Calendar

Aug
28
Fri
Colloquium Thesis Proposal: Laura Mayorga
Aug 28 @ 3:15 pm – 4:15 pm
Colloquium Thesis Proposal: Laura Mayorga @ BX102

Probing Exoplanet Atmospheric Properties from Phase Variations and Polarization

Laura Mayorga, NMSU

The study of exoplanets is evolving past simple transit and Doppler method discovery and characterization. One of the many goals of the upcoming mission WFIRST-AFTA is to directly image giant exoplanets with a coronagraph. We undertake a study to determine the types of exoplanets that missions such as WFIRST will encounter and what instruments these missions require to best characterize giant planet atmospheres. We will first complete a benchmark study of how Jupiter reflects and scatters light as a function of phase angle. We will use Cassini flyby data from late 2000 to measure Jupiter’s phase curve, spherical albedo, and degree of polarization. Using Jupiter as a comparison, we will then study a sample of exoplanet atmosphere models generated to explore the atmospheric parameter space of giant planets and estimate what WFIRST might observe. Our study will provide valuable refinements to Jupiter-like models of planet evolution and atmospheric composition. We will also help inform future missions of what instruments are needed to characterize similar planets and what science goals will further our knowledge of giant worlds in our universe.

Feb
12
Fri
Colloquium: Lauren Woolsey
Feb 12 @ 3:15 pm – 4:15 pm
Colloquium:  Lauren Woolsey @ BX102

Magnetic Influences on Coronal Heating and the Solar Wind

Lauren Woolsey, Harvard University

 

Abstract

The physical mechanism(s) that generate and accelerate the solar wind have not been conclusively determined after decades of study, though not for lack of possibilities. The long list of proposed processes can be grouped into two main paradigms: 1) models that require the rearranging of magnetic topology through magnetic reconnection in order to release energy and accelerate the wind and 2) models that require the launching of magnetoacoustic and Alfvén waves to propagate along the magnetic field and generate turbulence to heat the corona and accelerate the emanating wind. After a short overview of these paradigms, I will present my ongoing dissertation work that seeks to investigate the latter category of theoretical models and the role that different magnetic field profiles play in the resulting solar wind properties with Alfvén-wave-driven turbulent heating. I will describe the computer modeling in 1D and 3D that I have done of bundles of magnetic field (flux tubes) that are open to the heliosphere, and what our results can tell us about the influences of magnetic field on the solar wind in these flux tubes, including the latest time-dependent modeling that produces bursty, nanoflare-like heating. Additionally, I will present the latest results of our study of chromospheric network jets and the magnetic thresholds we are finding in magnetogram data.

Apr
1
Fri
Colloquium: Hwiyun Kim (Host: Rene Walterbos)
Apr 1 @ 3:15 pm – 4:15 pm
Colloquium:  Hwiyun Kim     (Host: Rene Walterbos) @ BX102

High Resolution Spectroscopy with Immersion Grating Infrared Spectrometer (IGRINS)

Hwihyun Kim, KASI/UT Austin

 

The Immersion Grating Infrared Spectrometer (IGRINS) is a revolutionary instrument that exploits broad spectral coverage at high-resolution (R=45,000) in the near-infrared. IGRINS employs a silicon immersion grating as the primary disperser of the white pupil, and volume-phase holographic gratings cross-disperse the H and K bands onto Teledyne Hawaii-2RG arrays. IGRINS provides simultaneous wavelength coverage from 1.45 – 2.45 microns in a compact cryostat. I will summarize the performance and various science programs of IGRINS since commissioning in Summer 2014. With IGRINS we have observed such as Solar System objects, nearby young stars, star-forming regions like Taurus and Ophiuchus, the Galactic Center, and planetary nebulae.

The second half of my talk will be focused on the study of ionized and neutral gas in an ultracompact HII region Monoceros R2. We obtained the IGRINS spectra of Mon R2 to study the kinematic patterns in the areas where ionized and molecular gases interact. The position-velocity maps from the IGRINS spectra demonstrate that the ionized gases (Brackett and Pfund series, He and Fe emission lines;Δv ≈ 40km/s) flow along the walls of the surrounding clouds. This is consistent with the model by Zhu et al. (2005, 2008). In the PV maps of the H2 emission lines there is no obvious motion (Δv < ~10km/s) of the molecular hydrogen right at the ionization boundary. This implies that the molecular gas is not taking part in the flow as the ionized gas is moving along the cavity walls.

Apr
8
Fri
Colloquium PhD Defense: Meredith Rawls
Apr 8 @ 3:00 pm – 4:00 pm
Colloquium PhD Defense: Meredith Rawls @ BX102

Red Giants in Eclipsing Binaries as a Benchmark for Asteroseismology

Meredith Rawls, NMSU

Sep
20
Wed
Colloquium PhD Defense: Jean McKeever
Sep 20 @ 3:00 pm – 4:15 pm
Colloquium PhD Defense: Jean McKeever @ Business College 103

Asteroseismology of Red Giants: The Detailed Modeling of Red Giants in Eclipsing Binary Systems

Jean McKeever, NMSU

Asteroseismology is an invaluable tool that allows one to peer into the inside of a star and know its fundamental stellar properties with relative ease. There has been much exploration of solar-like oscillations within red giants with recent advances in technology, leading to new innovations in observing. The Kepler mission, with its 4-year observations of a single patch of sky, has opened the floodgates on asteroseismic studies. Binary star systems are also an invaluable tool for their ability to provide independent constraints on fundamental stellar parameters such as mass and radius. The asteroseismic scaling laws link observables in the light curves of stars to the physical parameters in the star, providing a unique tool to study large populations of stars quite easily. In this work we present our 4-year radial velocity observing program to provide accurate dynamical masses for 16 red giants in eclipsing binary systems. From this we find that asteroseismology overestimates the mass and radius of red giants by 15% and 5% respectively. We further attempt to model the pulsations of a few of these stars using stellar evolution and oscillation codes. The goal is to determine which masses are correct and if there is a physical cause for the discrepancy in asteroseismic masses. We find there are many challenges to modeling evolved stars such as red giants and we address a few of the major concerns. These systems are some of the best studied systems to date and further exploration of their asteroseismic mysteries is inevitable.