Manfred W. Pakull

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We have examined X-ray and optical observations of two ultra-luminous X-ray sources, X7 and X10 in NGC4559, using XMM-Newton, Chandra and HST. The UV/X-ray luminosity of X7 exceeds 2.1 × 10 40 erg s −1 in the XMM-Newton observation, and that of X10 is > 1.3×10 40 erg s −1. X7 has both thermal and power-law spectral components, The characteristic temperature(More)
We obtained deep optical imaging of the thermally emitting X-ray bright and radio-quiet isolated neutron star RX J1605.3+3249 with the Subaru telescope in 1999 and 2003. Together with archival HST images acquired in 2001 these data reveal a proper motion of µ = 144.5 ± 13.2 mas/yr. This implies a relatively high spatial velocity and indicates that the star(More)
Optical studies of ultraluminous X-ray sources (ULX) in nearby galaxies have turned out to be instrumental in discriminating between various models including the much advertised intermediate mass black hole hypothesis and various beaming scenarios. Here we report on ESO VLT and SUBARU observations of ULX that have revealed the parent stellar clusters with(More)
We discuss our radio (Australia Telescope Compact Array and Australian Long Baseline Array) and X-ray (XMM-Newton) monitoring observations of the unusual ultraluminous supernova SN 1978K in NGC 1313 at ∼ 25 years after the explosion. SN 1978K is a rare example of a Type IIn supernova that has remained bright enough to have long-term X-ray and radio(More)
We present optical observations of an ultraluminous X-ray source (ULX) in Holmberg IX, a dwarf galaxy near M81. The ULX has an average X-ray luminosity of some 10 40 erg/s. It is located in a huge (400pc x 300pc) ionized nebula being much larger than normal supernova remnants. From the observed emission lines (widths and ratios) we find that the structure(More)
  • C Motch, P Guillout, +6 authors F.-J Zickgraf
  • 1997
We report on optical searches in the error circles of 93 ROSAT survey sources located at low galactic latitudes (|b| < 20 •). These sources were extracted from the ROSAT Galactic Plane Survey using various selection criteria on hardness ratio, X-ray and optical brightness and integrated galactic absorption in the direction of the source. We find optical(More)
The nature of extra-nuclear ultraluminous X-ray sources (ULX) in nearby galaxies continues to be an enigma, since their adopted isotropic high-energy output would surpass the Eddington limit of even the most massive stellar black holes. Many ultraluminous X-ray sources are surrounded by emission nebulae that show indications of both shock ionization and(More)
We present a summary of our ongoing efforts to study one of the brightest ultraluminous X-ray source, NGC 1313 X-2. Despite a large coverage in the X-rays, much of the information we have about the source and its environment comes from optical wavelenghts. Here, we report on the properties of the stellar environment, and the differences in the optical(More)
Black-hole accretion states near or above the Eddington luminosity (the point at which radiation force outwards overcomes gravity) are still poorly known because of the rarity of such sources. Ultraluminous X-ray sources are the most luminous class of black hole (L(X) approximately 10(40) erg s(-1)) located outside the nuclei of active galaxies. They are(More)