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Spectral and temporal features in bursts from 2S 1636-536 observed with EXOSAT.
Turner, M. J. L.; Breedon, L. M.
The well-known X-ray burster 2S 1636-536 (Nor X-1) was observed for 7 hr by the ME instrument on EXOSAT. During this time 7 bursts of unusual shape were detected. The bursts have similar profiles. The results suggest that each burst has two components with an initial helium thermonuclear flash triggering a stronger hydrogen flash; the ratio of con…
Non-LTE analysis of subluminous O-stars. VI. Feige 110.
Heber, U.; Kudritzki, R. P.; Hamann, W. -R. +3 more
An analysis of the ultraviolet (1150-2000 A) and the blue 4000-5100 A) spectra of the subdwarf O-star Feige 110 is presented. Effective temperature, gravity and helium abundance of Feige 110 are determined on the basis of NLTE model atmospheres. The effective temperature of Feige 110 is found to be 40,000 K (+5000 or -3000 K). Helium abundances in…
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…
The double Seyfert nucleus of MKN 266.
Kollatschny, W.; Fricke, K. J.
A long-exposure short-wavelength UV spectrum of the double nucleus galaxy Mkn 266 is discussed along with earlier optical data. The spectra of the two nuclei are well separated and both show evidence of a nonthermal origin. The weaker nucleus towards the SW is of Seyfert type 2 while the NE nucleus has characteristics intermediate between Seyferts…
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…