. We develop an analytic theory to study the effects of evection resonance on circumbinary planets and multiplanet systems. We derive the general conditions for effective eccentricity excitation or re…
Most exoplanetary systems in binary stars are of S--type, and consist of one or more planets orbiting a primary star with a wide binary stellar companion. Gravitational forcing of a single planet by a sufficiently inclined binary orbit can induce large amplitude oscillations of the planet's eccentricity and inclination through the Kozai-Lidov (KL) instability. KL cycling was invoked to explain: the large eccentricities of planetary orbits; the family of close--in hot Jupiters; and the retrograde planetary orbits in eccentric binary systems. However, several kinds of perturbations can quench th…
We study the excitation of mutual inclination between planetary orbits by a novel secular-orbital resonance in multiplanet systems perturbed by binary companions which we call "ivection". The ivection resonance happens when the nodal precession rate of the planet matches a multiple of the orbital frequency of the binary, and its physical nature is similar to the previously-studied evection resonance. Capture into an ivection resonance requires encountering the resonance with slowly increasing nodal precession rate, and it can excite the mutual inclination of the planets without affecting their…
Many Kepler multiplanet systems have planet pairs near low-order, mean-motion resonances. In addition, many Kepler multiplanet systems have planets with orbital periods less than a few days. With the exception of Kepler-42, however, there are no examples of systems with both short orbital periods and nearby companion planets while our statistical analysis predicts ~17 such pairs. For orbital periods of the inner planet that are less than three days, the minimum period ratio of adjacent planet pairs follows the rough constraint P_2/P_1 >~ 2.3 (P_1/day)^(-2/3). This absence is not due to a lack …
Given the tendency of planets to form in multiples, and the observational evidence in support of the existence of potential planet-hosting stars in binaries or clusters, it is expected that extrasolar terrestrial planes are more likely to be found in multiple body systems. This paper discusses the prospects of the detection of terrestrial/habitable planets in multibody systems by presenting the results of a study of the long-term stability of these objects in systems with multiple giant planets (particularly those in eccentric and/or in mean-motion resonant orbits), systems with close-in Jupit…
When exploring the stability of multiplanet systems in binaries, two parameters are normally exploited: the critical semimajor axis ac computed by Holman and Wiegert (1999) within which planets are stable against the binary perturbations, and the Hill stability limit Delta determining the minimum separation beyond which two planets will avoid mutual close encounters. Our aim is to test whether these two parameters can be safely applied in multiplanet systems in binaries or if their predictions fail for particular binary orbital configurations. We have used the frequency map analysis (FMA) to m…
We have detected the Rossiter-Mclaughlin effect during a transit of WASP-47b, the only known hot Jupiter with close planetary companions. By combining our spectroscopic observations with Kepler photometry, we show that the projected stellar obliquity is $λ= 0^\circ \pm 24^\circ$. We can firmly exclude a retrograde orbit for WASP-47b, and rule out strongly misaligned prograde orbits. Low obliquities have also been found for most of the other compact multiplanet systems that have been investigated. The Kepler-56 system, with two close-in gas giants transiting their subgiant host star with an obl…
Kepler has identified over 600 multiplanet systems, many of which have several planets with orbital distances smaller than that of Mercury -- quite different from the Solar System. Because these systems may be difficult to explain in the paradigm of core accretion and disk migration, it has been suggested that they formed in situ within protoplanetary disks with high solid surface densities. The strong connection between giant planet occurrence and stellar metallicity is thought to be linked to enhanced solid surface densities in disks around metal-rich stars, so the presence of a giant planet…
We announce confirmation of Kepler-418b, one of two proposed planets in this system. This is the first confirmation of an exoplanet based primarily on the transit color signature technique. We used the Kepler public data archive combined with multicolor photometry from the Gran Telescopio de Canarias and radial velocity follow-up using FIES at the Nordic Optical Telescope for confirmation. We report a confident detection of a transit color signature that can only be explained by a compact occulting body, entirely ruling out a contaminating eclipsing binary, a hierarchical triple, or a grazing …
Extrasolar planets abound in almost any possible configuration. However, until five years ago, there was a lack of planets orbiting closer than 0.5 au to giant or subgiant stars. Since then, recent detections have started to populated this regime by confirming 13 planetary systems. We discuss the properties of these systems in terms of their formation and evolution off the main sequence. Interestingly, we find that $70.0\pm6.6$ % of the planets in this regime are inner components of multiplanetary systems. This value is 4.2$σ$ higher than for main-sequence hosts, which we find to be $42.4\pm0.…
We present precise Doppler observations of WASP-47, a transiting planetary system featuring a hot Jupiter with both inner and outer planetary companions. This system has an unusual architecture and also provides a rare opportunity to measure planet masses in two different ways: the Doppler method, and the analysis of transit-timing variations (TTV). Based on the new Doppler data, obtained with the Planet Finder Spectrograph on the Magellan/Clay 6.5m telescope, the mass of the hot Jupiter is $370 \pm 29~M_{\oplus}$. This is consistent with the previous Doppler determination as well as the TTV d…
The stellar spin orientation relative to the orbital planes of multiplanet systems are becoming accessible to observations. Here, we analyze and classify different types of spin-orbit evolution in compact multiplanet systems perturbed by an inclined outer companion. Our study is based on classical secular theory, using a vectorial approach developed in a separate paper. When planet-planet perturbations are truncated at the second order in eccentricity and mutual inclination, and the planet-companion perturbations are developed at the quadrupole order, the problem becomes integrable. The motion…
Stars hosting hot Jupiters are often observed to have high obliquities, whereas stars with multiple co-planar planets have been seen to have low obliquities. This has been interpreted as evidence that hot-Jupiter formation is linked to dynamical disruption, as opposed to planet migration through a protoplanetary disk. We used asteroseismology to measure a large obliquity for Kepler-56, a red giant star hosting two transiting co-planar planets. These observations show that spin-orbit misalignments are not confined to hot-Jupiter systems. Misalignments in a broader class of systems had been pred…
Assuming that giant planets are formed in thin protoplanetary discs, a '3D' system can form, provided that the mutual inclination is excited by some dynamical mechanism. Resonant interactions and close planetary encounters are thought to be the primary inclination-excitation mechanisms, resulting in a resonant and non-resonant system, respectively. Here we propose an alternative formation scenario, starting from a system composed of three giant planets in a nearly coplanar configuration. As was recently shown for the case of the Solar system, planetary migration in the gas disc (Type II migrat…
The stellar spin orientation relative to the orbital planes of multiplanet systems are becoming accessible to observations. For example, 55 Cancri is a system composed of 5 planets orbiting a member of a stellar binary for which a projected obliquity of 72+-12 deg relative to the orbit of the innermost planet has been reported (Bourrier & Hebrard 2014). This large obliquity has been attributed to the perturbation induced by the binary. Here we describe the secular evolution of similar systems and we discuss the case of the 55 Cancri system more deeply. We provide two different orbital configur…
We confirm 27 planets in 13 planetary systems by showing the existence of statistically significant anti-correlated transit timing variations (TTVs), which demonstrates that the planet candidates are in the same system, and long-term dynamical stability, which places limits on the masses of the candidates---showing that they are planetary. %This overall method of planet confirmation was first applied to \kepler systems 23 through 32. All of these newly confirmed planetary systems have orbital periods that place them near first-order mean motion resonances (MMRs), including 6 systems near the 2…
We report a multiplanetary system found from the analysis of microlensing event OGLE-2018-BLG-1011, for which the light curve exhibits a double-bump anomaly around the peak. We find that the anomaly cannot be fully explained by the binary-lens or binary-source interpretations and its description requires the introduction of an additional lens component. The 3L1S (3 lens components and a single source) modeling yields three sets of solutions, in which one set of solutions indicates that the lens is a planetary system in a binary, while the other two sets imply that the lens is a multiplanetary …
Even though tens of directly imaged companions have been discovered in the past decades, the number of directly confirmed multiplanet systems is still small. Dynamical analysis of these systems imposes important constraints on formation mechanisms of these wide-orbit companions. As part of the Young Suns Exoplanet Survey (YSES) we report the detection of a second planetary-mass companion around the 17 Myr-old, solar-type star TYC 8998-760-1 that is located in the Lower Centaurus Crux subgroup of the Scorpius-Centaurus association. The companion has a projected physical separation of 320 au and…
A Korean-Japanese planet search program has been carried out using the 1.8m telescope at Bohyunsan Optical Astronomy Observatory (BOAO) in Korea, and the 1.88m telescope at Okayama Astrophysical Observatory (OAO) in Japan to search for planets around intermediate-mass giant stars. The program aims to show the properties of planetary systems around such stars by precise Doppler survey of about 190 G or K type giants together with collaborative surveys of the East-Asian Planet Search Network. So far, we detected two substellar companions around massive intermediate-mass giants in the Korean-Japa…
Kepler-419 is a planetary system discovered by the Kepler photometry which is known to harbour two massive giant planets: [...] 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 stell…
We report a new giant planet orbiting the K giant HD 155233, as well as four stellar-mass companions from the Pan-Pacific Planet Search, a southern hemisphere radial velocity survey for planets orbiting nearby giants and subgiants. We also present updated velocities and a refined orbit for HD 47205b (7 CMa b), the first planet discovered by this survey. HD 155233b has a period of 885$\pm$63 days, eccentricity e=0.03$\pm$0.20, and m sin i=2.0$\pm$0.5 M_jup. The stellar-mass companions range in m sin i from 0.066 M_sun to 0.33 M_sun. Whilst HD 104358B falls slightly below the traditional 0.08 M_…
A precise radial velocity survey conducted by a Korean-Japanese planet search program revealed a planetary companion around the intermediate-mass clump giant HD 100655. The radial velocity of the star exhibits a periodic Keplerian variation with a period, semi-amplitude and eccentricity of 157.57 d, 35.2 m s^-1 and 0.085, respectively. Adopting an estimated stellar mass of 2.4 M_Sun, we confirmed the presence of a planetary companion with a semi-major axis of 0.76 AU and a minimum mass of 1.7 M_Jup. The planet is the lowest-mass planet yet discovered around clump giants with masses greater tha…
Recent observations suggest that a large fraction of Kepler super-Earth systems have external giant planet companions (cold Jupiters), which can shape the architecture of the inner planets, in particular their mutual inclinations. The dynamical perturbation from cold Jupiters may account for the population of misaligned planets in the Kepler data. The effectiveness of this mechanism can be hindered by a strong planet--planet coupling in the inner system. In this paper, we study how mean-motion resonances (MMRs) affect this coupling and the expected misalignment. We derive approximate analytica…
11 UMi and HD 32518 belong to a sample of 62 K giant stars that has been observed since February 2004 using the 2m Alfred Jensch telescope of the Thüringer Landessternwarte (TLS) to measure precise radial velocities (RVs). The aim of this survey is to investigate the dependence of planet formation on the mass of the host star by searching for planetary companions around intermediate-mass giants. An iodine absorption cell was used to obtain accurate RVs for this study. Our measurements reveal that the RVs of 11 UMi show a periodic variation of 516.22 days. The RV curve of HD 32518 shows sinusoi…
Auns. The aim of our paper is to investigate the low-amplitude and long-period variations in evolved stars with a precise radial velocity (RV) survey. Methods. The high-resolution, the fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) was used from 2003 to 2013 for a radial velocity survey of giant stars as part of the exoplanet search program at Bohyunsan Optical Astronomy Observatory (BOAO). Results. We report the detection of three new planetary companions orbiting the K giants beta Cnc, mu Leo, and beta UMi. The planetary nature of the radial velocity variations is supported by a…
Stellar companions can influence the formation and evolution of planetary systems, but there are currently few observational constraints on the properties of planet-hosting binary star systems. We search for stellar companions around 77 transiting hot Jupiter systems to explore the statistical properties of this population of companions as compared to field stars of similar spectral type. After correcting for survey incompleteness, we find that $47\%\pm7\%$ of hot Jupiter systems have stellar companions with semi-major axes between 50-2000 AU. This is 2.9 times larger than the field star compa…
We report the discovery of a substellar companion around the intermediatemass giant HD 175679. Precise radial velocity data of the star from Xinglong Station and Okayama Astrophysical Observatory (OAO) revealed a Keplerian velocity variation with an orbital period of 1366.8 \pm 5.7 days, a semiamplitude of 380.2 \pm 3.2m s.1, and an eccentricity of 0.378 \pm 0.008. Adopting a stellar mass of 2.7 \pm 0.3 M\odot, we obtain the minimum mass of the HD 175679 b is 37.3 \pm 2.8 MJ, and the semimajor axis is 3.36 \pm 0.12 AU. This discovery is the second brown dwarf companion candidate from a joint p…
We conducted a Doppler survey at Keck combined with NIRC2 K-band AO imaging to search for massive, long-period companions to 123 known exoplanet systems with one or two planets detected using the radial velocity (RV) method. Our survey is sensitive to Jupiter mass planets out to 20 AU for a majority of stars in our sample, and we report the discovery of eight new long-period planets, in addition to 20 systems with statistically significant RV trends indicating the presence of an outer companion beyond 5 AU. We combine our RV observations with AO imaging to determine the range of allowed masses…
We aim to detect and characterize substellar companions to K giant stars, to further our knowledge of planet formation and stellar evolution of intermediate-mass stars. For more than a decade we have used Doppler spectroscopy to acquire high precision radial velocity measurements of K giant stars. All data for this survey have been taken at Lick Observatory. Our survey includes 373 G and K giants. Radial velocity data showing periodic variations are fitted with Keplerian orbits using a chi^2 minimization technique. We report the presence of two substellar companions to the K giant stars tau Ge…
We report the results of a direct imaging survey of A- and F-type main sequence stars searching for giant planets. A/F stars are often the targets of surveys, as they are thought to have more massive giant planets relative to solar-type stars. However, most imaging is only sensitive to orbital separations $>$30 AU, where it has been demonstrated that giant planets are rare. In this survey, we take advantage of the high-contrast capabilities of the Apodizing Phase Plate coronagraph on NACO at the Very Large Telescope. Combined with optimized principal component analysis post-processing, we are …
For the past 3 years we have been monitoring 62 K giant stars using precise stellar radial velocity (RV) measurements with the 2m Alfred Jensch telescope of the Thüringer Landessternwarte Tautenburg (TLS). To probe the dependence of planet formation on stellar mass by finding planets around intermediate-mass giant stars. We present high accuracy RV measurements of the K1.5 III star 42 Dra and the K4 III star HD 139357. The wavelength reference for the RV measurements was provided by an iodine absorption cell placed in the optical path of the spectrograph. Our measurements reveal that the time …
We report the discovery of three new substellar companions to solar-type stars, HD191806, HD214823, and HD221585, based on radial velocity measurements obtained at the Haute-Provence Observatory. Data from the SOPHIE spectrograph are combined with observations acquired with its predecessor, ELODIE, to detect and characterise the orbital parameters of three new gaseous giant and brown dwarf candidates. Additionally, we combine SOPHIE data with velocities obtained at the Lick Observatory to improve the parameters of an already known giant planet companion, HD16175 b. Thanks to the use of differe…
We present results from a radial-velocity survey of 373 giant stars at Lick Observatory, which started in 1999. The previously announced planets iota Dra b and Pollux b are confirmed by continued monitoring. The frequency of detected planetary companions appears to increase with metallicity. The star nu Oph is orbited by two brown dwarf companions with masses of 22.3 M_Jup and 24.5 M_Jup in orbits with a period ratio close to 6:1. It is likely that the two companions to nu Oph formed in a disk around the star.
As of August 2008, over 30 multiple exoplanet systems are known, and 28% of stars with planets show significant evidence of a second companion. I briefly review these 30 systems individually, broadly grouping them into five categories: 1) systems with 3 or more giant (Msini > 0.2 M_Jup) planets, 2) systems with two giant planets in mean motion resonance (MMR), 3) systems with two giant planets not in MMR but whose dynamical evolution is affected by planet-planet interactions, 4) highly hierarchical systems, having two giant planets with very large period ratios (> 30:1), and 5) systems of ``Su…
We present a new method for confirming transiting planets based on the combination of transit timingn variations (TTVs) and dynamical stability. Correlated TTVs provide evidence that the pair of bodies are in the same physical system. Orbital stability provides upper limits for the masses of the transiting companions that are in the planetary regime. This paper describes a non-parametric technique for quantifying the statistical significance of TTVs based on the correlation of two TTV data sets. We apply this method to an analysis of the transit timing variations of two stars with multiple tra…
Transiting Planetary Systems with Distant Giant Companions Remain Moderately Coplanar
State Key Laboratory of Dark Matter Physics, Tsung-Dao Lee Institute & School of Physics and Astronomy, Shanghai Jiao Tong University（暗物质物理国家重点实验室，李政道理论与计算科学中心及物理与天文学院，上海交通大学）；CAS Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences（中国科学院光学天文重点实验室，国家天文台，中国科学院）；Institute for Astronomy, University of Hawai‘i（夏威夷大学天体物理研究所）
Aims. We report the detection of long-period radial velocity (RV) variations in three giant stars, HD 19615, HD 150010, and HD 174205, using precise RV measurements. Methods. These detections are part of the Search for Exoplanets around Northern Circumpolar Stars (SENS) survey being conducted at the Bohyunsan Optical Astronomy Observatory (BOAO). The nature of the RV variations was investigated by analyzing the photometric and line shape variations. We found no variability with the RV period in these quantities and conclude that the RV variations are most likely caused by planetary companions.…
We present the discovery of planet-mass companions to two giant stars by the ongoing Penn State- Toruń Planet Search (PTPS) conducted with the 9.2 m Hobby-Eberly Telescope. The less massive of these stars, K5-giant BD+20 274, has a 4.2 MJ minimum mass planet orbiting the star at a 578-day period and a more distant, likely stellar-mass companion. The best currently available model of the planet orbiting the K0-giant HD 219415 points to a Jupiter-mass companion in a 5.7-year, eccentric orbit around the star, making it the longest period planet yet detected by our survey. This planet has an ampli…
In this paper we search for distant massive companions to known transiting gas giant planets that may have influenced the dynamical evolution of these systems. We present new radial velocity observations for a sample of 51 planets obtained using the Keck HIRES instrument, and find statistically significant accelerations in fifteen systems. Six of these systems have no previously reported accelerations in the published literature: HAT-P-10, HAT-P-22, HAT-P-29, HAT-P-32, WASP-10, and XO-2. We combine our radial velocity fits with Keck NIRC2 adaptive optics (AO) imaging data to place constraints …
We present results from an ongoing multiwavelength radial velocity (RV) survey of the Taurus-Auriga star forming region as part of our effort to identify pre--main sequence giant planet hosts. These 1-3 Myr old T Tauri stars present significant challenges to traditional RV surveys. The presence of strong magnetic fields gives rise to large, cool star spots. These spots introduce significant RV jitter which can mimic the velocity modulation from a planet-mass companion. To distinguish between spot-induced and planet-induced RV modulation, we conduct observations at ~6700 Angstroms and ~2.3 micr…
If it is commonly agreed that the presence of a (moderately) close stellar companion affects the formation and the dynamical evolution of giant planets, the frequency of giant planets residing in binary systems separated by less than 100 AU is unknown. To address this issue, we have conducted with VLT/NACO a systematic adaptive optics search for moderately close stellar companions to 130 nearby solar-type stars. According to the data from Doppler surveys, half of our targets host at least one planetary companion, while the other half show no evidence for short-period giant planets. We present …
Direct imaging has led to the discovery of several giant planet and brown dwarf companions. These imaged companions populate a mass, separation and age domain (mass>1MJup, orbits>5AU, age<1Gyr) quite distinct from the one occupied by exoplanets discovered by the radial velocity or transit methods. This distinction could pinpoint that different formation mechanisms are at play. We aim at investigating correlations between the host star's mass and the presence of wide-orbit giant planets, and at providing new observational constraints on planetary formation models. We observed 58 young and nearb…
The limited completeness of the Kepler sample for planets with orbital periods $\gtrsim$ 1 yr leaves open the possibility that exoplanetary systems may host undetected giant planets. Should such planets exist, their dynamical interactions with the inner planets may prove vital in sculpting the final orbital configurations of these systems. Using an $N$-body code with additional forces to emulate the effects of a protoplanetary disc, we perform simulations of the assembly of compact systems of super-Earth-mass planets with unseen giant companions. The simulated systems are analogous to Kepler-1…
We present Keck/OSIRIS 1.1-1.8 um adaptive optics integral field spectroscopy of the planetary-mass companion to GSC 06214-00210, a member of the ~5 Myr Upper Scorpius OB association. We infer a spectral type of L0+/-1, and our spectrum exhibits multiple signs of youth. The most notable feature is exceptionally strong PaBeta emission (EW=-11.4 +/- 0.3 A) which signals the presence of a circumplanetary accretion disk. The luminosity of GSC 06214-00210 b combined with its age yields a model-dependent mass of 14 +/- 2 MJup, making it the lowest-mass companion to show evidence of a disk. With a pr…
Direct imaging has confirmed the existence of substellar companions on wide orbits. To understand the formation and evolution mechanisms of these companions, the full population properties must be characterized. We aim at detecting giant planet and/or brown dwarf companions around young, nearby, and dusty stars. Our goal is also to provide statistics on the population of giant planets at wide-orbits and discuss planet formation models. We report a deep survey of 59 stars, members of young stellar associations. The observations were conducted with VLT/NaCo at L'-band (3.8 micron). We used angul…
We present the discovery of substellar-mass companions to three giant stars by the ongoing Penn State-Toruń Planet Search (PTPS) conducted with the 9.2 m Hobby-Eberly Telescope. The most massive of the three stars, K2-giant HD 240237, has a 5.3 MJ minimum mass companion orbiting the star at a 746-day period. The K0-giant BD +48 738 is orbited by a > 0.91 MJ planet which has a period of 393 days and shows a non-linear, long-term radial velocity trend that indicates a presence of another, more distant companion, which may have a substellar mass or be a low-mass star. The K2-giant HD 96127, has a…
Our Keck/NIRC2 imaging survey searches for stellar companions around 144 systems with radial velocity (RV) detected giant planets to determine whether stellar binaries influence the planets' orbital parameters. This survey, the largest of its kind to date, finds eight confirmed binary systems and three confirmed triple systems. These include three new multi-stellar systems (HD 30856, HD 86081, and HD 207832) and three multi-stellar systems with newly confirmed common proper motion (HD 43691, HD 116029, and HD 164509). We combine these systems with seven RV planet-hosting multi-stellar systems …
We use radial velocity observations to search for long-period gas giant companions in systems hosting inner super-Earth (1-4 R_Earth, 1-10 M_Earth) planets to constrain formation and migration scenarios for this population. We consistently re-fit published RV datasets for 65 stars and find 9 systems with statistically significant trends indicating the presence of an outer companion. We combine these RV data with AO images to constrain the masses and semi-major axes of these companions. We quantify our sensitivity to the presence of long-period companions by fitting the sample with a power law …
The chance that a planetary system will interact with another member of its host star's nascent cluster would be greatly increased if gas giant planets form in situ on wide orbits. In this paper, we explore the outcomes of planet-planet scattering for a distribution of multiplanet systems that all have one of the planets on an initial orbit of 100 AU. The scattering experiments are run with and without stellar flybys. We convolve the outcomes with distributions for protoplanetary disk and stellar cluster sizes to generalize the results where possible. We find that the frequencies of large mutu…
Evolved stars are crucial pieces to understand the dependency of the planet formation mechanism on the stellar mass and to explore deeper the mechanism involved in star-planet interactions. Over the past ten years, we have monitored about 1000 evolved stars for radial velocity variations in search for low-mass companions under the Penn State - Torun Centre for Astronomy Planet Search program with the Hobby-Eberly Telescope. Selected prospective candidates that required higher RV precision measurements have been followed with HARPS-N at the 3.6 m Telescopio Nazionale Galileo under the TAPAS pro…
The existence of hot Jupiters has challenged theories of planetary formation since the first extrasolar planets were detected. Giant planets are generally believed to form far from their host stars, where volatile materials like water exist in their solid phase, making it easier for giant planet cores to accumulate. Several mechanisms have been proposed to explain how giant planets can migrate inward from their birth sites to short-period orbits. One such mechanism, called Kozai-Lidov migration, requires the presence of distant companions in orbits inclined by more than $\sim40$ degrees with r…
Recent studies have proposed that most warm Jupiters (WJs, giant planets with semi-major axes in the range of 0.1-1 AU) probably form in-situ, or arrive in their observed orbits through disk migration. However, both in-situ formation and disk migration, in their simplest flavors, predict WJs to be in low-eccentricity orbits, in contradiction with many observed WJs that are moderately eccentric (e=0.2-0.7). This paper examines the possibility that the WJ eccentricities are raised by secular interactions with exterior giant planet companions, following in-situ formation or migration on a circula…
Hydrodynamical simulations of two giant planets embedded in a gaseous disk have shown that in case of a smooth convergent migration they end up trapped into a mean motion resonance. These findings have led to the conviction that the onset of dynamical instability causing close encounters between the planets can occur only after the dissipation of the gas when the eccentricity damping is over. We show that a system of three giant planets may undergo planet-planet scattering when the gaseous disk, with density values comparable to that of the Minimum Mass Solar Nebula, is still interacting with …
Context. Our knowledge of populations and occurrence of planets orbiting evolved intermediate-mass stars is still incomplete. In 2010 we started a planet-search program among 95 giant stars observed by the Kepler mission to increase the sample of giant stars with planets and with reliable estimates of stellar masses and radii. Aims. We present the two systems KIC 3526061 and HD 187878 from our planet-search program for which we could characterise their companions. Methods. We used precise stellar radial velocity measurements taken with four different echelle spectrographs to derive an orbital …
