The following are talks given by the ExoExplorers and ExoGuides. Recordings of the webinars, along with transcripts, will be posted as soon as possible after the events. When available, slides may be downloaded by clicking on the talk title.
April 16, 2021 - ExoExplorer Science Series
- David Coria (U Kansas)
The Missing Link: Connecting Exoplanets and Galactic Chemical Evolution via Stellar Abundances
Video | Transcript (coming soon)+ more
Abstract: This research project seeks to: (1) test the feasibility of determining stellar ages from isotopic measurements; and (2) identify how unexplored stellar abundances correlate with galactic chemical evolution, formation, interior, age, metallicity, activity, and planetary properties for a wide range of host stars. Past isotopic searches have been hindered by limited sensitivity & resolution, strong telluric absorption, and the opacity due to millions of other molecular absorption lines that dominate the observed spectrum of cool stars. Now, however, isotopic abundance analysis is not only possible via high resolution spectroscopy but is also the next logical step for many cool stars. I am measuring the first multi-isotopic (carbon monoxide) abundances in a sample of FGKM stars, to identify possible discrepancies in planetary chemical evolution and accretion models. These isotopic abundance measurements may provide a new means of determining stellar ages and help identify the “missing link” between current Galactic Chemical Evolution models and inconsistent observations. Since most of spectral lines useful in isotopic analysis have low statistical significance and are barely discerned by eye when considered individually, I use a custom list of the strongest lines and create a single line profile for each isotopologue. We create a single, high- S/N line profile by taking the weighted mean, after continuum-normalizing, of each line to create a stacked absorption line. I then create corresponding line profiles for synthetic stellar models corresponding to various enrichments of the targeted isotopologue and compare them to the observed spectra in order to determine final abundances. I will repeat this process for a sample of solar twins, stars in FGK(+M) binaries, stars in known moving groups, and (eventually) any exoplanet host stars that exhibit isotopic signatures. This will provide host star parameters for the currently lacking database as well as the necessary foundations for corollary exoplanet characterization studies and ultimately contribute to the exploration of galactic, stellar, and planetary origins and evolution.
- Jason Williams (USC/Carnegie)
The Design and Construction of Henrietta, a high-precision low resolution near-infrared spectrograph to explore exoatmospheres
Video | Transcript (coming soon)+ more
Abstract: When JWST comes online in 2022, it will usher in a golden age of exoatmosphere characterization. Given that available time for exoatmosphere studies will be limited with JWST, it will be impossible for it to survey most exoplanet atmospheres. Thus, it is critically important not only that we have the capability to prioritize the most promising targets for JWST follow-ups, but also multiple instruments available to study the multitude of targets JWST won’t get a chance to survey. These considerations have led to the design of Henrietta, a high-precision, low resolution near-infrared spectrograph for the 1-m Swope Telescope at Las Campanas Observatory. I will talk about why high-precision ground-based spectrophotometry is so challenging in the infrared and how Henrietta’s design choices seek to mitigate these issues. If successful, Henrietta will operate near the photon noise limit and will have ample amounts of telescope time. This will not only provide a consistent stream of targets to JWST, but will also be extremely scientifically productive in its own right - allowing us to begin to place exoplanet atmospheres in a statistical context - and serve as a pathfinder instrument for future ground-based exoatmosphere instruments.
- David Coria (U Kansas)
March 12, 2021 - ExoExplorer Science Series||
- Quang Tran (UT Austin)
Establishing the Epoch of Giant Planet Migration
Abstract: Most giant planets are expected to have formed beyond the water ice line where their assembly is most efficient. The presence of giant planets interior to ~3 AU around Sun-like stars indicates that inward orbital migration is likely a common phenomenon. However, the processes by which these gas giants arrived at their present-day locations are poorly constrained because radial velocity and transit surveys have largely avoided young stars. As a result, our knowledge of giant planet statistics is primarily confined to old ages (~1-10 Gyr) after most migration has terminated. One solution to find planets around young stars is to move from optical RVs to the near-infrared (NIR), where jitter is reduced as starspot-to-stellar photosphere contrasts are lower than in the optical. In 2018 we launched a precise RV survey of over one hundred intermediate-age (~20-200 Myr) GK dwarfs with the Habitable-Zone Planet Finder near-infrared spectrograph (HPF) at McDonald Observatory's Hobby Eberly Telescope to determine the timescale and dominant physical mechanism of giant planet migration. The Epoch of Giant Planet Migration survey aims to improve our understanding of how and when giant planets migrate to small separations. In this talk, I will summarize results from the first 14 months of this program. We find that RV scatter is significantly reduced in the NIR compared to the optical, facilitating the search for planets around young, active stars.
- Amy Glazier (UNC Chapel Hill)
Constraints on Post-Superflare Exo-Auroral Emission with SOAR and the Evryscope Fast Transient Engine
Abstract: High-energy particles from M-dwarf superflares -- flares with energy greater than or equal to 1033 erg -- can dramatically impact habitable-zone planets around these cool stars, with possible effects including the excitation of intense aurorae as particles interact with planetary atmospheres. Prior work has demonstrated that Earthlike atmospheres can produce excess emission in M-dwarf spectra, with the star/planet contrast ratio increasing by orders of magnitude in the green 5577-Å auroral line to levels potentially detectable by future surveys. The Evryscopes are gigapixel-scale telescope arrays at Mount Laguna Observatory and Cerro-Tololo Inter-American Observatory; these systems are coupled with the Evryscope Fast Transient Engine (EFTE), which scans Evryscope images in real time for transient phenomena. Together, these systems have the unprecedented ability to identify superflares across the entire sky as they begin, enabling rapid spectroscopic follow-up. With the Evryscopes' all-sky coverage, far more -- and far brighter -- flares are observable than in surveys that focus on individual targets. Using the Goodman spectrograph on the 4.1-m SOAR telescope, we follow the spectroscopic evolution of M-dwarf superflares as they happen, and build a pathfinder survey to constrain upper limits on possible auroral emission from impacted planets. We present our survey here.
February 12, 2021 - ExoExplorer Science Series
- Caprice Phillips (OSU)
Detecting Biosignatures In Gas Dwarf Planet Atmospheres With JWST
Abstract: No Solar System analog planet to super-Earths exists, a class of exoplanets with masses 2-10x Earth’s mass which can retain a hydrogen atmosphere. Super-Earth atmospheres can have different compositions from nitrogen and oxygen dominated atmosphere of Earth. The James Webb Space Telescope (JWST) will offer unprecedented insight into the atmospheric composition of potentially habitable super-Earths through transmission and emission spectroscopy. I will present work on the investigation of NH3 (ammonia, a potential biosignature) detectability on super-Earths with an H2-dominated atmosphere using the Mid-Infrared Instrument (MIRI) and the Near InfraRed Spectrograph (NIRSpec) on the upcoming JWST mission. We use a radiative transfer code, petitRADTRANS, to generate synthetic spectra of optimal targets for observations given their proximity to Earth (<50 pc), radii (1.7-3.36 Earth radii), and equilibrium temperature (< 450 K). I will review the constraints of the MIRI LRS Instrument (flux ratio contrast of host star and planet ~ 10^-4), and discuss optimal targets for this instrument. For NIRSpec, I explore how varying cloud conditions, mean molecular weights (MMWs), and NH3 mixing ratios affects spectral features. Finally, I will discuss the use of PandExo to simulate mock observations with JWST and the detection significance findings for ammonia features with transmission spectroscopy.
- Samson Johnson (OSU)
Science Enabled by the Roman Galactic Exoplanet Survey
Abstract: The Nancy Grace Roman Space Telescope (Roman) will perform its Galactic Exoplanet Survey when it launches in the mid-2020's. With this first space-based microlensing survey, Roman will be sensitive to planets with orbital separations from roughly 1 AU to those unbound from any host star with masses as low as ten percent that of Earth's. The Roman Galactic Exoplanet Survey will be similar in scale to the Kepler mission, and will produce statistics on exoplanet demographics vital in improving planet formation models that are otherwise inaccessible. In this talk, I will give a brief overview of the Roman Galactic Exoplanet Survey and how it will use microlensing to detect these planets. I will highlight some of the unique insights Roman will give us, including its ability to detect Earth-analog systems and what it can teach us about the presence of free-floating planets in our Galaxy.
January 15, 2021 - ExoGuide Talk