We report on a search for X-ray emission from quasars with redshifts greater than 4 using the ROSAT public database. Our search has doubled the number of z > 4 quasars detected in X-rays from six to 12. Most of those known prior to this work were radio-loud and X-ray-selected sources; our study increases the number of X-ray-detected, optically selected z > 4 quasars from one to seven. We present their basic X-ray properties and compare these with those of lower redshift quasars. We do not find any evidence for strong broadband spectral differences between optically selected z > 4 quasars and those at lower redshifts.

Original languageEnglish (US)
Pages (from-to)2031-2037
Number of pages7
JournalAstronomical Journal
Issue number5
StatePublished - May 2000

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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