The Experts below are selected from a list of 234 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, Seth Redfield, Adam G Jensen, Travis Barman, 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, Seth Redfield, Adam G Jensen, Travis Barman, 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.
Tamas I. Gombosi - One of the best experts on this subject based on the ideXlab platform.
-
THE DYNAMICS OF STELLAR CORONAE HARBORING HOT JUPITERS. I. A TIME-DEPENDENT MAGNETOHYDRODYNAMIC SIMULATION OF THE INTERPlanetary ENVIRONMENT IN THE HD 189733 Planetary SYSTEM
The Astrophysical Journal, 2011Co-Authors: Ofer Cohen, Vinay L. Kashyap, Jeremy J. Drake, Igor V. Sokolov, Cecilia Garraffo, Tamas I. GombosiAbstract:We carry out the first time-dependent numerical magnetohydrodynamic modeling of an extrasolar Planetary system to study the interaction of the stellar Magnetic Field and wind with the Planetary magnetosphere and outflow. We base our model on the parameters of the HD 189733 system, which harbors a close-in giant planet. Our simulation reveals a highly structured stellar corona characterized by sectors with different plasma properties. The star-planet interaction (SPI) varies in magnitude and complexity, depending on the Planetary phase, Planetary Magnetic Field strength, and the relative orientation of the stellar and Planetary Fields. It also reveals a long, comet-like tail which is a result of the wrapping of the Planetary magnetospheric tail by its fast orbital motion. A reconnection event occurs at a specific orbital phase, causing mass loss from the Planetary magnetosphere that can generate a hot spot on the stellar surface. The simulation also shows that the system has sufficient energy to produce hot spots observed in Ca II lines in giant planet hosting stars. However, the short duration of the reconnection event suggests that such SPI cannot be observed persistently.
-
the dynamics of stellar coronae harboring hot jupiters i a time dependent mhd simulation of the interPlanetary environment in the hd 189733 Planetary system
arXiv: Solar and Stellar Astrophysics, 2011Co-Authors: O Cohen, Jeremy J. Drake, Igor V. Sokolov, Cecilia Garraffo, V Kashyap, Tamas I. GombosiAbstract:We carry out the first time-dependent numerical MagnetoHydroDynamic modeling of an extrasolar Planetary system to study the interaction of the stellar Magnetic Field and wind with the Planetary magnetosphere and outflow. We base our model on the parameters of the HD 189733 system, which harbors a close-in giant planet. Our simulation reveals a highly structured stellar corona characterized by sectors with different plasma properties. The star-planet interaction varies in magnitude and complexity, depending on the Planetary phase, Planetary Magnetic Field strength, and the relative orientation of the stellar and Planetary Fields. It also reveals a long, comet-like tail which is a result of the wrapping of the Planetary magnetospheric tail by its fast orbital motion. A reconnection event occurs at a specific orbital phase, causing mass loss from the Planetary magnetosphere that can generate a hot spot on the stellar surface. The simulation also shows that the system has sufficient energy to produce hot-spots observed in Ca II lines in giant planet hosting stars. However, the short duration of the reconnection event suggests that such SPI cannot be observed persistently.
Jeremy J. Drake - One of the best experts on this subject based on the ideXlab platform.
-
an earth like stellar wind environment for proxima centauri c
arXiv: Solar and Stellar Astrophysics, 2020Co-Authors: Julian D Alvaradogomez, Jeremy J. Drake, Cecilia Garraffo, O Cohen, Katja Poppenhager, Rakesh K Yadav, Sofia P MoschouAbstract:A new planet has been recently discovered around Proxima Centauri. With an orbital separation of $\sim$$1.44$ au and a minimum mass of about $7$ $M_{\oplus}$, Proxima c is a prime direct imaging target for atmospheric characterization. The latter can only be performed with a good understanding of the space environment of the planet, as multiple processes can have profound effects on the atmospheric structure and evolution. Here, we take one step in this direction by generating physically-realistic numerical simulations of Proxima's stellar wind, coupled to a magnetosphere and ionosphere model around Proxima c. We evaluate their expected variation due to the Magnetic cycle of the host star, as well as for plausible inclination angles for the exoplanet orbit. Our results indicate stellar wind dynamic pressures comparable to present-day Earth, with a slight increase (by a factor of 2) during high activity periods of the star. A relatively weak interPlanetary Magnetic Field at the distance of Proxima c leads to negligible stellar wind Joule heating of the upper atmosphere (about $10\%$ of the solar wind contribution on Earth) for an Earth-like Planetary Magnetic Field ($0.3$ G). Finally, we provide an assessment of the likely extreme conditions experienced by the exoplanet candidate Proxima d, tentatively located at $0.029$ au with a minimum mass of $0.29$ $M_{\oplus}$.
-
THE DYNAMICS OF STELLAR CORONAE HARBORING HOT JUPITERS. I. A TIME-DEPENDENT MAGNETOHYDRODYNAMIC SIMULATION OF THE INTERPlanetary ENVIRONMENT IN THE HD 189733 Planetary SYSTEM
The Astrophysical Journal, 2011Co-Authors: Ofer Cohen, Vinay L. Kashyap, Jeremy J. Drake, Igor V. Sokolov, Cecilia Garraffo, Tamas I. GombosiAbstract:We carry out the first time-dependent numerical magnetohydrodynamic modeling of an extrasolar Planetary system to study the interaction of the stellar Magnetic Field and wind with the Planetary magnetosphere and outflow. We base our model on the parameters of the HD 189733 system, which harbors a close-in giant planet. Our simulation reveals a highly structured stellar corona characterized by sectors with different plasma properties. The star-planet interaction (SPI) varies in magnitude and complexity, depending on the Planetary phase, Planetary Magnetic Field strength, and the relative orientation of the stellar and Planetary Fields. It also reveals a long, comet-like tail which is a result of the wrapping of the Planetary magnetospheric tail by its fast orbital motion. A reconnection event occurs at a specific orbital phase, causing mass loss from the Planetary magnetosphere that can generate a hot spot on the stellar surface. The simulation also shows that the system has sufficient energy to produce hot spots observed in Ca II lines in giant planet hosting stars. However, the short duration of the reconnection event suggests that such SPI cannot be observed persistently.
-
the dynamics of stellar coronae harboring hot jupiters i a time dependent mhd simulation of the interPlanetary environment in the hd 189733 Planetary system
arXiv: Solar and Stellar Astrophysics, 2011Co-Authors: O Cohen, Jeremy J. Drake, Igor V. Sokolov, Cecilia Garraffo, V Kashyap, Tamas I. GombosiAbstract:We carry out the first time-dependent numerical MagnetoHydroDynamic modeling of an extrasolar Planetary system to study the interaction of the stellar Magnetic Field and wind with the Planetary magnetosphere and outflow. We base our model on the parameters of the HD 189733 system, which harbors a close-in giant planet. Our simulation reveals a highly structured stellar corona characterized by sectors with different plasma properties. The star-planet interaction varies in magnitude and complexity, depending on the Planetary phase, Planetary Magnetic Field strength, and the relative orientation of the stellar and Planetary Fields. It also reveals a long, comet-like tail which is a result of the wrapping of the Planetary magnetospheric tail by its fast orbital motion. A reconnection event occurs at a specific orbital phase, causing mass loss from the Planetary magnetosphere that can generate a hot spot on the stellar surface. The simulation also shows that the system has sufficient energy to produce hot-spots observed in Ca II lines in giant planet hosting stars. However, the short duration of the reconnection event suggests that such SPI cannot be observed persistently.
Cecilia Garraffo - One of the best experts on this subject based on the ideXlab platform.
-
an earth like stellar wind environment for proxima centauri c
arXiv: Solar and Stellar Astrophysics, 2020Co-Authors: Julian D Alvaradogomez, Jeremy J. Drake, Cecilia Garraffo, O Cohen, Katja Poppenhager, Rakesh K Yadav, Sofia P MoschouAbstract:A new planet has been recently discovered around Proxima Centauri. With an orbital separation of $\sim$$1.44$ au and a minimum mass of about $7$ $M_{\oplus}$, Proxima c is a prime direct imaging target for atmospheric characterization. The latter can only be performed with a good understanding of the space environment of the planet, as multiple processes can have profound effects on the atmospheric structure and evolution. Here, we take one step in this direction by generating physically-realistic numerical simulations of Proxima's stellar wind, coupled to a magnetosphere and ionosphere model around Proxima c. We evaluate their expected variation due to the Magnetic cycle of the host star, as well as for plausible inclination angles for the exoplanet orbit. Our results indicate stellar wind dynamic pressures comparable to present-day Earth, with a slight increase (by a factor of 2) during high activity periods of the star. A relatively weak interPlanetary Magnetic Field at the distance of Proxima c leads to negligible stellar wind Joule heating of the upper atmosphere (about $10\%$ of the solar wind contribution on Earth) for an Earth-like Planetary Magnetic Field ($0.3$ G). Finally, we provide an assessment of the likely extreme conditions experienced by the exoplanet candidate Proxima d, tentatively located at $0.029$ au with a minimum mass of $0.29$ $M_{\oplus}$.
-
THE DYNAMICS OF STELLAR CORONAE HARBORING HOT JUPITERS. I. A TIME-DEPENDENT MAGNETOHYDRODYNAMIC SIMULATION OF THE INTERPlanetary ENVIRONMENT IN THE HD 189733 Planetary SYSTEM
The Astrophysical Journal, 2011Co-Authors: Ofer Cohen, Vinay L. Kashyap, Jeremy J. Drake, Igor V. Sokolov, Cecilia Garraffo, Tamas I. GombosiAbstract:We carry out the first time-dependent numerical magnetohydrodynamic modeling of an extrasolar Planetary system to study the interaction of the stellar Magnetic Field and wind with the Planetary magnetosphere and outflow. We base our model on the parameters of the HD 189733 system, which harbors a close-in giant planet. Our simulation reveals a highly structured stellar corona characterized by sectors with different plasma properties. The star-planet interaction (SPI) varies in magnitude and complexity, depending on the Planetary phase, Planetary Magnetic Field strength, and the relative orientation of the stellar and Planetary Fields. It also reveals a long, comet-like tail which is a result of the wrapping of the Planetary magnetospheric tail by its fast orbital motion. A reconnection event occurs at a specific orbital phase, causing mass loss from the Planetary magnetosphere that can generate a hot spot on the stellar surface. The simulation also shows that the system has sufficient energy to produce hot spots observed in Ca II lines in giant planet hosting stars. However, the short duration of the reconnection event suggests that such SPI cannot be observed persistently.
-
the dynamics of stellar coronae harboring hot jupiters i a time dependent mhd simulation of the interPlanetary environment in the hd 189733 Planetary system
arXiv: Solar and Stellar Astrophysics, 2011Co-Authors: O Cohen, Jeremy J. Drake, Igor V. Sokolov, Cecilia Garraffo, V Kashyap, Tamas I. GombosiAbstract:We carry out the first time-dependent numerical MagnetoHydroDynamic modeling of an extrasolar Planetary system to study the interaction of the stellar Magnetic Field and wind with the Planetary magnetosphere and outflow. We base our model on the parameters of the HD 189733 system, which harbors a close-in giant planet. Our simulation reveals a highly structured stellar corona characterized by sectors with different plasma properties. The star-planet interaction varies in magnitude and complexity, depending on the Planetary phase, Planetary Magnetic Field strength, and the relative orientation of the stellar and Planetary Fields. It also reveals a long, comet-like tail which is a result of the wrapping of the Planetary magnetospheric tail by its fast orbital motion. A reconnection event occurs at a specific orbital phase, causing mass loss from the Planetary magnetosphere that can generate a hot spot on the stellar surface. The simulation also shows that the system has sufficient energy to produce hot-spots observed in Ca II lines in giant planet hosting stars. However, the short duration of the reconnection event suggests that such SPI cannot be observed persistently.
Wilson P Cauley - One of the best experts on this subject based on the ideXlab platform.
-
Magnetic Field strengths of hot jupiters from signals of star planet interactions
Nature Astronomy, 2019Co-Authors: Wilson P Cauley, Evgenya L Shkolnik, Joe Llama, A F LanzaAbstract:Evidence of star–planet interactions in the form of planet-modulated chromospheric emission has been noted for a number of hot Jupiters. Magnetic star–planet interactions involve the release of energy stored in the stellar and Planetary Magnetic Fields. These signals thus offer indirect detections of exoPlanetary Magnetic Fields. Here, we report the derivation of the Magnetic Field strengths of four hot Jupiter systems, using the power observed in calcium ii K emission modulated by Magnetic star–planet interactions. By approximating the fractional energy released in the calcium ii K line, we find that the surface Magnetic Field values for the hot Jupiters in our sample range from 20 G to 120 G, around 10–100 times larger than the values predicted by dynamo scaling laws for planets with rotation periods of around 2–4 days. However, these values are in agreement with scaling laws relating the Magnetic Field strength to the internal heat flux in giant planets. Large Planetary Magnetic Field strengths may produce observable electron cyclotron maser radio emission by preventing the maser from being quenched by the planet’s ionosphere. Intensive radio monitoring of hot Jupiter systems will help to confirm these Field values and inform the generation mechanism of Magnetic Fields in this important class of exoplanets. The measured Magnetic Field strengths of four close-in gas giant planets are reported, using a technique based on Magnetic star–planet interactions. Values range from 20 G to 120 G, close to estimates based on Planetary internal heat flux, but ~10–100 times larger than predicted by dynamo scaling laws.
-
optical hydrogen absorption consistent with a thin bow shock leading the hot jupiter hd 189733b
The Astrophysical Journal, 2015Co-Authors: Wilson P Cauley, Seth Redfield, Adam G Jensen, Travis Barman, 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, Seth Redfield, Adam G Jensen, Travis Barman, 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.