Astronomy 393S - Fall 2013
Seminar in Interstellar Matter
F 2:00 · RLM 15.216B · Not for credit Fall 2013
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Speaker
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Title
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Aug 30
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Neal Evans
University of Texas at Austin
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Organizational meeting.
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Sep 6
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Joel Green
University of Texas at Austin
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"Episodic Accretion in Young Stars"
abstract
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Sep 13
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Charles "Chat" Hull
University of California, Berkeley
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"From Clouds to Cores to Envelopes to Disks: A Multi-scale View of Magnetized Star Formation" (host: Joel Green)
abstract
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Sep 20
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Mike Pavel
University of Texas at Austin
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"Polarimetric Tomography of the Galactic Magnetic Field"
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Sep 27
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Adam Kraus, Joel Green, Michael Gully-Santiago, Neal Evans
University of Texas at Austin
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"Highlights from the Protostars & Planets VI Conference (Heidelberg, Germany: 15-20 July 2013)"
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Oct 4
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Vanessa Bailey
University of Arizona
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(host: Neal Evans) "Hole-y Debris Disks, Batman! (Giant planets sculpting disks and the technology we need to image them)"
abstract
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Oct 11
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No talk scheduled, to avoid conflict with the Bashfest 2013 Symposium (on 7-8 October).
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Oct 18
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Megan Reiter
University of Arizona
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"Jets from Intermediate-mass Protostars as a Fossil Record of Accretion"
abstract
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Oct 18
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Johanna Teske
University of Arizona
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"Diamonds in the Rough: A Cautionary Tale of C/O Ratios in Exoplanet Host Stars"
It is currently unknown how, or to what extent, the elemental compositions of planetary atmospheres correlate with those of their host stars. Also unclear is how different host star compositions influence planet occurrence. The C/O ratio is one measurement that may be used to better understand the compositional connection between stars and their planets. In gas giant atmospheres, the C/O ratio indicates the abundances of the primary oxygen and carbon species, which, along with nitrogen species, regulate the climates of planets in the Solar System. The composition of a planetary atmosphere affects its temperature and chemistry structure, and therefore its observable signatures. The C/O ratio also establishes interior mineralogy - i.e., whether the planet is silicate or carbon rich. Currently carbon and oxygen are the only elements that can potentially be measured in both star and exoplanet atmospheres. Large samples of planets and host star C/O measurements may reveal trends indicative of processes in the protoplanetary disk or planetary interior that shift the elemental composition of the planet away from that of the star. However, estimating C/O ratios in transiting exoplanet atmospheres is in most cases still based on only a few photometric observations. Moreover, even with high resolution, high S/N data, determinations of the stellar C/O ratios can be challenging. There are only a few oxygen abundance indicators at optical wavelengths and they are weak, blended with other atomic or molecular lines, and/or subject to non-LTE effects. I will present a small but methodologically consistent sample of C/O ratios measured in high-resolution spectra of transiting exoplanet host stars from several different carbon and oxygen abundance indicators, using traditional stellar abundance analysis techniques (including a differential, line-by-line abundance analysis with respect to the Sun as measured with the same instrument and set-up). I will discuss the challenges of host star measurements and what insights into planet formation and composition are possible from such analyses. In particular, I will highlight the case of 55 Cnc, a cool and metal-rich star whose oxygen measurements are even more complicated, and that hosts the "diamond" super-Earth planet 55 Cnc e.
close
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Oct 25
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Yao-Lun Yang
University of Texas at Austin
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"Molecular Hydrogen in the Diffuse Medium of the Large Magellanic Cloud"
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Nov 1
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"NRAO Community Day: NRAO Data Analysis Workshop (8 AM - 6 PM: POB 2.302 Avaya Auditorium)
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Nov 8
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Jeong-Eun Lee
Kyung Hee University, South Korea
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"Detailed Analysis of DIGIT Embedded Protostars"
abstract
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Nov 15
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Presentations by Manuel Merello and Emma Yu have been rescheduled to next week (22 November).
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Nov 22
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Manuel Merello
University of Texas at Austin
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"Physical Characterization of Galactic Star-forming Clumps using (Sub)millimeter Continuum Surveys"
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Nov 22
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Emma Yu
University of Texas at Austin
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"Probing the Protoplanetary Disks with ALMA - a CO Perspective"
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Nov 29
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Day after Thanksgiving Day: Staff Holiday. University Closed: No classes or seminars held today.
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Dec 6
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Harriet Dinerstein
University of Texas at Austin
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"Kappa Distributions: A Possible Solution to the Nebular Abundance Problem"
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Dec 6
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Amanda Turbyfill
University of Texas at Austin
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"Application of Kappa Distributions to Planetary Nebulae Spectra"
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