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The nearby interstellar material in the general direction towards M 22.
Bates, B.; Gilheany, S.; Wood, K. D.
High-resolution optical spectra of interstellar absorption lines are used to examine reddening variations across the globular cluster M22 which are produced by the nearby low-velocity gas. Fifteen cluster stars together with three stars within 1.3 deg of the cluster were observed in the Na D lines and in some case also the K I (7699 A) line. Optic…
Implications of the ionizing continuum of 3C 263.
Fabian, A. C.; Naylor, T.; George, I. M. +1 more
We present ultraviolet IUE and soft X-ray EXOSAT observations of the quasar 3C 263 which reveal the low-energy part of the ionizing continuum and allow the high-energy tail to be strongly constrained. The ionizing spectrum confirms that the pressure of the extra-nuclear emission-line gas discovered earlier by us around the quasar is greater than 1…
Time-resolved ultraviolet spectroscopy of the cataclysmic variable PG 1711+336.
Prinja, R. K.; Rosen, S. R.; Supelli, K.
Low-resolution IUE ultraviolet observations of the cataclysmic variable, PG 1711 + 336, are presented. The spectra reveal extensive variability in the wind-formed C IV 1550 A resonance line P Cygni profiles, on time-scales as short as several hours. The high-resolution IUE spectrum of the nova-like system V3885 Sgr, convolved with the IUE low-reso…
Speckle interferometry of HIPPARCOS link stars - III.
White, G. L.; Argue, A. N.; Reynolds, J. E. +5 more
A third list of stars is presented which have been tested by speckle interferometry for use in the Hubble Space Telescope link between the Hipparcos astrometric reference frame and the extragalactic VLBI reference frame. Structural information on angular scales of 0.15-1.2 arcsec for 34 Southern Hemisphere stars is reported from observations made …
The missing UV absorption lines of NGC 4151.
Penston, M. V.; Snijders, M. A. J.; Leech, K. J.
In this paper we discuss new, near-simultaneous high-dispersion long- and short- wavelength International Ultraviolet Explorer (IUE) observations of the Seyfert galaxy NGC 4151. Previous observations revealed a narrow absorption system in Mg II not present in Lyα or C IV. The new observations confirm the presence of this system in Mg II and its ab…
Erratic profiles of type II bursts of very low fluence from the rapid burster.
Lewin, Walter H. G.; van Paradijs, Jan; Lubin, Lori M. +2 more
Results are presented of approximately 17 hr of Exosat observations of the Rapid Burster in September 1985 during which about 541 type II bursts lasting less than 30 s were observed. Although these bursts are known to have an approximately time-invariant profile showing successive peaks in the burst's decay portion, most of the 20-s bursts at the …
Multi-frequency variations of the Wolf-rayet system HD 193793 - I. Infrared, X-ray and radio observations.
van der Woerd, H.; van der Hucht, K. A.; Pollock, A. M. T. +3 more
Observations made of the Wolf-Rayet system HD 193793 over the 1979-1989 period in the radio, X-ray, and IR regions reveal great variations in all three regimes. The most complete coverage obtained was in the IR; attention is given to an IR outburst in 1985 during which the IR flux increased by as much as an order of magnitude over the course of se…
The ultra-compact broad emision line region in NGC 4151.
Perola, G. C.; Boksenberg, A.; Penston, M. V. +6 more
New observations of the UV continuum and emission lines of a Seyfert I galaxy are presented in which the time resolution is adequate to describe the character of variability. Using the IUE satellite, the nucleus of NGC 4151 was observed with a mean interval of 3.4 d during 2 months. The flux of the continuum and of most emission lines underwent la…
The X-ray emission of 3C 273.
Koyama, K.; Nandra, K.; Tanaka, Y. +12 more
The X-ray emission of 3C273 in the 0.2-35 keV band has been studied, with EXOSAT and Ginga, over the period 1983 December to 1985 December. The overall flux is variable on a time-scale of weeks by a factor of 2. The spectral index in the 2-10 keV band (α ~0.5) is significantly different from the 'canonical' AGN index of α = 0.7. There are small bu…
A model for the planetary nebula NGC 7027.
Middlemass, D.
Extensive photoionization modeling of NGC 7027 is presented using the most recent observations available. The effects of the differential extinction caused by the local dust cloud are considered and corrections are made to large-aperture line fluxes. Abundances are derived from a large number of collisionally excited and recombination emission lin…