The Experts below are selected from a list of 354 Experts worldwide ranked by ideXlab platform
William D Cochran - One of the best experts on this subject based on the ideXlab platform.
-
optical hydrogen absorption consistent with a thin bow shock leading the hot jupiter hd 189733b
The Astrophysical Journal, 2015Co-Authors: Wilson P Cauley, Travis Barman, Seth Redfield, Adam G Jensen, Michael Endl, William D CochranAbstract:Bow shocks are ubiquitous astrophysical phenomena resulting from the supersonic passage of an object through a gas. Recently, pre-transit absorption in UV metal transitions of the hot Jupiter (HJ) exoplanets HD 189733b and WASP12-b have been interpreted as being caused by material compressed in a Planetary bow shock. Here we present a robust detection of a time-resolved pre-transit, as well as in-transit absorption signature around the HJ exoplanet HD 189733b using high spectral resolution observations of several hydrogen Balmer lines. The line shape of the pre-transit feature and the shape of the timeseries absorption provide the strongest constraints on the morphology and physical characteristics of extended structures around an exoplanet. The in-transit measurements confirm the previous exospheric Hα detection, although the absorption depth measured here is ∼50% lower. The pre-transit absorption feature occurs 125 minutes before the predicted optical transit, a projected linear distance from the planet to the stellar disk of 7.2 Rp. The absorption strength observed in the Balmer lines indicates an optically thick, but physically small, geometry. We model this signal as the early ingress of a Planetary bow shock. If the bow shock is mediated by a Planetary magnetosphere, the large standoff distance derived from the model suggests a large Planetary magnetic field strength of Beq = 28 G. Better knowledge of exoplanet magnetic field strengths is crucial to understanding the role these fields play in Planetary Evolution and the potential development of life on planets in the habitable zone.
-
optical hydrogen absorption consistent with a thin bow shock leading the hot jupiter hd 189733b
arXiv: Earth and Planetary Astrophysics, 2015Co-Authors: Wilson P Cauley, Travis Barman, Seth Redfield, Adam G Jensen, Michael Endl, William D CochranAbstract:Bow shocks are ubiquitous astrophysical phenomena resulting from the supersonic passage of an object through a gas. Recently, pre-transit absorption in UV metal transitions of the hot Jupiter exoplanets HD 189733b and WASP12-b have been interpreted as being caused by material compressed in a Planetary bow shock. Here we present a robust detection of a time-resolved pre-transit, as well as in-transit, absorption signature around the hot Jupiter exoplanet HD 189733b using high spectral resolution observations of several hydrogen Balmer lines. The line shape of the pre-transit feature and the shape of the time series absorption provide the strongest constraints on the morphology and physical characteristics of extended structures around an exoplanet. The in-transit measurements confirm the previous exospheric H-alpha detection although the absorption depth measured here is ~50% lower. The pre-transit absorption feature occurs 125 minutes before the predicted optical transit, a projected linear distance from the planet to the stellar disk of 7.2 Planetary radii. The absorption strength observed in the Balmer lines indicates an optically thick, but physically small, geometry. We model this signal as the early ingress of a Planetary bow shock. If the bow shock is mediated by a Planetary magnetosphere, the large standoff distance derived from the model suggests a large equatorial Planetary magnetic field strength of 28 G. Better knowledge of exoplanet magnetic field strengths is crucial to understanding the role these fields play in Planetary Evolution and the potential development of life on planets in the habitable zone.
C Regulo - One of the best experts on this subject based on the ideXlab platform.
-
kepler 91b a planet at the end of its life planet and giant host star properties via light curve variations
Astronomy and Astrophysics, 2014Co-Authors: J Lillobox, D Barrado, A Moya, B Montesinos, J Montalban, A Bayo, M Barbieri, C ReguloAbstract:Context. The Evolution of Planetary systems is intimately linked to the Evolution of their host star. Our understanding of the whole Planetary Evolution process is based on the large planet diversity observed so far. To date, only few tens of planets have been discovered orbiting stars ascending the Red Giant Branch. Although several theories have been proposed, the question of how planets die remains open due to the small number statistics, making clear the need of enlarging the sample of planets around post-main sequence stars. Aims. In this work we study the giant star Kepler-91 (KIC 8219268) in order to determine the nature of a transiting companion. This system was detected by the Kepler Space Telescope, which identified small dims in its light cur ve with a period of 6.246580±0.000082 days. However, its Planetary confirmation is needed due to th e large pixel size of the Kepler camera which can hide other stellar configurations able to mimic planet-like transit events. Methods. We analyse Kepler photometry to: 1) re-calculate transit parameters, 2) stud y the light-curve modulations, and 3) to perform an asteroseismic analysis (accurate stellar parameter det ermination) by identifying solar-like oscillations on the periodogram. We also used a high-resolution and high signal-to-noise ratio spec trum obtained with the Calar Alto Fiber-fed ´ Echelle spectrograph (CAFE) to measure stellar properties. Additionally, false-positiv e scenarios were rejected by obtaining high-resolution images with the AstraLux lucky-imaging camera on the 2.2 m telescope at the Calar Alto Observatory. Results. We confirm the Planetary nature of the object transiting the s tar Kepler-91 by deriving a mass of Mp = 0.88 +0.17 −0.33 MJup and a Planetary radius of Rp = 1.384 +0.011 −0.054 RJup. Asteroseismic analysis produces a stellar radius of R⋆ = 6.30± 0.16 R⊙ and a mass of M⋆ = 1.31± 0.10 M⊙. We find that its eccentric orbit ( e = 0.066 +0.013 −0.017 ) is just 1.32 +0.07 −0.22 R⋆ away from the stellar atmosphere at the pericenter. We also detected three small dims in the phase-folded light-curve. The combination of two of them agrees with the theoretical characteristics expected for secondary eclip se. Conclusions. Kepler-91b could be the previous stage of the planet engulfment, recently detected for BD+48 740. Our estimations show that Kepler-91b will be swallowed by its host star in less than 55 Myr. Among the confirmed planets around giant stars, this is the Planetary-mass body closest to its host star. At pericen ter passage, the star subtends an angle of 48 ◦ , covering around 10% of the sky as seen from the planet. The Planetary atmosphere seems to be inflated probably due to the high stellar irradiation.
-
kepler 91b a planet at the end of its life planet and giant host star properties via light curve variations
arXiv: Earth and Planetary Astrophysics, 2013Co-Authors: J Lillobox, D Barrado, A Moya, B Montesinos, J Montalban, A Bayo, M Barbieri, C ReguloAbstract:The Evolution of Planetary systems is intimately linked to the Evolution of their host star. Our understanding of the whole Planetary Evolution process is based on the large planet diversity observed so far. To date, only few tens of planets have been discovered orbiting stars ascending the Red Giant Branch. Although several theories have been proposed, the question of how planets die remains open due to the small number statistics. In this work we study the giant star Kepler-91 (KOI-2133) in order to determine the nature of a transiting companion. This system was detected by the Kepler Space Telescope. However, its Planetary confirmation is needed. We confirm the Planetary nature of the object transiting the star Kepler-91 by deriving a mass of $ M_p=0.88^{+0.17}_{-0.33} ~M_{\rm Jup}$ and a Planetary radius of $R_p=1.384^{+0.011}_{-0.054} ~R_{\rm Jup}$. Asteroseismic analysis produces a stellar radius of $R_{\star}=6.30\pm 0.16 ~R_{\odot}$ and a mass of $M_{\star}=1.31\pm 0.10 ~ M_{\odot} $. We find that its eccentric orbit ($e=0.066^{+0.013}_{-0.017}$) is just $1.32^{+0.07}_{-0.22} ~ R_{\star}$ away from the stellar atmosphere at the pericenter. Kepler-91b could be the previous stage of the planet engulfment, recently detected for BD+48 740. Our estimations show that Kepler-91b will be swallowed by its host star in less than 55 Myr. Among the confirmed planets around giant stars, this is the Planetary-mass body closest to its host star. At pericenter passage, the star subtends an angle of $48^{\circ}$, covering around 10% of the sky as seen from the planet. The Planetary atmosphere seems to be inflated probably due to the high stellar irradiation.
Hilke E Schlichting - One of the best experts on this subject based on the ideXlab platform.
-
sculpting the valley in the radius distribution of small exoplanets as a by product of planet formation the core powered mass loss mechanism
Monthly Notices of the Royal Astronomical Society, 2019Co-Authors: Akash Gupta, Hilke E SchlichtingAbstract:Author(s): Gupta, Akash; Schlichting, Hilke E | Abstract: Recent observations revealed a bimodal radius distribution of small, short-period exoplanets with a paucity in their occurrence, a radius 'valley', around 1.5-2.0 R⊕. In this work, we investigate the effect of a planet's own cooling luminosity on its thermal Evolution and atmospheric mass loss (core-powered mass-loss) and determine its observational consequences for the radius distribution of small, close-in exoplanets. Using simple analytical descriptions and numerical simulations, we demonstrate that Planetary Evolution based on the core-powered mass-loss mechanism alone (i.e. without any photoevaporation) can produce the observed valley in the radius distribution. Our results match the valley's location, shape and slope in planet radius-orbital period parameter space, and the relative magnitudes of the planet occurrence rate above and below the valley. We find that the slope of the valley is, to first order, dictated by the atmospheric mass-loss time-scale at the Bondi radius and given by d logR p/d logP ≃ 1/(3(1 - β)) that evaluates to -0.11 for β ≃ 4, where M c/M⊕ = (R c/R ⊕) β (ρ c*/ρ ⊕) β/3 is the mass-radius relation of the core. This choice for β yields good agreement with observations and attests to the significance of internal compression for massive Planetary cores. We further find that the location of the valley scales as ρc∗-4∕9 and that the observed planet population must have predominantly rocky cores with typical water-ice fractions of less than ~20 per cent. Furthermore, we show that the relative magnitude of the planet occurrence rate above and below the valley is sensitive to the details of the planet-mass distribution but that the location of the valley is not.
-
sculpting the valley in the radius distribution of small exoplanets as a by product of planet formation the core powered mass loss mechanism
arXiv: Earth and Planetary Astrophysics, 2018Co-Authors: Akash Gupta, Hilke E SchlichtingAbstract:Recent observations revealed a bimodal radius distribution of small, short-period exoplanets with a paucity in their occurrence, a radius `valley', around $1.5-2.0$ $R_\oplus$. In this work, we investigate the effect of a planet's own cooling luminosity on its thermal Evolution and atmospheric mass-loss (core-powered mass-loss) and determine its observational consequences for the radius distribution of small, close-in exoplanets. Using simple analytical descriptions and numerical simulations, we demonstrate that Planetary Evolution based on the core-powered mass-loss mechanism alone (i.e., without any photoevaporation) can produce the observed valley in the radius distribution. Our results match the valley's location, shape and slope in planet radius-orbital period parameter space, and the relative magnitudes of the planet occurrence rate above and below the valley. We find that the slope of the valley is, to first order, dictated by the atmospheric mass-loss timescale at the Bondi radius and given by $\text{d log} R_p/ \text{d log} P \simeq 1/(3(1-\beta)) \simeq -0.11$, where $M_c \propto R_c^{\beta}$ is the mass-radius relation of the core. $\beta \simeq 4$ yields good agreement with observations, attesting to the significance of internal compression for Planetary cores more massive than Earth. We further find that the location of the valley scales with the uncompressed core density as $\rho_{c*}^{-4/9}$ and that the observed planet population must have predominantly rocky cores with typical water-ice fractions of less than $\sim 20\%$. Furthermore, we show that the relative magnitude of the planet occurrence rate above and below the valley is sensitive to the details of the planet-mass distribution but that the location of the valley is not.
Wilson P Cauley - One of the best experts on this subject based on the ideXlab platform.
-
optical hydrogen absorption consistent with a thin bow shock leading the hot jupiter hd 189733b
The Astrophysical Journal, 2015Co-Authors: Wilson P Cauley, Travis Barman, Seth Redfield, Adam G Jensen, Michael Endl, William D CochranAbstract:Bow shocks are ubiquitous astrophysical phenomena resulting from the supersonic passage of an object through a gas. Recently, pre-transit absorption in UV metal transitions of the hot Jupiter (HJ) exoplanets HD 189733b and WASP12-b have been interpreted as being caused by material compressed in a Planetary bow shock. Here we present a robust detection of a time-resolved pre-transit, as well as in-transit absorption signature around the HJ exoplanet HD 189733b using high spectral resolution observations of several hydrogen Balmer lines. The line shape of the pre-transit feature and the shape of the timeseries absorption provide the strongest constraints on the morphology and physical characteristics of extended structures around an exoplanet. The in-transit measurements confirm the previous exospheric Hα detection, although the absorption depth measured here is ∼50% lower. The pre-transit absorption feature occurs 125 minutes before the predicted optical transit, a projected linear distance from the planet to the stellar disk of 7.2 Rp. The absorption strength observed in the Balmer lines indicates an optically thick, but physically small, geometry. We model this signal as the early ingress of a Planetary bow shock. If the bow shock is mediated by a Planetary magnetosphere, the large standoff distance derived from the model suggests a large Planetary magnetic field strength of Beq = 28 G. Better knowledge of exoplanet magnetic field strengths is crucial to understanding the role these fields play in Planetary Evolution and the potential development of life on planets in the habitable zone.
-
optical hydrogen absorption consistent with a thin bow shock leading the hot jupiter hd 189733b
arXiv: Earth and Planetary Astrophysics, 2015Co-Authors: Wilson P Cauley, Travis Barman, Seth Redfield, Adam G Jensen, Michael Endl, William D CochranAbstract:Bow shocks are ubiquitous astrophysical phenomena resulting from the supersonic passage of an object through a gas. Recently, pre-transit absorption in UV metal transitions of the hot Jupiter exoplanets HD 189733b and WASP12-b have been interpreted as being caused by material compressed in a Planetary bow shock. Here we present a robust detection of a time-resolved pre-transit, as well as in-transit, absorption signature around the hot Jupiter exoplanet HD 189733b using high spectral resolution observations of several hydrogen Balmer lines. The line shape of the pre-transit feature and the shape of the time series absorption provide the strongest constraints on the morphology and physical characteristics of extended structures around an exoplanet. The in-transit measurements confirm the previous exospheric H-alpha detection although the absorption depth measured here is ~50% lower. The pre-transit absorption feature occurs 125 minutes before the predicted optical transit, a projected linear distance from the planet to the stellar disk of 7.2 Planetary radii. The absorption strength observed in the Balmer lines indicates an optically thick, but physically small, geometry. We model this signal as the early ingress of a Planetary bow shock. If the bow shock is mediated by a Planetary magnetosphere, the large standoff distance derived from the model suggests a large equatorial Planetary magnetic field strength of 28 G. Better knowledge of exoplanet magnetic field strengths is crucial to understanding the role these fields play in Planetary Evolution and the potential development of life on planets in the habitable zone.
Jonathan J Fortney - One of the best experts on this subject based on the ideXlab platform.
-
Planetary radii across five orders of magnitude in mass and stellar insolation application to transits
The Astrophysical Journal, 2007Co-Authors: Jonathan J Fortney, Mark S Marley, Jason W BarnesAbstract:ToaidinthephysicalinterpretationofPlanetaryradii constrainedthroughobservationsoftransitingplanets,oreventuallydirectdetections,wecomputemodelradiiofpurehydrogen-helium,water,rock,andironplanets,alongwithvarious mixtures. Masses ranging from 0.01 Earth masses to 10 Jupiter masses at orbital distances of 0.02–10 AU are considered. For hydrogen-helium rich planets, our models are the first to couple Planetary Evolution to stellar irradiation over a wide range of orbital separations (0.02–10 AU) through a nongray radiative-convective equilibrium atmosphere model. Stellar irradiation retards the contraction of giant planets, but its effect is not a simple function of theirradiationlevel:aplanetat1AUcontractsasslowlyasaplanetat0.1AU.WeconfirmtheassertionofGuillotthat very old giant planets under modest stellar irradiation (like that received by Jupiter and Saturn) develop isothermal atmospheric radiative zones once the planet’s intrinsic flux drops to a small fraction of the incident flux. For hydrogenhelium planets, we consider cores up to 90% of the total planet mass, comparable to those of Uranus and Neptune. If ‘‘hot Neptunes’’ have maintained their original masses and are not remnants of more massive planets, radii of � 0.30– 0.45RJ areexpected.Waterplanetsare � 40%–50%largerthanrockyplanets,independentofmass.Finally,weprovide tables of Planetary radii at various ages and compositions, and for ice-rock-iron planets we fit our results to analytic functions, which will allow for quick composition estimates, given masses and radii, or mass estimates, given only Planetary radii. These results will assist in the interpretation of observations for both the current transiting planet surveys as well as upcoming space missions, including COROT and Kepler.
-
Planetary radii across five orders of magnitude in mass and stellar insolation application to transits
arXiv: Astrophysics, 2006Co-Authors: Jonathan J Fortney, Mark S Marley, Jason W BarnesAbstract:To aid in the physical interpretation of Planetary radii constrained through observations of transiting planets, or eventually direct detections, we compute model radii of pure hydrogen-helium, water, rock, and iron planets, along with various mixtures. Masses ranging from 0.01 Earth masses to 10 Jupiter masses at orbital distances of 0.02 to 10 AU are considered. For hydrogen-helium rich planets, our models are the first to couple Planetary Evolution to stellar irradiation over a wide range of orbital separations (0.02 to 10 AU) through a non-gray radiative-convective equilibrium atmosphere model. Stellar irradiation retards the contraction of giant planets, but its effect is not a simple function of the irradiation level: a planet at 1 AU contracts as slowly as a planet at 0.1 AU. For hydrogen-helium planets, we consider cores up to 90% of the total planet mass, comparable to those of Uranus and Neptune. If "hot Neptunes" have maintained their original masses and are not remnants of more massive planets, radii of 0.30-0.45 times Jupiter's radius are expected. Water planets are ~40-50% larger than rocky planets, independent of mass. Finally, we provide tables of Planetary radii at various ages and compositions, and for ice-rock-iron planets we fit our results to analytic functions, which will allow for quick composition estimates, given masses and radii, or mass estimates, given only Planetary radii. These results will assist in the interpretation of observations for both the current transiting planet surveys as well as upcoming space missions, including CoRoT and Kepler.