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Norio Narita - One of the best experts on this subject based on the ideXlab platform.
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two upper limits on the rossiter mclaughlin effect with differing implications wasp 1 has a high obliquity and wasp 2 is indeterminate
The Astrophysical Journal, 2011Co-Authors: Simon Albrecht, Joshua N Winn, Norio Narita, John Asher Johnson, Paul R Butler, Jeffrey D Crane, Stephen A Shectman, Ian B Thompson, Bunei Sato, Teruyuki HiranoAbstract:We present precise radial-velocity (RV) measurements of WASP-1 and WASP-2 throughout transits of their giant planets. Our goal was to detect the Rossiter-McLaughlin (RM) effect, the anomalous RV observed during eclipses of rotating stars, which can be used to study the obliquities of planet-hosting stars. For WASP-1, a weak signal of a prograde Orbit was detected with ≈2σ confidence, and for WASP-2 no signal was detected. The resulting upper bounds on the RM amplitude have different implications for these two systems because of the contrasting transit geometries and the stellar types. Because WASP-1 is an F7V star, and such stars are typically rapid rotators, the most probable reason for the suppression of the RM effect is that the star is viewed nearly pole-on. This implies that the WASP-1 star has a high obliquity with respect to the edge-on Planetary Orbit. Because WASP-2 is a K1V star, and is expected to be a slow rotator, no firm conclusion can be drawn about the stellar obliquity. Our data and our analysis contradict an earlier claim that WASP-2b has a retrograde Orbit, thereby revoking this system's status as an exception to the pattern that cool stars have low obliquities.
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two upper limits on the rossiter mclaughlin effect with differing implications wasp 1 has a high obliquity and wasp 2 is indeterminate
arXiv: Earth and Planetary Astrophysics, 2011Co-Authors: Simon Albrecht, Joshua N Winn, Norio Narita, John Asher Johnson, Paul R Butler, Jeffrey D Crane, Stephen A Shectman, Ian B Thompson, Bunei Sato, Teruyuki HiranoAbstract:We present precise radial-velocity measurements of WASP-1 and WASP-2 throughout transits of their giant planets. Our goal was to detect the Rossiter-McLaughlin (RM) effect, the anomalous radial velocity observed during eclipses of rotating stars, which can be used to study the obliquities of planet-hosting stars. For WASP-1 a weak signal of a prograde Orbit was detected with ~2sigma confidence, and for WASP-2 no signal was detected. The resulting upper bounds on the RM amplitude have different implications for these two systems, because of the contrasting transit geometries and the stellar types. Because WASP-1 is an F7V star, and such stars are typically rapid rotators, the most probable reason for the suppression of the RM effect is that the star is viewed nearly pole-on. This implies the WASP-1 star has a high obliquity with respect to the edge-on Planetary Orbit. Because WASP-2 is a K1V star, and is expected to be a slow rotator, no firm conclusion can be drawn about the stellar obliquity. Our data and our analysis contradict an earlier claim that WASP-2b has a retrograde Orbit, thereby revoking this system's status as an exception to the pattern that cool stars have low obliquities.
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the transit light curve project v system parameters and stellar rotation period of hd 189733
The Astronomical Journal, 2007Co-Authors: Joshua N Winn, Matthew J Holman, Gregory W Henry, Anna Roussanova, Keigo Enya, Yuzuru Yoshii, Avi Shporer, Tsevi Mazeh, John Asher Johnson, Norio NaritaAbstract:We present photometry of HD 189733 during eight transits of its close-in giant planet, and out-of-transit photometry spanning 2 yr. Using the transit photometry, we determine the stellar and Planetary radii and the photometric ephemeris. Outside of transits, there are quasi-periodic flux variations with a 13.4 day period that we attribute to stellar rotation. In combination with previous results, we derive upper limits on the Orbital eccentricity and on the true angle between the stellar rotation axis and Planetary Orbit (as opposed to the angle between the projections of those axes on the sky).
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the transit light curve project v system parameters and stellar rotation period of hd 189733
arXiv: Astrophysics, 2006Co-Authors: Joshua N Winn, Matthew J Holman, Gregory W Henry, Anna Roussanova, Keigo Enya, Yuzuru Yoshii, Avi Shporer, Tsevi Mazeh, John Asher Johnson, Norio NaritaAbstract:We present photometry of HD 189733 during eight transits of its close-in giant planet, and out-of-transit photometry spanning two years. Using the transit photometry, we determine the stellar and Planetary radii and the photometric ephemeris. Outside of transits, there are quasiperiodic flux variations with a 13.4 day period that we attribute to stellar rotation. In combination with previous results, we derive upper limits on the Orbital eccentricity, and on the true angle between the stellar rotation axis and Planetary Orbit (as opposed to the angle between the projections of those axes on the sky).
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measurement of spin Orbit alignment in an extrasolar Planetary system
The Astrophysical Journal, 2005Co-Authors: Joshua N Winn, R W Noyes, Matthew J Holman, David Charbonneau, Yasuhiro Ohta, Atsushi Taruya, Yasushi Suto, Norio Narita, Edwin L TurnerAbstract:We determine the stellar, Planetary, and Orbital properties of the transiting Planetary system HD 209458 through a joint analysis of high-precision radial velocities, photometry, and timing of the secondary eclipse. Of primary interest is the strong detection of the Rossiter-McLaughlin effect, the alteration of photospheric line profiles that occurs because the planet occults part of the rotating surface of the star. We develop a new technique for modeling this effect and use it to determine the inclination of the Planetary Orbit relative to the apparent stellar equator (λ = -4o.4 ± 1o.4), and the line-of-sight rotation speed of the star (v sin /_★ = 4.70 ± 0.16 km s^(-1)). The uncertainty in these quantities has been reduced by an order of magnitude relative to the pioneering measurements by Queloz and collaborators. The small but nonzero misalignment is probably a relic of the planet formation epoch, because the expected timescale for tidal coplanarization is larger than the age of the star. Our determination of v sin /★ is a rare case in which rotational line broadening has been isolated from other broadening mechanisms.
Joshua N Winn - One of the best experts on this subject based on the ideXlab platform.
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two upper limits on the rossiter mclaughlin effect with differing implications wasp 1 has a high obliquity and wasp 2 is indeterminate
The Astrophysical Journal, 2011Co-Authors: Simon Albrecht, Joshua N Winn, Norio Narita, John Asher Johnson, Paul R Butler, Jeffrey D Crane, Stephen A Shectman, Ian B Thompson, Bunei Sato, Teruyuki HiranoAbstract:We present precise radial-velocity (RV) measurements of WASP-1 and WASP-2 throughout transits of their giant planets. Our goal was to detect the Rossiter-McLaughlin (RM) effect, the anomalous RV observed during eclipses of rotating stars, which can be used to study the obliquities of planet-hosting stars. For WASP-1, a weak signal of a prograde Orbit was detected with ≈2σ confidence, and for WASP-2 no signal was detected. The resulting upper bounds on the RM amplitude have different implications for these two systems because of the contrasting transit geometries and the stellar types. Because WASP-1 is an F7V star, and such stars are typically rapid rotators, the most probable reason for the suppression of the RM effect is that the star is viewed nearly pole-on. This implies that the WASP-1 star has a high obliquity with respect to the edge-on Planetary Orbit. Because WASP-2 is a K1V star, and is expected to be a slow rotator, no firm conclusion can be drawn about the stellar obliquity. Our data and our analysis contradict an earlier claim that WASP-2b has a retrograde Orbit, thereby revoking this system's status as an exception to the pattern that cool stars have low obliquities.
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two upper limits on the rossiter mclaughlin effect with differing implications wasp 1 has a high obliquity and wasp 2 is indeterminate
arXiv: Earth and Planetary Astrophysics, 2011Co-Authors: Simon Albrecht, Joshua N Winn, Norio Narita, John Asher Johnson, Paul R Butler, Jeffrey D Crane, Stephen A Shectman, Ian B Thompson, Bunei Sato, Teruyuki HiranoAbstract:We present precise radial-velocity measurements of WASP-1 and WASP-2 throughout transits of their giant planets. Our goal was to detect the Rossiter-McLaughlin (RM) effect, the anomalous radial velocity observed during eclipses of rotating stars, which can be used to study the obliquities of planet-hosting stars. For WASP-1 a weak signal of a prograde Orbit was detected with ~2sigma confidence, and for WASP-2 no signal was detected. The resulting upper bounds on the RM amplitude have different implications for these two systems, because of the contrasting transit geometries and the stellar types. Because WASP-1 is an F7V star, and such stars are typically rapid rotators, the most probable reason for the suppression of the RM effect is that the star is viewed nearly pole-on. This implies the WASP-1 star has a high obliquity with respect to the edge-on Planetary Orbit. Because WASP-2 is a K1V star, and is expected to be a slow rotator, no firm conclusion can be drawn about the stellar obliquity. Our data and our analysis contradict an earlier claim that WASP-2b has a retrograde Orbit, thereby revoking this system's status as an exception to the pattern that cool stars have low obliquities.
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the transit light curve project v system parameters and stellar rotation period of hd 189733
The Astronomical Journal, 2007Co-Authors: Joshua N Winn, Matthew J Holman, Gregory W Henry, Anna Roussanova, Keigo Enya, Yuzuru Yoshii, Avi Shporer, Tsevi Mazeh, John Asher Johnson, Norio NaritaAbstract:We present photometry of HD 189733 during eight transits of its close-in giant planet, and out-of-transit photometry spanning 2 yr. Using the transit photometry, we determine the stellar and Planetary radii and the photometric ephemeris. Outside of transits, there are quasi-periodic flux variations with a 13.4 day period that we attribute to stellar rotation. In combination with previous results, we derive upper limits on the Orbital eccentricity and on the true angle between the stellar rotation axis and Planetary Orbit (as opposed to the angle between the projections of those axes on the sky).
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the transit light curve project v system parameters and stellar rotation period of hd 189733
arXiv: Astrophysics, 2006Co-Authors: Joshua N Winn, Matthew J Holman, Gregory W Henry, Anna Roussanova, Keigo Enya, Yuzuru Yoshii, Avi Shporer, Tsevi Mazeh, John Asher Johnson, Norio NaritaAbstract:We present photometry of HD 189733 during eight transits of its close-in giant planet, and out-of-transit photometry spanning two years. Using the transit photometry, we determine the stellar and Planetary radii and the photometric ephemeris. Outside of transits, there are quasiperiodic flux variations with a 13.4 day period that we attribute to stellar rotation. In combination with previous results, we derive upper limits on the Orbital eccentricity, and on the true angle between the stellar rotation axis and Planetary Orbit (as opposed to the angle between the projections of those axes on the sky).
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measurement of spin Orbit alignment in an extrasolar Planetary system
The Astrophysical Journal, 2005Co-Authors: Joshua N Winn, R W Noyes, Matthew J Holman, David Charbonneau, Yasuhiro Ohta, Atsushi Taruya, Yasushi Suto, Norio Narita, Edwin L TurnerAbstract:We determine the stellar, Planetary, and Orbital properties of the transiting Planetary system HD 209458 through a joint analysis of high-precision radial velocities, photometry, and timing of the secondary eclipse. Of primary interest is the strong detection of the Rossiter-McLaughlin effect, the alteration of photospheric line profiles that occurs because the planet occults part of the rotating surface of the star. We develop a new technique for modeling this effect and use it to determine the inclination of the Planetary Orbit relative to the apparent stellar equator (λ = -4o.4 ± 1o.4), and the line-of-sight rotation speed of the star (v sin /_★ = 4.70 ± 0.16 km s^(-1)). The uncertainty in these quantities has been reduced by an order of magnitude relative to the pioneering measurements by Queloz and collaborators. The small but nonzero misalignment is probably a relic of the planet formation epoch, because the expected timescale for tidal coplanarization is larger than the age of the star. Our determination of v sin /★ is a rare case in which rotational line broadening has been isolated from other broadening mechanisms.
E. K. Simpson - One of the best experts on this subject based on the ideXlab platform.
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A window on exoplanet dynamical histories: Rossiter-McLaughlin observations of WASP-13b and WASP-32b
Monthly Notices of the Royal Astronomical Society, 2014Co-Authors: R.d. Brothwell, D. R. Anderson, G. Hebrard, Christopher A. Watson, Amaury H. M. J. Triaud, Heather Cegla, Alexandre Santerne, E. Hébrard, Don Pollacco, E. K. SimpsonAbstract:We present Rossiter-McLaughlin observations of WASP-13b and WASP-32b and determine the sky-projected angle between the normal of the Planetary Orbit and the stellar rotation axis (lambda). WASP-13b and WASP-32b both have prograde Orbits and are consistent with alignment with measured sky-projected angles of lambda = 8 degrees(+13)(-12) and lambda = -2 degrees(+17)(-19), respectively. Both WASP-13 and WASP-32 have T-eff \textless 6250 K, and therefore, these systems support the general trend that aligned Planetary systems are preferentially found Orbiting cool host stars. A Lomb-Scargle periodogram analysis was carried out on archival SuperWASP data for both systems. A statistically significant stellar rotation period detection (above 99.9 per cent confidence) was identified for the WASP-32 system with P-rot = 11.6 +/- 1.0 days. This rotation period is in agreement with the predicted stellar rotation period calculated from the stellar radius, R-*, and nu sin i if a stellar inclination of i(*) = 90 degrees is assumed. With the determined rotation period, the true 3D angle between the stellar rotation axis and the Planetary Orbit, psi, was found to be psi = 11 degrees +/- 14 degrees. We conclude with a discussion on the alignment of systems around cool host stars with T-eff \textless 6150 K by calculating the tidal dissipation time-scale. We find that systems with short tidal dissipation time-scales are preferentially aligned and systems with long tidal dissipation time-scales have a broad range of obliquities.
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A window on exoplanet dynamical histories: Rossiter-McLaughlin observations of WASP-13b and WASP-32b
Monthly Notices of the Royal Astronomical Society, 2014Co-Authors: R.d. Brothwell, Christopher A. Watson, Guillaume Hébrard, Amaury H. M. J. Triaud, Heather Cegla, Alexandre Santerne, E. Hébrard, David R. Anderson, Don Pollacco, E. K. SimpsonAbstract:We present Rossiter-McLaughlin observations of WASP-13b and WASP-32b and determine the sky-projected angle between the normal of the Planetary Orbit and the stellar rotation axis ( ). WASP-13b and WASP-32b both have prograde Orbits and are consistent with alignment with measured sky-projected angles of = 8 +13 12 and = 2 +17 19 , respectively. Both WASP-13 and WASP-32 have Te < 6250K and therefore these systems support the general trend that aligned Planetary systems are preferentially found Orbiting cool host stars. A Lomb-Scargle periodogram analysis was carried out on archival SuperWASP data for both systems. A statistically significant stellar rotation period detection (above 99.9% confidence) was identified for the WASP-32 system with Prot = 11:6 1:0 days. This rotation period is in agreement with the predicted stellar rotation period calculated from the stellar radius, R?, and v sini if a stellar inclination ofi? = 90 is assumed. With the determined rotation period, the true 3D angle between the stellar rotation axis and the Planetary Orbit, , was found to be = 11 14. We conclude with a discussion on the alignment of systems around cool host stars with Te < 6150K by calculating the tidal dissipation timescale. We find that systems with short tidal dissipation timescales are preferentially aligned and systems with long tidal dissipation timescales have a broad range of obliquities.
Yasushi Suto - One of the best experts on this subject based on the ideXlab platform.
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determination of three dimensional spin Orbit angle with joint analysis of asteroseismology transit lightcurve and the rossiter mclaughlin effect cases of hat p 7 and kepler 25
Publications of the Astronomical Society of Japan, 2014Co-Authors: O Benomar, Kento Masuda, Hiromoto Shibahashi, Yasushi SutoAbstract:We develop a detailed methodology of determining three-dimensionally the angle between the stellar spin and the Planetary Orbit axis vectors, $\psi$, for transiting Planetary systems. The determination of $\psi$ requires the independent estimates of the inclination angles of the stellar spin axis and of the Planetary Orbital axis with respect to the line-of-sight, $i_\star$ and $i_{\rm orb}$, and the projection of the spin--Orbit angle onto the plane of the sky, $\lambda$. These are mainly derived from asteroseismology, transit lightcurve and the Rossiter-McLaughlin effect, respectively. The detailed joint analysis of those three datasets enables an accurate and precise determination of the numerous parameters characterizing the Planetary system, in addition to $\psi$. We demonstrate the power of the joint analysis for the two specific systems, HAT-P-7 and Kepler-25. HAT-P-7b is the first exoplanet suspected to be a retrograde (or polar) planet because of the significant misalignment $\lambda \approx 180^\circ$. Our joint analysis indicates $i_\star \approx {30D}$ and $\psi \approx 120^\circ$, suggesting that the Planetary Orbit is closer to polar rather than retrograde. Kepler-25 is one of the few multi-transiting Planetary systems with measured $\lambda$, and hosts two short-period transiting planets and one outer non-transiting planet. The projected spin--Orbit angle of the larger transiting planet, Kepler-25c, has been measured to be $\lambda \approx 0^\circ$, implying that the system is well-aligned. With the help of the tight constraint from asteroseismology, however, we obtain $i_\star={65.4}^{+{10.6}}_{-{6.4}}$ and $\psi={26.9}^{+{7.0}}_{-{9.2}}$, and thus find that the system is actually mildly misaligned.
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measurement of spin Orbit alignment in an extrasolar Planetary system
The Astrophysical Journal, 2005Co-Authors: Joshua N Winn, R W Noyes, Matthew J Holman, David Charbonneau, Yasuhiro Ohta, Atsushi Taruya, Yasushi Suto, Norio Narita, Edwin L TurnerAbstract:We determine the stellar, Planetary, and Orbital properties of the transiting Planetary system HD 209458 through a joint analysis of high-precision radial velocities, photometry, and timing of the secondary eclipse. Of primary interest is the strong detection of the Rossiter-McLaughlin effect, the alteration of photospheric line profiles that occurs because the planet occults part of the rotating surface of the star. We develop a new technique for modeling this effect and use it to determine the inclination of the Planetary Orbit relative to the apparent stellar equator (λ = -4o.4 ± 1o.4), and the line-of-sight rotation speed of the star (v sin /_★ = 4.70 ± 0.16 km s^(-1)). The uncertainty in these quantities has been reduced by an order of magnitude relative to the pioneering measurements by Queloz and collaborators. The small but nonzero misalignment is probably a relic of the planet formation epoch, because the expected timescale for tidal coplanarization is larger than the age of the star. Our determination of v sin /★ is a rare case in which rotational line broadening has been isolated from other broadening mechanisms.
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measurement of spin Orbit alignment in an extrasolar Planetary system
arXiv: Astrophysics, 2005Co-Authors: Joshua N Winn, R W Noyes, Matthew J Holman, David Charbonneau, Yasuhiro Ohta, Atsushi Taruya, Yasushi Suto, Norio Narita, Edwin L TurnerAbstract:We determine the stellar, Planetary, and Orbital properties of the transiting Planetary system HD 209458, through a joint analysis of high-precision radial velocities, photometry, and timing of the secondary eclipse. Of primary interest is the strong detection of the Rossiter-McLaughlin effect, the alteration of photospheric line profiles that occurs because the planet occults part of the rotating surface of the star. We develop a new technique for modeling this effect, and use it to determine the inclination of the Planetary Orbit relative to the apparent stellar equator [lambda = (-4.4 +/- 1.4) degrees], and the line-of-sight rotation speed of the star [v*sin(I) = (4.70 +/- 0.16) km/s]. The uncertainty in these quantities has been reduced by an order of magnitude relative to the pioneering measurements by Queloz and collaborators. The small but nonzero misalignment is probably a relic of the planet formation epoch, because the expected timescale for tidal coplanarization is larger than the age of the star. Our determination of v*sin(I) is a rare case in which rotational line broadening has been isolated from other broadening mechanisms.
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the rossiter mclaughlin effect and analytic radial velocity curves for transiting extrasolar Planetary systems
The Astrophysical Journal, 2005Co-Authors: Yasuhiro Ohta, Atsushi Taruya, Yasushi SutoAbstract:A transiting extrasolar planet sequentially blocks off the light coming from the different parts of the disk of the host star in a time-dependent manner. Because of the spin of the star, this produces an asymmetric distortion in the line profiles of the stellar spectrum, leading to an apparent anomaly in the the radial velocity curves, known as the Rossiter-McLaughlin effect. Here, we derive approximate but accurate analytic formulae for the anomaly in the radial velocity curves, taking into account the stellar limb darkening. The formulae are particularly useful in extracting information on the projected angle between the Planetary Orbit axis and the stellar spin axis, λ, and the projected stellar spin velocity, V sin Is. We create mock samples for the radial curves for the transiting extrasolar system HD 209458 and demonstrate that constraints on the spin parameters (V sin Is, λ) can be significantly improved by combining our analytic template formulae and the precision velocity curves from high-resolution spectroscopic observations with 8-10 m class telescopes. Thus, future observational exploration of transiting systems using the Rossiter-McLaughlin effect will be one of the most important probes for a better understanding of the origin of extrasolar Planetary systems, especially the origin of their angular momentum.
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the rossiter mclaughlin effect and analytic radial velocity curves for transiting extrasolar Planetary systems
arXiv: Astrophysics, 2004Co-Authors: Yasuhiro Ohta, Atsushi Taruya, Yasushi SutoAbstract:A transiting extrasolar planet sequentially blocks off the light coming from the different parts of the disk of the host star in a time dependent manner. Due to the spin of the star, this produces an asymmetric distortion in the line profiles of the stellar spectrum, leading to an apparent anomaly of the radial velocity curves, known as the Rossiter - McLaughlin effect. Here, we derive approximate but accurate analytic formulae for the anomaly of radial velocity curves taking account of the stellar limb darkening. The formulae are particularly useful in extracting information of the projected angle between the Planetary Orbit axis and the stellar spin axis, \lambda, and the projected stellar spin velocity, V sin I_s. We create mock samples for the radial curves for the transiting extrasolar system HD209458, and demonstrate that constraints on the spin parameters (V sin I_s, \lambda) may be significantly improved by combining our analytic template formulae and the precision velocity curves from high-resolution spectroscopic observations with 8-10 m class telescopes. Thus future observational exploration of transiting systems using the Rossiter - McLaughlin effect is one of the most important probes to better understanding of the origin of extrasolar Planetary systems, especially the origin of their angular momentum.
Matthew J Holman - One of the best experts on this subject based on the ideXlab platform.
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High Accuracy Planetary Orbit Integration
arXiv: Earth and Planetary Astrophysics, 2020Co-Authors: David M. Hernandez, Matthew J HolmanAbstract:We present a new, highly accurate code for Planetary Orbital dynamics, EnckeHH. It solves the Encke equations of motion, which assume perturbed Keplerian Orbits. By incorporating numerical techniques, we have made the code follow optimal roundoff error growth for fixed time steps, unlike other codes, such as IAS15. In a $10^ {12}$ day integration of the outer Solar System, EnckeHH was $3.5$ orders of magnitude more accurate than IAS15 in a fixed time step test.
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stellar rotation Planetary Orbit period commensurability in the hat p 11 system
The Astrophysical Journal, 2014Co-Authors: B Beky, Matthew J Holman, David M Kipping, R W NoyesAbstract:A number of planet host stars have been observed to rotate with a period equal to an integer multiple of the Orbital period of their close planet. We expand this list by analyzing Kepler data of HAT-P-11 and finding a period ratio of 6:1. In particular, we present evidence for a long-lived spot on the stellar surface that is eclipsed by the planet in the same position four times, every sixth transit. We also identify minima in the out-of-transit light curve and confirm that their phase with respect to the stellar rotation is mostly stationary for the 48 month time frame of the observations, confirming the proposed rotation period. For comparison, we apply our methods to Kepler-17 and confirm the findings of Bonomo & Lanza that the period ratio is not exactly 8:1 in that system. Finally, we provide a hypothesis on how interactions between a star and its planet could possibly result in an observed commensurability for systems where the stellar differential rotation profile happens to include a period at some latitude that is commensurable to the Planetary Orbit.
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the transit light curve project v system parameters and stellar rotation period of hd 189733
The Astronomical Journal, 2007Co-Authors: Joshua N Winn, Matthew J Holman, Gregory W Henry, Anna Roussanova, Keigo Enya, Yuzuru Yoshii, Avi Shporer, Tsevi Mazeh, John Asher Johnson, Norio NaritaAbstract:We present photometry of HD 189733 during eight transits of its close-in giant planet, and out-of-transit photometry spanning 2 yr. Using the transit photometry, we determine the stellar and Planetary radii and the photometric ephemeris. Outside of transits, there are quasi-periodic flux variations with a 13.4 day period that we attribute to stellar rotation. In combination with previous results, we derive upper limits on the Orbital eccentricity and on the true angle between the stellar rotation axis and Planetary Orbit (as opposed to the angle between the projections of those axes on the sky).
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the transit light curve project v system parameters and stellar rotation period of hd 189733
arXiv: Astrophysics, 2006Co-Authors: Joshua N Winn, Matthew J Holman, Gregory W Henry, Anna Roussanova, Keigo Enya, Yuzuru Yoshii, Avi Shporer, Tsevi Mazeh, John Asher Johnson, Norio NaritaAbstract:We present photometry of HD 189733 during eight transits of its close-in giant planet, and out-of-transit photometry spanning two years. Using the transit photometry, we determine the stellar and Planetary radii and the photometric ephemeris. Outside of transits, there are quasiperiodic flux variations with a 13.4 day period that we attribute to stellar rotation. In combination with previous results, we derive upper limits on the Orbital eccentricity, and on the true angle between the stellar rotation axis and Planetary Orbit (as opposed to the angle between the projections of those axes on the sky).
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measurement of spin Orbit alignment in an extrasolar Planetary system
The Astrophysical Journal, 2005Co-Authors: Joshua N Winn, R W Noyes, Matthew J Holman, David Charbonneau, Yasuhiro Ohta, Atsushi Taruya, Yasushi Suto, Norio Narita, Edwin L TurnerAbstract:We determine the stellar, Planetary, and Orbital properties of the transiting Planetary system HD 209458 through a joint analysis of high-precision radial velocities, photometry, and timing of the secondary eclipse. Of primary interest is the strong detection of the Rossiter-McLaughlin effect, the alteration of photospheric line profiles that occurs because the planet occults part of the rotating surface of the star. We develop a new technique for modeling this effect and use it to determine the inclination of the Planetary Orbit relative to the apparent stellar equator (λ = -4o.4 ± 1o.4), and the line-of-sight rotation speed of the star (v sin /_★ = 4.70 ± 0.16 km s^(-1)). The uncertainty in these quantities has been reduced by an order of magnitude relative to the pioneering measurements by Queloz and collaborators. The small but nonzero misalignment is probably a relic of the planet formation epoch, because the expected timescale for tidal coplanarization is larger than the age of the star. Our determination of v sin /★ is a rare case in which rotational line broadening has been isolated from other broadening mechanisms.