Article

An Optical Time Delay Estimate for the Double Gravitational Lens System B1600+434

I. BurudAcademia Sinica, Taipei, TaiwanJ. HjorthAstronomical Observatory, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark; Department of Physics and Research Center for the Early Universe, University of Tokyo, Hongo, Bunkyon, Tokyo 113-8654, JapanA. O. JaunsenUniversity of Oslo, Oslo, NorwayM. I. AndersenConsejo Superior de Investigaciones Científicas, Madrid, SpainH. KorhonenDivision of Astronomy, University of Oulu, PO Box 3000, FIN-90014 Oulun Yliopisto, Finland; Departament d'Astronomia i Meteorologia, Universitat de Barcelona, Av. Diagonal, 647, E-08028 Barcelona, Spain; J. W. ClasenVillanova University, Radnor, United StatesJ. PeltTartu Astrophysical Observatory, Tõravere, 61602, Estonia; Division of Astronomy and Astrophysics, UCLA, CA 90095-1562.; DeceasedF. P. PijpersTheoretical Astrophysics Center, University of Aarhus, DK-8000 Århus C, Denmark; Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127, Bologna, ItalyPierre MagainInstitut d’Astrophysique et de Géophysique de Liège, Avenue de Cointe 5, B-4000 Liège, BelgiumR. H. ØstensenDepartment of Physics, University of Tromsø, Tromsø, Norway; Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127, Bologna, Italy.; Dipartimento di Astronomia, Università di Bologna, via Ranzani 1, 40127 Bologna, Italy

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Abstract

We present optical I-band light curves of the gravitationally lensed double QSO B1600+434 from observations obtained at the Nordic Optical Telescope (NOT) between April 1998 and November 1999. The photometry has been performed by simultaneous deconvolution of all the data frames, involving a numerical lens galaxy model. Four methods have been applied to determine the time delay between the two QSO components, giving a mean estimate of \\Delta_t = 51+/-4 days (95% confidence level). This is the fourth optical time delay ever measured. Adopting a Omega=0.3, Lambda=0 Universe and using the mass model of Maller et al. (2000), this time-delay estimate yields a Hubble parameter of H_0=52 (+14, -8) km s^-1 Mpc^-1 (95% confidence level) where the errors include time-delay as well as model uncertainties. There are time-dependent offsets between the two (appropriately shifted) light curves that indicate the presence of external variations due to microlensing.

Identifiers

DOI: 10.1086/317213

Citations and references

Cited by 40 references

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