Abstracts

Adiv Paradise : University of Toronto : Blue Skies: The Role of pN2 in the Habitable Zone : Over the last twenty years, we have discovered thousands of planets. Transmission spectroscopy has quickly emerged as the dominant tool for characterizing the atmospheres of these planets. However, transmission spectroscopy is most sensitive to gases that have absorption lines—and nitrogen, the primary constituent of Earth’s atmosphere, has none in visible or infrared wavelengths. Because it has none, we often assume its role in the climate’s energy budget is mostly limited to heat transport. I will present results of an ensemble of 3D climate simulations that suggest that to the contrary, atmospheric nitrogen has a large, nonlinear impact on the climate’s energy budget. The expected nitrogen abundance in terrestrial exoplanet atmospheres is almost entirely unconstrained, so understanding how nitrogen affects the climate and how to measure its abundance will prove essential to the characterization of habitable climates.
Alan Reyes : Penn State : A Super-Jupiter Outside a Compact, High-Multiplicity Kepler System with an Unprecedented Architecture : Kepler-1130 is a transiting multi-planet system consisting of four short period planets orbiting in a near-resonant 2:3:4:5 chain. Using Keck HIRES, we monitored the star’s radial velocity and identified a highly eccentric (e=0.54), long period (P~2000d), giant planet (Msini~5.6 M_J) companion orbiting well beyond the known planets in what appears to be the first dynamical architecture of its kind. Due to the relatively low (n=15) number of current observations, the issue of the planet’s precise orbit has not been settled, and additional measurements are warranted to reject plausible model variants. We employ a residuals resampling bootstrap to estimate the optimal timing to continue targeted reconnaissance of this system with the aim of definitively ruling out alternative scenarios and constraining the orbital model further. The planet represents a novel case study to inform the ongoing debate in planetary formation theory ignited by the Kepler mission: whether a) multi-planet systems form in situ, or b) the constituents of compact multiples form at greater distances, proceed to migrate inward, and assemble within just a fraction of an AU from their hosts.
Alex Teachey : Columbia University : The Search for Exomoons with Surveys and Targeted Observations : As the search for exomoons continues, time domain photometric surveys will remain a critical component of the effort, in particular, for identifying and characterizing promising new candidates. However, with our recent HST observation of Kepler-1625b, the search has entered a new phase: targeted observations. Follow-up of individual candidates with premier space-based instruments like HST and JWST will generally be the only way to achieve the necessary precision for detecting sub-Earth radius moons. In this talk I will describe our ongoing work to identify new candidates in the time-domain surveys and discuss our recent efforts to observe individual targets we consider exceptionally attractive for the moon search. I will also highlight some of the challenges involved with targeted observations and comment on the outlook for the moon search going forward.
Alysa Obertas : University of Toronto : Dynamical sculpting of compact multi-planet systems : The Kepler mission discovered hundreds of multi-planet systems, many of which host four or more planets all with periods under a few hundred days. With system ages typically around 5Gyr, these compact systems have survived for 10^11 to 10^12 orbits. Furthermore, their orbits typically have small eccentricities and mutual inclinations, suggesting that they may have had relatively uneventful dynamical histories. N-body simulations investigating the stability and survival times of compact systems show that the compact Kepler systems are packed to their dynamical limit, but the mechanism which ultimately drives their long-term dynamics is not yet understood. I will discuss numerical and analytic work towards understanding the long-term dynamical evolution of the most compact planetary systems, and the implications it may have on sculpting observed systems to their present-day architectures.
Aritra Chakrabarty : Indian Institute of Astrophysics : Follow up observation of some hot Jupiters using astronomical facilities of India: update on their parameters : Transit photometry is a key tool for the detection and characterization of exoplanets. Repeated observations help us refine the physical parameters of the planets and probe into the dynamics. We’ve been using the 2m Himalayan Chandra Telescope and the 1.3m Jagadish Chandra Bhattacharyya Telescope for the photometric follow up of the known exoplanets. We have observed the transit events of WASP-50b, WASP-12b, HATS-18b, etc repeatedly. Using our self-developed pipeline we have perfomed the basic reduction, differenial photometry and the modelling. The results from the simultaneous modeling of the transit light curves of a planet using Python-based MCMC algorithm have demonstrated that we could reach a sensitivity of <1% in producing transit light curves. To further reduce the uncorrelated scattering in the light curves we have applied the wavelet denoising technique before modeling and to reduce the effect of the correlated noise contributed by the host star pulsation we have applied Gaussian process regression while modeling. As a result we could determine the physical properties of the planets with more precision than the already published results yet in accord with them.
Arthur D. Adams : Yale University : Antipodal Anticorrelations : There exist very few town pairs on Earth located on opposite points (“antipodes”) on the globe from each other. This is strikingly apparent when overlaying a map of the Earth on top of the corresponding reflected map, where most of the continental landmasses fit comfortably into their antipodal oceans. This state can be expressed in terms of a characteristic of the Earth’s topography; we quantify this by decomposing the map into spherical harmonics, to obtain a power spectrum in elevation. We explore the potential significance of this distribution, and calculate the analogous power spectra for all other bodies in the Solar System with available topographical maps to assess whether observed similarities in the power point to similarities in physical structure and evolution.
Arvind Gupta : Penn State University : The NEID Earth Twin Survey: Target Selection and Survey Strategy : NEID, a high-resolution optical spectrograph, will soon join the new generation of extreme precision radial velocity instruments in operation around the world. We will use the instrument to conduct the NEID Twin Earth Survey (NETS) over the course of the next 5 years, collecting hundreds of observations of some of the nearest and brightest G and K stars in an effort to probe the regime of Earth-like exoplanets. It will be difficult, however, to disentangle the weak (~10cm/s) signals induced by such low-mass, long-period exoplanets from stellar noise for all but the quietest host stars. If we hope to take advantage of the extreme instrumental precision conferred by NEID such that it is indeed feasible to detect and extract the signals of interest, our observational design must therefore carefully account for stellar radial velocity variability timescales. In this presentation, I describe our target selection criteria and anticipated survey strategy in light of past radial velocity surveys and recent and ongoing efforts to characterize stellar signals.
Christian Gilbertson : Penn State : Towards extreme precision radial velocities Distinguishing planets from stellar variability with Machine Learning : The radial velocity (RV) method is one of the most successful techniques for the discovery and characterization of exoplanets. New RV surveys are sensitive to planetary signals of 1 m/s or less, but the variability of stellar spectra caused by stellar activity can mimic and obscure true planet signals. This is expected to be a major obstacle for the detection of smaller planetary RV signals, especially around magnetically active stars. A data-driven approach for detecting planetary RV signals amidst stellar activity has recently been proposed by Rajpaul et al. (2015) and refined by Jones et al. (2017). This approach uses a physically motivated combination of multivariate Gaussian processes (GP) to jointly model apparent RV and multiple indicators of stellar activity, allowing the planetary RV component to be separated from the total RV signal. In this work, we simulate new high-fidelity time series spectra and compare the performance of several different GP kernel functions. By finding what combination of model parameters and kernel function yields the highest planetary detection power, we will have created a well-motivated, robust approach for discovering new, small exoplanets.
Christopher Spalding : Yale University : The primordial Solar wind as a sculptor of terrestrial planet formation : The Kepler mission revealed that a substantial fraction of stars in the Galaxy possess planets residing on orbits that lie significantly closer to their host stars than Mercury does to the Sun. Furthermore, these close-in worlds typically exceed the Earth in size, yet must have formed within the disk-hosting stage, lasting 1-10 million years. Our inner Solar system, on the other hand, is peculiarly deficient in mass, with absolutely no material detected interior to Mercury. In this talk, I will propose and test the hypothesis that the primordial wind emanating from the young Sun was sufficiently strong to remove planetary building blocks from interior to Mercury’s orbit, with this material instead enriching the Earth’s orbital vicinity. In this way, the mass deficit close to planet-hosting stars like our Sun arises as a natural consequence when planet formation occurs subsequent to the disk-hosting stage, as occurred in the Solar system. This wind-induced, outward migration of planetary building blocks predicts numerous compositional anomalies within the terrestrial planets and the asteroid belt that warrant further study.
Chuanfei Dong : Princeton University : How Flares regulate Atmospheric Losses from the TRAPPIST-1 planets : Stellar flares are considered an impediment to habitability, especially in the case of planets around M-dwarfs since these stars are highly active. In recent times, there has been a growing awareness that interplanetary coronal mass ejections (ICMEs) associated with stellar flares pose severe threats to planetary habitability. ICMEs, corresponding to fast moving magnetic clouds, act to impact the planets with significantly high dynamic pressure. Semi-analytical models imply that planets around active stars (~1 flare/day) may experience escape rates that are 1-3 orders of magnitude higher than those arising from erosion by stellar winds alone. Understanding atmospheric escape is very important from the standpoint of habitability since atmospheric evolution influences the climate and the fluxes of ionizing radiation reaching the surface, among other factors.

Hence, we carry out sophisticated 3D multi-species MHD simulations to assess how the atmospheric escape rates of the TRAPPIST-1 planets evolve during the passage of an ICME, where the ICME is initialized and modeled according the flare observations.
Darryl Seligman : Yale University : On the Anomalous Acceleration of 1I/2017 U1 `Oumuamua : We show that the $P\sim8\,{\rm h}$ photometric period and the astrometrically measured non-gravitational acceleration of the interstellar object 1I/2017 (`Oumuamua) can be explained by a nozzle-like venting of volatiles whose activity migrated to track the sub-solar location on the object’s surface. Adopting the assumption that `Oumuamua was an elongated ellipsoid, this model produces a pendulum-like rotation of the body and implies a long semi-axis 260m. This scale agrees with the independent estimates of `Oumuamua’s size that stem from its measured brightness, assuming an albedo of $p\sim0.1$. Using ray-tracing, we generate light curves for ellipsoidal bodies that are subject to both physically consistent sub-solar torques and to the time-varying geometry of the Sun-Earth-`Oumuamua configuration. Our synthetic light curves display variations from chaotic tumbling and changing cross-sectional illumination that are consistent with the observations, while avoiding significant secular changes in the photometric periodicity. If our model is correct, `Oumuamua experienced mass loss that wasted 10% of its total mass and had an icy composition with a very low [C/O]~0.003.
Emily Deibert : University of Toronto : High-Resolution Spectroscopy of Exoplanet Atmospheres : Thousands of transiting exoplanets have been discovered, but the extreme brightness contrast between these planets and their host stars makes characterizing their atmospheres particularly challenging. Recent work has focused on transmission spectroscopy during transits, when the light from the host star passes through the planet’s atmosphere and allows for the detection of any atomic or molecular species present. While this method has been used to make atmospheric detections around several hot Jupiters, the atmospheres of cooler, lower-mass planets remain elusive. In this talk, I will present my recent analyses of high-resolution observations of atmospheres ranging from hot Jupiters to super-Earths, using both visible and infrared data from a range of instruments. I will share both constraints on these exoplanets’ atmospheric compositions as well as potential atmospheric detections, and discuss the significance of these results. I will then look ahead to upcoming high-resolution ground-based facilities that will revolutionize the study of exoplanetary atmospheres, and highlight the utility of transmission spectroscopy in atmospheric characterization.
Emily Gilbert : University of Chicago : M Dwarf Flares Through Time : As the most common planet-hosting stars, M dwarfs are essential for understanding the occurrence, evolution, and potential habitability of exoplanets. M dwarf stars make up more than 70% of stellar content in our galaxy and are a large focus of the TESS mission. These stars are smaller, cooler, and more active than our own Sun, but their activity is not well-understood. Since these stars are highly magnetically active, the planets they host are subjected to significantly more radiation than we experience from the Sun. Just how much this affects their potential habitability remains unsolved. We present our new flare detection and characterization software that allows us to study relationships between stellar parameters such as age, rotation, and spectral type on flare activity. This allows us to asses the effects of this activity on the exoplanet population. We present early results on the flare energy distribution for two active stars, AU Mic and YZ CMi, and discuss our plan to explore many hundreds of additional M dwarfs observed by TESS that span a wide range of masses and ages.
Garett Brown : University of Toronto : Quantifying the Long-term Effects of Stellar Fly-bys on Planetary Systems : Previous studies on the effects of stellar fly-bys on planetary systems have examined populations that result in immediate ejections, planet-planet encounters, and the general stability of multi-planetary systems after an encounter. However, subtle changes to the orbital structure of established planetary systems create small cascading effects which can build up over the lifetime of the system, without entirely destabilizing the system. My work has been to quantify these effects. Using the n-body integrator REBOUND and quantitative frequency analysis, I have simulated varying strengths of extra-solar fly-by events and examined how fly-by events affect the long-term variations of planetary orbital elements. The results provide a better understanding of how stellar flybys affect long-term changes to orbital structure and help enrich our understanding of the evolution of exoplanet systems.
Jack Madden : Cornell University : Effect of surface type for Earth-like planets orbiting FGKM stars : Modeling the atmosphere of Earth-like exoplanets has been accomplished using 1D climate and photochemistry codes. As a simplification, these codes have usually contained a single value for the surface reflectivity across all wavelengths. We have added color into the code by turning these gray, single value, planet albedos into wavelength dependent inputs spanning the UV, visible, and near infrared. The interaction between the incoming stellar flux and the surface is much more realistic and gives habitability measures, like surface temperature, a much stronger dependence on stellar type. Using this method produces significant deviations in surface temperature from what would be seen using a single value. These models are used to help determine the best places to look for life around other stars and our results show that realistically modeling the surface albedo can have a large impact on how the habitability of a system is characterized. This could lead to searches for life in regions previously considered uninhabitable or save telescope time by cautioning against older predictions of the habitable zone.
Jiayin Dong : Penn State : Probing Young Planetary Systems from Their Debris Disks: Are We Messed by Unseen Planets? : Debris disks features (e.g., warps, offsets, edges and gaps, azimuthal asymmetries, thickened rings, scale heights) have often been recognized as the signposts of planets. Most existing models assume a single planet is sculpting the disk feature, but recent observations of mature planetary systems (e.g., by radial velocity surveys and Kepler) have revealed that many planets reside in multi-planet systems. We investigate if/how planet properties inferred from single-planet models are compromised when multiple planets reside in the system. For each disk feature, we build a two-planet model that includes a planet b with fixed parameters and a planet c with a full range of possible parameters. We investigate these two planet systems with N-body simulations and summarize the configurations for which assuming a single planet leads to significantly flawed inferences of that planet’s properties from the disk feature.
Jonathan Jackson : The Pennsylvania State University : Analysis of Perturber-driven High-eccentricity Tidal Migration for Warm Jupiters in the Context of Known Observables : The origin of hot Jupiters (Jupiter mass planets with periods less than 10 days) is an open question in exoplanet formation and evolution. If we assume hot Jupiters migrated from larger semi-major axes, we can treat warm Jupiters (periods between 10 and 200 days) as intermediaries between newly formed gas giants and hot Jupiters. Warm Jupiters thus provide a testbed for assessing migration theories. We investigate the validity of the perturber-modulated high-eccentricity tidal migration scenario, in which a migrating Jupiter is periodically secularly perturbed by a companion planet or star to an eccentricity large enough for its orbit to tidally shrink and circularize. We develop an observationally motivated population of warm Jupiters and assign a corresponding perturber capable of inducing migration to each planet. We then calculate the distributions of observational signals (transit timing variations, transit duration variations, and radial velocities) these perturbers would produce and compare them to current detection limits.
Lile Wang : MIT/Princeton : Dusty Outflows in Planetary Atmospheres: Understanding “Super-puffs” and Transmission Spectra of Sub-Neptunes : “Super-puffs” are planets with anomalously low mean densities . With a low surface gravity, the extended atmosphere is susceptible to extreme hydrodynamic mass loss (“boil-off”) on a timescale that is much shorter than the system’s age. Even more puzzling, super-puffs are estimated to have a scale height of 3000km, yet recent observations revealed completely flat transmission spectra for Kepler 51b and 51d. We investigate a new scenario that explains both observations: non-static outflowing atmospheres that carry very small dust grains to high altitudes. Dust at high altitudes inflates the observed transit radius of the planet while flattening the transmission spectra. Previous static atmospheric models struggle to achieve cloud elevation and production of photochemical haze at such high altitudes. We propose to test this scenario by extending the wavelength coverage of transmission spectra. If true, dusty atmospheric outflows may affect many young, low-mass exoplanets, thereby limiting our ability to study the atmospheric composition in transmission, and inflate the observed transit radius of a planet, hence obscuring the underlying mass–radius relationship.
Malena Rice : Yale University : The Case for a Large-Scale Occultation Network : We discuss the feasibility of and present initial designs and approximate cost estimates for a large (N~2000) network of small photometric telescopes that is purpose-built to monitor V<15 Gaia Mission program stars for occultations by minor solar system bodies. Occultation monitoring would generate direct measurements of the size distributions of asteroid populations including those of the Kuiper belt and Main belt – the solar system’s debris disk – permitting a better understanding of their origins. Furthermore, ephemerides of all small solar system bodies observed in occultation would be significantly improved using this network, which would permit measurement of the solar system’s tidal gravity field to high precision. As a detailed example of the network capabilities, we investigate how occultations by Jovian Trojans can be monitored to track the accumulation of gravitational perturbations, constraining the presence of undetected massive solar system bodies such as the proposed “Planet Nine.”
Mariah MacDonald : Penn State : Disentangling the In-Situ Formation Conditions in Establishing the ”Dichotomy” in Super-Earth Orbital Architectures : The formation and subsequent evolution of the planetary systems seen by Kepler are subjects of active debate. In this study, we aim to identify which conditions of the disk reproduce the orbital and compositional properties of planetary systems that are similar to those of the Kepler population. We generate ensembles of simulated transiting planets, evolving through the giant impact phase using N-body simulations. We vary the initial surface density slope, the solid surface density, and the damping caused by a residual gas disk. For all ensembles, we find that reweighting the initial solid surface density by an exoponential distribution, rather than a log uniform distribution, leads to an equivalent or better match to the observables. We find that a moderate amount of damping from a residual gas disk and a surface density profile of $\alpha$ = -1.5 are both necessary to producing a population similar to Kepler. A continuum of disk parameters rather than a mixture model can account for the so called ”Kepler dichotomy,” as we match the observed distributions of period ratio, Hill spacing, and planetary multiplicity.
Matthias Yang He : The Pennsylvania State University : Forward Modeling the Kepler Exoplanet Population to Inform System Architectures : Kepler has discovered thousands of exoplanet candidates and hundreds of multi-transiting systems to date, enabling detailed population studies. I will present a framework for forward modeling the Kepler population of exoplanetary systems by simulating underlying populations of exoplanet systems and accounting for the Kepler detection pipeline. I will show that while models assuming independent periods and sizes cannot adequately reproduce the observed population, a clustered model for planet periods and sizes is a significantly improved description of the Kepler multi-planet systems, especially in modeling the observed multiplicity, period ratio, and radius ratio distributions. These models adequately reproduce both the bulk distribution of period ratios and the features near mean motion resonances for multi-planet systems. I will also talk about how I explored the large parameter space with Gaussian Processes. Finally, I will discuss the implications and utility of our models for probing the true underlying populations of planets, including how we may use our results to inform RV follow-up observations of TESS discoveries.
Michael Pu : Cornell : Low-Eccentricity Migration of Ultra-Short Period Planets in Multi-Planet Systems : Recent studies suggest that ultra-short period planets (USPs), Earth-sized planets with sub-day periods, constitute a statistically distinct sub-sample of {\it Kepler} planets: USPs have smaller radii ($1-1.4R_\oplus$) and larger mutual inclinations with neighboring planets than nominal {\it Kepler} planets, and their period distribution is steeper than longer-period planets. We study a “low-eccentricity” migration scenario for the formation of USPs, in which a low-mass planet with initial period of a few days maintains a small but finite eccentricity due to secular forcings from exterior companion planets, and experiences orbital decay due to tidal dissipation. USP formation in this scenario requires that the initial multi-planet system have modest eccentricities ($\gtrsim 0.1$) or angular momentum deficit. Through a population synthesis calculation, we demonstrate that the”low-$e$ migration” mechanism can naturally produce USPs from the large population of {\it Kepler} multis under a variety of conditions, with little fine tuning of parameters. The resulting USPs have properties that are consistent with observations.
Miranda Herman : University of Toronto : Search for TiO in the Atmosphere of WASP-33b : With a temperature akin to an M-dwarf, WASP-33b is one of the hottest known hot Jupiters, making it an ideal target for high-resolution optical spectroscopy. When the planet is in transit, we are able to characterize the atmospheric composition by observing light from the host star that has passed through the planet’s atmosphere, as some of that light is absorbed by atomic and molecular species. In contrast, observing the planet’s day side allows us to analyze light emitted from the planet directly and provides additional information about the atmospheric structure. We observe two transits and six phase curves of WASP-33b with HIRES on the Keck telescope and ESPaDOns on the Canada-France-Hawai’i Telescope. We employ the Doppler cross-correlation technique to search for the molecular signatures of water and TiO in these transmission and emission spectra, with the aim to further substantiate a previous detection of atmospheric TiO and compare the composition and structure of WASP-33b’s atmosphere to other known hot Jupiters.
Nora Bailey : University of Chicago : Stellar Flybys Interrupting Planet-Planet Scattering Generates Oort Planets : We propose a population of “Oort” planets around other stars, forming by a mechanism analogous to how the Solar System’s Oort cloud of comets was populated. Gravitational scattering among planets is inferred from the eccentricity distribution of gas-giant exoplanets measured by the Doppler technique. This scattering is thought to commence while the protoplanetary disk is dissipating, 1-10 Myr after formation of the star, or perhaps soon thereafter, when the majority of stars are expected to be part of a natal cluster. Previous calculations of planet-planet scattering around isolated stars have one or more planets spending >10 kyr at distances >100 AU before ultimately being ejected. During that time, a close flyby of another star in the cluster may dynamically lift the periastron of the planet, ending further scattering with the inner planets. We present numerical simulations demonstrating this mechanism as well as an analysis of the efficiency. We estimate an occurrence of planets between 100 and 5000 AU by this mechanism to be <1% for gas giants and up to a few percent for Neptunes and super-Earths.
Ryan Petersburg : Yale University : Novel Methods in the EXPRES Data Pipeline : The extremely high resolution and multiple observing modes on the Extreme PREcision Spectrograph (EXPRES) has enabled new possibilities of precise and highly characterized data extraction. Using a novel LED flat field source through an “extended flat” fiber—a rectangular fiber with larger height and width than the “science” fiber—we are able to construct a wavelength-dependent master flat field image that aligns with each spectral order on the detector by construction. We are also able to extract spectra using a “flat-normalized optimal extraction” algorithm that uses information from the flat field (fed by the “science” fiber) to accurately model the slit function. Similarly, we have implemented a “spectro-perfectionism” extraction algorithm that uses two-dimensional information about EXPRES’s point spread function to extract spectra beyond the theoretical resolution of the instrument. Finally, we are able to implement a two-dimensional fit to our laser frequency comb that enables local systematic correlations in the detector to be reflected in the wavelength solution. We intend to discuss the advantages and disadvantages of each of these methods.
Sarah E Moran : Johns Hopkins University : Exoplanet Hazes in the Lab and Atmospheric Models : Using a custom PHAZER (Planetary HAZE Research) laboratory set-up, we experimentally simulated several regimes of exoplanetary atmospheres relevant to the phase space of Earths to mini-Neptunes. Laboratory data is necessary to provide many physical and chemical properties pertaining to possible aerosols in their atmospheres. These properties have implications for the radiative transfer from the top of the atmosphere to the surface, for the feasibility of observations from the Hubble Space Telescope (HST) and the upcoming James Webb Space Telescope (JWST), and for possible exoplanetary habitability. Photochemical haze analogues formed in all of our experiments. We analyzed these laboratory products with a suite of techniques. Using these laboratory data, we utilize a version of the CHIMERA (CaltecH Inverse ModEling and Retrieval Algorithms) modeling code to explore the effects these haze analogues have on the spectra of atmospheres of smaller, temperate exoplanets, including those of the recently discovered TRAPPIST-1 system and several newly discovered TESS planets.
Sarah Millholland : Yale University : Tidally-Induced Radius Inflation of Sub-Neptunes : Recent work suggests that many short-period super-Earth and sub-Neptune planets may have significant spin axis tilts (“obliquities”). When planets are locked in high-obliquity states, the tidal dissipation rate increases by several orders of magnitude. This intensified interior heat deposition should generate significant atmospheric inflation. Using up-to-date radius estimates from Gaia DR2 and the California-Kepler Survey, we show evidence for larger average radii of planets wide of first-order mean-motion resonances, a population of planets with theorized frequent occurrence of high obliquities. We investigate whether this radius trend could be a signature of obliquity tides. Using an adaptation of the Modules for Experiments in Stellar Astrophysics (MESA) stellar evolution toolkit, we model the evolution of the H/He envelopes of sub-Neptune-mass planets in response to additional heat from obliquity tides. The degree of radius inflation predicted by the models is indeed consistent with the observations. We present several case studies, such as Kepler-31 c, Kepler-49 c, and Kepler-79 d, that are particularly strong candidates for having undergone tidally-induced radius inflation.
Songhu Wang : Yale : HD202772A b: the first confirmation of a hot Jupiter discovered by TESS : We report the first confirmation of a hot Jupiter discovered by TESS: HD202772A b. The presence of light contamination from the bright stellar companion makes the confirmation of planetary nature technically hard. The talk will focus on the follow-up efforts made by TFOP collaboration that entirely rules out the false positives. HD 202772A b is one of few known transiting hot Jupiters orbiting bright, quickly evolved stars. I will also discuss the follow-up observational and theoretical efforts we are performing for the system. In the end, I will discuss the RV efforts we made with CHIRON for other TESS Alerts, shedding first light on the false positive rate of TESS Alerts of gas giants.
Taylor Kutra : Univeristy of Toronto : Super-Earth Size and Occurrence as a Function of Stellar Mass or Metallicity : Despite the ubiquity of planets with radii between 0.5 and 4 Earth radii, we are only beginning to understand which stellar parameters influence their size and occurrence. One of the assumed implications of a strong metallicity and size dependence for giant planets is that terrestrial planets would follow suit and their size and occurrence would strongly depend on stellar metallicity. This scaling is likely due to the amount of solids in a metal-rich protoplanetary disk: disks with high metallicities have more solids that can coalesce to frequently form the large cores necessary for forming giant planets via core-accretion. Using updated planet and stellar parameters from the Kepler California Survey VII, we have found that the radius scaling of super-Earths with respect to their host star’s metallicity is consistent with zero. We also find that super-Earths and sub-Neptunes have the same metallicity distribution and therefore the same occurrence rate. Using a Monte-Carlo forward model and field stars from the LAMOST survey, we constrain the occurrence of planetary systems with Kepler planets and discuss our findings in the context of the binary stars metallcity dependence.
Thea Kozakis : Carl Sagan Institute, Cornell University : Dying to Live: Post-Main Sequence Habitability : During the post-main sequence phase of stellar evolution the orbital distance of the habitable zone, which allows for liquid surface water on terrestrial planets, moves out past the system’s original frost line, providing an opportunity for outer planetary system surface habitability. We use a 1D climate/photochemistry code to study the impact of the stellar environment on the planetary atmospheres of Earth-like planets/moons throughout its time in the post-main sequence habitable zone. We also explore the ground UV environments of such planets/moons and compare them to Earth’s. We model the evolution of star-planet systems with host stars ranging from 1.0 to 3.5 Solar masses throughout the post-main sequence, calculating stellar mass loss and its effects on planetary orbital evolution and atmospheric erosion. The maximum amount of time a rocky planet can spend continuously in the evolving post-MS habitable zone ranges between 56 and 257 Myr for our grid stars. Thus, during the post-MS evolution of their host star, subsurface life on cold planets and moons could become remotely detectable once the initially frozen surface melts.
Tyler Gordon : University of Washington : A fast, two-dimensional Gaussian process method for modeling stellar variability : Gaussian processes are a model of stochastic variability frequently used in analyzing astrophysical time-series. They have been used to study variability in light curves ofstars and AGN, as well as the spatial distribution of the extragalactic dust distribution.In the realm of stellar variability, GP regression is used to characterise stellar rotationperiods, search for transit signals in noisy data, and analyze RV curves. One of thechief limitations of this method is the computational time incurred in computing aGP model for large or multi-dimensional data-sets. While approximate methods canmake GP regression feasible for some of these applications, in others exact methodsare preferable. Here we present a method based on the celerite GP implementation which enables fast, exact computation of two-dimensional GP models for data-sets with a small second dimension. This includes multi-bandpass photometry of transitand microlensing light curves. Our method also may have applications to RV and direct imaging methods
Tyler Richey-Yowell : Arizona State University : Auroral Emission from L Dwarfs : Photometric variability commonly occurs on brown dwarfs with spectral types near the transition from L to T dwarfs. While this variability is typically attributed to cloud phenomena, recent studies suggest that localized magnetic heating from aurorae may play a role. We have observed 17 brown dwarfs with known optical and/or infrared variability using the Karl G. Jansky Very Large Array (VLA) to statistically study the relationship between brown dwarf aurorae and cloud phenomena. Of these, only one L4.5 dwarf was detected in Stokes I. A sharp flare from this object was additionally detected in Stokes V, indicating the presence of 74% circularly polarized auroral emission. We constrain the magnetic field strength in the region of radio emission to be above 1.4 kG. Our detection rate (~6%) is significantly lower than recent smaller studies of photometric variability and auroral emission, suggesting that these two phenomena are no more than weakly correlated. However, the presence of Ha emission on this object suggests that Ha instead may be a more accurate indicator of the presence of auroral activity.