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Unidentified Infrared Emission Bands in the Diffuse Interstellar Medium
Okumura, K.; Nakagawa, T.; Onaka, T. +7 more
Using the mid-infrared spectrometer on board the Infrared Telescope in Space and the low-resolution grating spectrometer (PHT-S) on board the Infrared Space Observatory, we obtained 820 mid-infrared (5-12 µm) spectra of the diffuse interstellar medium (DIM) in the Galactic center, W51, and Carina Nebula regions. These spectra indicate that t…
Observational Tests and Predictive Stellar Evolution
Liebert, James; Mamajek, E. E.; Arnett, David +1 more
We compare 18 binary systems with precisely determined radii and masses from 23 to 1.1 Msolar and stellar evolution models produced with our newly revised code TYCHO. ``Overshooting'' and rotational mixing were suppressed in order to establish a baseline for isolating these and other hydrodynamic effects. Acceptable coeval fits are foun…
Detection of Coronal Mass Ejections in V471 Tauri with the Hubble Space Telescope
Bond, Howard E.; Sion, Edward M.; Mullan, D. J. +1 more
V471 Tauri, an eclipsing system consisting of a hot DA white dwarf (WD) and a dK2 companion in a 12.5 hr orbit, is the prototype of the precataclysmic binaries. The late-type component is magnetically active, due to its being constrained to rotate synchronously with the short orbital period. During a program of ultraviolet spectroscopy of V471 Tau…
Distant Cluster Hunting: A Comparison Between the Optical and X-Ray Luminosity Functions from an Optical/X-Ray Joint Survey
Dickinson, Mark; Mack, Jennifer; Donahue, Megan +6 more
We present a comparison of X-ray and optical luminosities and luminosity functions of cluster candidates from a joint optical/X-ray survey, the ROSAT Optical X-Ray Survey. Completely independent X-ray and optical catalogs of 23 ROSAT fields (4.8 deg2) were created by a matched-filter optical algorithm and by a wavelet technique in the X…
Infrared Properties of Weak Radio Sources in the ρ Ophiuchi Molecular Cloud
André, Philippe; Greene, Thomas P.; Wilking, Bruce A. +2 more
We report mid-infrared ISOCAM observations for a sample of radio continuum sources in the ρ Ophiuchi molecular cloud core with unknown or poorly studied infrared counterparts. These data are combined with existing infrared photometry, including recently published ISOCAM data, for previously studied radio sources to investigate the evolutionary sta…
Subarcsecond Mid-Infrared Structure of the Dust Shell around IRAS 22272+5435
Ueta, Toshiya; Fazio, Giovanni G.; Meixner, Margaret +6 more
We report subarcsecond imaging of extended mid-IR emission from a proto-planetary nebula (PPN), IRAS 22272+5435, performed at the MMT observatory with its newly upgraded 6.5 m aperture telescope and at the Keck observatory. The mid-IR emission structure is resolved into two emission peaks separated by 0.5"-0.6" in the MMT 11.7 µm image and i…
The Relative Star Formation Histories of Spiral Bulges and Elliptical Galaxies in the Hubble Deep Fields
Dickinson, Mark; Ellis, Richard S.; Abraham, Roberto G.
Hierarchical galaxy formation models make specific predictions concerning the relative assembly rates and star formation histories of spiral bulges and field ellipticals. Independently of the cosmological model and initial power spectrum of fluctuations, at all epochs the stellar populations in spiral bulges should be older and redder than those i…
The Solar Helium Abundance in the Outer Corona Determined from Observations with SUMER/SOHO
Feldman, U.; Laming, J. M.
At altitudes of about 1.05 Rsolar or more, the corona above quiet solar regions becomes essentially isothermal. This obviates many of the difficulties associated with the inverse problem of determining emission measure distributions and allows for fairly straightforward relative element abundance measurements. We present new values for …
Preliminary Astrometric Masses for Proposed Extrasolar Planetary Companions
Han, Inwoo; Gatewood, George; Black, David C.
As a first step in the implementation of an astrometric survey, we have reduced the Hipparcos intermediate astrometric data (IAD) for 30 stars that currently exhibit small-amplitude periodic radial velocity variations. We consider only systems with periods longer than 10 days, where the motion is attributed to the presence of an ``extrasolar plane…
Quasi-periodic Oscillation in Seyfert Galaxies: Significance Levels. The Case of Markarian 766
Yaqoob, Tahir; Staubert, Rüdiger; Wilms, Jörn +2 more
We discuss methods to compute significance levels for the existence of quasi-periodic oscillations (QPOs) in active galactic nuclei (AGNs) that take the red-noise character of the X-ray light curves of these objects into account. Applying epoch folding and periodogram analysis to the XMM-Newton observation of the Seyfert galaxy Mrk 766, a possible…