Abstract

I will discuss how studying observed heterogeneities in stellar kinematic and chemistry space with large datasets lend insight into galactic processes and dynamics. Kinematics — Trick+19 identified overdensities, or “wrinkles”, of stars in eccentric orbits thought to result from the kinematic heating during spiral arm passages. Using photometry from TESS and gyrochronology age-rotation relations, we are calculating stellar age distributions in wrinkles to, for the first time, place a timestamp on transient spiral arm passages. Chemistries — The Sun shows a trend of relative depletion in refractory elements compared to ~80% of its counterparts. We use data-driven learning to infer 13 abundances with Gaia RVS spectra for > 17,000 sun-like stars and 50 planet hosts. With these data, we show the Sun remains relatively refractory depleted compared to sun-like stars regardless of our current knowledge of planet host status, inconsistent with theories of planets locking up refractories. Thus, we take a galactic-scale approach and assess the role of nucleosynthetic heterogeneities.  We find that the Sun is enriched in type 1a supernovae material by > 3sigma compared to its solar counterparts, corresponding to its observed refractory depletion.

Abstract

JWST has brought on a new dawn of discovery and has completely revolutionized our understanding of exoplanet atmospheres. It has brought the opportunity to understand exoplanetary atmospheres in unprecedented detail. One of the least constrained atmospheric processes in exoplanet atmospheres is atmospheric vertical dynamics, often parametrized with the eddy diffusion parameter - Kzz. The vertical mixing process significantly impacts atmospheric chemistry and clouds, but it's currently uncertain by 6-8 orders of magnitude. I will briefly introduce atmospheric mixing and show how uncertainty in the Kzz parameter leads to uncertainty in our overall understanding of exoplanet atmospheres. I will show how the similarities between brown dwarf and exoplanet atmospheres can help us to constrain and understand the vertical mixing process better. I will present results where, using a new generation of state-of-the-art Sonora Elf Owl atmospheric models and spectroscopic data from JWST, Spitzer, and AKARI telescopes, we have constrained the vigor of atmospheric vertical mixing in the deep atmospheres of brown dwarfs. We find that the observed Kzz constraints from our work are several orders of magnitude lower than theoretical predictions. I will present what this theory-observation mismatch teaches us about the deep atmospheres of directly imaged planets and brown dwarfs. I will also discuss our recent measurement of the strength of vertical mixing and internal heat of a very young transiting sub-Neptune progenitor with JWST data.

Abstract

Abstract

In this talk, I will explore the impact of temperature anisotropies in the crust of neutron stars on the evolution of their magnetic fields, particularly through thermoelectric interactions. Large thermal variations, often misaligned with density gradients, can activate the Biermann battery effect, leading to the generation of electromotive forces. By considering a neutron star crust with significant temperature gradients, associated with long-lived hot spots modeled by a localized Gaussian function, we numerically simulate the interplay between the battery term, Hall drift, and Ohmic evolution in axisymmetric systems. I will present results showing how temperature gradients impact the magnetic field evolution, with stronger effects observed at high crustal temperatures (~10^9 K), leading to significant field amplification and structural changes after several hundred thousand years, whereas at lower temperatures (~10^8 K), the generated fields are weaker. I will conclude by discussing how these thermoelectric effects may impact neutron stars with moderate-strength magnetic fields, provided that the temperature gradients persist over kiloyear timescales.

Abstract

70 years after Al Hiltner used the McDonald Observatory 82” telescope to discover interstellar polarization, we finally understand the physics of the underlying grain alignment.   Over the last three decades the “Radiative Alignment Torque” (RAT) paradigm has been developed and successfully tested.  Because of the quantitative nature of the theory, it can be used to better probe the magnetic fields of the ISM, and to constrain the characteristics of the dust, radiation fields and other environmental factors.   I will discuss the basics of RAT alignment, describe some recent results testing and utilizing the process and some remaining challenges in interstellar grain alignment and polarization studies.

Abstract

FU Ori outbursts are the most energetic events that protoplanetary disks experience. An outburst occurs when a disk instability increases the disk to star accretion rate by a factor of 10,000 for as long as 100-200 years. The truncation radius of the disk moves rapidly inward, collapsing the magnetospheric accretion funnel flow and causing the star to accrete material directly from the disk at its equator. The disk midplane can have temperatures of 30,000+ K and the disk atmosphere we observe has an effective temperature of 6,000-8,000 K. I will discuss the work I have done during my PhD thesis to model these disks, how my detailed study of the time evolution of two recent outbursts constrains the physics of the events, and how my recent detection of FUV continuum emission from FU Ori challenges previous models of the system. I will then discuss how we can leverage ALMA and JWST as well as existing chemical network models to study the impact of the outbursts on the planet forming environment in protoplanetary disks.