A5074725752- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
- Calibration and Measurement Techniques
- Pulsars and Gravitational Waves Research
- Planetary Science and Exploration
- Spacecraft and Cryogenic Technologies
- Atmospheric Ozone and Climate
- Particle Accelerators and Free-Electron Lasers
- Isotope Analysis in Ecology
- High-pressure geophysics and materials
- Atomic and Molecular Physics
- Adaptive optics and wavefront sensing
- History and Developments in Astronomy
- Spectroscopy and Laser Applications
- Space Exploration and Technology
- Solar and Space Plasma Dynamics
- Geophysics and Gravity Measurements
- Nuclear Physics and Applications
University of Minnesota
2014-2023
University of Minnesota System
1992-2021
Joint Institute for Nuclear Astrophysics
2018-2019
Macalester College
2010
George Mason University
2010
Sandia National Laboratories
2010
University of Hawaii System
2001-2005
Twin Cities Orthopedics
1990-2004
European Southern Observatory
1998-2001
Cerro Tololo Inter-American Observatory
1998
The Spitzer Space Telescope, NASA's Great Observatory for infrared astronomy, was launched 2003 August 25 and is returning excellent scientific data from its Earth-trailing solar orbit. combines the intrinsic sensitivity achievable with a cryogenic telescope in space great imaging spectroscopic power of modern detector arrays to provide user community huge gains capability exploration cosmos infrared. observatory systems are largely performing as expected, projected lifetime excess 5 years....
We report 4.5 micron luminosities for 27 nearby (D < 5 Mpc) dwarf irregular galaxies measured with the Spitzer Infrared Array Camera. have constructed luminosity-metallicity (L-Z) relation 25 secure distance and interstellar medium oxygen abundance measurements. The L-Z is 12+log(O/H) = (5.78 +/- 0.21) + (-0.122 0.012) M_[4.5], where M_[4.5] absolute magnitude at micron. dispersion in near-infrared smaller than corresponding optical relation. subsequently derived stellar mass-metallicity...
The Stratospheric Observatory For Infrared Astronomy (SOFIA) is an airborne observatory consisting of a specially modified Boeing 747SP with 2.7 m telescope, flying at altitudes as high 13.7 km (45,000 ft). Designed to observe wavelengths from 0.3 μm 1.6 mm, SOFIA operates above 99.8% the water vapor that obscures much infrared and submillimeter. has seven science instruments under development, including occultation photometer, near-, mid-, far-infrared cameras, spectrometers, heterodyne...
Classical novae, explosions that result from thermonuclear runaways (TNRs) on the surfaces of white dwarfs (WDs) accreting hydrogen‐rich matter in close binary systems, are sporadically injecting material processed by explosive hydrogen‐burning nucleosynthesis into interstellar medium (ISM). Although novae probably have less than ∼0.3% Galaxy, both theoretical and observational evidence suggests they may be important sources nuclides 7Li, 15N, 17O, as well radioactive isotopes 22Na 26Al. The...
We examine thermal infrared images of η Car at wavelengths from 4.8 to 25 μm obtained with the MIRAC3 camera system Magellan Observatory, and we conclude that Car's circumstellar Homunculus Nebula contains much more mass (12 M⊙) kinetic energy (1049.6–1050 ergs) than had previously been recognized. Excess far-infrared emission a large cold dust discovered recently by Morris et al., which they attributed 110 K in compact equatorial torus. Our suggest, however, roughly 10 M⊙ or resides instead...
view Abstract Citations (378) References (39) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Infrared observations of Be stars from 2.3 to 19.5 microns. Gehrz, R. D. ; Hackwell, J. A. Jones, T. W. 33 "classical" and 26 early-type comparison objects are presented. Excess infrared radiation in the 2.3-19.5 IL spectral region was observed for 28 stars. Circumstellar-dust emission models ruled out. Free-free a hot (T > 10,000" K) circumstellar plasma shell is...
view Abstract Citations (365) References (24) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Mass Loss from M Stars Gehrz, R. D. ; Woolf, N. J. Infrared observations of giants and supergiants show that circumstellar dust shells are frequently present. The permit the radii densities to be determined. It is shown radiation pressure drives particles through gas at a velocity varies with density. momentum coupling out star. Velocities ejection estimated compared...
Evolutionary models have shown the substantial effect that strong mass-loss rates ($\dot{M}$) can on fate of massive stars. Red supergiant (RSG) is poorly understood theoretically, and so stellar rely purely empirical \mdot-luminosity relations to calculate evolution. Empirical prescriptions usually scale with luminosity effective temperature, but $\dot{M}$ should also depend current mass hence surface gravity star, yielding more than one possible for same position Hertzsprung-Russell...
We present HST/WFPC2 images plus ground-based infrared and photometry of the very luminous OH/IR star VY Canis Majoris. Our WFPC2 data show a complex distribution knots filamentary arcs in asymmetric reflection nebula around obscured central star. The may result from multiple, ejection episodes due to localized events on CMa's surface. Such probably involve magnetic fields convection, by analogy with solar activity. Surface indicates that have experienced enhanced mass loss over past 1000...
My life has been an interesting voyage. I became astronomer because could not imagine living on Earth and trying to understand how the Universe works. scientific career revolved around observing motions of stars within galaxies ...Read More
We report the first results of imaging Carina Nebula with Spitzer/IRAC, providing a catalog point sources and YSOs based on SED fits. discuss several aspects extended emission, including dust pillars that result when clumpy molecular cloud is shredded by massive star feedback. There are few "extended green objects" (EGOs) normally taken as signposts outflow activity, none HH jets detected optically seen EGOs. A population red tends to be found around OB stars, some clear bow-shocks. These...
Abstract We present an ongoing, five-year systematic search for extragalactic infrared transients, dubbed SPIRITS—SPitzer InfraRed Intensive Transients Survey. In the first year, using Spitzer /IRAC, we searched 190 nearby galaxies with cadence baselines of one month and six months. discovered over 1958 variables 43 transients. Here, describe survey design highlight 14 unusual transients no optical counterparts to deep limits, which refer as SPRITEs (eSPecially Red Intermediate-luminosity...
The DUSTiNGS survey (DUST in Nearby Galaxies with Spitzer) is a 3.6 and 4.5 μm imaging of 50 nearby dwarf galaxies designed to identify dust-producing asymptotic giant branch (AGB) stars massive stars. Using two epochs, spaced approximately six months apart, we total 526 dusty variable AGB (sometimes called "extreme" or x-AGB stars; [3.6]–[4.5] > 0.1 mag). Of these, 111 are [Fe/H] < −1.5 12 −2.0, making them the most metal-poor known. We compare these identifications those literature find...
Luminous Red Novae (LRNe) are astrophysical transients associated with the partial ejection of a binary system's common envelope (CE) shortly before its merger. Here we present results our photometric and spectroscopic follow-up campaign AT2018bwo (DLT18x), LRN discovered in NGC45, investigate progenitor system using stellar-evolution models. The transient reached peak magnitude $M_r=-10.97\pm0.11$ maintained this brightness during optical plateau $t_p = 41\pm5$days. During phase, it showed...
We present 3.6, 4.5, 5.8, 8.0, 24, and 70 μm images of the Crab Nebula obtained with Spitzer Space Telescope IRAC MIPS cameras, low- high-resolution IRS spectra selected positions within nebula, a near-infrared ground-based image made in light [Fe II] 1.644 μm. The 8.0 image, bandpass that includes [Ar 7.0 μm, resembles general morphology visible Hα near-IR line emission, while 3.6 4.5 are dominated by continuum synchrotron emission. 24 show enhanced emission may be due to or presence small...
Mid-infrared observations of the Andromeda galaxy, M31, obtained with Infrared Array Camera on board Spitzer Space Telescope, are presented. The image mosaics cover areas approximate 3.7deg x 1.6deg and include satellite galaxies M32 NGC 205. appearance M31 varies dramatically in different mid-infrared bands, from smooth bulge disk old stellar population seen at 3.6um to well-known '10 kpc ring' dominating 8um image. similarity optical isophotes nearly constant optical-mid-infrared color...
We present spectral energy distribution modelling of 6875 stars in omega Centauri, obtaining stellar luminosities and temperatures by fitting literature photometry to state-of-the-art MARCS models. By comparison four different sets isochrones, we provide a new distance estimate the cluster 4850 +/- 200 (random) 120 (systematic error) pc, reddening E(B-V) = 0.08 0.02 mag differential Delta[E(B-V)] < for an age 12 Gyr. Several post-early-AGB candidates are also found. Infra-red excesses...
Aims.We investigate the energy sources of infrared (IR) emission and their relation to radio continuum at various spatial scales within Scd galaxy M 33.
view Abstract Citations (142) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Infrared color and the diffuse interstellar bands. Sneden, C. ; Gehrz, R. D. Hackwell, J. A. York, G. Snow, T. P. Broad-band infrared photometric measurements have been gathered for 105 stars which exhibit bands in their spectra. All normal obey a single reddening law, value of R equal to 3.08 + or - 0.15 is derived. This consistent with other recent determinations...
We present a systematic study of mid-infrared (mid-IR) emission from 141 nearby supernovae (SNe) observed with the InfraRed Array Camera (IRAC) on Spitzer.These SNe reside in one 190 galaxies within 20 Mpc drawn ongoing SPIRITS program. detect 8 Type Ia and 36 core-collapse SNe. All I become undetectable 3 years explosion. About 22$\pm$11% II continue to be detected at late-times. Dust luminosity, temperature, lower liit mass are obtained by fitting SED using photometry IRAC bands 1 2. The...