Found 31 talks width keyword exoplanets

Tuesday September 12, 2017
Dr. Monika Lendl
Austrian Academy of Sciences, Space Research Institute


Planetary transits have proven to be one of the most efficient means of finding planets outside the Solar system, counting over 2500 exoplanet discoveries. These transiting planets are paramount for the study of exoplanet atmospheres as the stellar light is filtered through the planetary atmosphere during transit and planetary absorption signatures become imprinted on the stellar spectrum. Observations of hot-Jupiter transmission spectra have become increasingly numerous and reliable throughout recent years, allowing detailed constrains on the planet's physical and chemical atmospheric properties, interactions between planet and host star, and planet formation history. While early work relied largely on space-based facilities, ground-based techniques have seen major advances recently and have become instrumental in performing an extensive and comparative study of exoplanet atmospheres. I will review the current state of knowledge, summarize recent results and discuss future prospects of exoplanet characterization, with a focus on the potential of ground-based facilities. In particular, I will present recent and new results by our team on the transmission spectra of hot Jupiters.

Thursday July 9, 2015
Mr. Néstor Espinoza
Pontificia Universidad Católica de Chile


One of the most exciting possibilities enabled by transiting exoplanets is to measure their atmospheric properties through the technique of transmission spectroscopy: the variation of the transit depth as a function of wavelength due to starlight interacting with the atmosphere of the exoplanet. Motivated by the need of optical transmission spectra of exoplanets, we recently launched the Arizona-CfA-Católica Exoplanet Spectroscopy Survey (ACCESS), which aims at studying the atmospheres of ~20 exoplanets ranging from super-Earths to hot-Jupiters in the entire optical atmospheric window using ground-based facilities. In this talk, I will present the survey, the astrostatistical challenges it poses and first results.

Thursday June 11, 2015
Dr. Federico Marocco
University of Hertforshire


 A comprehensive understanding of sub-stellar objects (brown dwarfs and extrasolar giant planets) and their population characteristics (e.g. IMF, formation history) is only possible through the robust interpretation of ultra-cool objects spectroscopy. However, the physics of ultra-cool atmospheres is complicated by a variety of challenging ingredients (dust properties, non-equilibrium chemistry, molecular opacities). Moreover, while hydrogen-burning stars stabilize on the stellar main-sequence, sub-stellar objects continuously cool down (since they lack an internal source of energy) and evolve towards later spectral types. Their atmospheric parameters are a strong function of age. In this talk I will present the spectroscopic analysis of a large sample of L and T dwarfs, complementing the spectroscopic data with astrometry from the PARSEC program, in order to constrain the sub-stellar initial mass function and formation history. I will then describe our new effort to identify and characterize a large sample of benchmark systems, combining Gaia capabilities with large area near-infrared surveys such as UKIDSS, SDSS, and VVV, in order to calibrate effectively the theoretical models.

Tuesday March 17, 2015
Mr. Bartek Gauza


Direct imaging of wide planetary mass companions provide a unique opportunity to fully characterize their spectroscopic and photometric properties. They share similar physical properties to gas giant exoplanets found by radial velocity and transit techniques, with overlapping temperatures in the range of ~1000–1500K and masses from a few to a dozen Jupiter masses. We have recently identified a young L-type companion at ~100 AU of a previously unrecognized M dwarf. We determined the parallactic distance of the system of 12.7 ± 1.0 pc. By comparison with evolutionary models we derived a mass of 73 (+20, -15) MJup for the primary, at around the substellar mass limit and 11.2 (+9.7, -1.8) MJup for the secondary, near the deuterium burning mass limit. In this talk I will present the properties of the two components of this new pair and discuss the possibilities for future thorough characterization.

Tuesday February 10, 2015
Dr. Hannu Parviainen
University of Oxford


Detection and characterisation of weak periodic signals from noisy time series is a common problem in many different fields of astrophysics. Here I detail one approach for testing whether a signal with roughly known characteristics exists in the data, using a search of secondary eclipses from Kepler-observed photometric time series as an example. The method is based on Bayesian model selection and uses Gaussian processes to model the stochastic variability in the data in non-parametric fashion.

Thursday January 29, 2015
Dr. France Allard
Centre de Recherche Astronomique de Lyon


Understanding the atmospheric and evolutive properties of very low mass stars, brown dwarfs, and gas giant exoplanets have been important challenges for modelers around the world since the discovery of the first brown dwarfs in the Pleiades cluster (Rebolo et al. 1995) and in the field (Nakajima et al. 1995). The early studies of brown dwarfs have provided rich insights into atmospheric physics, with discoveries ranging from cloud formation (Tsuji et al. 1996), methane bands (Oppenheimer et al. 1995) and ammonia bands (Delorme et al. 2008), to the formation of wasi-molecular KI-H2 absorption (Allard et al. 2007), and to disequilibrium chemistry (Yelle & Griffith 2001). New classical 1D models yield spectral energy distribution (SED) that match relatively well despite these complexities. These models have for instance explained the spectral transition from M to L, T and now Y brown dwarf spectral types (Allard et al. 2013). However, in presence of surface inhomogeneities revealed recently for a nearby (2 pc) brown dwarf (Crossfield et al. 2014), the SED may well fit even exactly, but the model parameters could be far from exact, e.g. with the effective temperature by several hundred kelvins too cool in the case of dusty brown dwarfs and young gas giant exoplanets! I will review the progress achieved in reproducing the spectral properties of very low mass stars, brown dwarfs and gas giant exoplanets, and review progress in modeling more accurately their atmospheres using Radiation HydroDynamical (RHD) simulations.

Tuesday December 2, 2014
Prof. Tsevi Mazeh
Tel Aviv University


The angle between the stellar spin axis and the orbital planetary angular momentum of a planet, also referred to as the obliquity of the system, is a matter of intense study in recent years, for the transiting planets of the Kepler mission in particular. Some evidence was found for two populations of hot Jupiters - one around cool stars with orbits well-aligned with the stellar rotational axes, and the other one around hot stars with isotropic distribution of obliquities, including planets with retrograde motion. It was suggested that the primordial planetary obliquity is isotropic, and cool stars have reached their zero-obliquity state by tidal re-alignment.

The talk will summarize the observational techniques for measuring planetary obliquities, and the different theoretical approaches to interpret this new, unexpected feature of exo-planet population. Finally, I will present a surprising statistical new result that emerges from the study of Kepler light curves of stellar rotation, suggesting the alignment of cool stars is probably not the result of tidal interaction.

Thursday October 23, 2014
Prof. Sara Seager


The discovery and characterization of exoplanets have the potential to offer the world one of the most impactful findings ever in the history of astronomy?the identification of life beyond Earth. Life can be inferred by the presence of atmospheric biosignature gases? Gases produced by life that can accumulate to detectable levels in an exoplanet atmosphere. Detection will be made by remote sensing by sophisticated space telescopes. The conviction that biosignature gases will actually be detected in the future is moderated by lessons learned from the dozens of exoplanet atmospheres studied in last decade, namely the difficulty in robustly identifying molecules, the possible interference of clouds, and the permanent limitations from a spectrum of spatially unresolved and globally mixed gases without direct surface observations. The vision for the path to assess the presence of life beyond Earth is being established.

Thursday October 2, 2014
Dr. Adam Burgasser
University of California San Diego


Over the past two decades, advances in infrared instrumentation have allowed us to identify a vast and previously unseen population of low-temperature stars, brown dwarfs and free-floating extrasolar planets, collectively called ultracool dwarfs. These sources, with surface temperatures reaching below 0ºC, encompass three new spectral classes and include some of the nearest systems to the Sun. Research in this field is now concentrating on the physical characterization of the ultracool dwarf population and application to Galactic studies. In this talk, I will summarize the recent observational advances in ultracool dwarf research, including the recent discovery of the Y dwarf spectral class. I will then describe our ongoing IRTF/SpeX survey, which has measured the low-resolution, near-infrared spectra of over 1500 late M, L and T dwarfs and uncovered new subpopulations of young (5-30 Myr) brown dwarf, metal-poor halo brown dwarfs and short-period spectral binaries.

Thursday February 20, 2014
Dr. Enric Pallé


Our group is presently conducting an observational campaign, using the 10-meter Gran Telescopio Canarias (GTC), to obtain the transmission spectrum of several exoplanets during a transit event. The GTC instrument OSIRIS is used in its long-slit spectroscopic mode, covering the spectral range of 520-1040 nm, and observations are taken using a set of custom-built slits of various, broad, widths. We integrate the stellar flux of both stars in different wavelength regions producing several light curves and fit transit models in order to obtain the star-to-planet radius ratio Rp/Rs across wavelength. A Markov Chain Monte Carlo (MCMC) Bayesian approach is used for the transit fitting. With our instrumental setup, OSIRIS has been able to reach precisions down to 250 ppm (WASP-48b, V=11.06 mag) for each color light curve 10 nm wide, in a single transit. Central transit timing accuracies have been measured down to 6 seconds.

Here, we will present refined planet parameters, the detection of planet color signatures, and the transmission spectrum of a set of know transiting exoplanets, namely: WASP-43b, HAT-P-32b, HAT-P-12b, WASP-48b. We will also discuss the capabilities and limitations of GTC with current and future instrumentation, and the role of GTC as tool for the follow up of faint Kepler targets. In particular, we will present the GTC observations of the intriguing evaporating planet KIC 12557548b, for which we performed simultaneous color light curves, and a search for alkali elements in its planetary tail. Other setups for observations (Broad and tunable filter photometry) have also been used and will be briefly discussed. The lessons learned from our GTC exoplanet observations will be discussed in the context of the E-ELT future capabilities.


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