Search Publications
A Detailed Study of the C IV lambda 1550 Line Profile and Adjacent Spectral Features in NGC 4151 from 1978 to 1983
Perola, G. C.; Altamore, A.; Boksenberg, A. +7 more
The 1450 - 1720 Å spectral region of NGC 4151 is analyzed by means of Gaussian decomposition for 69 different epochs, from early 1978 to the end of 1983. The C IV λ1550 emission profile is well represented by a core, whose full width at half-maximum varies between 2600 and 5500 km s-1, and an ultrabroad component (14,600 km s-1
Expansion Velocity and Temperatures of Gas and Ions Measured in the Coma of Comet p/ Halley
Berthelier, J. J.; Eberhardt, P.; Krankowsky, D. +9 more
In situ measurements of flow velocity and temperature in the inner coma were obtained from ram energy spectra of molecules and ions observed by the NMS experiment onboard the Giotto probe to comet Halley. Radial flow speed was (800 ± 50) m s-1 at distances from the nucleus between 1000km and 4000 km. Whereas ions became stagnant just ou…
A spectrophotometric study of the emission lines in the quiescent dwarf nova Z Chamaeleontis.
Horne, Keith; Marsh, T. R.; Shipman, H. L.
The main goal of the present time-resolved spectrophotometric study of Z Cha is to examine the behaviour of the emission lines during the eclipse of the disc by the secondary star. The observations and data reduction techniques are presented first. Then, the white dwarf spectrum is examined, which produces broad absorption wings around the Balmer …
Soft X-ray transients in quiescence : observations of AQL X-1 and CenX-4.
van Paradijs, J.; Verbunt, F.; Arnaud, K. A. +1 more
The authors observed the soft X-ray transients Aql X-1 and Cen X-4 during quiescence with EXOSAT. For Aql X-1 they obtain a 3σ upper limit to the X-ray luminosity Lx (in the energy range between 0.5 and 4.5 keV) of <3.0×1033erg s-1, Cen X-4 was detected at Lx (0.5 - 4.5 keV) ≅ 1.5 to 4.2×1033
On the Theory of Type I X-Ray Bursts. The Energetics of Bursts and the Nuclear Fuel Reservoir in the Envelope
Lewin, Walter H. G.; Fujimoto, Masayuki Y.; Sztajno, Mirek +1 more
A comparison is made between the observed properties of type I X-ray bursts from 4U/MXB 1636-53 and those of models of thermonuclear flashes on accreting neutron stars. Possible explanations of variations in the burst recurrence properties without an apparent correlation with accretion rate are discussed. The strongest bursts with photospheric exp…
IUE Observations of the Dwarf Nova HL Canis Majoris and the Winds of Cataclysmic Variables
Raymond, John C.; Mauche, Christopher W.
In order to investigate the nature of the winds of cataclysmic variables the authors present an observational and theoretical study of the P Cygni profiles of these systems, giving particular attention to the profiles of the dwarf nova HL CMa. After presenting the IUE observations of HL CMa, the authors give the results of a synthetic spectral cod…
Nova Aquilae 1982.
Snijders, M. A. J.; Seaton, M. J.; Blades, J. C. +4 more
Observations of Nova Aquilae obtained from the IUE, the Anglo-Australian Telescope, and the Westerbork Synthesis Radio Telescope are discussed. Light curves for B, V, and continuum fluxes at 2800 and 1300 A are presented. Velocities obtained from line profiles indicate the presence of three main gaseous components: a high velocity gas (HVG) compon…
Intensity and Source State Dependence of the Quasi-periodic Oscillations in Scorpius X-1
Stella, L.; Parmar, A. N.; van der Klis, M. +2 more
Quasi-periodic oscillations (QPO) at 6 Hz were discovered from EXOSAT observations of Sco X-1 in its quiescent state by Middleditch and Priedhorsky. The authors report here on the properties of the QPO seen in earlier EXOSAT observations of Sco X-1. During these observations QPO were also detected when Sco X-1 was in an active state, in ≡20 minute…
Giotto magnetic-field results on the boundaries of the pile-up region and the magnetic cavity
Neubauer, F. M.
Data from Giotto's magnetometer collected during the encounter at Comet Halley on March 13/14, 1986, were used to investigate the most conspicuous boundaries in the inner plasma region surronding Comet Halley, i.e., the pile-up boundary and the ionopause. The normal vectors at the boundary crossings were determined using the minimum variance techn…
X-ray observations of the Ophiuchus, PKS 0745-191 and Cygnus-A clusters of galaxies.
Fabian, A. C.; Mushotzky, R. F.; Nulsen, P. E. J. +4 more
The authors report observations of the X-ray emission from three bright clusters of galaxies at low Galactic latitudes; the Ophiuchus, PKS 0745-191 and Cygnus-A clusters. Temperatures and iron abundances are determined from EXOSAT spectral data. Images of the Ophiuchus cluster show it to have a high central density and a cooling flow. The authors …