Using the Mid-infrared to Measure the Thermal Structure of M Supergiant Winds Where it Matters

Event date
Speaker
Graham Harper
Affiliation
University of Colorado, Boulder
Location
N/A
Event Type

The mid-IR lends itself to the study of the low temperatures found in the circumstellar envelopes of M supergiants, e.g., with the Kuiper Airborne Observatory. To make quantitative tests of  mass loss models requires us to probe the dynamics and thermodynamics within the first few stellar radii - where most of the energy is input into the wind. We describe our results of using forbidden Fe II diagnostics observed with the EXES and TEXES R=50,000 spectrographs on NASA-DLR's SOFIA and NASA IRTF, respectively.

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Searching for Cool Dust in the Mid-to-Far Infrared: the Mass Loss Histories of the Hypergiants mu Cep, VY CMa, IRC +10420 & rho Cas

Event date
Speaker
Dinesh Shenoy
Affiliation
University of Minnesota
Location
N/A
Event Type

We present mid- and far- IR imaging of four famous hypergiant stars:  the red supergiants mu Cep and VY CMa, and the warm hypergiants IRC +10420 and rho Cas.  Our 11 to 37 micron SOFIA/FORCAST imaging probes cool dust not detected in visual and near-IR imaging studies.  We find mu Cep's mass-loss rate to have declined by about a factor of 5 over a 13,000 year history, ranging from 5E-06 down to ~1E-06 M_sun /yr.  The morphology of VY CMa indicates a cooler dust component coincident with the highly asymmetric reflection nebulae seen in the visual and near-IR.  The lack of cold dust at greate

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The upGREAT Heterodyne Arrays for the SOFIA Telescope

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Speaker
Christophe Risacher
Affiliation
MPIfR Bonn
Location
N/A
Event Type

We present the upGREAT heterodyne arrays for astronomy, used with the SOFIA airborne observatory. The upGREAT array receivers will operate at two different frequency ranges, the low frequency array (LFA) covering the 1.9-2.5 THz band with 14 pixels, and the high frequency array (HFA) covering the 4.745 THz line of atomic oxygen [O I] with 7 pixels. The frontend operates superconducting Hot Electron Bolometers (HEB) waveguide mixers. The local oscillators are based on commercial synthesizer driven solid-state multiplier chains for the LFA and a QCL for the HFA.

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Infrared Observations of Novae in the SOFIA Era

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Speaker
Bob Gehrz
Affiliation
University of Minnesota
Location
N/A
Event Type

Classical novae may contribute to some of the isotopic anomalies that are present in the remnants of the primitive solar system. We describe the way infrared (IR) photometric and spectroscopic observations can quantify the physical parameters of nova explosions and their contributions to the Inter-Stellar Medium (ISM). Metal abundances in the ejecta can be deduced from both IR dust emission features and forbidden line emission. We show that some novae have produced ejecta extremely overabundant in CNO, Ne, Mg, Al, and Si.

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An Apparent Precessing Helical Outflow from a Massive Evolved Star: Evidence for Binary Interaction?

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Speaker
Ryan Lau
Affiliation
Caltech/JPL
Location
N/A
Event Type

Massive, evolved stars play a crucial role in the metal-enrichment, dust budget, and energetics of the interstellar medium; however, the details of their evolution are uncertain because of their rarity and short lifetimes before exploding as supernovae. Discrepancies between theoretical predictions from single-star evolutionary models and observations of massive stars have evoked a shifting paradigm that implicates the importance of binary interaction.

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A Map of D/H on Mars using EXES Aboard SOFIA

Event date
Speaker
Thérèse Encrenaz
Affiliation
Paris Observatory - Meudon
Location
N/A
Event Type

CANCELED, rescheduled for April 13, 2016. Integrated over the planetary disk, the measurement of the D/H ratio on Mars is an important indicator of the loss of water over the history of the planet, through the process of differential escape. At a local scale, it is also a diagnostic of the water exchange with surface regolith, through fractionation due to differential condensation processes. A global measurement of D/H on Mars was first achieved by Owen et al. (1988), indicating an enrichment by a factor 6 (+/- 3) wrt the terrestrial value (VSMOW).

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A Map of D/H on Mars using EXES Aboard SOFIA

Event date
Speaker
Thérèse Encrenaz
Affiliation
Paris Observatory - Meudon
Location
N/A
Event Type

(Rescheduled from March 30) Integrated over the planetary disk, the measurement of the D/H ratio on Mars is an important indicator of the loss of water over the history of the planet, through the process of differential escape. At a local scale, it is also a diagnostic of the water exchange with surface regolith, through fractionation due to differential condensation processes. A global measurement of D/H on Mars was first achieved by Owen et al. (1988), indicating an enrichment by a factor 6 (+/- 3) wrt the terrestrial value (VSMOW).

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Characterizing the Life Cycle of the Interstellar Medium and Star Formation in Galaxies with the [CII] 158 um Line

Event date
-
Speaker
Jorge Pineda
Affiliation
JPL
Location
N232, Room 227
Event Type

The [CII] 158 um line is a powerful tool to understand the evolution of the interstellar medium and star formation in galaxies. The [CII] line traces different phases of the interstellar medium (ISM), including the diffuse ionized medium, warm and cold atomic clouds, clouds in transition from atomic to molecular, and dense and warm photon dominated regions (PDRs).  In particular, the [CII] line is a tracer of the CO-dark H2 gas, in which hydrogen is molecular but carbon is ionized and thus is not traced by CO.

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Formation and Evolution of Dust and Molecules in the Inhomogeneous Ejecta of Cassiopeia A

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Speaker
Chiara Biscaro
Affiliation
University of Copenhagen
Location
N232, Room 227
Event Type

Dust and molecules are observed in various supernovae and their remnants, but their formation and evolution in these hostile, shocked environments are still unclear. In the 330 years-old remnant Cas A, the reverse shock is currently reprocessing the material formed in the supernova ejecta. Our aim is to assess whether supernovae are important contributors to the dust budget of galaxies. The Cas A remnant results from the explosion of a 19 Msun star as a Type IIb supernova characterised by a low-density ejecta.

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From Protostars to Clouds: Stellar Feedback During the Early Stages of Star Formation

Event date
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Speaker
Hector Arce
Affiliation
Yale University
Location
N232, Room 103
Event Type

Outflows from young stars are among the most prominent signposts of star formation. They deposit energy and momentum into their surroundings and have a considerable impact on the dynamics, distribution, and chemical composition of the gas in star-forming clouds. Protostellar winds originate within a few AU (or less) of the forming star and may reach linear sizes of a few parsecs. Thus, they interact with a variety of environments in the interstellar medium, from the high-density envelope surrounding the protostar to the low-density atomic medium surrounding the parent molecular cloud.

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New Views of Planet-Forming Disks with Millimeter Interferometry

Event date
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Speaker
David Wilner
Affiliation
Harvard University
Location
N232, Room 227
Event Type

The circumstellar disks that naturally arise from the star formation process are the sites where planets are made. Many hundreds of these analogs to the disk that spawned our Solar System are nearby and accessible to detailed investigation. Millimeter interferometers provide direct access to the cool material in these disks, enabling resolved observations of morphology and properties of solids, as well as the thermal, chemical, and dynamical structure of gas, all of which impact what kind of planetary systems, if any, may form (or may be forming now).

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