Search Publications
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…
Quantitative UV spectroscopy of early O stars in the Magellanic Clouds. The determination of the stellar metallicities
Lennon, D. J.; Pauldrach, A. W. A.; Puls, J. +4 more
UV spectra of 4 O-stars in the Magellanic Clouds obtained with the Faint Object Spectrograph of the Hubble Space Telescope are analyzed with respect to metallicity. With the stellar parameters T_eff,log g, R_{*}, and the mass loss rates dot {M} known from optical analyses, the metal abundances including iron group elements are derived in two steps…
Asymmetry and Frequencies of Low-Degree p-Modes and the Structure of the Sun's Core
Kosovichev, A. G.; Scherrer, P. H.; Appourchaux, T. +3 more
An accurate determination of the frequencies of low-degree solar p-modes is an important task of helioseismology. Using 679 days of solar oscillation data observed in Doppler velocity and continuum intensity from two Solar and Heliospheric Observatory instruments (the Michelson Doppler Imager and the SunPhotoMeter), we show that fitting the spectr…
Global model of the corona with heat and momentum addition
Wu, S. T.; Poletto, G.; Suess, S. T. +1 more
We have been developing a series of global coronal models directed at a better simulation of empirical coronal hole and streamer properties. In a previous study, a volumetric heat source was used to produce a thin current sheet above streamers and high solar wind speed in the coronal hole. This improved the preexisting coronal structure for corona…
The HR-diagram from HIPPARCOS data. Absolute magnitudes and kinematics of BP - AP stars
Luri, X.; Figueras, F.; Royer, F. +5 more
The HR-diagram of about 1000 Bp - Ap stars in the solar neighbourhood has been constructed using astrometric data from Hipparcos satellite as well as photometric and radial velocity data. The LM method \cite{luri95,luri96} allows the use of proper motion and radial velocity data in addition to the trigonometric parallaxes to obtain luminosity cali…