Calendar

Sep
21
Mon
Pizza Lunch: Drew Chojnowski
Sep 21 @ 12:30 pm – 1:30 pm
Pizza Lunch: Drew Chojnowski

APOGEE Be stars

Nov
6
Fri
Colloquium: John Wisniewski
Nov 6 @ 3:15 pm – 4:15 pm
Colloquium:  John Wisniewski @ BX102

Diagnosing the SEEDS of Planet Formation

John Wisniewski, University of Oklahoma

Circumstellar disks provide a useful astrophysical diagnostic of the formation and early evolution of exoplanets. It is commonly believed that young protoplanetary disks serve as the birthplace of planets, while older debris disks can provide insight into the architecture of exoplanetary systems. In this talk, I will discuss how one can use high contrast imaging techniques to spatially resolve nearby circumstellar disk systems, and how this imagery can be used to search for evidence of recently formed planetary bodies. I will focus on results from the Strategic Exploration of Exoplanets and Disks with Subaru (SEEDS) project, as well as some ongoing follow-up work.

Sep
19
Mon
Pizza Lunch: Reta Beebe
Sep 19 @ 12:30 pm – 1:30 pm
Pizza Lunch: Reta Beebe @ AY 119

Title: JUNO

Reta Beebe

A .pdf of the talk can be found here.

 

 

Nov
14
Mon
Pizza Lunch: Drew Chojnowski
Nov 14 @ 12:30 pm – 1:30 pm
Pizza Lunch: Drew Chojnowski @ AY 119

Title: H-band Spectral Variability of Classical Be Stars

Drew Chojnowski

 

Feb
24
Fri
Colloquium: Thomas Rivinius
Feb 24 @ 3:15 pm – 4:15 pm
Colloquium: Thomas Rivinius

Our Current Understanding of Classical Be Stars

Dr. Thomas Rivinius, Chile, ESO Paranal

I will introduce Be stars as B-type stars with gaseous disks in Keplerian rotation. These disks form by mass ejection from the star itself and their evolution is then governed by viscosity. The observables and their formation in the disk will be discussed, as well as what we know about the central stars: they are the most rapidly rotating non-degenerate stars, they are non-radial pulsators, and they do not show magnetic fields. The pulsation is clearly (phenomenologically) linked to the mass ejection, but the physical mechanism responsible for the ejection and disk formation is not known. Finally, I will discuss several open questions of broader interest, including the (possibly absent) chemical mixing of very rapid rotators and the unexpectedly large viscosity of Be star disks.

 

Apr
7
Fri
Colloquium: Lauren Waszek (Host: Jason Jackiewicz)
Apr 7 @ 3:15 pm – 4:15 pm
Colloquium: Lauren Waszek (Host: Jason Jackiewicz) @ BX102

The growth of Earth’s inner core: a new technique to constrain seismic properties in its outermost layers

Dr. Lauren Waszek, Department of Physics, NMSU

The inner core displays a hemispherical difference in seismic velocity, attenuation, and anisotropy, which is well-established from seismic studies. Recent observations reveal increasingly complex and regional features. However, geodynamical models generally only attempt to explain the basic east-west asymmetry. Regional seismic features, such as depth-dependence anisotropy or variation in hemisphere boundaries, are difficult to reproduce and relatively poorly constrained by seismic data. Processes to generate these complex features are debated.

The structures of the inner core are suggested to be formed as the inner core grows over time. Thus, the most recently-formed outermost layers likely hold the key to understanding the geodynamical mechanisms generating the inner core properties. Current datasets of the uppermost inner core and inner core boundary are limited by uneven data coverage, however. In the very uppermost inner core, seismic waves arrive with similar travel times and interfere, making measurements difficult.

Despite the uneven coverage of current datasets, we can use them to infer a very slow inner core super-rotation. The first ever global tomographical inversion for the inner core allows us to make regional observations, and map the lateral variation in the hemispherical structures. In the uppermost inner core, we have developed a new waveform modeling technique with synthetic data to separate these seismic phases, allowing us to measure the seismic properties in the very uppermost inner core. This, in combination with geodynamical modeling, will help us determine how the inner core hemispheres and other features are generated.