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
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…
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…
Ultraviolet Observations of SN 1987A
Kirshner, Robert P.; Sonneborn, George; Crenshaw, D. Michael +1 more
UV observations of the supernova in the LMC, SN 1987A, were carried out with the IUE satellite. The earliest data show that the UV flux from the supernova was already declining while the optical flux was still rising. The UV spectrum at these epochs consists of broad features associated with the supernova atmosphere punctuated by sharp interstella…
The Dependence of Ultraviolet Chromospheric Emission upon Rotation among Late-Type Stars
Simon, Theodore; Fekel, Francis C., Jr.
The authors have obtained low-resolution IUE spectra of a large number of chromospherically active stars. Integrated fluxes of chromospheric and transition region emission lines have been measured. These fluxes, supplemented by published observations and measurements of IUE archival spectra, have been used to search for correlations between activi…
Physical Parameters for 12 Planetary Nebulae and Their Central Stars in the Magellanic Clouds
Gull, Theodore R.; Aller, Lawrence H.; Maran, Stephen P. +3 more
Nebular and central star parameters and elemental abundances of C, N, O, Ne, S, and Ar are presented for the planetary nebulae N2, N5, N43, N54, and N67 in the SMC and P2, P7, P9, P25, P33, and P40 in the LMC. The nebular chemical compositions are affected by nuclear processes in the precursor stars, which may not have been sufficiently massive to…
Highly Ionized Stellar Winds in Be Stars: The Evidence for Aspect Dependence
Grady, C. A.; Snow, T. P.; Bjorkman, K. S.
The authors present the results of an ultraviolet survey of stellar winds in 62 Be and 43 normal B stars covering spectral types B0.5 - B5 and luminosity classes V - III. They find that the wind absorption seen in the resonance lines of C IV, Si IV, and Si III in Be stars is often the result of blended absorption from multiple shortward-shifted di…
The Progenitor of SN 1987A: Spatially Resolved Ultraviolet Spectroscopy of the Supernova Field
Kirshner, Robert P.; Sonneborn, George; Altner, Bruce
Careful deconvolution of spatially resolved IUE ultraviolet spectra shows that only two of the three stars detected in plate material before 1987 are now present near the site of SN 1987A. The separation, magnitudes, and spectra of these two are consistent with their identification as star 2 and star 3 of the Sanduleak -69°202 trio. The clear impl…
EXOSAT Observations of Double-peaked Bursts with Radius Expansion from 4U/MXB 1820-30
Haberl, F.; Stella, L.; White, N. E. +2 more
A detailed analysis is presented of seven X-ray bursts from the X-ray source 4U/MXB 1820-30 in the globular cluster NGC 6624. The bursts were double-peaked, and recurred at almost equal time intervals of 3.2 hr. The persistent flux varied by only 10 percent on time scales of 60 minutes. The ratio of the total persistent energy emitted before a bur…