Research Note

The EUV variability of the luminous QSO HS 1700+6416

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 () over a decade. The amplitude of variations increases from ±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 ≥1/2 yr to years. We briefly discuss the consequences of the observed variations on the ionizing metagalactic UV background.