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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 …
Optical photometry and ultraviolet spectroscopy of the flare/BY DRA star GL 182(V 1005 Ori).
Doyle, J. G.; Butler, C. J.; Byrne, P. B.
G1 182 was previously reported to be a rapidly rotating BY Dra star which flares at an anomalously high rate. The present observations confirm its BY Dra nature but revise the rotation period, such that it is shown to rotate much more slowly. The time-averaged energy output in flares is shown to be normal for a flare star of its spectral type, and…
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…
Coordinated UV and optical observations of the AM Herculis object E 1405-451 in thehigh and low sta
Maraschi, L.; Tanzi, E. G.; Motch, C. +5 more
Simultaneous UV and optical observations of the magnetic white dwarf binary E1405-451 taken in February 1983, March, and April are reported. In March the source was found in a low state analogous to those observed in AM Her. In this state the ultraviolet spectrum of E1405-451 can be interpreted as the emission from a hot white dwarf/T = 26,500 K, …
Ultraviolet observations of interstellar extinction near the Cepheus OB3 molecular cloud.
Savage, B. D.; Massa, D.
IUE data are used to derive UV extinction curves for O and B stars in the Cep OB3 association. These data are analyzed in conjunction with ANS photometry of additional association stars. While the level of the far-UV extinction differs greatly throughout the region the shape of the 2175 Å bump does not. The authors demonstrate that the different c…