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Ultraviolet Imaging Telescope Observations of the Magellanic Clouds
Parker, Joel Wm.; O'Connell, Robert W.; Bohlin, Ralph C. +8 more
We present wide-field far-ultraviolet (FUV; 1300-1800 Å) images of the Large and Small Magellanic Clouds (LMC, SMC). These data were obtained by the Ultraviolet Imaging Telescope (UIT) during the Astro-1 (1990 December 1-10) and Astro-2 (1995 March 2-18) missions; the images provide an extensive FUV mosaic of the SMC and contain numerous regions i…
The Adiabatic Exponent in the Solar Core
Kosovichev, A. G.; Elliott, J. R.
We present helioseismic inversions of solar p-mode frequencies obtained by the Michelson Doppler Imager instrument of the Solar Oscillation Investigation project on board SOHO, which indicate a lower central value for the adiabatic exponent Γ1 in the Sun than in current models. We show how the inclusion of relativistic effects in the eq…
Fundamental stellar parameters for nearby visual binary stars: eta Cas, XI Boo, 70 OPH and 85 Peg. Helium abundance, age and mixing length parameter for low mass stars
Morel, P.; Baglin, A.; Lebreton, Y. +1 more
The calibration of nearby visual binary stars on the HR diagram is used to determine the helium abundance, age and mixing length parameter for stars other than the Sun. Four Population I low mass systems with high-quality data are analysed by means of standard evolutionary stellar models: eta Cas, 70 Oph, xi Boo and 85 Peg. Complementing these res…
Physical Structure of a Coronal Streamer in the Closed-Field Region as Observed from UVCS/SOHO and SXT/Yohkoh
Romoli, M.; Raymond, J. C.; Naletto, G. +4 more
We analyze a coronal helmet streamer observed on 1996 July 25 using instruments aboard two solar spacecraft, the Ultraviolet Coronagraph Spectrometer (UVCS) on board Solar and Heliospheric Observatory (SOHO) and the Soft X-Ray Telescope (SXT) on board Yohkoh. We derive temperatures and electron densities at 1.15 R⊙ from SXT/Yohkoh obser…
Infrared spectra of carbon stars observed by the ISO SWS. I. Molecular absorption in N-type and SC-type stars
Ohnaka, K.; Tsuji, T.; Aoki, W.
We carried out observations of bright optical carbon stars by the ISO SWS, and detected the absorption features of CO, CS, CH, SiS and HCN in N-type and SC-type stars. We found several characteristics of molecular absorption features corresponding to the spectral types. The CH fundamental bands in 3-4 mu m in N-type stars are stronger than those i…
Deep H-Band Galaxy Counts and Half-Light Radii from Hubble Space Telescope/NICMOS Parallel Observations
McCarthy, Patrick J.; Weymann, Ray J.; Yan, Lin +1 more
We present deep galaxy counts and half-light radii from F160W (λc=1.6 µm) images obtained with the Near-Infrared Camera and Multiobject Spectrograph on the Hubble Space Telescope. Nearly 9 arcmin2 have been imaged with camera 3, with 3 σ depths ranging from H=24.3 to 25.5 in a 0.6" diameter aperture. The slope of the co…
The kinematically peculiar cores of the Coma cluster early-type galaxies NGC 4816 and IC 4051
Saglia, R. P.; Bender, R.; Wegner, G. +1 more
The Coma cluster is one of the richest known cluster of galaxies, spanning about 4 dex in density. Hence it is the ideal place to study the structure of galaxies as a function of environmental density in order to constrain the theories of galaxy formation and evolution. For a magnitude limited sample of 35 E and S0 galaxies we obtained long slit s…
Infrared Imaging and Spectroscopy of the Helix with ISOCAM
Boulanger, F.; Bachiller, R.; Cernicharo, J. +8 more
We report infrared images of the Helix Nebula centered at 6.9 µm (LW2 filter) and 15 µm (LW3 filter) obtained with ISOCAM on board the Infrared Space Observatory (ISO). Three fields were also measured using the ISOCAM circular variable filter (CVF). The CVF data show that the 5-16.6 µm spectrum is dominated by the pure (v=0-0) ro…
The Lutz-Kelker bias in trigonometric parallaxes
Groenewegen, Martin A. T.; Schrijver, Hans; Oudmaijer, Rene D.
The theoretical prediction that trigonometric parallaxes suffer from a statistical effect has become topical again now that the results of the Hipparcos satellite have become available. This statistical effect, the so-called Lutz-Kelker bias, causes observed parallaxes to be too large. This has the implication that inferred distances, and hence in…
The birth of a planetary nebula around the carbon star IRC+10216
Meixner, M.; Skinner, C. J.; Bobrowsky, M.
Our current understanding of the evolution of solar-type stars suggests that after a period as a red giant star, during which mass loss occurs continuously in the form of a stellar wind, a period of intense mass loss known as a superwind occurs, during which a significant fraction of the envelope of the star is ejected into space, forming the mate…