Search Publications
Interstellar reddening from the HIPPARCOS and TYCHO catalogues. I. Distances to nearby molecular clouds and star forming regions
Knude, J.; Hog, E.
The Hipparcos and Tycho Catalogues offer an interesting possibility to study the local distribution of interstellar reddening from the combination of data contained in the catalogues: Hipparcos parallaxes, Tycho B - V and spectral and luminosity classification compiled from the literature. Parallactic distances may be derived for known absorbing f…
Galactocentric Distance with the Optical Gravitational Lensing Experiment and HIPPARCOS Red Clump Stars
Paczyński, Bohdan; Stanek, Krzysztof Z.
We compare red clump stars with parallaxes known to better than 10% in the Hipparcos catalog and corrected for interstellar extinction with the OGLE red clump stars in Baade's Window, also corrected for interstellar extinction. There are ~600 and ~10,000 such stars in the two data sets, respectively. We find empirically that the average I-band mag…
Energy Distribution of Heating Processes in the Quiet Solar Corona
Krucker, Säm; Benz, Arnold O.
We have determined the variations in the emission measure of the solar corona using EUV Imaging Telescope/Solar and Heliospheric Observatory observations of iron lines in a quiet region of the Sun. The emission measure is found to vary significantly in at least 85% of all the pixels within 42 minutes. The variations are interpreted as heating even…
An Edge-On Circumstellar Disk in the Young Binary System HK Tauri
Ménard, François; Krist, John E.; Stapelfeldt, Karl R. +3 more
Hubble Space Telescope (HST) images of HK Tauri reveal that the companion star in this 2.4" (340 AU) pre-main-sequence binary system is an entirely nebulous object at visual wavelengths. HK Tau/c appears as two elongated reflection nebulosities separated by a dark lane. Near-infrared adaptive optics observations made at the Canada-France-Hawaii Te…
Improved Evidence for a Black Hole in M32 from HST/FOS Spectra. II. Axisymmetric Dynamical Models
van der Marel, Roeland P.; Rix, Hans-Walter; de Zeeuw, P. Tim +1 more
Axisymmetric dynamical models are constructed for the E3 galaxy M32 to interpret high spatial resolution stellar kinematical data obtained with the Hubble Space Telescope (HST). Models are studied with two-integral, f(E, Lz), phase-space distribution functions and with fully general three-integral distribution functions. The latter are …
Multiwavelength Observations of a Dramatic High-Energy Flare in the Blazar 3C 279
Maraschi, L.; Ghisellini, G.; Pian, E. +69 more
The blazar 3C 279, one of the brightest identified extragalactic objects in the γ-ray sky, underwent a large (factor of ~10 in amplitude) flare in γ-rays toward the end of a 3 week pointing by Compton Gamma Ray Observatory (CGRO), in 1996 January-February. The flare peak represents the highest γ-ray intensity ever recorded for this object. During …
Hubble Space Telescope Imaging of the CFRS and LDSS Redshift Surveys. I. Morphological Properties
Tresse, Laurence; Brinchmann, Jarle; Broadhurst, Tom +9 more
We analyze Hubble Space Telescope images of a complete sample of 341 galaxies drawn from the CFRS and LDSS ground-based redshift surveys. In this, the first paper in the series, each galaxy has been morphologically classified according to a scheme similar to that developed for the Medium Deep Survey. We discuss the reproducibility of these classif…
The Far-Ultraviolet Oxygen Airglow of Europa and Ganymede
Feldman, P. D.; Strobel, D. F.; McGrath, M. A. +1 more
Far-UV spectra of Europa and Ganymede, acquired by the Hubble Space Telescope Goddard High Resolution Spectrograph, indicate that, in addition to faintly reflected sunlight, both satellites emit O I 1304 Å and O I 1356 Å airglow radiation. The observed brightnesses of the reflected solar C II 1335 Å feature indicate that the disk-averaged albedos …
The Optical Properties of Gravitational Lens Galaxies as a Probe of Galaxy Structure and Evolution
Keeton, C. R.; Kochanek, C. S.; Falco, E. E.
We combine photometry and lens modeling to study the properties of 17 gravitational lens galaxies between z = 0.1 and ~1. Most of the lens galaxies are passively evolving early-type galaxies, with a few spirals. The colors, scale lengths, and ellipticities of lens galaxies are similar to those of the general population of early-type galaxies, alth…
Ulysses' return to the slow solar wind
Forsyth, R.; Balogh, A.; McComas, D. J. +9 more
After ten long years of wandering the uncharted seas, Ulysses returned to his home port of Ithaca. Similarly, after its unprecedented five year odyssey through the previously uncharted regions over the poles of the Sun, the Ulysses spacecraft has returned to the slow, variable solar wind which dominates observations near the ecliptic plane. Solar …