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The discovery of high-velocity flares in NV and the detection of carbon in the double degenerate binary GP COM
Horne, Keith; Marsh, T. R.; Wood, Janet H. +1 more
We present time-resolved ultraviolet spectra of the ultrashort-period binary GP Com taken with the Hubble Space Telescope. During our observations GP Com displayed spectacular variability in the dominant NV emission line which showed three large flares in 13h of observations. We isolate the flare spectrum which reveals CIV emission at a level of 0…
ROSAT observations of the flare star CC ERI
Jordan, C.; Pan, H. C.
The flare/spotted spectroscopic binary star CC Eri was observed with the Position Sensitive Proportional Counter (PSPC) on the X-ray satellite ROSAT on 1990 July 9-11 and 1992 January 26-27. During the observations, the source was variable on time-scales from a few minutes to several hours, with the X-ray (0.2-2 keV) luminosity in the range ~(2.5-…
The orbital period of the pre-cataclysmic binary RE 2013+400 and a study of the atmosphere of the DAO white dwarf primary
Rutten, R. G. M.; Barstow, M. A.; Koester, D. +8 more
Several pre-cataclysmic binaries, comprising a hot white dwarf with a red dwarf companion, have been discovered as a result of the optical identification of EUV sources from the ROSAT all-sky survey. The optical spectra have the steep blue continuum and Balmer absorption typical of a hot white dwarf, but there are bright, narrow emission lines of …
Soft X-ray and ultraviolet observations of MRK 841: implications for the blue bump
Nandra, K.; Turner, T. J.; Fabian, A. C. +3 more
We present an analysis of an extended ROSAT observation of the Seyfert galaxy Mrk 841. The source is clearly variable on short time-scales with distinctive changes in the hardness ratio, indicating that more than one spectral component is present in the PSPC band. Spectral modelling of the soft X-ray data confirms this complex picture. The data sh…
X-ray observations of NGC 1851 and the globular cluster LMXBs
Charles, P. A.; Callanan, P. J.; Penny, A. J.
We present new Ginga observations of the globular cluster X-ray source 4U 0513-40 in NGC 1851. Despite the 2-d time-base of the observations, no eclipsing or dipping modulation was found. The spectrum can be well modelled by a power law of index 2.1 to energies of at least 10 keV. We find from archive EXOSAT data that an additional blackbody contr…
The HST ultraviolet spectrum of the nucleus of NGC 1275: Fermi-accelerated Lyalpha emission
Fabian, A. C.; Johnstone, R. M.
We present an HST FOS spectrum of the nucleus of NGC 1275. The narrow part of the Lyalpha line is double-peaked, with one emission line centred at the systemic velocity of the 5000 km s^-1 system and the other blueshifted by ~450 km s^-1. We show that the short-wavelength component is probably formed by Fermi acceleration across a shock front. The…
X-ray timing and spectral behaviour of the Rapid Burster
Lewin, Walter H. G.; van Paradijs, Jan; Lubin, Lori M. +3 more
We present an X-ray fast-timing and spectral analysis of the type II bursts and the persistent emission (PE) of the Rapid Burster observed with the EXOSAT Medium-Energy Instrument. The hardness-intensity and colour-colour diagrams of the Rapid Burster are somewhat different from those of the majority of other low-mass X-ray binaries, which fall in…
Photoionization modelling based on HST images of Magellanic Cloud planetary nebulae - I. SMCN2 and SMCN5
Barlow, M. J.; Blades, J. C.; Liu, X. -W. +2 more
We construct fully self-consistent, detailed photoionization models for two planetary nebulae (PNe) in the Small Magellanic Cloud (SMC), namely SMC N 2 and SMC N 5, to fit optical and UV spectrophotometric observations as well as HST Faint Object Camera (FOC) narrow-band images taken in the light of Hβ. The derived density structure shows that bot…
HST polarization map of the ultraviolet emission from the outer jet in M87 and a comparison with the 2-cm radio emission
Boksenberg, A.; Mackay, C. D.; Tanvir, N. R. +2 more
We present the first high-resolution polarization map of the ultraviolet emission from the outer jet in M87. The data were obtained by the Faint Object Camera (FOC) on the Hubble Space Telescope. The polarization map has a resolution of 0.2 arcsec and was derived using data from three linearly polarized images combined with the best available cali…
Optical and UV spectroscopy of stars in the direction of the Riegel & Crutcher cold cloud
Bates, B.; Kemp, S. N.; Montgomery, A. S.
Optical and UV spectral data are presented for the stars HD 165202, 168708 which lie in the direction of the Riegel & Crutcher cold cloud. These observations complement our earlier studies in which high-resolution HI profiles mapped the cold cloud in self-absorption (Montgomery et al.). HD 165202 lies in a direction close to where we observe a…