Time-delay measurement of the lensed quasar HE 1104-1805

Eran O. Ofek*, Dan Maoz

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


We have measured the time delay between the two images of the gravitationally lensed quasar HE 1104-1805 by combining observations made with the Wise Observatory 1 m telescope and published observations of this system by Schechter et al., spanning a total of 5 years, from 1997 to 2002. Based on a variety of techniques, we find that the best-fit time delay is -161 -7,-11+7,+34 days. The 68% and 95% confidence intervals include the systematic errors due to an observed component of uncorrelated variability between images. The delay is shorter than predicted by simple models and may indicate a large external shear or a large value of the Hubble parameter, h > 0.75 (95% confidence). The residual light curve between the two images shows a long-term trend of ∼0.04 mag yr-1, presumably the result of microlensing by stars in the lens galaxy, but also short-timescale (∼ 1 month) variability with a mean amplitude of about 0.07 mag.

Original languageEnglish
Pages (from-to)101-106
Number of pages6
JournalAstrophysical Journal
Issue number1 I
StatePublished - 1 Sep 2003


  • Gravitational lensing
  • Quasars: general
  • Quasars: individual (HE 1104-1805)


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