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The carrier of the ``30'' mu m emission feature in evolved stars. A simple model using magnesium sulfide
Waters, L. B. F. M.; Hony, S.; Tielens, A. G. G. M.
We present 2-45 mu m spectra of a large sample of carbon-rich evolved stars in order to study the ``30'' mu m feature. We find the ``30'' mu m feature in a wide range of sources: low mass loss carbon stars, extreme carbon-stars, post-AGB objects and planetary nebulae. We extract the profiles from the sources by using a simple systematic approach t…
Tightly Correlated X-Ray/Hα-emitting Filaments in the Superbubble and Large-Scale Superwind of NGC 3079
Veilleux, Sylvain; Bland-Hawthorn, Joss; Cecil, Gerald
Using Chandra and HST, we show that X-ray and Hα filaments that form the 1.3 kpc diameter superbubble of NGC 3079 have strikingly similar patterns at ~0.8" resolution. This tight optical line/X-ray match seems to arise from cool disk gas that has been driven by the wind, with X-rays being emitted from upstream, standoff bow shocks or by conductive…
The Star Formation Rate Intensity Distribution Function: Implications for the Cosmic Star Formation Rate History of the Universe
Chen, Hsiao-Wen; Lanzetta, Kenneth M.; Pascarelle, Sebastian +2 more
We address the effects of cosmological surface brightness dimming on observations of faint galaxies by examining the distribution of ``unobscured'' star formation rate intensities versus redshift. We use the star formation rate intensity distribution function to assess the ultraviolet luminosity density versus redshift, based on our photometry and…
ISO spectroscopy of compact H II regions in the Galaxy. II. Ionization and elemental abundances
Kessler, M. F.; Morisset, C.; Schaerer, D. +9 more
Based on the ISO spectral catalogue of compact H II regions by \cite{peeters:catalogue}, we present a first analysis of the hydrogen recombination and atomic fine-structure lines originated in the ionized gas. The sample consists of 34 H II regions located at galactocentric distances between RGal,= 0 and 15 kpc. The SWS H I recombinatio…
Sources of the solar wind at solar activity maximum
Smith, E. J.; Neugebauer, M.; Zurbuchen, T. H. +2 more
The photospheric sources of solar wind observed by the Ulysses and ACE spacecraft from 1998 to early 2001 are determined through a two-step mapping process. Solar wind speed measured at the spacecraft is used in a ballistic model to determine a foot point on a source surface at a solar distance of 2.5 solar radii. A potential-field source-surface …
WIYN Open Cluster Study. X. The K-Band Magnitude of the Red Clump as a Distance Indicator
Sarajedini, Ata; Grocholski, Aaron J.
In an effort to improve the utility of the helium-burning red clump luminosity as a distance indicator, we explore the sensitivity of the K-band red clump absolute magnitude [MK(RC)] to metallicity and age. We rely upon JK photometry for 14 open clusters and two globular clusters from the Second Incremental Data Release of the Two Micro…
Crystalline silicate dust around evolved stars. I. The sample stars
Waters, L. B. F. M.; Barlow, M. J.; Tielens, A. G. G. M. +1 more
This is the first paper in a series of three where we present the first comprehensive inventory of solid state emission bands observed in a sample of 17 oxygen-rich circumstellar dust shells surrounding evolved stars. The data were taken with the Short and Long Wavelength Spectrographs on board of the Infrared Space Observatory (ISO) and cover the…
Ten Low-Mass Companions from the Keck Precision Velocity Survey
Butler, R. Paul; Vogt, Steven S.; Fischer, Debra A. +4 more
Ten new companions have emerged from the Keck precision Doppler velocity survey, with minimum (Msini) masses ranging from 0.8 MJUP to 0.34 Msolar. Five of these are planet candidates with Msini<12 MJUP, two are brown dwarf candidates with Msini~30 MJUP, and three are low-mass stellar companions. Hippa…
Magnetic Topology of Impulsive and Gradual Solar Energetic Particle Events
Reames, Donald V.
We examine the magnetic topology at the Sun that leads to the two classes of impulsive and gradual solar energetic particle (SEP) events so as to address new observations that seem to blur this classification, for example, that coronal mass ejections (CMEs) can accompany events of both classes. In our model, the unusual element abundances in impul…
The Star Formation History of the Large Magellanic Cloud
Cole, Andrew A.; Gallagher, John S., III; Stetson, Peter B. +1 more
Using WFPC2 on board the Hubble Space Telescope, we have created deep color-magnitude diagrams in the V and I passbands for approximately 105 stars in a field at the center of the LMC bar and another in the disk. The main-sequence luminosity functions (LFs) from 19<=V<=23.5, the red clump and horizontal branch morphologies, and th…