March 12, 2021

The ExoExplorer Science Series on March 12 from 1-2 PM Pacific / 4-5 PM Eastern. Connection information is below.

Speaker: Quang Tran (UT Austin)

Title: "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.

Speaker: Amy Glazier (UNC Chapel Hill)

Title: "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.

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