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A Robust Determination of the Time Delay in 0957+561A, B and a Measurement of the Global Value of Hubble's Constant

Tomislav KundićTheoretical Astrophysics, California Institute of Technology, Mail Code 130-33, Pasadena, CA 91125Edwin L. TurnerPrinceton University Observatory, Peyton Hall, Princeton, NJ 08544Wesley N. ColleyPrinceton University Observatory, Peyton Hall, Princeton, NJ 08544J. Richard GottPrinceton University Observatory, Peyton Hall, Princeton, NJ 08544James E. RhoadsCurrently at the Kitt Peak National ObservatoryY. WangPrinceton University Observatory, Peyton Hall, Princeton, NJ 08544Louis BergeronApache Point Observatory, 2001 Apache Point Road, P.O. Box 59, Sunspot, NM 88349Karen A. GloriaDaniel C. LongSangeeta MalhotraInfrared Processing and Analysis Center, California Institute of Technology, Mail Code 100-22, Pasadena, CA 91125J. WambsganßAstrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany

1997en

ABI

Annotatsiya

Photometric monitoring of the gravitational lens system 0957+561A,B in the g and r bands with the Apache Point Observatory (APO) 3.5 m telescope during 1996 shows a sharp g band event in the trailing (B) image light curve at the precise time predicted from the observation of an event during 1995 in the leading (A) image with a delay of 415 days. This success confirms the "short delay," and the lack of any feature at a delay near 540 days rejects the "long delay" for this system, resolving a long-standing controversy. A series of statistical analyses of our light curve data yield a best fit delay of 417 +/- 3 days (95% confidence interval). Recent improvements in the modeling of the lens system (consisting of a galaxy and cluster) allow us to derive a value of the global (at z = 0.36) value of Hubble's constant H_0 using Refsdal's method, a simple and direct distance determination based on securely understood physics and geometry. The result is H_0 = 63 +/- 12 km/s/Mpc (for Omega = 1) where this 95% confidence interval is dominated by remaining lens model uncertainties.

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DOI: 10.1086/304147

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