* Astronomy

Blobrana · L

RE: Transiting Exoplanet Systems

Blobrana · L

Title: Characterising the Atmospheres of Transiting Rocky Planets Around Late-type Dwarfs
Authors: E. Pallé (IAC), M. R. Zapatero Osorio (CAB, CSIC-INTA), A. García Muñoz (IAC)

Visible and near-infrared spectra of transiting hot Jupiter planets have recently been observed, revealing some of the atmospheric constituents of their atmospheres. In the near future, it is probable that primary and secondary eclipse observations of Earth-like rocky planets will also be achieved. The characterisation of the Earth's transmission spectrum has shown that both major and trace atmospheric constituents may present strong absorption features, including important bio-markers such as water, oxygen and methane. Our simulations using a recently published empirical Earth's transmission spectrum, and the stellar spectra for a variety of stellar types, indicate that the new generation of extremely large telescopes, such as the proposed 42-meter European Extremely Large Telescope(E-ELT), could be capable of retrieving the transmission spectrum of an Earth-like planet around very cool stars and brown dwarfs (Teff < 3100 K). For a twin of Earth around a star with Teff around 3100 K (M4), for example, the spectral features of water vapour, methane, carbon dioxide, and oxygen in the wavelength range between 0.9 and 2.4 micron can simultaneously be detected within a hundred hours of observing time, or even less for a late-M star. Such detection would constitute a proof for the existence of life in that planet. The detection time can be reduced to a few hours for a super-Earth type of planet with twice the Earth's radius.

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Blobrana · L

Title: Evidence of Possible Spin-Orbit Misalignment Along the Line of Sight in Transiting Exoplanet Systems
Authors: Kevin C. Schlaufman

Of the 26 transiting exoplanet systems with measurements of the Rossiter-McLaughlin (RM) effect, eight have now been found to be significantly spin-orbit misaligned in the plane of the sky. Unfortunately, the RM effect only measures the angle between the orbit of a transiting exoplanet and the spin of its host star projected in the plane of sky, leaving unconstrained the compliment misalignment angle between the orbit of the planet and the spin of its host star along the line of sight. I use a simple model of stellar rotation benchmarked with observational data to statistically identify ten exoplanet systems from a sample of 75 for which there is likely a significant degree of misalignment along the line of sight between the orbit of the planet and the spin of its host star. I find that HAT-P-7, HAT-P-14, HAT-P-16, HD 17156, Kepler-5, Kepler-7, TrES-4, WASP-1, WASP-12, and WASP-14 are likely spin-orbit misaligned along the line of sight. All ten systems have host stellar masses M_star in the range 1.2 M_sun <= M_star <= 1.5 M_sun, and the probability of this occurrence by chance is less than one in ten thousand. In addition, the planets in the candidate misaligned systems are preferentially massive and eccentric. The coupled distribution of misalignment from the RM effect and from this analysis suggests that transiting exoplanets are more likely to be spin-orbit aligned than expected given predictions for a transiting planet population produced entirely by planet-planet scattering or Kozai cycles and tidal friction. For that reason, there are likely two populations of close-in exoplanet systems: a population of aligned systems and a population of apparently misaligned systems in which the processes that lead to misalignment or to the survival of misaligned systems operate more efficiently in systems with massive stars and planets.

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