* Astronomy

Members Login
Post Info TOPIC: HAT-P-7b


L

Posts: 131433
Date:
RE: HAT-P-7b
Permalink  
 


Title: Variability in the Atmosphere of the Hot Giant Planet HAT-P-7 b
Author: David J. Armstrong, Ernst de Mooij, Joanna Barstow, Hugh P. Osborn, James Blake, Nessa Fereshteh Saniee

As an exoplanet orbits its host star it reflects and emits light, forming a distinctive phase curve. By observing this light, we can study the atmosphere and surface of distant planets. The planets in our Solar System show a wide range of atmospheric phenomena, with stable wind patterns, changing storms, and evolving anomalies. Brown dwarfs also exhibit atmospheric variability. Such temporal variability in the atmosphere of a giant exoplanet has not to date been observed. HAT-P-7 b is an exoplanet with a known offset in the peak of its phase curve. Here we present variations in the peak offset ranging between -0.086+0.033-0.033 to 0.143+0.040-0.037 in phase, implying that the peak brightness repeatedly shifts from one side of the planet's substellar point to the other. The variability occurs on a timescale of tens to hundreds of days. These shifts in brightness are indicative of variability in the planet's atmosphere, and result from a changing balance of thermal emission and reflected flux from the planet's dayside. We suggest that variation in wind speed in the planetary atmosphere, leading to variable cloud coverage on the dayside and a changing energy balance, is capable of explaining the observed variation.

Read more (6157kb, PDF)



__________________


L

Posts: 131433
Date:
Permalink  
 

Weather observed for first time on a hot, giant, Jupiter-like alien planet

A weather system - including strong winds and changing cloud cover - has been observed in the atmosphere of a giant gas planet outside our solar system for the first time.
HAT-P-7b is 16 times the size of Earth and lies more than 1,000 light years away in the Cygnus constellation.

Read more



__________________


L

Posts: 131433
Date:
Permalink  
 

First exoplanet weather report shows clouds of ruby and sapphire

A super-sized planet 1000 light years from Earth has clouds that may contain the building blocks of rubies and sapphires, according to the first exoplanet meteorology report.
David Armstrong at the University of Warwick, UK, and colleagues scrutinised four years of data from the Kepler satellite, and noticed that the brightness of a planet called HAT-P-7b changed over time.

Read more



__________________


L

Posts: 131433
Date:
HATS-7b
Permalink  
 


Title: HATS-7b: A Hot Super Neptune Transiting a Quiet K Dwarf Star
Author: G.A.Bakos (1), K.Penev (1), D.Bayliss (2,3), J.D.Hartman (1), G.Zhou (2,1), R.Brahm (4,5), L.Mancini (6), M.deVal-Borro (1), W.Bhatti (1), A.Jordán (4,5), M.Rabus (4,6), N.Espinoza (4,5), Z.Csubry (1), A.W.Howard (7), B.J.Fulton (7,8), L.A.Buchhave (9,10), S.Ciceri (6), T.Henning (6), B.Schmidt (2), H.Isaacson (11), R.W.Noyes (9), G.W.Marcy (11), V.Suc (4), A.R.Howe (1), A.S.Burrows (1), J.Lázár (12), I.Papp (12), P.Sári (12) ((1) Princeton, (2) ANU/Australia, (3) Obs.Geneva, (4) PUC/Chile, (5) MAS, (6) MPIA, (7) IfA, (8) NSF Fellow, (9) CfA, (10) Uni Copenhagen, (11) UCB, (12) HAS/Budapest)

We report the discovery by the HATSouth network of HATS-7b, a transiting Super-Neptune with a mass of 0.120±0.012 M_Jup, a radius of 0.563+0.046-0.034 R_Jup, and an orbital period of 3.1853 days. The host star is a moderately bright (V = 13.340±0.010 mag, K_S = 10.976±0.026 mag) K dwarf star with a mass of 0.849±0.027 M_Sun, a radius of 0.815+0.049-0.035 R_Sun, and a metallicity of [Fe/H]= +0.250±0.080. The star is photometrically quiet to within the precision of the HATSouth measurements, has low RV jitter, and shows no evidence for chromospheric activity in its spectrum. HATS-7b is the second smallest radius planet discovered by a wide-field ground-based transit survey, and one of only a handful of Neptune-size planets with mass and radius determined to 10% precision. Theoretical modelling of HATS-7b yields a hydrogen-helium fraction of 18±4% (rock-iron core and H2-He envelope), or 9±4% (ice core and H2-He envelope), i.e.it has a composition broadly similar to that of Uranus and Neptune, and very different from that of Saturn, which has 75% of its mass in H2-He. Based on a sample of transiting exoplanets with accurately (<20%) determined parameters, we establish approximate power-law relations for the envelopes of the mass-density distribution of exoplanets. HATS-7b, which, together with the recently discovered HATS-8b, is one of the first two transiting Neptunes discovered in the Southern sky, is a prime target for additional follow-up observations with southern hemisphere facilities to characterize the atmospheres of super-Neptunes.

Read more (154kb, PDF)



__________________


L

Posts: 131433
Date:
HAT-P-7
Permalink  
 


The Origin and Maintenance of a Retrograde Exoplanet

Astronomers have used the Subaru Telescope to show that the HAT-P-7 planetary system, which is about 1040 light years from Earth in the constellation Cygnus, includes at least two giant planets and one companion star. The discovery of a previously unknown companion (HAT-P-7B) to the central star (HAT-P-7) as well as confirmation of another giant planet (HAT-P-7c) orbiting outside of the retrograde planet HAT-P-7b offer new insights into how retrograde planets may form and endure.
Read more



__________________


L

Posts: 131433
Date:
RE: HAT-P-7b
Permalink  
 


Title: Properties of extrasolar planets and their host stars - a case study of HAT-P-7
Authors: Vincent Van Eylen, Hans Kjeldsen, Joergen Christensen-Dalsgaard, Conny Aerts

Data from the Kepler satellite (Q0-Q11) are used to study HAT-P-7. The satellite's data are extremely valuable for asteroseismic studies of stars and for observing planetary transits; in this work we do both. An asteroseismic study of the host star improves the accuracy of the stellar parameters derived by Christensen-Dalsgaard et al. (2010), who followed largely the same procedure but based the analysis on only one month of Kepler data. The stellar information is combined with transit observations, phase variations and occultations to derive planetary parameters. In particular, we confirm the presence of ellipsoidal variations as discovered by Welsh et al. (2010), but revise their magnitude, and we revise the occultation depth (Borucki et al. 2009), which leads to different planetary temperature estimates. All other stellar and planetary parameters are now more accurately determined.

Read more (933kb, PDF)



__________________


L

Posts: 131433
Date:
HAT-P-7
Permalink  
 


Title: A Common Proper Motion Stellar Companion to HAT-P-7
Authors: Norio Narita, Yasuhiro H. Takahashi, Masayuki Kuzuhara, Teruyuki Hirano, Takuya Suenaga, Ryo Kandori, Tomoyuki Kudo, Bun'ei Sato, Ryuji Suzuki, Shigeru Ida, Makiko Nagasawa, Lyu Abe, Wolfgang Brandner, Timothy D. Brandt, Joseph Carson, Sebastian E. Egner, Markus Feldt, Miwa Goto, Carol A. Grady, Olivier Guyon, Jun Hashimoto, Yutaka Hayano, Masahiko Hayashi, Saeko S. Hayashi, Thomas Henning, Klaus W. Hodapp, Miki Ishii, Masanori Iye, Markus Janson, Gillian R. Knapp, Nobuhiko Kusakabe, Jungmi Kwon, Taro Matsuo, Satoshi Mayama, Michael W. McElwain, Shoken Miyama, Jun-Ichi Morino, Amaya Moro-Martin, Tetsuo Nishimura, Tae-Soo Pyo, Eugene Serabyn, Hiroshi Suto, Michihiro Takami, Naruhisa Takato, Hiroshi Terada, Christian Thalmann, Daigo Tomono, Edwin L. Turner, Makoto Watanab, John P. Wisniewski, et al. (4 additional authors not shown)

We report that HAT-P-7 has a common proper motion stellar companion. The companion is located at \sim3.9 arcsec to the east and estimated as an M5.5V dwarf based on its colours. We also confirm the presence of the third companion, which was first reported by Winn et al. (2009), based on long-term radial velocity measurements. We revisit the migration mechanism of HAT-P-7b given the presence of those companions, and propose sequential Kozai migration as a likely scenario in this system. This scenario may explain the reason for an outlier in the discussion of the spin-orbit alignment timescale for HAT-P-7b by Albrecht et al. (2012).

Read more (1610kb, PDF)



__________________


L

Posts: 131433
Date:
HAT-P-7 System
Permalink  
 


Title: The EVIL-MC Model for Ellipsoidal Variations of Planet-Hosting Stars and Applications to the HAT-P-7 System
Authors: Brian K. Jackson, Nikole K. Lewis, Jason W. Barnes, L. Drake Deming, Adam P. Showman, Jonathan J. Fortney

We present a new model for Ellipsoidal Variations Induced by a Low-Mass Companion, the EVIL-MC model. We employ several approximations appropriate for planetary systems to substantially increase the computational efficiency of our model relative to more general ellipsoidal variation models and improve upon the accuracy of simpler models. This new approach gives us a unique ability to rapidly and accurately determine planetary system parameters. We use the EVIL-MC model to analyse Kepler Quarter 0-2 (Q0-2) observations of the HAT-P-7 system, an F-type star orbited by a nearly Jupiter-mass companion. Our analysis corroborates previous estimates of the planet-star mass ratio q = (1.10 ± 0.06) x 10^(-3), and we have revised the planet's dayside brightness temperature to 2680 +10/-20 K. We also find a large difference between the day- and nightside planetary flux, with little nightside emission. Preliminary dynamical+radiative modelling of the atmosphere indicates this result is qualitatively consistent with high altitude absorption of stellar heating. Similar analyses of Kepler and CoRoT photometry of other planets using EVIL-MC will play a key role in providing constraints on the properties of many extrasolar systems, especially given the limited resources for follow-up and characterisation of these systems. However, as we highlight, there are important degeneracies between the contributions from ellipsoidal variations and planetary emission and reflection. Consequently, for many of the hottest and brightest Kepler and CoRoT planets, accurate estimates of the planetary emission and reflection, diagnostic of atmospheric heat budgets, will require accurate modelling of the photometric contribution from the stellar ellipsoidal variation.

Read more (1026kb, PDF)



__________________


L

Posts: 131433
Date:
RE: HAT-P-7b
Permalink  
 


Two teams of astronomers have found a planet outside the solar system that might be orbiting backwards compared to its stars rotation, a discovery that could shed light on how unique the relatively perfect alignment of our solar system is compared to that of other planetary systems.
By measuring the rotation of the parent star of HAT-P-7b, a planet discovered in 2008, the two teams, including one led by MIT assistant professor of physics Joshua Winn and the other by Norio Narita at the National Astronomical Observatory of Japan, found that the orbit is tilted by at least 86 degrees with respect to the stars equator. The drastic misalignment of the exoplanet, or planet outside our solar system, suggests that it is either rotating over both poles of its star or actually rotating backwards, a phenomenon that does not occur in our solar system and that could help explain why life thrives here.

Read more

__________________


L

Posts: 131433
Date:
Exoplanet HAT-P-7b
Permalink  
 


Title: First Evidence of a Retrograde Orbit of Transiting Exoplanet HAT-P-7b
Authors: Norio Narita, Bun'ei Sato, Teruyuki Hirano, Motohide Tamura
(Version v2)

We present the first evidence of a retrograde orbit of the transiting exoplanet HAT-P-7b. The discovery is based on a measurement of the Rossiter-McLaughlin effect with the Subaru HDS during a transit of HAT-P-7b, which occurred on UT 2008 May 30. Our best-fit model shows that the spin-orbit alignment angle of this planet is \lambda = -132.6 (+10.5, -16.3) degrees. The existence of such a retrograde planet have been predicted by recent planetary migration models considering planet-planet scattering processes or the Kozai migration. Our finding provides an important milestone that supports such dynamic migration theories.

Read more (305kb, PDF)

__________________
1 2  >  Last»  | Page of 2  sorted by
Quick Reply

Please log in to post quick replies.



Create your own FREE Forum
Report Abuse
Powered by ActiveBoard