The extreme X-ray luminosity of the z=4.72 radio-loud quasar GB 1428+4217
Abstract
We report on a ROSAT High Resolution Imager observation of the radio-loud quasar GB 1428+4217, which is at a redshift z=4.72. The quasar was well detected, with a flux in the observed 0.1-2.4 keV band of ~10^-12ergcm^-2s^-1. Our result confirms that the object in the catalogue of serendipitous X-ray sources, WGACAT, is indeed the quasar. GB 1428+4217 is therefore the brightest X-ray source above a redshift of 4 and has an extremely high isotropic X-ray luminosity, which exceeds that in other (observed) bands. The observed spectral energy distribution of the object therefore peaks at X-ray, or even shorter, wavelengths. We speculate that the emission in the object is beamed toward us.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- October 1997
- DOI:
- 10.1093/mnras/291.1.L5
- Bibcode:
- 1997MNRAS.291L...5F
- Keywords:
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- QUASARS: GENERAL;
- QUASARS: INDIVIDUAL: GB 1428+4217;
- X-RAYS: GALAXIES