Chexo Schedule - 2019 Sep 6
The version of the browser you are using is no longer supported. Please upgrade to a supported browser.Dismiss

View only
Chexo Schedule
9:00-9:45Arrive/Coffee/Poster Set-Up
9:45-10:00Opening Remarks
10:00-10:45David SingJHUInvited Talk
10:45-11:00Maryam Haytham EsmatSpace Telescope Science Institute and Lycoming CollegeSimulating James Webb Space Telescope Observations for Transiting ExoplanetsThis project involves using MIRaGe, a python package developed at STScI that is used to simulate NIRCam, NIRISS, and FGS data, to create TSO datasets that can be used to test the JWST calibration pipeline as well as TSO analysis software.
11:00-11:15Kristin Showalter SotzenJHU Applied Physics LaboratoryTransmission Spectroscopy of WASP-79b from 0.6 to 5.0 micronsAs part of the PanCET program, we have conducted a spectroscopic study of WASP-79b, a Jupiter-size exoplanet orbiting an F-type star in Eridanus with a period of 3.66 days. Building on the original WASP and TRAPPIST photometry of Smalley et al (2012), we have performed reduction and light curve fitting on HST/WFC3 (1.125 – 1.650 um) and Magellan/LDSS-3C (0.6 – 1 um) observations for WASP-79b, and we have conducted photometric extraction on Spitzer observations (3.6 and 4.5 um). Additionally, we will validate our light curve against the transit depths estimated from the Sector 4 and Sector 5 TESS observations of this exoplanet. We will present our light curve results, which show indications of a water feature at 1.4 um. Finally, we will discuss the results of an atmospheric retrieval analysis and simulated JWST data based on best-fit retrieval models for these data. The suggested water feature makes WASP-79b a target of interest for the approved JWST Director’s Discretionary Early Release Science (DD ERS) program, with ERS observations planned to be the first to execute in Cycle 1. Transiting exoplanets were recently approved for 78.1 hours of data collection, and with the delay in the JWST launch, WASP-79b is now a target for the Panchromatic Transmission program. This program will observe WASP-79b for 42 hours in 4 different instrument modes over 0.8-5.0 um, at which time WASP-79b will be the best-characterized exoplanet to date.
11:15-11:30Ashley BakerUniversity of PennsylvaniaA Novel Multiband Photometer for Exoplanet Atmospheric CharacterizationWith TESS and ground-based surveys searching for rocky exoplanets around cooler, nearby stars, the number of Earth-sized exoplanets that are well-suited for atmospheric follow-up studies will increase significantly. For atmospheric characterization, the James Webb Space Telescope will only be able to target a small fraction of the most interesting systems, and the usefulness of ground-based observatories will remain limited by a range of effects related to Earth's atmosphere. Here, we explore a new method for ground-based exoplanet atmospheric characterization that relies on simultaneous, differential, ultra-narrow-band photometry. The instrument uses a narrow-band interference filter and an optical design that enables simultaneous observing over two 0.3 nm wide bands spaced 1 nm apart. We consider the capabilities of this instrument in the case where one band is centered on an atmospheric molecular absorption feature and the other on an absorption free region. We present the design of a prototype instrument we built and the detection of a 50 ppm simulated transit signal in the laboratory. We also present data from an on-sky test with the instrument, demonstrating the ease of use of the compact instrument design.
11:30-11:45Avi MandellNASA GSFCMIRECLE: Exploring the Nearest M-Earths Through Ultra-Stable Mid-IR Transit and Phase-Curve Spectroscopy We present MIRECLE (MIR Exoplanet CLimate Explorer), a moderately sized (2 meters) cryogenic telescope with broad wavelength coverage (4 - 25 um) and ultra-stable detectors capable of efficiently characterizing a statistically significant sample of terrestrial planets around ultra-cool dwarfs, many of which will be in their host stars's habitable zones. Spectroscopic characterization of terrestrial atmospheres will provide constraints for the distribution of planets with tenuous vs. substantial atmospheres, on the inner and outer edges of the habitable zone, and climate models to assess the potential for habitability. For the few brightest targets, the detection of specific combinations of molecules would provide evidence of biosignatures. For all other targets, this comprehensive survey would filter out the airless, desiccated, or lifeless worlds, thus providing a subset of potentially habitable worlds ready for in-depth atmospheric characterization using a larger aperture telescope.
11:45-12:00Flash Talks
12:00-1:30Lunch Break
1:30-1:45Julien GirardSTScIThe 2019 WFIRST (CGI) Exoplanet Imaging Data ChallengeThe 2019 WFIRST Exoplanet Imaging Data Challenge ( will be launched in mid October just prior to this Spirit of Lyoon October 16-17t Conference (at the Flatiron Institute in NY Hack Day on October 20 in Tokyo). It is a unique opportunity for exoplanet scientists of all backgrounds and experience levels to get acquainted with realistic WFIRST CGI simulated data. Candidate teams will be invited to recover the components of an exoplanetary system from two to six imaging epochs throughout the mission life time with with Hybrid-Lyot Coronagraph (HLC) and Star Shade (SS) coronagraph. CGI’s contrast regimes at 10^-8 to 10^-9 is unlike what the community is used to from the ground. To perform accurate orbital fitting with a few imaging epochs, we will provide the corresponding simulated radial velocity data. Possible hurdles to overcome are contamination sources (stellar, extragalactic, exozodiacal light, etc). Do you want to know what it feels like to directly image a Neptune-mass planet in reflected light? Then, join our data challenge! It is an excellent way to get involved with the intricacies of the first spaceborne high contrast exoplanet imaging mission, as a pathfinder to future flagship missions.
1:45-2:00Michele L. SilversteinNASA Goddard Space Flight CenterSizing Up Red Dwarfs in the Solar NeighborhoodWe present the Systematic Investigation of Radii and Environments of Nearby Stars (SIRENS) project: the characterization of 1593 stars including 1504 red dwarfs within 25 parsecs. The primary goal is to provide radii for the all-sky sample of single and spatially resolved primary red dwarfs with accurate, pre-Gaia, trigonometric parallaxes placing them within 25 parsecs. We combine these parallaxes with optical to mid-infrared photometry and apply spectral energy distribution model fitting to determine temperature, luminosity, and radius for the sample. Comparison of our results for 26 stars to their radii determined using interferometry indicates a median absolute difference of only 6%. The result is a set of fundamental parameters for a comprehensive all-sky sample of red dwarfs spanning an unprecedented range of red dwarf spectral types, from approximately M0 to the end of the stellar main sequence at L2.5. We reveal trends in the dispersion and slope of the radius-effective temperature relationship of red dwarfs and link these trends to star spot coverage. We demonstrate that an effective temperature-radius relation cannot be used to accurately or precisely calculate either of these parameters without additional information --- the radius of a star at effective temperatures greater than 2850 K can span a ~0.35 solar radius range. We compare the core main sequence sample to control samples of 53 pre-main sequence stars and 36 cool subdwarfs to identify 56 new young star candidates and 31 cool subdwarf candidates within 25 parsecs using radius arguments. The data required for our technique are photometry and parallaxes only, and form the basis for a much larger future effort using Gaia data combined with infrared data for low-mass stars over the entire sky.
2:00-2:25Christian EistrupUniversity of VirginiaFrom Midplane to Planets. The Chemical Fingerprint of a Disk.Planets are formed in the midplanes of protoplanetary disks, and the chemical composition in the midplanes largely set the chemical composition of the forming planets. However, the chemistry in midplanes remains largely unconstrained. I will present results from chemical modeling of these planet-forming disk midplanes, with a focus on how the carbon-to-oxygen ratio of the planet-forming material here can change over time as a consequence of chemical reactions leading to chemical evolution. This evolution may have a profound impact on the final compositions of planets, exoplanets, and comets. Understanding the evolution is crucial for relating exoplanetary atmospheric abundances to where and when these exoplanets were formed.
2:25-2:50Jaehan BaeCarnegie DTMA perfect testbed for planet-disk interaction: two giant protoplanets in resonance shaping the PDS 70 protoplanetary diskWhile numerical simulations have been playing a key role in the studies of planet-disk interaction, testing numerical results against observations has been limited so far. With the two directly imaged protoplanets embedded in its circumstellar disk, PDS 70 offers a perfect testbed for planet-disk interaction studies. Using two-dimensional hydrodynamic simulations we show that the observed features can be well explained with the two planets in formation, providing strong evidence that previously proposed theories of planet-disk interaction are in action, including particle trapping, size segregation, and filtration. We discuss potential implications to planet formation in the solar system and mature extrasolar planetary systems.
2:50-3:05Jacob HamerJHUHot Jupiters are Tidally Destroyed While Their Hosts are on the Main SequenceOn their extreme orbits, hot Jupiters represent the perfect testing ground for our understanding of tidal dissipation. While cooler giant planets are often observed with non-zero eccentricities, the small, circular orbits of hot Jupiters suggest that tidal dissipation plays a significant role in their formation. Once on these circular orbits, tidal dissipation should allow the rapidly orbiting planet to transfer angular momentum to the slowly spinning host star, which may result in the inspiral of the planet. However, we do not yet know if hot Jupiters survive the main sequence of their host stars, as the efficiency of this process is uncertain by orders of magnitude, and because tidal decay has never been unambiguously observed. If tidal decay causes hot Jupiters to be destroyed while their host stars are on the main sequence, then hot Jupiter hosts should be relatively young compared to a sample of similar field stars not hosting hot Jupiters. We use data from Gaia DR2 to show that hot Jupiter hosts have a smaller Galactic velocity dispersion than similar stars without hot Jupiters. As Galactic velocity dispersion is correlated with the age of a population, this implies that hot Jupiter hosts are a relatively younger population due to the inspiral of their planets. This observation requires that the tidal quality factor be less than 10^7.
3:05-3:35Coffee Break/Poster Session
3:35-4:00Kevin SchlaufmanJohns Hopkins UniversityThe Typical Terrestrial-mass Planet Discovered by Transit Surveys and Its Implications for Planet Formation and EvolutionAll mass--radius relations for low-mass planets published to date have been affected by observational biases. Since planet occurrence and primordial atmospheric retention probability increase with period, the "typical" planet discovered by transit surveys may bear little resemblance to the short-period planets sculpted by atmospheric escape ordinarily used to calibrate mass--radius relations. I'll present an occurrence-weighted mass--radius relation for the typical low-mass planets in the Galaxy observed so far by transit surveys. Even at M = 1 M_Earth, to explain its observed radius the typical planet must have 1% of its mass in a H/He atmosphere. Unlike the terrestrial planets in our own solar system that finished forming long after the protosolar nebula was dissipated, these terrestrial-mass planets discovered in transit surveys must have formed early in their systems' histories. The existence of significant H/He atmospheres around 1 M_Earth planets confirms an important prediction of the core--accretion model of planet formation. It also implies that such planets can retain their primordial atmospheres and requires an order-of-magnitude reduction in the fraction of incident XUV flux converted into work usually assumed in photo-evaporation models. Because the short-period planets likely to be discovered by NASA's Transiting Exoplanet Survey Satellite (TESS) are not representative of the Galaxy's planet population, it will be important to use occurrence-weighting when considering the implications for models of planet formation of the masses and radii of TESS discoveries.
4:00-4:15Gabrielle SuissaNASA Goddard Space Flight CenterModeling transit spectra for M-star Aqua-Earths using GCMsThe hunt for water-rich Earth-sized exoplanets around low-mass stars is rapidly gaining attention because of their potential for both detectability and habitability. Understanding the atmospheres of these planets and determining the optimal strategy for characterizing them through transmission spectroscopy with our upcoming instrumentation is essential if we are ever to constrain their environments. For this study, we present simulated transmission spectra of tidally locked Earth-sized ocean-covered planets around M and K stars, utilizing GCM modeling results previously published by Kopparapu et al. (2017) as inputs for our radiative transfer calculations performed using NASA’s Planetary Spectrum Generator (Villanueva et al. 2018). We identify trends in the expected transmission spectral signal of H2O features. These trends allow us to calculate the exposure times necessary to detect water vapor in the atmospheres of aquaplanets with the upcoming James Webb Space Telescope (JWST) as well as several future flagship space telescope concepts under consideration (LUVOIR and OST) for the brightest M- and K-type stars from the TESS Input Catalog (TIC). Our calculations reveal that transmission spectra for water-rich Earth-sized planets around low-mass stars will be dominated by clouds, with spectral features < 20 ppm, and only a small subset of TIC stars would allow for the characterization of an ocean planet in the habitable zones. We thus present a careful prioritization of targets that are most amenable to follow-up characterizations with next-generation instrumentation, in order to assist the community in efficiently utilizing precious telescope time.
4:15-4:30Sarah Moran Johns Hopkins University Chemistry of Temperate Exoplanet Atmospheric Hazes from the Laboratory Very little experimental work has been done to explore the properties of photochemical hazes formed in exoplanets. With now thousands of exoplanet discoveries, this untapped phase space merits exploration. I will present the first results of the composition of haze particles produced from exoplanet laboratory studies. We used very high resolution mass spectrometry to measure the chemical components of the solid particles. Many complex molecular species with general chemical formulas CwHxNyOz were detected. Molecules of interest discovered in the data include those with prebiotic implications, including amino acids, nucleobases, and simple sugars.
Additionally, we found that the experimental exoplanetary haze analogues exhibit diverse solubility characteristics, which may provide insight into the possibility of further chemical or physical alteration of photochemical hazes in the atmospheres of super-earth and mini-neptune exoplanets. These particles can help us better understand chemical processes happening in exo-atmospheres and are a possible source of prebiotic chemistry on distant worlds.
4:30-4:45McCullen SandoraU PennBiosignature Surveys and Exoplanet YieldsUpcoming biosignature searches focus on indirect indicators to infer the presence of life on other worlds. Aside from just signaling the presence of life, however, proposed biosignatures also contain information about the state that a planet’s biosphere has achieved. This additional information can be used to measure what fractions of planets achieve certain key stages, corresponding to the advent of life, photosynthesis, multicellularity, and technological civilization. We forecast the uncertainties of each measurement for upcoming surveys, and outline the key factors that determine these uncertainties. The dependence on survey size, likeliness of the transition, and several measures of degrees of confidence are discussed, as well as how combining data from different missions can affect the inference. Our analysis can be used to determine policy recommendations for mission design to minimize these measurement uncertainties.
4:45-5:00Closing Remarks