G. Borner

Publications (3)0 Total impact

• Source

  Available from: arxiv.org

  Article: Soft X-ray Properties of ULIRGs Based on a Large and Complete Sample

  X. Y. Xia, Th. Boller, Z. G. Deng, G. Borner
  [show abstract] [hide abstract]
  ABSTRACT: We report on the results of the cross-correlation of a sample of 903 Ultraluminous IRAS galaxies (ULIRGs) with the ROSAT-All Sky Survey Bright Source Catalogue and the ROSAT archived pointing observations. The sample of ULIRGs has been compiled from the PSCz redshift survey. In total, 35 ULIRGs are securely detected by the ROSAT All-Sky Survey and pointing observations, five of which are blazars. The statistical properties of these sources in the soft X-ray band are determined and compared with their properties in other wavebands. We find that the ratio of the soft X-ray to the far-infrared flux spans about 5 orders of magnitude and reaches values of about unity. This ratio is a good indicator of the main energy source of ULIRGs. Those with soft X-ray to far-infrared flux exceeding 0.01 are probably powered by accretion onto central supermassive black holes while those with ratios smaller than 0.001 are probably caused by starbursts or other heating processes, or are Compton thick sources. Some ULIRGs have energy contributions from both. This ratio is low for most ULIRGs and hyperluminous infrared galaxies, which explains their low detection rate by ROSAT and ASCA. We also find that some ULIRGs have a similar soft X-ray luminosity vs. temperature relation to that for groups of galaxies and elliptical galaxies, suggesting a common origin of these systems. Our study also reveals a correlation between the hardness ratio and the soft X-ray luminosity for Seyfert 1s/QSOs.
  04/2001;
• Source

  Available from: Yu Gao

  Article: An X-ray Luminous, Dwarf Seyfert Companion of Mrk 273

  X. Y. Xia, Th. Boller, H Wu, Z. G. Deng, Y Gao, Z. -L. Zou, Shude Mao, G. Borner
  [show abstract] [hide abstract]
  ABSTRACT: We report the discovery of the brightest X-ray source hosted by a faint (M_B=-16) dwarf galaxy in the immediate vicinity of the ultraluminous IRAS merging galaxy Mrk 273. The dwarf galaxy, 1.3 arcmin away from Mrk 273, is at the tip of a faint northeast plume of Mrk 273. Its spectrum exhibits strong [OIII], Halpha, [NII] emission lines, which establish the redshift of the dwarf galaxy, $z=0.0376$, the same as that of Mrk 273. The emission line ratios are typical of Seyfert galaxies. The X-ray emission is consistent with a point-like source coincident with the center of the dwarf galaxy. The intrinsic X-ray luminosity, 6.3x10^{41} ergs, in the 0.1--2.4 keV energy range, is about seven times larger than the B band luminosity. The X-ray spectrum of the source can be fit with a power-law. All the evidence is consistent with the source being a Seyfert galaxy. It is mysterious why out of $\sim 10$ faint objects in the same field only one is detected by ROSAT and its ratio of soft X-ray to optical luminosity is as high as those for BL Lac objects and few active galactic nuclei (AGNs). If there is a population of such dwarf AGNs hidden as companions of major merger galaxies (such as Mrk 273), they may contribute to the luminosity function of AGNs and the cosmic X-ray background at the faint end. Comment: 15 pages, 2 figures, ApJ Letters, in press
  01/1998;
• Source

  Available from: articles.adsabs.harvard.edu

  Article: A Possible Way to Determine Deceleration Parameter q

  H. J. Mo, X. Y. Xia, Z. G. Deng, G. Börner, G. Borner, L. Z. Fang
  08/1991; 23:1342.