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Issue A&A
Volume 436, Number 2, June III 2005
Page(s) 465 - 468
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20042303



A&A 436, 465-468 (2005)
DOI: 10.1051/0004-6361:20042303

Research Note

The EUV variability of the luminous QSO HS 1700+6416

D. Reimers1, H.-J. Hagen1, J. Schramm1, G. A. Kriss2 and J. M. Shull3

1  Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
    e-mail: dreimers@hs.uni-hamburg.de
2  STScI, 3700 San Martin Dr. Baltimore, MD 21218, USA
3  CASA, Department of Astrophysical and Planetary Science, University of Colorado, Boulder, CO 80309, USA

(Received 3 November 2004 / Accepted 27 February 2005)

Abstract
We report on the first observations of variations in UV (intrinsic EUV 330 Å) flux of the luminous QSO HS 1700+6416 (z = 2.72) over a decade. The amplitude of variations increases from $\pm$0.1 mag in the optical (R) to up to a factor of 3 at 1250 Å. This is apparently an extension of the increase in amplitude of variations towards shorter wavelengths observed with IUE in low z AGN (Paltani & Courvoisier 1996) to the EUV. The time-scale for variations with the largest amplitudes is $\geq$1/2 yr to years. We briefly discuss the consequences of the observed variations on the ionizing metagalactic UV background.


Key words: galaxies: clusters: individual HS 1700+6416 -- galaxies: quasars: general

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© ESO 2005


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