Search Publications
The Problem of V444 Cygni
Underhill, A. B.; Fahey, R. P.
The authors have studied the changes of the spectrum of V444 Cygni (WN5+O6) shown on 13 high-resolution spectrograms obtained with the IUE. Evidence is found for an orbital-phase-dependent "third light" both in line and in continuum wavelengths. A model for the V444 Cygni system consisting of an O star with Teff = 40,000K, R/R_sun; = 10…
The Properties of Bursts with Short Recurrence Times from the Transient X-Ray Source EXO 0748-676
Haberl, Frank; Parmar, Arvind N.; White, Nick E. +1 more
On January 13/14 1986 Exosat performed a 11.3-hr observation of the transient X-ray burst source EXO 0748-676. The source was in a low state and emitted 11 type I X-ray bursts, of which 10 were analyzed in detail. The properties of the bursts were similar to those found in previous low-state observations reported in Gottwald et al. (1986). The tot…
The Giotto magnetometer experiment
Neubauer, F. M.; Ungstrup, E.; Burlaga, L. F. +9 more
The Giotto magnetometer experiment employs a low-mass (1.357 kg), low-power (818 mW) instrument in a dual magnetometer configuration using flux gate sensors of the ring core type. It has provided accurate vector magnetic field measurements on its way to and near comet Halley, working flawlessly from switch-on on August 22, 1985 to the formal end o…
Radio detection of the Be star psi Persei.
Waters, L. B. F. M.; Lamers, H. J. G. L. M.; Taylor, A. R. +2 more
The authors present the results of a VLA survey for radio emission from a sample of Be stars having strong excess emission in the IRAS bands. Radio emission was detected from one star, ψ Persei. The radio flux density, together with nearly simultaneous ultraviolet and near-infrared observations, argue strongly against a spherically symmetric model…
The Initial Mass Function for Early-Type Stars in Starburst Galaxies
Sekiguchi, Kazuhiro; Anderson, Kurt S.
The IMF slope of early-type stars in starburst galaxies is investigated using IUE observations and a technique that utilizes mass-linewidth relations for early-type stars. Fourteen low-resolution IUE spectra of eight starburst galaxies and three H II region galaxies are used to obtain line-strength ratios Si IV (λ1400)/C IV (λ1550). These are comp…
Description of the Main Boundaries Seen by the Giotto Electron Experiment Inside Comet p/ Halley - Solar Wind Interaction Region
Anderson, K. A.; Reme, H.; Korth, A. +8 more
The Giotto electron-plasma experiment identified several boundaries inside the comet Halley-solar wind region. Two of them are particularly interesting; they separate very different plasma regimes on quite sharp length scales and furthermore their existence was not foreseen in theoretical models. They are the limit between the transition region an…
The fading of R Coronae Borealis.
Holm, A. V.; Wu, C. C.; Donn, B. +1 more
Using the International Ultraviolet Explorer (IUE) low-resolution spectra were obtained of R CrB, the prototype of its class of variable stars, shortly after the beginning of its 1983-84 minimum and during its rise to maximum again. The behavior of the spectra during the rise to maximum is similar to the behavior of the spectra of RY Sgr during a …
X-ray and optical flickering in EF Eri.
King, A. R.; Watson, M. G.; Williams, G. A.
A study of the short-time-scale variability of the polar system EF Eri is presented based on simultaneous hard and soft X-ray monitoring with the Exosat Observatory and optical photometry from CTIO. The observations are used to investigate the nature of the flickering in this system, and the correlations between the variability in the three bands.…
The X-Ray Spectrum of Markarian 509 Observed by EXOSAT
Molteni, D.; Morini, M.; Lipani, N. A.
Mrk 509 was observed with Exosat at three different epochs during October and November 1983. Variability of about 30 percent was apparent both in the medium-energy (1-10 keV) and in the low-energy (less than 2 kev) X-ray bands between the different observations, on a time scale of 10 days. No correlation between the two energy bands was observed. …
Dramatic X-ray variability in the narrow emission line galaxy NGC 7314.
Turner, T. J.
EXOSAT observations of the narrow emission line galaxy NGC 7314 have shown remarkable variability in the 2 - 10 keV band of the medium energy (ME) detectors. The most obvious feature in the ME light curve is a factor of 4 increase in the count rate over 5000 s, with some evidence for a softening of the spectrum as the source brightened. The lack o…