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Tyler Gardner

Publications and source records attributed to Tyler Gardner.

5 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2021

The orbit and stellar masses of the archetype colliding-wind binary WR 140

We present updated orbital elements for the Wolf–Rayet (WR) binary WR 140 (HD 193793; WC7pd + O5.5fc). The new orbital elements were derived using previously published measurements along with 160 new radial velocity measurements across the 2016 periastron passage of WR 140. Additionally, four new measurements of the orbital astrometry were collected with the CHARA Array. With these measurements, we derive stellar masses of M(WR)=10.31±0.45Mꙩ and M(O)=29.27±1.14Mꙩ⁠. We also include a discussion of the evolutionary history of this system from the Binary Population and Spectral Synthesis model grid to show that this WR star likely formed primarily through mass-loss in the stellar winds, with only a moderate amount of mass lost or transferred through binary interactions.

Joshua D. Thomas↗
NASA NTRS2019

The Future of Exoplanet Direct Detection

Diffraction fundamentally limits our ability to image and characterize exoplanets. Currant and planned coronagraphic searches for exoplanets are making incredible strides but are fundamentally limited by the inner working angle of a few λ/D. Some crucial topics, such as demographics of exoplanets within the first 50 Myr and the infrared characterization of terrestrial planets, are beyond the reach of the single aperture angular resolution for the foreseeable future. Interferometry offers some advantages in exoplanet detection and characterization and we explore in this white paper some of the potential scientific breakthroughs possible. We demonstrate here that investments in "exoplanet interferometry" could open up new possibilities for speckle suppression through spatial coherence, a giant boost in astrometric precision for determining exoplanet orbits, ability to take a census of young giant exoplanets (clusters <50 Myr age), and an unrivaled potential for infrared nulling from space to detect terrestrial planets and search for atmospheric biomarkers. All signs point to an exciting future for exoplanets and interferometers, albeit a promise that will take decades to fulfill.

John Monnier↗
NASA NTRS2019

Imaging the Key Stages of Planet Formation

New images of young stars are revolutionizing our understanding of planet formation. ALMA detects large grains in planet‐forming disks with few AU scale resolution and scattered light imaging with extreme adaptive optics systems reveal small grains suspended on the disks’ flared surfaces. Tantalizing evidence for young exoplanets is emerging from line observations of CO and H‐alpha. In this white paper, we explore how even higher angular resolution can extend our understanding of the key stages of planet formation, to resolve accreting circumplanetary disks themselves, and to watch planets forming in situ for the nearest star‐forming regions. We focus on infrared observations which are sensitive to thermal emission in the terrestrial planet formation zone and allow access to molecular tracers in warm ro‐vibrational states. Successful planet formation theories will not only be able to explain the diverse features seen in disks, but will also be consistent with the rich exoplanet demographics from RV and transit surveys. While we are far from exhausting ground‐based techniques, the ultimate combination of high angular resolution and high infrared sensitivity can only be achieved through mid‐infrared space interferometry.

John Monnier↗