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A Third X-Ray Spectral Mode in Scorpius X-1: Similarities to the Other Bright Bulge Sources
Hasinger, G.; Priedhorsky, W. C.; Middleditch, J.
Sco X-1 normally shows two spectral/quasi-periodic oscillation (QPO) modes. In this paper, new observations of Sco X-1 are reported which show it in a third mode which is similar to the 'horizontal branch' displayed by Cyg X-2 and suggests that the Galactic bulge sources follow a common, Z-shaped spectral pattern. In this mode, the spectral hardne…
Ultraviolet Spectrophotometry and Optical and Infrared Photometry of the Old Nova GK Persei
Raymond, John C.; Wu, Chi-Chao; Swank, Jean H. +3 more
IUE observations in the 1150-3250-A region were obtained of GK Per during the rise, at the maximum, and during the decline of the 2.5-mag optical outburst in 1981. The results support previous predictions for the interaction of an accretion disk with the magnetic field of an accretion star. The luminosity at minimum is found to be 2.3 solar lumino…
Fast Winds in Central Stars of Some Planetary Nebulae
Perinotto, M.; Cerruti-Sola, M.
Winds from the central stars of the planetary nebulae NGC 1535, NGC 6210, NGC 7009, IC 418, and IC 4593 have been investigated with high-resolution IUE spectra. All these stars present P Cygni profiles in some of the following lines: N V 1240, O IV 1342, O V 1371, Si IV 1397, C IV 1549, and N IV 1719 A. These profiles have been analyzed with the S…
Ultraviolet Observations of Interstellar Absorption Lines toward SN 1987A
Jenkins, Edward B.; Savage, Blair D.; Joseph, Charles L. +1 more
An average of all high-resolution UV spectra of SN 1987A recorded by IUE a few days after the explosion reveals numerous interstellar absorption lines between 1200 and 3100 A. Features produced in the neutral medium of our Galaxy and the LMC (e.g., those arising from O I, C I, C II, Mg I, Mg II, Fe II, Mn II, Si II, Ni II, etc.), together with lin…
The Discovery of 2.93 Hour Periodic Intensity Dips from X1323-619
Parmar, A. N.; van Paradijs, J.; van der Klis, M. +1 more
A 30 hr duration Exosat observation of the low-mass X-ray binary X1323-619 is reported. The 1-8 keV light curve obtained with the medium-energy (ME) instrument shows irregular intensity dips that recur every 2.93 hr as well as type 1 X-ray bursts. The intensity declines to about 50 percent of its unaffected value during the 50-minute duration dips…
X-Ray Spectroscopy of the Ultrasoft Transient 4U 1543-47
White, N. E.; van der Woerd, H.; Kahn, S. M.
The X-ray transient 4U 1543 - 47 was observed in August 1983 by the Exosat observatory near the maximum of an outburst. The X-ray spectrum was measured using a gas scintillation proportional counter (GSPC) and a transmission grating spectrometer (TGS). A broad (FWHM about 2.7 keV) line at 5.9 keV is detected in the GSPC, which is interpreted as a …
Chromospheric Structure of Cool Carbon Stars
Johnson, Hollis R.; Luttermoser, Donald G.; Avrett, Eugene H. +1 more
A semiempirical chromospheric model is proposed for TX Psc which is a prototype for the N-type carbon stars. Observational data imply that the chromospheric temperature rise must begin at a low density, that the temperature gradient in the lower chromosphere must be steep, that partial redistribution must be employed in the Mg II calculation, and …
Fast Winds from the Central Stars of NGC 6543 and NGC 6826
Lamers, H. J. G. L. M.; Perinotto, M.; Cerruti-Sola, M.
The Sobolev exact integration method and high-resolution IUE data are used to examine the properties of the fast winds exhibited by the central stars of the planetary nebulae NGC 6543 and NGC 6826. An attempt is made to evaluate the parameters of the central stars as accurately as possible. The associated mass-loss rates (M-dot) are (4.0 + 10 or -…
Highly Ionized Stellar Winds in Be Stars. II. Winds in B6--B9.5e Stars
Shore, Steven N.; Sonneborn, George; Grady, C. A. +3 more
The results of a UV survey of stellar winds and circumstellar shells in 40 B6-B9.5e stars covering luminosity classes V-III are presented. A graph is presented of the region from 1520-1560 A, which includes both the Si II UV multiplet 2 transitions and the C IV resonance transition for selected Be stars in the sample. The detection of shortward-sh…
On the Size Distribution of Newly Formed Grains in Red Supergiant Atmospheres
Snow, Theodore P.; Seab, C. Gregory
Theoretical ultraviolet extinction curves have been calculated for comparison with observed curves for circumstellar dust in M supergiants. The theoretical curves assume a silicate grain composition, because silicate grains are expected in the oxygen-rich environments that are observed. Calculations were performed with and without the inclusion of…