Search Publications
V - (V-I) distance to Lupus 2
Knude, J.; Nielsen, A. S.
We report a possible distance to the star forming cloud Lupus 2 of 360 pc, at least 150 pc larger than previously suggested. Despite the cloud's small angular size and remoteness this distance estimate is corroborated by Hipparcos/Tycho data for field stars. The increased distance changes the mass estimate from 100 to ~ 600 cal Msun mor…
Testing Hydrodynamic Models of LMC X-4 with Ultraviolet and X-Ray Spectra
Boroson, Bram; Kallman, Timothy; Blondin, John M. +1 more
We compare the predictions of hydrodynamic models of the LMC X-4 X-ray binary system with observations of UV P Cygni lines with the Goddard High Resolution Spectrograph and Space Telescope Imaging Spectrograph on the Hubble Space Telescope. The hydrodynamic model determines density and velocity fields of the stellar wind, wind-compressed disk, acc…
Magnetometer measurements from the Cassini Earth swing-by
Russell, C. T.; Dougherty, M. K.; Balogh, A. +9 more
Magnetometer data recorded by the Cassini spacecraft during the spacecraft's Earth swing-by maneuver in August 1999 are discussed. The primary purpose of this paper is to show the instrument's performance in detection of magnetic phenomena in a planetary environment. Companion papers put the data in a broader geophysical context. The low noise and…
The distance to Galactic globular clusters through RR Lyrae pulsational properties
Piersimoni, A. M.; Cassisi, S.; De Santis, R.
By adopting the same approach outlined by De Santis & Cassisi, we evaluate the absolute bolometric magnitude of the zero-age horizontal branch (ZAHB) at the level of the RR Lyrae variable instability strip in selected Galactic globular clusters. This allows us to estimate the ZAHB absolute visual magnitude for these clusters and to investigate…
Ionization structure in accretion shocks with a composite cooling function
Cropper, Mark; Wu, Kinwah; Ramsay, Gavin
We have investigated the ionization structure of the post-shock regions of magnetic cataclysmic variables, using an analytic density and temperature structure model in which effects caused by bremsstrahlung and cyclotron cooling are considered. We find that in the majority of the shock-heated region where H- and He-like lines of the heavy elements…
Singular value decomposition: A tool to separate elementary contributions in ISOCAM spectral maps
Joblin, C.; Boissel, P.; Pernot, P.
Singular value decomposition (SVD) is applied to a mid-infrared ISOCAM spectral map of NGC 7023. As a first result, this decomposition provides a mathematical analysis of the map in terms of a linear combination of elementary spectra. After further processing, it is shown that the spectrum observed on each pixel can be described as the physical su…
A High-Resolution H I Study of the Interstellar Medium Local to HD 193793
Arnal, E. Marcelo
A 2° field centered at the optical position of the Wolf-Rayet (WR) star HD 193793 (≡ WR 140) was surveyed in the H I 21 cm line and in the 1420 MHz radio continuum, using the Dominion Radio Astrophysical Observatory interferometer. The aim of this observations was to look for evidence of an interaction between the WR star and its local interstella…
Detection of the Faint Companion in the Massive Binary HD 199579
Bolton, C. T.; Fullerton, A. W.; Gies, D. R. +14 more
We present new radial velocity data for the massive binary HD 199579 O6 V((f)) based upon spectra obtained from IUE, the Canada-France-Hawaii Telescope, KPNO, the David Dunlap Observatory, and the GSU Multiple-Telescope Telescope. We derive a revised period, P=48.5216+/-0.0015 days, and improved orbital elements that agree with the earlier element…
Spectra of binaries classified as lambda Bootis stars
Bonifacio, P.; Gerbaldi, M.; François, P. +1 more
High angular resolution observations have shown that some stars classified as lambda Boo are binaries with low values of angular separation and magnitude difference of the components; therefore the observed spectrum of these objects is a combination of those two components. These composite spectra have been used to define spectroscopic criteria ab…
Barnard's Merope Nebula Revisited: New Observational Results
Simon, Theodore; Herbig, G. H.
IC 349 is a small, fan-shaped reflection nebula located only 30" from 23 Tau; its nucleus is, by a factor 15, the brightest area of the Pleiades nebulosity. We propose that IC 349 is a fragment of the Taurus-Auriga molecular cloud that has been encountered by the Pleiades in that cluster's southward motion and is being illuminated and shaped by th…