Search Publications
Low-frequency divergent X-ray variability in the Seyfert galaxy NGC4051
Elvis, M.; Watson, M. G.; Lawrence, A. +1 more
The X-ray emission from NGC4051, a nearby low luminosity Type 1 Seyfert galaxy, exhibits variations that are both rapid and apparently quasi-periodic1,2. Many Seyfert galaxies are variable3 but our knowledge of the form of variability has not advanced substantially since early well-resolved observations4 and attemp…
Fractal X-ray time variability and spectral invariance of the Seyfert galaxy NGC5506
McHardy, Ian; Czerny, Bozena
Rapid X-ray variability has long been sought after in active galactic nuclei (AGN) as an indicator of such parameters as the mass-to-energy conversion efficiency and black hole mass. Although some interesting variability information has been gained from early observations (for example see ref. 1 for a review) the faintness of AGN, combined with th…
The progenitor of SN1987A
Panagia, N.; Talavera, A.; Clavel, J. +6 more
One of the reasons why the bright supernova SN1987A is of such importance is the fact that its proximity would allow for the first time, the identification of a supernova progenitor star. Attempts to establish which star was the progenitor have led to uncertainties, however. Here we use spatial and spectroscopic information from International Ultr…
Giotto measurements of cometary and solar wind plasma at the Comet Halley bow shock
Coates, A. J.; Winningham, J. D.; Anderson, K. A. +19 more
The interaction of comets with the solar wind depends on the ionization of the heavy cometary neutrals (mostly H2O and its dissociation products O, OH) which flow out from the nucleus, and the coupling of these newly produced cometary ions with the solar wind through its embedded magnetic field. The 'pick-up' of these heavy ions slows t…
Ultraviolet detection of the nucleus of NGC2440
Heap, S. R.
In a recent letter, Atherton et al.1 announced the detection of the central, exciting star of the planetary nebula, NGC2440, on a narrow-band charge-coupled device (CCD) image obtained under excellent seeing conditions (1 arc s). They found it to be one of the hottest stars known. Here, we report the detection of the same star in ultrav…
Observations of active galaxies
Mushotzky, Richard
New information obtained by the EXOSAT satellite on the nature of the X-ray variability in AGNs is discussed. From the EXOSAT data, it is seen that many more AGNs vary on short timescales; in some cases, the character of the time variability is quantitatively and qualitatively different than expected from the flare model of the variability. Data o…