Browsing by Subject "giant planets"
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Item An Alma Disk Mass for the Candidate Protoplanetary Companion to FW Tau(2015-01) Kraus, Adam L.; Andrews, Sean M.; Bowler, Brendan P.; Herczeg, Gregory; Ireland, Michael J.; Liu, Michael C.; Metchev, Stanimir; Cruz, Kelle L.; Kraus, Adam L.We present ALMA observations of the FW Tau system, a close binary pair of M5 stars with a wide-orbit (300 AU projected separation) substellar companion. The companion is extremely faint and red in the optical and near-infrared, but boasts a weak far-infrared excess and optical/near-infrared emission lines indicative of a primordial accretion disk of gas and dust. The component-resolved 1.3mm continuum emission is found to be associated only with the companion, with a flux (1.78 +/- 0.03 mJy) that indicates a dust mass of 1-2M(circle plus). While this mass reservoir is insufficient to form a giant planet, it is more than sufficient to produce an analog of the Kepler-42 exoplanetary system or the Galilean satellites. The mass and geometry of the disk-bearing FW Tau companion remains unclear. Near-infrared spectroscopy shows deep water bands that indicate a spectral type later than M5, but substantial veiling prevents a more accurate determination of the effective temperature (and hence mass). Both a disk-bearing "planetary-mass" companion seen in direct light or a brown dwarf tertiary viewed in light scattered by an edge-on disk or envelope remain possibilities.Item Circumbinary Planet Formation In The Kepler-16 System. II. A Toy Model For In Situ Planet Formation Within A Debris Belt(2014-07) Meschiari, Stefano; Meschiari, StefanoRecent simulations have shown that the formation of planets in circumbinary configurations (such as those recently discovered by Kepler) is dramatically hindered at the planetesimal accretion stage. The combined action of the binary and the protoplanetary disk acts to raise impact velocities between kilometer-sized planetesimals beyond their destruction threshold, halting planet formation within at least 10 AU from the binary. It has been proposed that a primordial population of "large" planetesimals (100 km or more in size), as produced by turbulent concentration mechanisms, would be able to bypass this bottleneck; however, it is not clear whether these processes are viable in the highly perturbed circumbinary environments. We perform two-dimensional hydrodynamical and N-body simulations to show that kilometer-sized planetesimals and collisional debris can drift and be trapped in a belt close to the central binary. Within this belt, planetesimals could initially grow by accreting debris, ultimately becoming "indestructible" seeds that can accrete other planetesimals in situ despite the large impact speeds. We find that large, indestructible planetesimals can be formed close to the central binary within 10(5) yr, therefore showing that even a primordial population of "small" planetesimals can feasibly form a planet.Item Detection Of Low-Mass-Ratio Stellar Binary Systems(2013-01) Gullikson, Kevin; Dodson-Robinson, Sarah; Gullikson, Kevin; Dodson-Robinson, SarahO- and B-type stars are often found in binary systems, but the low binary mass-ratio regime is relatively unexplored due to observational difficulties. Binary systems with low mass ratios may have formed through fragmentation of the circumstellar disk rather than molecular cloud core fragmentation. We describe a new technique sensitive to G-and K-type companions to early B stars, a mass ratio of roughly 0.1, using high-resolution, high signal-to-noise spectra. We apply this technique to a sample of archived VLT/CRIRES observations of nearby B stars in the CO bandhead near 2300 nm. While there are no unambiguous binary detections in our sample, we identify HIP 92855 and HIP 26713 as binary candidates warranting follow-up observations. We use our non-detections to determine upper limits to the frequency of FGK stars orbiting early B-type primaries.Item Dynamical Masses of Young M Dwarfs: Masses and Orbital Parameters of GJ 3305 AB, the Wide Binary Companion To the Imaged Exoplanet Host 51 Eri(2015-11) Montet, Benjamin T.; Bowler, Brendan P.; Shkolnik, Evgenya L.; Deck, Katherine M.; Wang, Ji; Horch, Elliott P.; Liu, Michael C.; Hillenbrand, Lynne A.; Kraus, Adam L.; Charbonneau, David; Kraus, Adam L.We combine new high resolution imaging and spectroscopy from Keck/NIRC2, Discovery Channel Telescope/DSSI, and Keck/HIRES with published astrometry and radial velocities to measure individual masses and orbital elements of the GJ 3305 AB system, a young (similar to 20 Myr) M+M binary (unresolved spectral type M0) member of the beta Pictoris moving group comoving with the imaged exoplanet host 51 Eri. We measure a total system mass of 1.11 +/- 0.04 M-circle dot, a period of 29.03 +/- 0.50 year, a semimajor axis of 9.78 +/- 0.14 AU, and an eccentricity of 0.19 +/- 0.02. The primary component has a dynamical mass of 0.67 +/- 0.05 M-circle dot and the secondary has a mass of 0.44 +/- 0.05 M-circle dot. The recently updated BHAC15 models are consistent with the masses of both stars to within 1.5 sigma. Given the observed masses the models predict an age of the GJ 3305 AB system of 37 +/- 9 Myr. Based on the observed system architecture and our dynamical mass measurement, it is unlikely that the orbit of 51 Eri b has been significantly altered by the Kozai-Lidov mechanism.Item Kepler-424 B: A "Lonely" Hot Jupiter That Found A Companion(2014-11) Endl, Michael; Caldwell, Douglas A.; Barclay, Thomas; Huber, Daniel; Isaacson, Howard; Buchhave, Lars A.; Brugamyer, Erik; Robertson, Paul; Cochran, William D.; MacQueen, Phillip J.; Havel, Mathieu; Lucas, Phillip; Howell, Steve B.; Fischer, Debra; Quintana, Elisa; Ciardi, David R.; Endl, MichaelHot Jupiter systems provide unique observational constraints for migration models in multiple systems and binaries. We report on the discovery of the Kepler-424 (KOI-214) two-planet system, which consists of a transiting hot Jupiter (Kepler-424b) in a 3.31 day orbit accompanied by a more massive outer companion in an eccentric (e = 0.3) 223 day orbit. The outer giant planet, Kepler-424c, is not detected transiting the host star. The masses of both planets and the orbital parameters for the second planet were determined using precise radial velocity (RV) measurements from the Hobby-Eberly Telescope (HET) and its High Resolution Spectrograph (HRS). In stark contrast to smaller planets, hot Jupiters are predominantly found to be lacking any nearby additional planets; they appear to be "lonely". This might be a consequence of these systems having a highly dynamical past. The Kepler-424 planetary system has a hot Jupiter in a multiple system, similar to. Andromedae. We also present our results for Kepler-422 (KOI-22), Kepler-77 (KOI-127), Kepler-43 (KOI-135), and Kepler-423 (KOI-183). These results are based on spectroscopic data collected with the Nordic Optical Telescope (NOT), the Keck 1 telescope, and HET. For all systems, we rule out false positives based on various follow-up observations, confirming the planetary nature of these companions. We performed a comparison with planetary evolutionary models which indicate that these five hot Jupiters have heavy element contents between 20 and 120 M-circle plus.Item Modules for Experiments in Stellar Astrophysics (MESA): Planets, Oscillations, Rotation, and Massive Stars(2013-09) Paxton, Bill; Cantiello, Matteo; Arras, Phil; Bildsten, Lars; Brown, Edward F.; Dotter, Aaron; Mankovich, Christopher; Montgomery, M. H.; Stello, Dennis; Timmes, F. X.; Townsend, Richard; Montgomery, M. H.We substantially update the capabilities of the open source software package Modules for Experiments in Stellar Astrophysics (MESA), and its one-dimensional stellar evolution module, MESAstar. Improvements in MESAstar's ability to model the evolution of giant planets now extends its applicability down to masses as low as one-tenth that of Jupiter. The dramatic improvement in asteroseismology enabled by the space-based Kepler and CoRoT missions motivates our full coupling of the ADIPLS adiabatic pulsation code with MESAstar. This also motivates a numerical recasting of the Ledoux criterion that is more easily implemented when many nuclei are present at non-negligible abundances. This impacts the way in which MESAstar calculates semi-convective and thermohaline mixing. We exhibit the evolution of 3-8 M-circle dot stars through the end of core He burning, the onset of He thermal pulses, and arrival on the white dwarf cooling sequence. We implement diffusion of angular momentum and chemical abundances that enable calculations of rotating-star models, which we compare thoroughly with earlier work. We introduce a new treatment of radiation-dominated envelopes that allows the uninterrupted evolution of massive stars to core collapse. This enables the generation of new sets of supernovae, long gamma-ray burst, and pair-instability progenitor models. We substantially modify the way in which MESAstar solves the fully coupled stellar structure and composition equations, and we show how this has improved the scaling of MESA's calculational speed on multi-core processors. Updates to the modules for equation of state, opacity, nuclear reaction rates, and atmospheric boundary conditions are also provided. We describe the MESA Software Development Kit that packages all the required components needed to form a unified, maintained, and well-validated build environment for MESA. We also highlight a few tools developed by the community for rapid visualization of MESAstar results.Item Planet Formation in Circumbinary Configurations: Turbulence Inhibits Planetesimal Accretion(2012-12) Meschiari, Stefano; Meschiari, StefanoThe existence of planets born in environments highly perturbed by a stellar companion represents a major challenge to the paradigm of planet Formation. In numerical simulations, the presence of a close binary companion stirs up the relative velocity between planetesimals, which is fundamental in determining the balance between accretion and erosion. However, the recent discovery of circumbinary planets by Kepler establishes that planet Formation in binary systems is clearly viable. We perform N-body simulations of planetesimals embedded in a protoplanetary disk, where planetesimal phasing is frustrated by the presence of stochastic torques, modeling the expected perturbations of turbulence driven by the magnetorotational instability. We examine perturbation amplitudes relevant to dead zones in the midplane (conducive to planet Formation in single stars), and find that planetesimal accretion can be inhibited even in the outer disk (4-10 AU) far from the central binary, a location previously thought to be a plausible starting point for the Formation of circumbinary planets.Item A Precise Radial Velocity Search for Giant Planets orbiting polluted White Dwarfs(2018-07) Endl, M.; Williams, K.A.; Castanheira, B.; Vanderbosch, Z.; Montgomery, M.We present a feasibility study for extending the well-known radial velocity technique to search for planetary companions around white dwarfs. Typically, the spectra of white dwarfs contain only a few pressure-broadened hydrogen and/or helium lines, which do not permit to measure the radial velocity with sufficient precision to detect planets. A small subset of white dwarfs do also show sharp metal lines, presumably from infalling circumstellar material. We suggest to search these “polluted” white dwarfs for possible giant planets using the Doppler reflex motion technique. We show here first results to estimate the Doppler information content from simulated spectra of the metal-polluted WD GD 362.Item Protostellar Disk Evolution Over Million-Year Timescales With A Prescription For Magnetized Turbulence(2013-07) Landry, Russell; Dodson-Robinson, Sarah E.; Turner, Neal J.; Abram, Greg; Dodson-Robinson, Sarah E.Magnetorotational instability (MRI) is the most promising mechanism behind accretion in low-mass protostellar disks. Here we present the first analysis of the global structure and evolution of non-ideal MRI-driven T-Tauri disks on million-year timescales. We accomplish this in a 1+1D simulation by calculating magnetic diffusivities and utilizing turbulence activity criteria to determine thermal structure and accretion rate without resorting to a three-dimensional magnetohydrodynamical (MHD) simulation. Our major findings are as follows. First, even for modest surface densities of just a few times the minimum-mass solar nebula, the dead zone encompasses the giant planet-forming region, preserving any compositional gradients. Second, the surface density of the active layer is nearly constant in time at roughly 10 g cm(-2), which we use to derive a simple prescription for viscous heating in MRI-active disks for those who wish to avoid detailed MHD computations. Furthermore, unlike a standard disk with constant-alpha viscosity, the disk midplane does not cool off over time, though the surface cools as the star evolves along the Hayashi track. Instead, the MRI may pile material in the dead zone, causing it to heat up over time. The ice line is firmly in the terrestrial planet-forming region throughout disk evolution and can move either inward or outward with time, depending on whether pileups form near the star. Finally, steady-Statemass transport is an extremely poor description of flow through an MRI-active disk, as we see both the turnaround in the accretion flow required by conservation of angular momentum and peaks in (M) over dot(R) bracketing each side of the dead zone. We caution that MRI activity is sensitive to many parameters, including stellar X-ray flux, grain size, gas/small grain mass ratio and magnetic field strength, and we have not performed an exhaustive parameter study here. Our 1+1D model also does not include azimuthal information, which prevents us from modeling the effects of Rossby waves.Item Retired A Stars and Their Companions. VII. 18 New Jovian Planets(2011-12) Johnson, J. Aasher; Clanton, Christian; Howard, Andrew W.; Bowler, Brendan P.; Henry, Gregory W.; Marcy, Geoffrey W.; Crepp, Justin R.; Endl, Michael; Cochran, William D.; MacQueen, Phillip J.; Wright, Jason T.; Isaacson, Howard; Endl, Michael; Cochran, William D.; MacQueen, Phillip J.We report the detection of 18 Jovian planets discovered as part of our Doppler survey of subgiant stars at Keck Observatory, with follow-up Doppler and photometric observations made at McDonald and Fairborn Observatories, respectively. The host stars have masses 0.927 <= M(star)/M(circle dot) <= 1.95, radii 2.5 <= R(star)/R(circle dot) <= 8.7, and metallicities -0.46 <= [Fe/H] <= +0.30. The planets have minimum masses 0.9 M(Jup) <= M(P) sin i less than or similar to 13 M(Jup) and semimajor axes a >= 0.76 AU. These detections represent a 50% increase in the number of planets known to orbit stars more massive than 1.5M(circle dot) and provide valuable additional inFormation about the properties of planets around stars more massive than the Sun.Item A Search for Multi-Planet Systems Using the Hobby-Eberly Telescope(2009-05) Wittenmyer, Rrobert A.; Endl, Michael; Cochran, William D.; Levison, Henry F.; Henry, Gregory W.; Wittenmyer, Rrobert A.; Endl, Michael; Cochran, William D.Extrasolar multiple-planet systems provide valuable opportunities for testing theories of planet Formation and evolution. The architectures of the known multiple-planet systems demonstrate a fascinating level of diversity, which motivates the search for additional examples of such systems in order to better constrain their Formation and dynamical histories. Here we describe a comprehensive investigation of 22 planetary systems in an effort to answer three questions: (1) are there additional planets? (2) where could additional planets reside in stable orbits? and (3) what limits can these observations place on such objects? We find no evidence for additional bodies in any of these systems; indeed, these new data do not support three previously announced planets (HD 20367 b: Udry et al.; HD 74156 d: Bean et al.; and 47 UMa c: Fischer et al.). The dynamical simulations show that nearly all of the 22 systems have large regions in which additional planets could exist in stable orbits. The detection-limit computations indicate that this study is sensitive to close-in Neptune-mass planets for most of the systems targeted. We conclude with a discussion on the implications of these nondetections.Item Seasonal Variability In The Ionosphere Of Uranus(2011-03) Melin, H.; Stallard, T.; Miller, S.; Trafton, L. M.; Encrenaz, T.; Geballe, T. R.; Trafton, L. M.Infrared ground-based observations using IRTF, UKIRT, and Keck II of Uranus have been analyzed as to identify the long-term behavior of the H-3(+) ionosphere. Between 1992 and 2008 there are 11 individual observing runs, each recording emission from the H-3(+) Q branch emission around 4 mu m through the telluric L' atmospheric window. The column-averaged rotational H-3(+) temperature ranges between 715 K in 1992 and 534 K in 2008, with the linear fit to all the run-averaged temperatures decreasing by 8 K year(-1). The temperature follows the fractional illumination curve of the planet, declining from solstice (1985) to equinox (2007). Variations in H-3(+) column density do not appear to be correlated to either solar cycle phase or season. The radiative cooling by H-3(+) is similar to 10 times larger than the ultraviolet solar energy being injected to the atmosphere. Despite the fact that the solar flux alone is incapable of heating the atmosphere to the observed temperatures, the geometry with respect to the Sun remains an important driver in determining the thermospheric temperature. Therefore, the energy source that heats the thermosphere must be linked to solar mechanisms. We suggest that this may be in the form of conductivity created by solar ionization of atmospheric neutrals and/or seasonally dependent magnetospherically driven current systems.Item Spectroscopic Confirmation Of Young Planetary-Mass Companions On Wide Orbits(2014-03) Bowler, Brendan P.; Liu, Michael C.; Kraus, Adam L.; Mann, Andrew W.; Kraus, Adam L.; Mann, Andrew W.We present moderate-resolution ( R similar to 4000-5000) near-infrared integral field spectroscopy of the young (1-5 Myr) 6-14 M-Jup companions ROXs 42B b and FW Tau b obtained with Keck/OSIRIS and Gemini-North/NIFS. The spectrum of ROXs 42B b exhibits clear signs of low surface gravity common to young L dwarfs, confirming its extreme youth, cool temperature, and low mass. Overall, it closely resembles the free-floating 4-7 M-Jup L-type Taurus member 2MASS J04373705+2331080. The companion to FW Tau AB is more enigmatic. Our optical and near-infrared spectra show strong evidence of outflow activity and disk accretion in the form of line emission from [S II], [O I], H alpha, Ca II, [Fe II], Pa beta, and H-2. The molecular hydrogen emission is spatially resolved as a single lobe that stretches approximate to 0 ''.1 (15 AU). Although the extended emission is not kinematically resolved in our data, its morphology resembles shock-excited H-2 jets primarily seen in young Class 0 and Class I sources. The near-infrared continuum of FW Tau b is mostly flat and lacks the deep absorption features expected for a cool, late-type object. This may be a result of accretion-induced veiling, especially in light of its strong and sustained Ha emission (EW(H alpha)greater than or similar to 290 angstrom). Alternatively, FW Tau b may be a slightly warmer (M5-M8) accreting low-mass star or brown dwarf (0.03-0.15 M circle dot) with an edge-on disk. Regardless, its young evolutionary stage is in stark contrast to its Class III host FW Tau AB, indicating a more rapid disk clearing timescale for the host binary system than for its wide companion. Finally, we present near-infrared spectra of the young (similar to 2-10 Myr) low-mass (12-15 M-Jup) companions GSC 6214-210 B and SR 12 C and find they best resemble low- gravity M9.5 and M9 substellar templates.Item The Three-Dimensional Architecture Of The Upsilon Andromedae Planetary System(2015-01) Deitrick, Russell; Barnes, Rory; McArthur, Barbara; Quinn, Thomas R.; Luger, Rodrigo; Antonsen, Adrienne; Benedict, G. Fritz; McArthur, Barbara; Benedict, G. FritzThe upsilon Andromedae system is the first exoplanetary system to have the relative inclination of two planets' orbital planes directly measured, and therefore offers our first window into the three-dimensional configurations of planetary systems. We present, for the first time, full three-dimensional, dynamically stable configurations for the three planets of the system consistent with all observational constraints. While the outer two planets, c and d, are inclined by similar to 30 degrees the inner planet's orbital plane has not been detected. We use N-body simulations to search for stable threeplanet configurations that are consistent with the combined radial velocity and astrometric solution. We find that only 10 trials out of 1000 are robustly stable on 100 Myr timescales, or similar to 8 billion orbits of planet b. Planet b's orbit must lie near the invariable plane of planets c and d, but can be either prograde or retrograde. These solutions predict that b's mass is in the range of 2-9 M-Jup and has an inclination angle from the sky plane of less than 25 degrees Combined with brightness variations in the combined star/planet light curve ("phase curve"), our results imply that planet b's radius is similar to 1.8 R-jup, relatively large for a planet of its age. However, the eccentricity of b in several of our stable solutions reaches >0.1, generating upward of 10(19) W in the interior of the planet via tidal dissipation, possibly inflating the radius to an amount consistent with phase curve observations.Item Transiting Exoplanets From The CoRoT Space Mission XII. CoRoT-12B: A Short-Period Low-Density Planet Transiting A Solar Analog Star(2010) Gillon, M.; Hatzes, A.; Csizmadia, S.; Fridlund, M.; Deleuil, M.; Aigrain, S.; Alonso, R.; Auvergne, M.; Baglin, A.; Barge, P.; Barnes, S. I.; Bonomo, A. S.; Borde, P.; Bouchy, F.; Bruntt, H.; Cabrera, J.; Carone, L.; Carpano, S.; Cochran, W. D.; Deeg, H. J.; Dvorak, R.; Endl, M.; Erikson, A.; Ferraz-Mello, S.; Gandolfi, D.; Gazzano, J. C.; Guenther, E.; Guillot, T.; Havel, M.; Hebrard, G.; Jorda, L.; Leger, A.; Llebaria, A.; Lammer, H.; Lovis, C.; Mayor, M.; Mazeh, T.; Montalban, J.; Moutou, C.; Ofir, A.; Ollivier, M.; Patzold, M.; Pepe, F.; Queloz, D.; Rauer, H.; Rouan, D.; Samuel, B.; Santerne, A.; Schneider, J.; Tingley, B.; Udry, S.; Weingrill, J.; Wuchterl, G.; Cochran, W. D.; Endl, M.We report the discovery by the CoRoT satellite of a new transiting giant planet in a 2.83 days orbit about a V = 15.5 solar analog star (M(*) = 1.08 +/- 0.08 M(circle dot), R(*) = 1.1 +/- 0.1 R(circle dot), T(eff) = 5675 +/- 80 K). This new planet, CoRoT-12b, has a mass of 0.92 +/- 0.07 M(Jup) and a radius of 1.44 +/- 0.13 R(Jup). Its low density can be explained by standard models for irradiated planets.