Search Publications
Radial velocities of HIPPARCOS southern B8-F2 type stars
Gerbaldi, M.; Faraggiana, R.; Grenier, S. +5 more
Radial velocities have been determined for a sample of B8-F2 type stars observed by the Hipparcos satellite. Observations were obtained within the framework of an ESO key-program. Radial velocities have been measured using a cross-correlation method, the templates being a grid of synthetic spectra. The obtained precision depends on effective tempe…
Helioseismic Analysis of the Hydrogen Partition Function in the Solar Interior
Basu, Sarbani; Däppen, Werner; Nayfonov, Alan
The difference in the adiabatic gradient γ1 between inverted solar data and solar models is analyzed. To obtain deeper insight into the issues of plasma physics, the so-called intrinsic difference in γ1 is extracted, that is, the difference due to the change in the equation of state alone. Our method uses reference models bas…
The Very Young Starburst Merger System NGC 1741
Leitherer, Claus; Johnson, Kelsey E.; Vacca, William D. +2 more
We use Hubble Space Telescope (HST) Faint Object Camera (FOC) ultraviolet (UV) and WFPC2 optical images in conjunction with UV spectroscopic observations taken with the Goddard High Resolution Spectrograph to examine the star formation history and properties of the interacting galaxy system NGC 1741 in the Hickson Compact Group 31. The high spatia…
Very cold dust in galaxies
Siebenmorgen, R.; Chini, R.; Krügel, E.
We present multi-filter far infrared photometry of active and inactive galaxies obtained with ISOPHOT. We find that the far infrared and submillimeter spectrum of the active galaxies can be described by a single modified black-body at a color temperature of 31.5 +/- 2.8 K. The ratio of infrared luminosity to gas mass, L_IR/M_gas, where the latter …
Quasi-thermal noise in a drifting plasma: Theory and application to solar wind diagnostic on Ulysses
McComas, D. J.; Moncuquet, Michel; Issautier, Karine +2 more
The present paper provides the basic principles and analytic expressions of the quasi-thermal noise spectroscopy extended to measure the plasma bulk speed, as a tool for in situ space plasma diagnostics. This method is based on the analysis of the electrostatic field spectrum produced by the quasi-thermal fluctuations of the electrons and by the D…
Discovery of molecular hydrogen in a high-velocity cloud of the Galactic halo
de Boer, K. S.; Grewing, M.; Richter, P. +4 more
The Milky Way's halo contains clouds of neutral hydrogen with high radial velocities which do not follow the general rotational motion of the Galaxy. Few distances to these high-velocity clouds are known, so even gross properties such as total mass are hard to determine. As a consequence, there is no generally accepted theory regarding their origi…
A Multiwavelength Campaign on γ Cassiopeiae. III. The Case for Magnetically Controlled Circumstellar Kinematics
Smith, Myron A.; Robinson, Richard D.
In two previous papers, we have discussed simultaneous Rossi X-Ray Timing Explorer (RXTE) and Hubble Space Telescope GHRS observations made of γ Cas (B0.5e) over a full day on 1996 March 14-15. The light curves generated from these data show features that anticorrelate and led us to conclude that the star has multiple surface activity centers that…
The redshift evolution of clustering in the Hubble Deep Field
Magliocchetti, M.; Maddox, S. J.
We present a correlation function analysis for the catalogue of photometric redshifts obtained from the Hubble Deep Field image by Fernandez-Soto, Lanzetta & Yahil. By dividing the catalogue into redshift bins of width Deltaz=0.4 we measured the angular correlation function w(theta) as a function of redshift up to z~4.8. From these measurement…
Water line emission in low-mass protostars
Liseau, R.; Ceccarelli, C.; White, G. +7 more
Using the Long Wavelength Specrometer aboard ISO, we have detected far infrared rotational H_2O emission lines in five low-mass young stellar objects in a survey of seven such sources. The total H_2O fluxes are well correlated with the 1.3 mm continuum fluxes, but - surprisingly - not with the SiO millimeter emission originating in the outflows, s…
Hubble Space Telescope Ultraviolet Spectral Energy Distributions for Three Ultraluminous Infrared Galaxies
Sanders, D. B.; Kormendy, John; Trentham, Neil
We present Hubble Space Telescope Faint Object Camera ultraviolet (lambda=2300 Å, 1400 Å) images of three ultraluminous infrared galaxies (ULIGs: L_ir>10^12 L_solar) selected from the IRAS Revised Bright Galaxy Sample. The purpose is to estimate spectral energy distributions (SEDs) to facilitate the identification of similar objects at high red…