Search Publications
The outer atmospheres of the 'hybrid' bright giants : the chromospheres of alpha TrA (K4 II), IOTA AUR (K3 II), gamma AQL (K3 II) , and theta HER (K1 II).
Harper, Graham M.
Detailed models of the chromospheres of several 'hybrid' bright giants are presented. The models extend from the base of the chromosphere and into the transition area. These chromospheric models are based on radiative transfer calculations for a range of atoms and emission lines. The presence of steep turbulent velocity gradients leads to profiles…
Time dependence of the UV resonance lines in the cataclyspic variables YZCnc, IR GEM and V 3885 Sgr.
Verbunt, F.; Collier Cameron, A.; Woods, J. A. +2 more
Orbital variations are observed in the UV resonance lines of YZ Cnc, IR Gem and V3885 Sgr. Optical spectroscopic observations of YZ Cnc show that the maximum absorption in the UV lines occurs about 0.7-0.8 orbits after the transition from red to blue of the optical emission lines. IR Gem shows orbital variations in the UV lines that are as strong …
The central star of S 216.
Tweedy, R. W.; Napiwotzki, R.
Optical and high-resolution ultraviolet spectra of LS V + 46 21, the postulated central star of the large, nearby planetary nebula S 216, have been analyzed. From modeling the line profiles, this star is found to have an effective temperature of about 90,000 K, surface gravity log g of about 7, and a He:H ratio of about 0.01. These are as expected…
Beta Pictoris and the lambda Bootis stars : testing the accretion hypothesis.
King, Jeremy R.; Patten, Brian M.
It is suggested that Beta Pic may be an unrecognized Lambda Boo star, based on the recent discussion of its evolutionary status by Paresce and the proposal by Venn and Lambert linking circumstellar material with the Lambda Boo phenomenon. The star's metallicity, photometric indices and UV spectrum support this interpretation. If confirmed as a Lam…
UV spectroscopy of Z Chamaeleontis - I. Time-dependent dips in superoutburst.
Sonneborn, G.; Charles, P. A.; Hassall, B. J. M. +2 more
Extensive IUE observations of the dwarf nova Z Cha during the 1987 April superoutburst and IUE-Exosat observations during the 1985 July superoutburst are presented. The UV light curve shows two dips when folded on the orbital period. One dip, at orbital phase 0.8 becomes shallower as the superoutburst progresses and can be associated with decreasi…
IUE observations of the shells of RR PIC and GK Per.
Evans, A.; Bode, M. F.; Duerbeck, H. W. +1 more
We present UV observations of the resolved shells of the old novae RR Pic (1925) and GK Per (1901). On the assumption that the RR Pic nebula is photoionized by the ultraviolet continuum emitted by the stellar remnant, we conclude that nitrogen is overabundant relative to solar in both the 'equatorial ring' and 'polar blob' regions; there are steep…
Variability in the UV resonance lines of the cataclysmic variable V795 Herculis (PG 1711+336).
Drew, Janet E.; Prinja, Raman K.; Rosen, Simon R.
Variability in the UV resonance lines from the cataclysmic variable V795 Her is investigated on the basis of a total of 28 IUE SWP low-resolution spectra. Significant line profile fluctuations are evident in the C IV 1549 and Si IV 1400 doublets on time-scales down to less than about 30 min. There is little or no evidence for changes in N V 1240. …
UV spectroscopy of the X-ray binary AC 211 (= 4U 2127+11) in M 15.
Raymond, J. C.; Charles, P. A.; Hassall, B. J. M. +2 more
Time-resolved International Ultraviolet Explorer observations are presented of the low-mass X-ray binary AC211/4U2127 + 11 in the globular cluster M15 (NGC 7078). The spectra show He II 1640-A emission, the flux of which is modulated on the 8.5-hr orbital period of AC211. This modulation and the ratio of He II 1640 A to He II 4686 A and C IV 1550 …
The interrelation of UV and optical activity diagnostics in HK Lacertae.
Houdebine, E. R.; Butler, C. J.; Olah, K. +3 more
The study examines and compares optical photometric and UV (IUE) spectroscopic data on the active RS CVn star HK Lac gathered in the years 1979, 1980, and 1987. The photometry is modeled by representations of 'starspots' and, in general, it is found that the UV emission lines are stronger at times of spot maximum. The variable interstellar absorpt…
The hot subdwarf in the eclipsing binary HD 185510.
Simon, Theodore; Jeffery, C. S.; Evans, T. L.
High-resolution spectroscopic measurements of radial velocity are employed to characterize the eclipsing binary HD 185510 in terms of masses and evolutionary status. The IUE is used to obtain the radial velocities which indicate a large mass ratio Mp/Ms of 7.45 +/- 0.15, and Teff is given at 25,000 +/- 1000 K based on Ly alpha and UV spectrophotom…