Search Publications
BB Virginis: an RR Lyrae in a binary system?
Fernley, J. A.
On Mode Identification in delta Scuti
Cugier, H.; Monier, R.
UV light amplitudes and phase shifts obtained from the IUE observations are discussed for pulsating star delta Scuti. The published ground-based photometric and radial velocity data are also included in the analysis. The observations are compared with model calculations which take into account temperature and pressure changes during pulsation cycl…
The Hyades distance and white dwarf constraints.
Weidemann, V.
It is demonstrated how recent determinations of surface gravity and gravitational red shifts for the Hyades white dwarfs constrain the distance of the cluster for which very discrepant values between trigonometric and kinematic results are presently discussed. If the surface gravity data are correct, the Hyades modulus must be close to m - M = 3.3…
Massive star distribution in external galaxies and starburst regions
Conti, Peter S.
Counts of hot and luminous stars in a number of associations in the Galaxy and Magellanic Clouds enable one to directly investigate the numbers and types of massive stars. There seems to be little, if any, dependence of the slope of the Intial Mass Function, or theM upper on the initial composition of the stars. Indirect estimates of n…
The Extreme Ultraviolet Spectrograph: A Radial Groove Grating, Sounding Rocket--borne, Astronomical Instrument
Wilkinson, Erik; Green, James C.; Cash, Webster
The design, calibration, and sounding rocket flight performance of a novel spectrograph suitable for moderate-resolution EUV spectroscopy are presented. The sounding rocket-borne instrument uses a radial groove grating to maintain a high system efficiency while controlling the aberrations induced when doing spectroscopy in a converging beam. The i…
Optical, X-ray and γ-ray observations of compact objects in globular clusters
Grindlay, J. E.
In the past three years, a new era of study of globular clusters has begun with multiwavelength observations from the current generation of astronomical telescopes in space. We review the recent results obtained from our studies of compact binaries and x-ray sources in globulars with ROSAT and HST as well as our balloon-borne hard x-ray telescope …
Dust in the planetary system
Grün, E.
A continuous spectrum of particulates ranging from m-sized objects down to molecular sizes is found almost everywhere in the planetary system: in interplanetary space and surrounding planets. Remote observations and in situ analysis provide information on their abundance and properties. Zodiacal dust particles displayed their low eccentricity, low…
Systematic deformations of the apparent almucantar as derived from Danjon astrolabes in Paris and Santiago de Chile
Pesek, I.; Vondrak, J.; Chollet, F. +1 more
Systematic deformations of apparent almucantar based on long series of observations with Danjon astrolabes in Paris and Santiago de Chile are derived. It is shown that their amplitudes of order of 0".1 - 0".2 have significant seasonal character. Comparison of the results based on two different catalogs (FK4 and FK5) make us believe that at least 5…
Pulsar studies with GRO-COMPTEL
Strong, A. W.; Schönfelder, V.; Kuiper, L. +9 more
Pulsar measurements performed by the experiment COMPTEL, aboard the Compton Gamma Ray Observatory, are described. The main results refer to the Crab and Vela pulsars whose pulse shape characteristics are given in some detail and light curves are compared with those above 50 MeV, as observed by the COS-B satellite. No other gamma-ray pulsars have b…
Line blanketing by iron group elements in non-LTE model atmospheres of hot stars
Dreizler, Stefan; Werner, Klaus
We report on our recent progress in modeling non-LTE atmospheres of O-stars including blanketing by lines from the iron group elements. The numerical method to account for the huge number of atomic levels and line transitions is presented. Results of exploratory model calculations examining the effects on the temperature structure, the hydrogen an…