Browsing Faculty of Arts and Sciences by Keyword "X Ray Spectra"

Now showing items 1-10 of 10

    • Absorption in X-ray spectra of high-redshift quasars 

      Elvis, Martin S.; Fiore, Fabrizio; Wilkes, Belinda Jane; McDowell, Jonathan Christopher; Bechtold, Jill (IOP Publishing, 1994)
      We present evidence that X-ray absorption is common in high-redshift quasars. We have studied six high-redshift (z approximately 3) quasars with the ROSAT Position Sensitive Proportional Counter (PSPC) of which four are ...

    • Atlas of quasar energy distributions 

      Elvis, Martin S.; Wilkes, Belinda Jane; McDowell, Jonathan Christopher; Green, Richard F.; Bechtold, Jill; Willner, Steven P.; Oey, M. S.; Polomski, Elisha; Cutri, Roc (IOP Publishing, 1994)
      We present an atlas of the spectral energy distributions (SEDs) of normal, nonblazar, quasars over the whole available range (radio to 10 keV X-rays) of the electromagnetic spectrum. The primary (UVSX) sample includes 47 ...

    • The complex optical to soft x-ray spectrum of the low-redshift radio-quiet quasars 

      Fiore, Fabrizio; Elvis, Martin S.; McDowell, Jonathan Christopher; Siemiginowska, Aneta L.; Wilkes, Belinda Jane (IOP Publishing, 1994)
      Eight high signal-to-noise ROSAT Position Sensitive Proportional Counter (PSPC) observations of six low-redshift (o.048 less than z less than 0.155) radio-quiet quasars have been analyzed to study ant soft excess. All the ...

    • EXOSAT X-ray spectra of quasars 

      Comastri, Andrea; Setti, Giancarlo; Zamorani, Giovanni; Elvis, Martin; Wilkes, Belinda Jane; McDowell, Jonathan Christopher; Giommi, Paolo (IOP Publishing, 1992)
      Measurements of the X-ray spectra in the 0.1-10-keV energy range for 17 AGN (mostly PG quasars) using the Exosat Low and Medium Energy arrays are presented. For each object, the best-fit spectral parameters in the medium-energy ...

    • PKS 0483-436 - A high-redshift quasar with strong X-ray absorption 

      Wilkes, Belinda Jane; Elvis, Martin S.; Fiore, Fabrizio; McDowell, Jonathan Christopher; Tananbaum, Harvey D.; Lawrence, Andrew (IOP Publishing, 1992)
      The first X-ray spectrum of a high-redshift (z = 2.85) quasar is reported. The Rosat PSPC spectrum of PKS 0438-436, covering 0.3-9 keV in the quasar's rest frame, reveals unexpected absorption of about 1 x 10 exp 22/sq cm, ...

    • The soft x-ray properties of a complete sample of optically selected quasars. 1: First results 

      Laor, Ari; Fiore, Fabrizio; Elvis, Martin S.; Wilkes, Belinda Jane; McDowell, Jonathan Christopher (IOP Publishing, 1994)
      We present the results of ROSAT position sensitive proportional counter (PSPC) observations of 10 quasars. These objects are part of our ROSAT program to observe a complete sample of optically selected quasars. This sample ...

    • Weak bump quasars 

      McDowell, Jonathan Christopher; Elvis, Martin; Wilkes, Belinda Jane; Willner, Steven P.; Oey, M. S.; Polomski, Elisha; Bechtold, Jill; Green, Richard F. (IOP Publishing, 1989)
      The recent emphasis on big bumps dominating the UV continuum of quasars has obscured the facts that bump properties vary widely and that there are objects in which no such component is evident. As part of a survey of quasar ...

    • X-ray absorption toward the red quasar 3C 212 

      Elvis, Martin S.; Fiore, Fabrizio; Mathur, Smita; Wilkes, Belinda Jane (IOP Publishing, 1994)
      A Roentgen Satellite (ROSAT) X-ray spectrum of the z = 1.049 'red quasar' 3C 212 has a strong low-energy cutoff. The spectrum can be fitted with a power law (of energy index 1.4(+0.8, -0.6) with low-energy photoelectric ...

    • The X-ray and ultraviolet absorbing outflow in 3C 351 

      Mathur, Smita; Wilkes, Belinda Jane; Elvis, Martin S.; Fiore, Fabrizio (IOP Publishing, 1994)
      3C 351 (z = 0.371), and X-ray-'quiet' quasar, is one of the few quasars showing signs of a 'warm absorber' in its X-ray spectrum; i.e., partially ionized absorbing material in the line of sight whose opacity depends on its ...

    • X-ray spectral evolution of high redshift quasars 

      Bechtold, Jill; Elvis, Martin S.; Fiore, Fabrizio; Kuhn, Olga; Cutri, Roc M.; McDowell, Jonathan Christopher; Rieke, Marcia; Siemiginowska, Aneta L.; Wilkes, Belinda Jane (IOP Publishing, 1994)
      At z approx. equals 3, the x-ray spectra of radio-loud and radio-quiet quasars are different. High-redshift radio-quiet quasars either have large absorbing columns, NH, and steeper power law spectral indices, alphaepsilon, ...