Search Publications
EXOSAT Observations of 4U 1705-44: Type I Bursts and Persistent Emission
Hasinger, G.; Gottwald, M.; Sztajno, M. +2 more
During four Exosat observations, the bright galactic X-ray source 4U 1705-44 exhibited persistent emission variations from 1.3 to 10.7 x 10 to the -9th ergs/sq cm per sec in the 1-20 keV band. Type I X-ray bursts have been detected from this source whose properties correlate with source intensity. The burst shape changed with increasing intensity …
Spectroscopy of the Rapidly Rotating K Star HD 36705
Gustafsson, B.; Edvardsson, B.; Vilhu, O.
Spectroscopic observations of HD 36705 are reported. Values of 100 + or - 5 km/s and 29 + or - 2 km/s are derived for the v sin i and radial velocity, respectively. The central wavelength of the broad H-alpha emission varies as a function of rotation phase with an amplitude of 16 km/s and with the maximum redshift at the photometric minimum. Using…
Simultaneous Multifrequency Observations of the BL Lacertae Object Markarian 421
Koyama, K.; Matsuoka, M.; Kondo, Y. +26 more
Simultaneous multifrequency observations of the BL Lac object Mrk 421 covering radio through X-ray wavelengths were performed on two occasions separated by 5 weeks in January and March 1984, and each observation was coordinated for about 1 week. Composite multifrequency spectra of the central nonthermal component were obtained at the two epochs af…
Correlation between Spectral State and Quasi-periodic Oscillation Parameters in GX 5-1
van Paradijs, J.; van der Klis, M.; Lewin, W. H. G. +3 more
In a series of seven Exosat observations, the bimodal spectral behavior and the quasi-periodic oscillation (QPO)/red noise properties of GX 5-1 show a strict correlation. In one of the two spectral states (characterized by a 'horizontal branch' in the hardness-intensity diagram), strong 20-40 Hz QPO and red noise below about 60 Hz were always pres…
IUE Observations of Hydrogen and Deuterium in the Local Interstellar Medium
Moos, H. W.; Murthy, J.; Linsky, J. L. +4 more
The authors present and analyze high-dispersion IUE observations of the interstellar hydrogen and deuterium Lyα absorption profiles toward the late-type stars ɛ Eri (3.3 pc), Procyon (3.5 pc), Altair (5.1 pc), Capella (13.2 pc), and HR 1099 (33 pc). They derive values for the density nH I, the velocity dispersion bH I, the bu…
Broad, Variable Absorption Lines in the Seyfert Galaxy NGC 3516: Probing the Structure of the Emssion-Line Regions
Voit, G. Mark; Shull, J. Michael; Begelman, Mitchell C.
Nineteen short-wavelength IUE archive images were analyzed in order to probe the structure of the active nucleus in NGC 3516, an SB0 Seyfert I galaxy. The measurements of these features are presented, and the strength, variability, and morphology of the emission and absorption lines and their relation to the continuum are analyzed. It is shown tha…
Detection of Neutral Oxygen and Sulfur Emissions near Io Using IUE
Skinner, T. E.; Feldman, P. D.; Moos, H. W. +6 more
Two very long IUE exposures obtained with precise control of the spacecraft pointing show emissions due to neutral oxygen and sulfur near Io. The emitting region is centered on Io and is less than five Io diameters across. The two spectra obtained near eastern and western elongation in 1986 July and October, respectively, are similar, independent …
Ultraviolet Observations of Extensive Variability in the Stellar Wind of ξ Persei
Howarth, Ian D.; Prinja, Raman K.; Henrichs, Huib F.
Fifty-six high-resolution ultraviolet IUE observations of ξ Per [O7.5 III] are presented. The optically thick C IV and N V resonance doublets yield a terminal velocity of v = 2600 km s-1. The spectra reveal dramatic variability in the Si IV P Cygni profiles down to short time scales (≡1 hr). The morphology of the variations is character…
EXOSAT Observations of 4U/MXB 1636-53: On the Relation between the Amount of Accreted Fuel and the Strength of an X-Ray Burst
van Paradijs, J.; van der Klis, M.; Lewin, W. H. G. +4 more
During EXOSAT observations of 4U/MXB 1636-53 in 1985 August, three bursts were observed in 6 hr and 24 bursts in 79 hr of uninterrupted observing. The persistent X-ray flux varied by about a factor of 2.4, the burst intervals by a factor of 24 (from 35 minutes to 14 hr), and the integrated burst fluxes (the burst fluences), and burst peak fluxes b…
High-Energy Gamma Rays Probing Cosmic-Ray Spectral Differences thoughout the Galaxy
Bloemen, J. B. G. M.
Detailed spectra of the Galactic γ-ray emission (50 MeV-6 GeV) are derived from a combination of all the observations obtained with the COS-B satellite. These spectra indicate that the cosmic-ray (CR) proton spectrum is on average flatter in the outer Galaxy than in the inner Galaxy and locally by approximately ∝ E0.4, and maybe more, s…