Calendar

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.

 

Mar
29
Thu
Colloquium (Joint with Physics): Jim Fuller (Host: Ethan Dederick)
Mar 29 @ 4:00 pm – 5:00 pm
Colloquium (Joint with Physics): Jim Fuller (Host: Ethan Dederick) @ Gardiner Hall 230

Surprising Impacts of Gravity Waves

Jim Fuller, Caltech

Gravity waves are low frequency fluid oscillations restored by buoyancy forces in planetary and stellar interiors. Despite their ubiquity, the importance of gravity waves in evolutionary processes and asteroseismology has only recently been appreciated. For instance, Kepler asteroseismic data has revealed gravity modes in thousands of red giant stars, providing unprecedented measurements of core structure and rotation. I will show how gravity modes (or lack thereof) can also reveal strong magnetic fields in the cores of red giants, and I will demonstrate that strong fields appear to be common within “retired” A stars but are absent in their lower-mass counterparts. In the late phase evolution of massive stars approaching core-collapse, vigorous convection excites gravity waves that can redistribute huge amounts of energy within the star. I will present preliminary models of this process, showing how wave energy redistribution can drive outbursts and enhanced mass loss in the final years of massive star evolution, with important consequences for the appearance of subsequent supernovae.
Oct
8
Mon
Pizza lunch: Patrick Gaulme
Oct 8 @ 12:30 pm – 1:30 pm
Pizza lunch: Patrick Gaulme @ AY 119

Red giants, eclipsing binaries, and asteroseismology.

Patrick Gaulme, Max Planck Institute for Solar System Research

Jan
23
Wed
Colloquium Thesis Defense: Lauren Kahre
Jan 23 @ 3:00 pm – 4:00 pm
Colloquium Thesis Defense: Lauren Kahre

Extinction Mapping and Dust-to-Gas Ratios of Nearby Galaxies

Lauren Kahre, NMSU

We present a study of the dust{to{gas ratios in 31 nearby (D >
10 Mpc) galaxies. Using Hubble Space Telescope broad band WFC3/UVIS UV and
optical images from the Treasury program LEGUS (Legacy ExtraGalactic UV
Survey) combined with archival HST/ACS data, we correct thousands of
individual stars for extinction across these galaxies using an
isochrone-matching (reddening-free Q) method. We generate extinction maps
for each galaxy from the individual stellar extinctions using both
adaptive and fixed resolution techniques, and correlate these maps with
neutral HI and CO gas maps from literature, including The HI Nearby Galaxy
Survey (THINGS) and the HERA CO-Line ExtraGalactic Survey (HERACLES). We
calculate dust-to-gas ratios and investigate variations in the dust-to-gas
ratio with galaxy metallicity. We find a power law relationship between
dust-to-gas ratio and metallicity. The single power law is consistent with
other studies of dust-to-gas ratio compared to metallicity, while the
broken power law shows a significantly shallower slope for low metallicity
galaxies than previously observed. We find a change in the relation when
H_2 is not included. This implies that underestimation of N_H2 in
low-metallicity dwarfs from a too-low CO-to-H2 conversion factor X_CO
could have produced too low a slope in the derived relationship between
dust-to-gas ratio and metallicity. We also
compare our extinctions to those derived from fitting the spectral energy
distribution (SED) using the Bayesian Extinction and Stellar Tool (BEAST)
for NGC 7793 and and systematically lower extinctions from SED-fitting as
compared to isochrone matching. Finally, we compare our extinction maps of
NGC 628 to maps of the dust obtained via IR emission from Aniano et al.
(2012) and find a factor of 2 difference in dust-to-gas ratios determined
from the two maps, consistent with previous work.

Jan
25
Fri
Pizza Lunch Talk: Dale Frail
Jan 25 @ 11:30 am – 12:30 pm
Pizza Lunch Talk: Dale Frail @ AY 119

How to Write A Competitive Prize Postdoc Application

Dale Frail, NRAO

Colloquium: Dale Frail (Host: Sarah Kovac)
Jan 25 @ 3:15 pm – 4:15 pm
Colloquium: Dale Frail (Host: Sarah Kovac) @ BX102

Multi-Messenger EM-GW Astronomy: The View from the Radio End of the EM Spectrum

Dale Frail, NRAO

Abstract: With the discovery of gravitational waves and electromagnetic radiation from the binary neutron star merger GW170817, the era of GW multi-messenger astronomy has begun with style. I will describe the discovery, show where progress has been made in several areas, and then move on to describe a controversy regarding the origin of the afterglow emission. After explaining the importance of this issue, I will show how late-time radio observations have decisively resolved the issue. I will end with a discussion of the future, with an emphasis on the role of radio observations in finding and studying EM counterparts.

Feb
20
Wed
Special Colloquium: Stella Kafka (Host: Karen Kinemuchi)
Feb 20 @ 3:15 pm – 4:15 pm
Special Colloquium: Stella Kafka (Host: Karen Kinemuchi) @ Domenici Hall

The AAVSO Program: A Resource for Variable Star Research

Stella Kafka, AAVSO

The AAVSO was formed in 1911 as a group of US-based amateur observers obtaining data in support of professional astronomy projects. Now, it has evolved into an International Organization with members and observers from both the professional and non-professional astronomical community, contributing photometry to a public photometric database of about 25,000 variable objects, and using it for research projects. As such, the AAVSO’s main claim to fame is that it successfully engages backyard Astronomers, educators, students and professional astronomers in astronomical research. I will present the main aspects of the association and how it has evolved with time to become a premium resource for variable star researchers. I will also discuss the various means that the AAVSO is using to support cutting-edge variable star science, and how it engages its members in projects building a stronger international astronomical community.

 

Dr. Stella Kafka, is the Director of the AAVSO (American Association of Variable Star Observers). Before her tenure at the AAVSO, Dr Kafka held positions at CTIO, Spitzer Science center/Caltech, Carnegie Institution of Washington/DTM and AIP Publishing. The AAVSO is an international non-profit organization of variable star observers whose mission is to enable anyone, anywhere, to participate in scientific discovery through variable star astronomy.

Feb
22
Fri
Pizza Lunch Talk: Takashi Sekii
Feb 22 @ 12:15 pm – 1:15 pm
Pizza Lunch Talk: Takashi Sekii @ AY 119

Title

Takashi Sekii, National Astronomical Observatory of Japan

Abstract

Mar
1
Fri
Colloquium: RESERVED (Host: TBD)
Mar 1 @ 3:15 pm – 4:15 pm
Colloquium: RESERVED (Host: TBD) @ BX102

Colloquium Title

Colloquium Speaker Name, Affiliation

Abstract text

Mar
4
Mon
Pizza Lunch Talk: Mark Rutkowski
Mar 4 @ 12:30 pm – 1:30 pm
Pizza Lunch Talk: Mark Rutkowski @ AY 119

Ultraviolet Observations of Galaxies

Mark Rutkowski, Minnesota State Univeristy

Ultraviolet observations are essential for answering fundamental questions regarding the role and impact of galaxies in universe. I’ll discuss a number of past, ongoing, and future UV-optical-near IR high redshift surveys with which I am involved and the specific constraints the UV provides on these open questions. Specifically, I’ll highlight the utility of UV observations of starbursts and quiescent galaxies alike for constraining the history of reionization, hierarchical assembly, and (if there’s time) the cosmic history of metals.