Aavso paper Session I sunday Sunday, May 22, 2011, 9: 30 am – 12: 00 pm

128

Extrasolar Planets: Detection and Characterization

Poster Session

Essex Ballroom

8:00 AM - 7:00 PM

Using an array of modest ground-based telescopes, the MEarth Project is photometrically monitoring nearby mid-to-late M dwarfs with sufficient precision to detect transiting exoplanets as small as twice the radius of the Earth. Having a reliably characterized input catalog of 2,000, high proper-motion, low-mass stars enables us to simulate our planet detection sensitivity in detail and place limits on the occurrence rate of planets orbiting mid-to-late M dwarfs. I will present preliminary results from a statistical analysis of the first 1,000 M dwarfs with MEarth light curves, including constraints on the fraction of such stars that may host super-Earth or Neptune-sized planets. Neither the Kepler Mission nor the optical radial velocity surveys probe substantial numbers of stars cooler than 3500K; the MEarth Project's occurrence rate estimates are highly complimentary to these other large efforts. Our statistical estimates will continue to improve as MEarth collects more data and we progress toward our ultimate goal of detecting a transiting super-Earth in the habitable zone of its host M dwarf. Importantly, thanks to its favorable planet-to-star contrast ratio, the atmosphere of such a habitable planet could be spectroscopically characterized using JWST.

128.02

Modeling The Detectability Of Exoplanets For The Palomar Extreme Adaptive Optics Palm-3000 System.

Rahul Patel¹, S. Metchev^1
1SUNY Stony Brook.

8:00 AM - 7:00 PM

In this study, we present the projected capabilities and detection limitations for the PALM-3000 Extreme Adaptive Optics system to directly image super-Jupiter planets around nearby stars. PALM-3000 is the new adaptive optics system for the Palomar 5 m telescope, which employs a 3366 - actuator deformable mirror and is expected to deliver contrast ratios near 107 at 1 arc second from bright stars. The PALM-3000 system will be an upgrade from the current Adaptive Optics system at Palomar and commissioning will begin in the summer of 2011. Planetary and orbital parameters (mass, eccentricity, semi-major axis) were randomly sampled from known distributions, which have been established or extrapolated from radial velocity observations. Parent stars were modeled in accordance with the stellar initial mass function (IMF) and given randomized ages and distances from Earth. Probability for detection was modeled using a Monte-Carlo simulation written in IDL. Projected contrast curves in the H band for PALM-3000 were used as the constraints for planetary detection.

128.03

Improving Transit Predictions of Known Exoplanets with TERMS

Stephen R. Kane¹, D. Ciardi¹, D. Dragomir¹, D. Fischer², G. Henry³, A. Howard⁴, E. Jensen⁵, G. Laughlin⁶, S. Mahadevan⁷, G. Pilyavsky⁷, K. von Braun¹, J. Wright^7
1NASA Exoplanet Science Institute, Caltech, ²Department of Astronomy, Yale University, ³Tennessee State University, ⁴Department of Astronomy, University of California, ⁵Dept of Physics & Astronomy, Swarthmore College, ⁶UCO/Lick Observatory, University of California, ⁷Department of Astronomy and Astrophysics, Pennsylvania State University.

8:00 AM - 7:00 PM

Transiting planet discoveries have yielded a plethora of information regarding the internal structure and atmospheres of extra-solar planets. These discoveries have largely been restricted to the low-periastron distance regime due to the bias inherent in the geometric transit probability. Monitoring known radial velocity planets at predicted transit times is a proven method of detecting transits, and presents an avenue through which to explore the mass-radius relationship of exoplanets in new regions of period/periastron space for the brightest exoplanet host stars. Here we describe transit window calculations for known radial velocity planets, techniques for refining their transit ephemerides, and present results for radial velocity planets which have been successfully monitored during predicted transit times. These methods are currently being implemented by the Transit Ephemeris Refinement and Monitoring Survey (TERMS).

128.04

Warm Spitzer Secondary Transit Photometry of Hot Jupiters HAT-P-6b, HAT-P-8b and XO-4b

Kamen 0. Todorov¹, D. Deming², H. Knutson³, A. Burrows⁴, P. Sada⁵, E. Agol⁶, J. Desert⁷, J. J. Fortney⁸, D. Charbonneau⁷, N. B. Cowan⁹, G. Laughlin⁸, J. Langton¹⁰, A. P. Showman¹¹, N. K. Lewis^11
1The Pennsylvania State University, ²NASA’s Goddard Space Flight Center, ³University of California at Berkeley, ⁴Princeton University, ⁵University of Monterrey, Mexico, ⁶University of Washington, ⁷Harvard-Smithsonian Center for Astrophysics, ⁸University of California at Santa Cruz, ⁹Northwestern University, ¹⁰Principia College, ¹¹University of Arizona.

8:00 AM - 7:00 PM

An increasing number of transiting exoplanets have been observed at secondary eclipse. By measuring the depth of these eclipses at different wavelengths it is possible to distinguish between planets that have a temperature inversion in the upper layers of their atmospheres and ones that do not. We observed XO-4b, HAT-P-6b and HAT-P-8b during secondary eclipse with the IRAC instrument on Warm Spitzer at 3.6 and 4.5 microns. We compare the resulting eclipse depths to atmospheric models with and without temperature inversions, and thereby place constraints on the properties of their day-side atmospheres and heat redistribution efficiencies. The XO-4b and HAT-P-6b eclipse depths agree best with inverted models, while HAT-P-8b exhibits no temperature inversion. Knutson et al. (2010) hypothesized a correlation between lack of a temperature inversion and host star activity. Also, Cowan & Agol (2011), investigated the dependence between planetary effective temperatures, assuming no redistribution, and heat redistribution efficiency, finding that the hottest planets re-distribute heat inefficiently. We compare our planets with the Knutson and Cowan-Agol relations, and we find that they are consistent with the Knutson et al. activity hypothesis, but they are not hot enough to test the Cowan & Agol hypothesis.

128.05

New Analyzing Tools for the Rossiter-McLaughlin Effect

TERUYUKI HIRANO¹, J. N. WINN¹, S. ALBRECHT¹, Y. SUTO², N. NARITA³, B. SATO^4
1MIT, ²The University of Tokyo, Japan, ³NAOJ, Japan, ⁴Tokyo Institute of Technology, Japan.

8:00 AM - 7:00 PM

The Rossiter-McLaughlin (RM) effect is a radial velocity anomaly during a planetary transit caused by a partial occultation of the rotating stellar disk. Measurements of the RM effect tell us the sky-projected angle between the stellar spin axis and the planetary orbital axis. This angle is associated with the dynamical history of close-in planets and so very important to test theoretical hypotheses regarding planetary migration. So far, the interpretation of the radial velocity anomaly has been based mainly on analytic approximations with limited applicability, or with numerical simulations. We have developed a new and more accurate analytic formula which specifies the RM velocity anomaly in terms of the position of the planet, the stellar spin velocity, and other intrinsic line parameters such as macroturbulence. Although our formula is derived for the case in which the radial velocity anomaly is derived from a cross-correlation analysis, the formula also gives a good agreement with the simulated results based on the forward-modeling approach that is used for spectra obtained with an iodine gas cell. We discuss the results of reanalyses of the RM effect for several selected transiting systems with our new analytic formula and show that it is a useful new tool for precise estimations of planetary parameters.

128.06

Improving the RV Precision of HET/HRS

Xuesong Wang¹, J. T. Wright^1
1Pennsylvania State University.

8:00 AM - 7:00 PM

We present our work on improving the radial velocity precision of the High Resolution Spectrograph (HRS) on Hobby-Eberly Telescope (HET). This stable, fiber-fed spectrograph had a reported RV precision of around 3-5 m/s. Our current precision is 3m/s, and we are pushing this limit towards 1m/s upon HET/HRS upgrades and improvement of our pipeline. Some results on newly discovered exoplanets by this pipeline are also presented.

128.07

Null Detection of a Substellar Companion to HD 149382

Jackson Norris¹, J. T. Wright¹, R. A. Wade¹, S. Mahadevan^1
1The Pennsylvania State University.

8:00 AM - 7:00 PM

Soker (1998) argued that a substellar companion may significantly influence the evolution of the progenitors of sdB stars. Recently, Geier et al. (2009) have claimed that the bright sdB star HD 149382 hosts a substellar companion with a period of 2.391 days and mass of 8-23 Jupiter masses. If true, this would have important implications for the evolution of the progenitors of sdB stars as well as the source of the UV-excess seen in elliptical galaxies. In order to verify this putative substellar companion, we obtained 40 exposures of HD 149382 over 17 days with the High Resolution Spectrograph at the Hobby-Eberly Telescope. Our data are inconsistent with the claim by Geier et al. and support the absence of the substellar companion.

128.08

IRTF/SpeX NIR Emission Spectra of WASP-1b

Heather Bloemhard¹, M. Creech-Eakman¹, P. D. Deroo², M. Zhao^2
1New Mexico Institute of Mining and Technology, ²Jet Propulsion Laboratory, California Institute of Technology.

8:00 AM - 7:00 PM

Of the more than 500 known exoplanets, the detailed chemical composition of only a handful of exoplanet atmospheres is known. We endeavor to remedy this imbalance by using ground-based spectroscopy, which has been demonstrated to reliably reproduce space-based results (Swain et al., Nature 463, 2010) while obtaining new and unexpected information. Our IRTF/SpeX SXD (0.8-2.4 micron cross-dispersed) observations of two secondary eclipses of the exoplanet WASP-1b, obtained September and October 2010, will be used to accomplish two main goals: first, to extend the application of exoplanet ground-based spectroscopy to a wider range of targets than are presently characterized; and second, to probe the temperature structure and begin to characterize the composition of the dayside of the atmosphere. We will show our data reduction steps and initial results based on the reduction method introduced by the Exospec team (Swain et al., Nature 463, 2010)

128.09

8:00 AM - 7:00 PM

The effect of stellar X-rays on their nearby gas-giant planets appear to be significant. The X-rays have been cited at the cause of excess heating of the planet which can induce mass loss. Further, several lines of argument indicate that the magnetic fields of the two bodies can interact. We report on XMM-Newton observations of the planetary host star HD 189733. The system has a close-in planet and it can potentially affect the coronal structure via interactions with the magnetosphere. We have obtained X-ray spectra and light curves during the primary transit and secondary eclipse. During transit, only variability due to weak flares is recognized. During the eclipse, we observed a significant softening of the X-ray spectrum at a level of ~3σ. Furthermore, we observed the most intense flare recorded at either epoch. This flare occurred 3 ks after the end of the eclipse. The flare decay shows several minor ignitions perhaps linked to the main event and hinting at secondary loops that are triggered by the main loop. Magnetohydrodynamic (MHD) simulations show that the magnetic interaction between planet and star enhances the density and the magnetic field in a region between the planet and the star because of their relative orbital/rotation motion. X-ray observations and model predictions are globally found in agreement, despite the quite simple MHD model and the lack of precise estimate of parameters including the alignment and the intensity of stellar and planetary magnetic fields. We discuss the significance of higher area and high spectral resolution on such observations.

128.10

The Value of K2 in Determining Interior Composition of Terrestrial Planets

Adam Maxwell¹, D. Ragozzine², L. A. Rogers³, S. Seagar⁴, L. Zeng^5
1Cambridge School Of Weston, ²Institute for Theory and Computation, Smithsonian Astrophysical Observatory, ³Department of Physics, massachusetts Institute of Technology, ⁴Department of Earth, atmospheric and Planetary Sciences, Massachusetts Institute of Technology, ⁵Department of Astronomy, Harvard University.

8:00 AM - 7:00 PM

The composition of exoplanets is interesting for theoretical reasons and for possible implications of planet habitability. Currently, only the mass and radius are able to be used to estimate the composition of well-understood transiting exoplanets. With only these parameters to depend on, there is still significant uncertainty in the interior composition, as there are many possible interior compositions for a planet with a given mass and radius. Another observable parameter that could be used is k2, the planetary Love number, a measurement of the central condensation of a planet (equivalent to J2) that could be measurable in the future via repeated transit measurements (Ragozzine & Wolf 2009, Batygin et al. 2009). We have developed a program that calculates the k2 of planets from their interior density distribution by numerically integrating the Clairaut-Radau equation. The model has been applied to a large sample of terrestrial planets ranging from 0.5-8 Earth masses and 0.5-5 Earth radii. These sample planets have a wide variety of compositions iron, rock, ice, and gas (from Rodgers & Seager 2009 and Zeng & Seager 2008) to explore how k2 can be used to break the degeneracy of interior composition, even for model planets with well-known masses and radii (see also Kramm et al. 2011). We will present the value of k2 measurements in narrowing the range of possible interior structures of terrestrial planets.  We will make the software that calculates k2 available for theorists to use in related studies of exoplanets.

128.11

The University of Arizona Astronomy Club Observations of Transiting Extrasolar Planets TrES-3b and TrES-4b

Jake Turner¹, K. Hardegree-Ullman¹, B. Smart¹, A. Walker-LaFollette¹, K. Cunningham¹, E. E. Hardegree-Ullman², B. Crawford¹, J. Mueting¹, T. Carleton¹, K. Schwarz¹, A. Robertson¹, B. Guvenen¹, A. Towner¹, C. Austin¹, T. Henz¹, D. Keys¹, K. Johnson^1
1University of Arizona, ²Rensselaer Polytechnic Institute.

8:00 AM - 7:00 PM

Using the Steward Observatory 61" Kuiper Telescope, The University of Arizona Astronomy Club observed extrasolar planets TrES-3b and TrES-4b. We observed the planets with the Harris-B, V, and R filters as they transited their parent stars during the months of May-July 2009. The main goal of this project was to get undergraduates involved with a research astronomy project and allow them to gain experience beyond what they would receive in the classroom. Many of the team members were introduced to astronomical observing techniques and data reduction using IRAF. Part of the project involved determining the optimum number of flat-field and bias frames required for image calibrations. With our results, we have been able to confirm and refine previously published values for the planets' orbital inclination, mass, radius, and density.