Calendar

Sep
1
Fri
Colloquium: Isak Wold (Host: Moire Prescott)
Sep 1 @ 3:15 pm – 4:15 pm
Colloquium: Isak Wold (Host: Moire Prescott) @ BX102

A Faint Flux-Limited LAE Sample at z = 0.3

Isak Wold, UT Austin

Observational surveys of Lya emitters (LAEs) have proven to be an efficient method to identify and study large numbers of galaxies over a wide redshift range. To understand what types of galaxies are selected in LAE surveys – and how this evolves with redshift – it is important to establish a low-redshift reference sample that can be directly compared to high-redshift samples.  The lowest redshift where a direct Lya survey is currently possible is at a redshift of z~0.3 via the Galaxy Evolution Explorer (GALEX ) FUV grism data. Using the z~0.3 GALEX sample as an anchor point, it has been suggested that at low redshifts high equivalent width (EW) LAEs become less prevalent and that the amount of escaping Lya emission declines rapidly.  A number of explanations for these trends have been suggested including increasing dust content, increasing neutral column density, and/or increasing metallicity of star-forming galaxies at lower redshifts. However, the published z~0.3 GALEX sample is pre-selected from bright NUV objects.  Thus, objects with strong Lya emission but faint continuum (high-EW LAEs) could be missed.  In this talk, I will present my efforts to re-reduce the deepest archival GALEX FUV grism data and obtain a sample that is not biased against high-EW LAEs.  I will discuss the implications of this new sample on the evolutionary trends listed above.

Sep
8
Fri
Colloquium: Travis Metcalfe (Host: Jason Jackiewicz)
Sep 8 @ 3:15 pm – 4:15 pm
Colloquium: Travis Metcalfe (Host: Jason Jackiewicz) @ BX102

The Magnetic Mid-life Crisis of the Sun

Dr. Travis Metcalfe, Space Sciences Institute

After decades of effort, the solar activity cycle is exceptionally well characterized but it remains poorly understood. Pioneering work at the Mount Wilson Observatory demonstrated that other sun-like stars also show regular activity cycles, and suggested two possible relationships between the rotation rate and the length of the cycle. Neither of these relationships correctly describe the properties of the Sun, a peculiarity that demands explanation. Recent discoveries have started to shed light on this issue, suggesting that the Sun’s rotation rate and magnetic field are currently in a transitional phase that occurs in all middle-aged stars. We have recently identified the manifestation of this magnetic transition in the best available data on stellar cycles. The results suggest that the solar cycle may be growing longer on stellar evolutionary timescales, and that the cycle might disappear sometime in the next 0.8-2.4 Gyr. Future tests of this hypothesis will come from ground-based activity monitoring of Kepler targets that span the magnetic transition, and from asteroseismology with the TESS mission to determine precise masses and ages for bright stars with known cycles.

Sep
11
Mon
Pizza Lunch: Drew Chojnowski and Sten Hasselhof
Sep 11 @ 12:30 pm – 1:30 pm
Pizza Lunch: Drew Chojnowski and Sten Hasselhof @ AY 119

A Peculiar Supergiant and One Weird Binary

Sep
15
Fri
Colloquium: Lisa Winter (Host: Laura Boucheron)
Sep 15 @ 3:15 pm – 4:15 pm
Colloquium: Lisa Winter (Host: Laura Boucheron) @ BX102

Long duration solar gamma ray flares

Lisa Winter, LANL

Long duration solar gamma ray flares (LDGRFs) present a challenge to models of solar flares. While the gamma ray emission initially was thought to be the high energy extension of emission produced at the footprints of flare loops, LDGRFs are more energetic than expectations and last hours after the X-ray emission subsides. Evidence of gamma ray emission from flares on the backside of the Sun prompted the idea that LDGRFs instead are created from acceleration of particles in the shock waves of coronal mass ejections (CMEs). To determine which of these scenarios is more likely, we conducted a study of the flare and CME properties for LDGRFs detected by the Fermi Gamma-Ray Observatory. We also performed a reverse association analysis to determine which flares and CMEs do not produce gamma-ray emission. In this talk, these results are presented, showing that LDGRFs are most likely associated with CME acceleration.

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.

 

Sep
29
Fri
Campus Observatory Open House
Sep 29 @ 8:00 pm – 9:00 pm
Campus Observatory Open House @ Campus Observatory

Welcome to the first open house of the 2017 Fall Semester. Your hosts will be: James McAteer, Jodi Berdis, Carlos Vargas, and Julie Imig.

The (September) Autumnal Equinox.

September Night Sky Chart.

Oct
2
Mon
Pizza Lunch: Sarah Kovac
Oct 2 @ 12:30 pm – 1:30 pm
Pizza Lunch: Sarah Kovac @ AY 119

The Citizen Cate Project

Oct
6
Fri
No Colloquium
Oct 6 @ 3:15 pm – 4:15 pm
No Colloquium @ BX102

Colloquium Title

Speaker name, institution

Abstract text

Oct
13
Fri
Colloquium: Kyoung-Soo Lee (Host: Moire Prescott)
Oct 13 @ 3:15 pm – 4:15 pm
Colloquium: Kyoung-Soo Lee (Host: Moire Prescott) @ BX102

Colloquium Title

Kyoung-Soo Lee, Purdue University

Abstract text

Oct
16
Mon
Pizza Lunch: Ken Naiff
Oct 16 @ 12:30 pm – 1:30 pm
Pizza Lunch: Ken Naiff @ AY 119

Dark Sky Images

Ken Naiff

Ken, an retired engineer, is a highly technically skilled and artistic
astrophotographer.  He will be sharing some of his work and elaborating on
the technical methods and processing techniques he applies to obtain his
unique and enhanced images.  You can see Ken’s work at:

https://darkskyimagesbyken.com/products