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Rotational Modulation in IUE Spectra of Cool Dwarf Chromospheres. I. Data Analysis and Period Search Techniques
Hallam, K. L.; Altner, B.; Endal, A. S.
Time-sequenced IUE spectra of a number of a bright F-K dwarfs have been used to investigate rotational modulation in several important chromospheric and transition emission lines. Stellingwerf's phase dispersion minimization (PDM) technique forms the basis of this time-series analysis of these sparsely sampled, irregularly spaced observational seq…
Faint Object Spectrograph Observations of the Low-Luminosity Seyfert Galaxy NGC 1566
Kriss, G. A.; Blair, William P.; Armus, L. +3 more
FOS observations of the Seyfert galaxy NGC 1566 show it to possess the broad lines characteristic of a typical Seyfert 1 galaxy, even in states of very low luminosity. The continuum, however, is steep (f_v_~v^- 1.5^) with no suggestion of the ultraviolet excess seen in higher luminosity AGNs. The broad emission lines have symmetric profiles, but a…
The nebular stage of nova PW Vulpeculae.
Snijders, M. A. J.; Andreae, J.; Drechsel, H. +1 more
UV and optical nebular spectra of Nova PW Vul were used to derive plasma parameters of the ejected shell. From the visual lightcurve decay times of t2 = 83 days and t3 = 147 days are estimated, which indicate that PW Vul is a slow nova. A color excess of E(B - V) = 0.55 and a distance of about 1.3 kpc were derived. Emission line fluxes were deredd…
Dust scattering in the high-state eclipse of CEN X-3.
Tennant, A. F.; Day, C. S. R.
Exosat data from two high-state eclipses of Cen X-3 are analyzed for the effects of dust scattering. The light curves show bright (2 per cent of the out-of-eclipse flux), smoothly varying emission which reaches its minimum after mideclipse. Of this emission, the soft flux falls monotonically with orbital phase. This soft component with dust scatte…
First Results from the Goddard High-Resolution Spectrograph: Element Abundances as a Function of Velocity in the Neutral Gas toward XI Persei
Ebbets, Dennis C.; Sembach, Kenneth R.; Savage, Blair D. +3 more
Observations of ultraviolet interstellar absorption lines toward Xi Persei obtained with the echelle mode of the Goddard High-Resolution Spectrograph (GHRS) aboard the HST at a resolution of 3.5 km/s are presented. The data for O I, C II, Mg II, S II, Fe II, Si II, Mn II, and Zn II are converted into representations of apparent column density per …
Oscillator strengths for Y III and Zr III in the IUE region
Redfors, A.
Oscillator strengths for Y III and Zr III in the region 1190-3100 A have been calculated for transitions from all levels below 13 eV. The presence of these spectra in IUE observations of chemically peculiar stars is discussed.
The Cataclysmic Variable Ss-Cygni
Giovannelli, F.; Martinez-Pais, I. G.
In this work we will try to give the most general panorama, comparatively with the conciseness, on SS Cygni which is the brightest dwarf nova. The dwarf novae form a sub-class of the more vaste panorama of the Cataclysmic Variables (CVs). For this reason firstly we will describe in general the CVs and the current theories which attempt to describe…
Chromospherically active stars. IX. HD 33798 = V390 Aurigae: a lithium-rich rapidly rotating single giant.
Fekel, Francis C.; Marschall, Laurence A.
Results are presented of spectroscopic observations of HD 33798 obtained to determine if this star is a short-period binary and to examine its evolutionary status. Analysis of 40 radial velocities indicates no periodic velocity variations, suggesting that the star is single, so its rapid rotation is highly unusual. This rotation is inconsistent wi…
Evidence for a Thermally Unstable Shock Wave in the VELA Supernova Remnant
Raymond, John C.; Balick, Bruce; Wallerstein, George
The emission and absorption line signatures of supernova remnant shock waves provide complementary diagnostic capabilities. This paper presents IUE spectra of the nebulosity and new spectra of HD 72088. Models of the emission and absorption lines from shocked gas are used to derive a shock velocity and elemental depletions. There is evidence from …
The rapid burster and its type II burst profiles.
Stella, L.; van Paradijs, J.; van der Klis, M. +5 more
Type-II bursts with durations ranging from about 2 to about 680 seconds are examined to study burst-peak fluxes, burst intervals, integrated energies, and luminosities associated with MXB 1730-335, the Rapid Burster. The data regarding the bursts are compared to develop general correlations between burst variables, and some general characteristics…