The ultraviolet spectrum and continuum energy distribution of the bright quasar H1821 + 643

Autor:	Alexei V. Filippenko, Michiel Kolman, Chris Shrader, Jules P. Halpern
Rok vydání:	1991
Předmět:	Physics Continuum (design consultancy) Astronomy Astronomy and Astrophysics Quasar Astrophysics medicine.disease_cause Astronomical spectroscopy Lyman limit Black hole Space and Planetary Science medicine Spectral energy distribution Emission spectrum Ultraviolet
Zdroj:	The Astrophysical Journal. 373:57
ISSN:	1538-4357 0004-637X
DOI:	10.1086/170022
Popis:	The first UV observations of the bright QSO H1821 + 643 are reported. With V = 14.2 mag and z = 0.297, H1821 + 643 is the second brightest object in the sky at z above 0.1. The IUE data are combined with new optical spectroscopy, and existing IR and X-ray data, to reveal a strong optical/UV 'big bump', which continues past the Lyman limit in the rest frame of the QSO. A possible turnover at the high-frequency side of the UV continuum constrains fits of a thin accretion disk model to a large black hole mass and high accretion rate, but a small disk size. The shape of the UV continuum was found to be variable, with a hardening of the spectrum when the source was brighter. Because of its location, only 3 deg from the ecliptic pole, H1821 + 643 will be an important object for simultaneous UV and soft X-ray monitoring to test for a common origin of the UV bump and soft X-ray excess.
Databáze:	OpenAIRE
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