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A Three-mode, Variable Velocity Jet Model for HH 34
Noriega-Crespo, A.; Raga, A.
Variable ejection velocity jet models can qualitatively explain the appearance of successive working surfaces in Herbig-Haro (HH) jets. This paper presents an attempt to explore which features of the HH 34 jet can indeed be reproduced by such a model. From previously published data on this object, we find evidence for the existence of a three-mode…
Infrared Observations of Ongoing Star Formation in the 30 Doradus Nebula and a Comparison with Hubble Space Telescope WFPC 2 Images
Walborn, Nolan R.; Barbá, Rodolfo H.; Rubio, Mónica +3 more
Intercomparisons of ground-based IR continuum and H_2 images with Hubble Space Telescope WFPC2 images of the 30 Dor Nebula reveal detailed structural relationships, which provide new information about current star formation there. Numerous stellar IR sources have been discovered in or near the bright nebular filaments west and northeast of R136; t…
Optical and Near-Infrared Model Images of the Circumstellar Environments of Classical T Tauri Stars
Wood, Kenneth; Kenyon, Scott J.; Whitney, Barbara +1 more
We describe model calculations of optical and near-infrared scattered light images expected from class II T Tauri stars--the star-plus-disk systems. The parameters controlling the disk shape, size, and mass are chosen to be within theoretically and observationally derived limits. We restrict our models to nearly edge-on disks, since for lower incl…
Ulysses' rapid crossing of the polar coronal hole boundary
Forsyth, R.; Balogh, A.; McComas, D. J. +2 more
The Ulysses spacecraft crossed from the slow dense solar wind characteristic of the solar streamer belt into the fast, less dense flow from the northern polar coronal hole over a very short interval (several days) in late March 1995. The spacecraft, which was at 1.35 AU and ~19° north heliographic latitude, moving northward in its orbit, remained …
Evidence for a 20 Parsec Disk at the Nucleus of Centaurus A
Marconi, Alessandro; Axon, David J.; Capetti, Alessandro +6 more
We report Hubble Space Telescope NICMOS observations of the central region of NGC 5128 at 2.2 µm and in Paα. The continuum images show extended emission typical of an elliptical galaxy and a strong unresolved central source we identify as the nucleus of the galaxy. Its position is consistent with ground-based IR and radio data, and with the …
Modelling the Cloverleaf: contribution of a galaxy cluster at Z ~ 1.7
Kneib, J. -P.; Antonucci, R.; Alloin, D. +3 more
We present a new investigation of the Cloverleaf (z=2.558) based on the combination of archival HST/WFPC2 data, recent IRAM CO(7-6) maps and wide field CFHT/FOCAM images. The deepest WFPC2 observation (F814W) shows a significant overdensity of I814W ~ 23--25 galaxies around the Cloverleaf that we interpret as the presence of a cluster o…
Solar H i Lyman alpha full disk profile obtained with the SUMER/SOHO spectrometer
Wilhelm, K.; Curdt, W.; Lemaire, P. +2 more
An uncalibrated solar hydrogen Lyman alpha profile was obtained with the use of the spectrometer on SOHO. The collection of the light scattered by the telescope permitted to average the profile over the full solar disk. The profile taken at the L1 Sun-Earth Lagrangian position is free of the central geocoronal absorption. Then, taking a…
Infrared Space Observatory Observations of Molecular Hydrogen in HH 54:Measurement of a Nonequilibrium Ratio of Ortho- to Para-H2
Neufeld, David A.; Melnick, Gary J.; Harwit, Martin
We have detected the S(1), S(2), S(3), S(4), and S(5) pure rotational lines of molecular hydrogen toward the outflow source HH 54 using the Short Wavelength Spectrometer on board the Infrared Space Observatory. The observed H2 line ratios indicate the presence of warm molecular gas with an H2 density of at least 105
The complex gravitational lens system B1933+503
Pearson, T. J.; Bremer, M.; Blandford, R. D. +15 more
We report the discovery of the most complex arcsec-scale radio gravitational lens system yet known. B1933+503 was found during the course of the CLASS survey and MERLIN and VLA radio maps reveal up to 10 components. Four of these are compact and have flat spectra; the rest are more extended and have steep spectra. The background lensed object appe…
Hot White Dwarfs in the Extreme-Ultraviolet Explorer Survey. IV. DA White Dwarfs with Bright Companions
Vennes, Stéphane; Thorstensen, John R.; Christian, Damian J.
We present an analysis of optical, ultraviolet, and X-ray spectral properties of a sample of 13 hot hydrogen-rich (DA) white dwarfs, each paired with a luminous unresolved companion. Using low-dispersion International Ultraviolet Explorer spectra, ROSAT photometry, and Extreme-Ultraviolet Explorer photometry and spectroscopy, we estimate the effec…