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The mass ratio of nu SGR from ultraviolet radial velocities.
Jeffery, C. S.; Dudley, R. E.
The first positive determination of the secondary orbit of the hydrogen-deficient binary υ Sgr has been achieved by the application of cross-correlation methods to high-resolution ultraviolet (UV) spectra obtained with IUE. The mass ratio thus obtained (q = 0.63±0.01) and the consequent minimum mass for the primary (Mp sin3i/…
Ultraviolet spectra of a large sample of quasars - II. Variability ofLy-alpha and C IV emission lines.
Gondhalekar, P. M.
The analysis of spectra of 34 quasars observed more than once with IUE is presented. The Lyα + N V and C IV emission lines in the spectra of some quasars in this sample change in intensity over a short time-scale. This time-scale is comparable to the time-scale for change observed in the intensity of emission lines in the spectra of low-luminosity…
Time dependence of the UV resonance lines in the cataclysmic variables SU UMa, RX And and 0623+71.
Verbunt, Frank; Drew, Janet E.; Woods, A. John
IUE observations of the dwarf novae SU UMa and RX And, and of the nova-like variable 0623 + 71 are presented. At the time of observation, SU UMa and RX And were in outburst. All three systems show variability in the wind-formed UV resonance lines of N V 1240 A, Si IV 1397 A and C IV 1549 A on timescales of hours. The amplitude of variation is smal…
Spectrophotometry of the shell around AG Carinae.
Dufour, Reginald J.; Mitra, P. Mila
Spatially-resolved long-slit spectrophotometry are presented for two regions of the shell nebula around the P-Cygni variable star AG Carinae. The spectra cover the 3700-6800 A wavelength range. Emission-line diagnostics are used to derive extinction, electron temperatures, and densities for various positions in the nebula. The chemical abundances …
The absolute magnitudes of RR Lyrae stars - III. DH Peg.
Jameson, R. F.; Fernley, J. A.; Skillen, I. +1 more
UV optical and IR photometry of the RRc Lyrae star DH Peg is presented. Using this photometry plus previously published data the IR Flux Method of Blackwell & Shallis (1977) is applied to estimate effective temperatures and angular diameters at all phases of the pulsation cycle. The angular diameters are then matched with the integrated radial…
The X-ray orbital lightcurve of TY Pyx : a 3.2-day eclipsing RS CVn system.
Parmar, A. N.; White, N. E.; Culhane, J. L. +1 more
An Exosat observation of one orbital cycle of the eclipsing 3.2-d RS CVn system TY Pyx is reported. This system contains two almost identical GV stars, which is unusual because most RS CVns contain F or G main-sequence star and a K subgiant. The X-ray light curves of the primary and secondary eclipses are different above and below 1 keV. At lower …
X-ray spectral variations in NGC 4151.
Perola, G. C.; Fiore, F.; Romano, M.
In their analysis of the EXOSAT ME data on the Seyfert NGC 4151, Yaqoob, Warwick & Pounds found that the observed tendency of the spectrum to soften as the X-ray flux increases is due to variations in the absorbing column, which are anti-correlated with the source intensity, thus favouring a 'warm absorber' model. In this paper a re-analysis o…
Coronal X-ray emission from the short-period eclipsing binary XY UMa.
Jeffries, R. D.; Bedford, D. K.; Vilhu, O. +1 more
XY UMa, a close binary showing photospheric and chromospheric activity, has been observed with Exosat through 1.26 orbital cycles, with supporting optical photometry. The G2-5 V primary star is found to be responsible for the observed soft X-ray flux, which shows a clear primary eclipse. The X-ray-emitting coronal plasma is modeled to have two com…
Photospheric absorption lines in the UV spectra of O and B type stars.
Prinja, R. K.
Measurements of the equivalent widths of ultraviolet photo spheric lines of He II λ1640, C III λ1247, N III λλ1748, 1752, O IV λ1339, Si II λ1265, Si III λ1299, Si III λ1417, Si IV λλ1394, 1403 and Fe IV λ1765 in O3 to B5 stars are presented, using high-resolution IUE spectra of 300 supergiant, giant and dwarf stars.
All the ions exhibit a we…High-velocity gas components towards 4 Lac.
Keenan, F. P.; Bates, B.; Catney, M. G.
A comparison of IUE ultraviolet spectra of the star 4 Lac with observations of a suitable comparison star have confirmed the presence of 'high-velocity gas components' in the former which are redshifted by a velocity about 100 km/s from the low-velocity interstellar gas. In addition to providing an unambiguous identification of the species which s…