Search Publications
Cygnus X-2 : neutron star or degenerate dwarf ?
Hammerschlag-Hensberge, G.; McClintock, J. E.; Remillard, R. A. +2 more
Some conflicting models have been proposed for Cyg X-2: a degenerate dwarf model which predicts a distance of 250 + or 50 pc; and a neutron star model which implies a distance of about 8000 pc. Based on a reddening study, it is found that the distance to Cyg X-2 is greater than 1100 pc, which rules strongly against the degenerate dwarf model. This…
The many faces of Capella : a search for rotational modulations and astudy of systematic velocities of emission lines in the ultraviolet.
Ayres, T. R.
The ultraviolet emission of the spectroscopic binary Capella has been monitored with IUE over the course of half an orbital cycle (2 months). The first objective was to detect changes in the fluxes or shapes of ultraviolet emission lines in response to the evolution of large-scale active regions or their rotation onto and off the visible hemispher…
Ultraviolet observations of starburst and mini-Seyfert galactic nuclei.
Thuan, T. X.
The high excitation emission line galaxies NGC 1667, NGC 5135, and IC 5135 show activity which, while similar to that of Seyfert 2 galaxies, is 1-2 orders of magnitude smaller. The line and continuum emission is in all three cases more extended than would correspond to a point source. In addition to showing such Seyfert-like characteristics as bro…
Variability of the ultraviolet spectrum of BL Lacertae objects.
Ulrich, M. H.; Kondo, Y.; Hackney, K. R. H. +1 more
Attention is given to repeated observations of the two nearby BL Lac objects, Mrk 421 and PKS 0521-36, comparing the temporal behavior of their continuum in the 1300-3000 A range with that observed in intrinsically bright BL Lac objects and in Seyfert galaxies. Also discussed are the emission lines in the UV and optical spectrum of PKS 0521-36. It…
Interstellar lines in spectra of extragalactic sources. III. Markarian 509, Arakelian 120 and 3C 273.
York, D. G.; Cowie, L. L.; Morton, D. C. +3 more
Spectra of two Seyfert galaxies, Mrk 509 and Akn 120, show galactic interstellar absorption lines of S II, Si II, and Fe II, while Si IV absorption is seen in the quasar 3C 273. The lines appear at LSR velocity of less than 100 km/s and probably lie within 3 kpc of the galactic disk. Extragalactic absorption lines are found in the spectrum of Mrk …
On the nature of the galactic gamma-ray sources.
Morfill, G. E.; Bignami, G.; Forman, M.
Available data constrain possible models of the gamma-ray point (or pointlike) sources found by COS B. Apart from the pulsars (Crab, Vela) and possibly the quasar 3C 273, which are "compact" objects, and which have been identified at other photon energies, there are some 20-odd other sources with no accepted or acceptable counterpart, as yet. This…
Feige 24 : wind : flare accretion by a hot DAZ1 degenerate.
Sion, E. M.; Starrfield, S. G.
Model stellar envelopes have been constructed in order to represent the outer layers of the hot DAZ white dwarf component of the spectroscopic binary Feige 24. The results of the calculations show that the metals, discovered by Dupree and Raymond (1983) should diffuse rapidly into the interior unless a continuous source of these elements is presen…
GD 323 : a white dwarf with a stratified H/He atmosphere ?
Sion, E. M.; Wesemael, F.; Liebert, J. +1 more
New optical and ultraviolet (IUE) spectrophotometry of the hot white dwarf GD 323 are presented. The optical spectra exhibit broad, shallow Balmer lines, together with weaker He I lambda-4471, lambda-4921 lines. However, the effective temperature and helium abundance derived from the optical spectrum appear incompatible with parameters derived fro…
The resonance lines of HG II in IUE spectra of chemically peculiar stars.
Leckrone, D. S.
High-dispersion IUE observations of the two resonance lines of Hg II, at 1650 and 1942 Å, are presented for two normal stars, ν Cap and π Cet; for the HgMn stars κ Cnc, µ Lep, 46 Dra, ι CrB, HR 4072, and χ Lup; and for the magnetic variable α2CVn. These peculiar stars have all been classified as Hg-rich on the basis of their stron…
Ultraviolet and optical spectroscopy of CN 1-1 (= HDE 330036).
Lutz, J. H.
Ultraviolet and optical spectra of Cn 1-1 are presented. This stellar object has strong emission lines superposed on the absorption spectrum of an F5 III-IV star. It has been called both a symbolic star and a planetary nebula. Optical spectra taken over a period of two years do not show any variations in radial velocities. The radial velocities of…