Kepler-16b Artists concept banner <h2>Presentations</h2>


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.

ExoExplorer Science Series

Presentation Archive

ExoExplorer Munazza Alam (Carnegie Earth & Planets Laboratory)

The First NIR Transmission Spectrum of HIP 41378 f, a Low-Mass Temperate Jovian World in a Multi-Planet System (PDF - 12.6 MB)

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Abstract: The First Near-Infrared Transmission Spectrum of HIP 41378 f, a Low-Mass Temperate Jovian World in a Multi-Planet System Abstract: We present a near-infrared transmission spectrum of the long period (P=542 days), temperate (T_eq=294 K) giant planet HIP 41378 f obtained with the Wide-Field Camera 3 (WFC3) instrument aboard the Hubble Space Telescope (HST). With a measured mass of ~12 M_earth and a radius of ~9R_earth, HIP 41378 f has an extremely low bulk density (0.09 g/cm^3). We measure the transit depth with a typical precision of 84 ppm in 30 spectrophotometric channels with uniformly-sized widths of 0.018 microns. Within this level of precision, the spectrum shows no evidence of absorption from gaseous molecular features between 1.1-1.7 microns. Comparing the observed transmission spectrum to a suite of 1D radiative-convective-thermochemical-equilibrium forward models, we rule out clear, low-metallicity atmospheres and find that the data prefer high-metallicity atmospheres or models with an additional opacity source such as high-altitude hazes and/or circumplanetary rings. We explore the ringed scenario for this planet further by jointly fitting the K2 and HST light curves to constrain the properties of putative rings. We also assess the possibility of distinguishing between hazy, ringed, and high-metallicity scenarios at longer wavelengths with JWST. HIP 41378 f provides a rare opportunity to probe the atmospheric composition of a cool giant planet spanning the gap between the Solar System giants, directly imaged planets, and the highly-irradiated hot Jupiters traditionally studied via transit spectroscopy.

ExoExplorer Matt Clement (Carnegie Earth & Planets Laboratory)

Solar and Exo-Solar terrestrial planet formation: The bleak prospects for habitability around the smallest stars (PDF - 34.6 MB)

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Abstract: Solar and extra-solar terrestrial planet formation: The bleak prospects for habitability around the smallest stars Abstract: While the solar system's geologic and observational accessibility makes it an unparalleled laboratory in which to study planet formation, exoplanet science has revealed a diverse continuum of evolutionary pathways followed by other systems. Emboldened by these advancements, recent investigations have reevaluated and modernized standard models of planet formation originally based on classic solar system studies. Building from this solar system analogy, contemporary work on exoplanet formation has found that the generic terrestrial planet growth regime is highly sensitive to several key processes. Namely, these include the presence of giant planets, the radial pebble flux, and the formation location of planetary cores. Further invigorating this field, pioneering exoplanet survey missions like Kepler and TESS have spurred a prolific output of multifaceted investigations into the formation of newly detected worlds. Through these advancements, a paradigm shift has occurred in exoplanet science, wherein low-mass stars are increasingly viewed as a foundational pillar of the search for potentially habitable worlds in the solar neighborhood. However, the processes that led to the formation of this rapidly accumulating sample of systems are still poorly understood. Moreover, it is unclear whether tenuous primordial atmospheres around these Earth-analogs could have survived the intense epoch of heightened stellar activity that is typical for low-mass stars. I will summarize our understanding of rocky planet formation and volatile delivery in the solar system, and how these ideas extend to the low-mass regime. I will then present results from new simulations of in-situ planet formation across the M-dwarf mass spectrum. From these calculations, we derive leftover debris populations of small bodies that might source delayed volatile delivery. We then follow the evolution of this debris with high-resolution models of real systems of habitable zone planets around low-mass stars such as TRAPPIST-1.

ExoExplorer Leonardo dos Santos (Space Telescope Science Institute)

An open-source framework to plan and interpret observations of atmospheric escape in exoplanets (PDF - 38.6 MB)

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Abstract: The last couple of years has seen a significant increase in detections of evaporating exoplanets, owing mainly to the discovery of the metastable helium as a probe for atmospheric escape. This process is thought to be an important factor to explain features in the exoplanet population, such as the hot-Neptune desert and the radius valley. While part of exoplanet community, in general, enjoys a swath of open-source codes that help them plan and interpret observations, the same cannot be said about those who study atmospheric escape. At least, not until recently. We developed a new open-source code, named p-winds, with the objective of supplying the community with an easy to use, well-documented tool designed for observations of evaporating exoplanets. In this talk, I will discuss the motivation, implementation, and use cases for p-winds. I will also briefly discuss some recent results that benefitted from this code, and future plans in sight.

ExoExplorer Quadry Chance (University of Florida)

Toward a binary probability for every known exoplanet host star: a statistical framework with Gaia (PDF - 5.5 MB)

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Abstract: The effect of stellar multiplicity on planet formation remains an open question. Investigations carried out using high-resolution imaging and constraints from RV planet searches have indicated that planet formation can be disrupted by close binaries while being relatively unaffected by wide companions. The magnitude and distance-limited nature of those tools have left unexplored companion parameter space in our best planet sample, the Kepler survey. The Early Data Release 3 (EDR3) from the Gaia Mission includes RV measurements of over 7 million targets that can be used to probe this parameter space. Many of these stars are members of unresolved multiple star systems and the effects of these orbits are generally seen as a source of contamination in the Gaia RV catalog. We will demonstrate that the published RV error estimates can provide evidence for the existence of an unresolved stellar companion for Kepler (and other) planet hosts and place constraints on their orbital parameters.

ExoExplorer Eckhart Spalding (University of Notre Dame)

The quest for exoplanet direct imaging with ELT apertures: A hunt for companions with the Large Binocular Telescope (PDF - 58.3 MB)

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Abstract: Direct imaging of exoplanets is a promising route to finding and characterizing exoplanets in the thermal infrared. Currently the technique is most sensitive to massive, young planets on wide orbits. Innovative observing techniques are necessary to probe smaller angles from host stars, or search for older or lower-mass planets. The Large Binocular Telescope (LBT) is in a unique position to push these frontiers in preparation for the era of 30-m-class extremely large telescopes. When light is combined coherently in a "Fizeau" mode between the LBT's twin 8.4-m sub-telescopes, the facility effectively becomes a masked 22.7-m telescope. I will present an observation of the nearby star Altair in this mode, which represents the first LBT Fizeau dataset with a degree of automated phase control. These data constrain the existence of companions of 1.3 M⊙ down to an inner angle of ≈0.15", closer than any previously published direct imaging of Altair. I outline ways forward, in terms of software and physical upgrades, and post-processing with longer integration times.

ExoExplorer Romy Rodríguez Martínez (The Ohio State University)

A reanalysis of the composition of K2-106b, an ultra-short period super-Mercury candidate (PDF - 3.4 MB)

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Abstract: Super-Mercuries are a class of exoplanets with radii less than ~1.5 Re, high bulk densities and relatively large core-mass fractions (CMFs). The study of super-Mercuries will shed light on the composition of low-mass, terrestrial exoplanets as well as on the mechanisms that lead to the formation of iron-rich planets. However, only a few exoplanets have been confirmed as super-Mercuries, in part because of the challenges of obtaining the precise stellar and planetary parameters required to confirm them. I present a reanalysis of the K2-106 system, which contains an ultra-short period, super-Mercury candidate with a density from the literature of 13.1 (+5.4 -3.6) g/cc, approximately twice the density of Earth. We globally model extant photometry and radial velocity of the system and derive a planetary mass and radius that leads to a considerably lower density than previously reported. We derive the host star’s Fe, Mg and Si abundances and combine them with planet interior models to infer the CMF and interior composition of K2-106b. Using a statistical framework, we compared the planet’s CMF as expected from the planet’s density and the CMF as expected from the host star. Our analysis suggests that, although K2-106b has a high density and CMF, it is statistically unlikely to be a super-Mercury.

ExoExplorer Briley Lewis (UCLA)

Small Pieces of the Solar System: Dust, Ice, Pluto, and More (PDF - 4.7 MB)

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Abstract: Small debris, both in and out of our Solar System, provides a window into planet formation. Within our Solar System, we have the Kuiper Belt, icy and dusty debris beyond Neptune, as well as the asteroid belt and Oort Cloud. In 2015, the New Horizons mission provided the first up-close view of a Kuiper Belt Object when it visited Pluto. Pluto’s surface was revealed to be geologically complex, with volatile ices that are mobile on seasonal and longer timescales. Using New Horizons data, we investigated the distributions and movements of ices on Pluto’s surface. Detailed studies of solar system objects, like this work on Pluto’s surface geology, are complementary to our investigations into other planetary systems that harbor debris disks, sometimes referred to as “Exo-Kuiper Belts”. Both provide insight into the processes of planet formation. High-contrast imaging has been key in providing new information about this extrasolar debris, such as measurements of disk extent and morphological asymmetry — information that is not available from infrared excesses alone. However, we are currently limited in our ability to discern composition of debris disks, relying on color measurements and other coarse methods. As characterization capabilities continue to grow, we can expect further discoveries in these complementary fields, especially as new observatories like JWST and the ELTs provide even more highly detailed observations of both solar system objects and debris disks. I will also briefly discuss another small piece of our “solar system” of astronomy—science writing, and pedagogical best practices for integrating writing into physics and astronomy curricula.

ExoExplorer Julia Seidel (ESO)

Observing exoplanet winds (PDF - 15.2 MB)

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Abstract: ESPRESSO, as the first high-resolution spectrograph of the 2020s, has brought a significant increase in line precision, as shown with the re-observation of WASP-76b (Tabernero et al. 2020) and WASP-121b (Borsa et al. 2021), and allows us to move beyond the sole observation of the sodium doublet with a plethora of resolved spectral lines - probing different altitudes in the atmosphere. Using the MERC code (Seidel et al. 2020a), a retrieval tool to determine winds in exoplanet atmospheres, the resolved lines can then be used to retrieve wind patterns directly. Compared to the analysis of the line shape on HARPS data only (e.g. Seidel et al. 2020a for HD189733b), the analysis of the line shape of ESPRESSO data permits to retrieve wind patterns in the upper atmosphere, but additionally also gives us unprecedented observational insights into the lower atmosphere from the line wings (Seidel et al. 2021). In this talk I will provide the community with a guide what we can, and can't. derive about atmospheric winds in exoplanet atmospheres with the current data quality and where our current limits lie as we move to smaller and cooler planets (Seidel et al. 2022). I will also provide a short introduction of ESPRESSO and other ESO instruments that might be useful for the cohort in future observing proposals.

ExoExplorer Kiersten Boley (Ohio State)

Impacts on Planet Formation: Planet Occurrence Rates around Metal-Poor Stars (PDF - 10.5 MB)

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Abstract: Planet formation models predict that below a certain protoplanetary disk metallicity, the surface density of solid material is too low to form planets. Observationally, previous works have indicated that short-period planets preferentially form around stars with solar and super solar metallicities. Given these findings, it is challenging to form planets within metal-poor environments. Due to the target selection process of previous surveys, there is little constraint on planet occurrence rates below [Fe/H] ~ -0.5, which is still higher than the predicted metallicity at which planet formation cannot occur. Expanding upon previous works, we construct a large sample of ~100,000 metal-poor stars with spectroscopically-derived stellar parameters observed by TESS. With this sample, we constrain planet occurrence rates within the metal-poor regime (-1.0 ≤ [Fe/H] ≤ -0.4) placing the most stringent upper limits on planet occurrence rates around metal-poor stars.

ExoExplorer Alison Farrish (GSFC)

Modeling Exoplanet Host Star Magnetic and Coronal Activity (PDF - 1.8 MB)

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Abstract: Exoplanet systems are of interest not only for their potential for habitability, but also in the opportunity they provide for the study of comparative heliophysics. In applying solar- and heliophysics-based modeling tools to exoplanet systems, we can expand our understanding of the influence of stellar behavior on planetary environments and processes such as atmospheric loss. I will discuss my work employing a surface flux transport (SFT) model to examine the dynamics of magnetic flux on the surfaces of cool stars like the Sun and exoplanet host stars of interest. This flux transport modeling approach has been used to examine stellar coronal X-ray emission and other asterospheric properties as a function of host star magnetic activity. I will provide an overview of current efforts to extend this modeling framework to investigate host star EUV emission and stellar wind parameters for a range of exoplanet host stars. Since stellar EUV emission is both a) a key driver of atmospheric loss processes and b) difficult to observe due to interstellar medium extinction, these simulations of energetic coronal emission could fill gaps in our understanding of exoplanet atmospheric evolution caused by this dearth of observational evidence.

ExoExplorer Aarynn Carter (UCSC)

Kickstarting a New Generation of Exoplanet Observations: Early Release Science with JWST (PDF - 32.5 MB)

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Abstract: Following the launch of JWST, in addition to a selection of ongoing commissioning activities, we now stand just months away from the beginning of scientific observations. Dispersed throughout these initial data will be a selection of Director’s Discretionary Early Release Science (ERS) observations which were designed under a primary goal of rapidly informing the community on JWST’s performance and capabilities. With respect to the study of exoplanets, only two ERS programs exist: “The Transit Community Early Release Science Program” (PI: N. Batalha, ERS-1366), and “High Contrast Imaging of Exoplanets and Exoplanetary Systems” (PI: S. Hinkley, ERS-1386). In totality, these two programs will set the tone for JWST exoplanet observations throughout its lifetime. In this talk I will provide an up-to-date overview of both of these programs, the timelines for their data releases, and a description of their technical and scientific goals. Additionally, I will discuss existing and ongoing preparatory work towards the production of a range of science enabling products. These products (e.g. data reduction pipelines, analyses of best practices) are an integral part of the ERS programs and will support JWST investigations throughout Cycle 2 and beyond.

ExoExplorer Aida Behmard (Caltech)

How Common is Planet Engulfment? (PDF - 23.2 MB)

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Abstract: Dynamical evolution within planetary systems can cause planets to be engulfed by their host stars. Following engulfment, the stellar photosphere abundance pattern will reflect accretion of rocky material from planetary cores by exhibiting refractory enhancements in order of condensation temperature $T_c$. Multi-star systems are excellent environments to search for such abundance trends because stellar companions share the same natal gas cloud and primordial chemical composition to within $\sim$0.05 dex. Thus, refractory differences above $\sim$0.05 dex that trend with $T_c$ between companions are a signpost of engulfment. Abundance measurements have occasionally yielded such engulfment signatures, but few observations targeted systems with known planets. To address this gap, we carried out a survey of 36 multi-star systems where one star is a known planet host with the Keck High Resolution Echelle Spectrometer. None of the 36 systems observed exhibit abundance patterns strongly indicative of engulfment events, which could be explained by our modeling efforts that show observable refractory enrichments from 10 $M_{\oplus}$ engulfment events are depleted on timescales of $\sim$1 Gyr for solar-like stars.

ExoGuide Talks

Elisa Quintana (GSFC)

José A. Caballero (CSIC-INTA)

Sarah Rugheimer (Oxford University)

Bruce Macintosh (Stanford University)