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

Abstract

Continued 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 in an earlier paper. The prediction was using gravitational lenses and some other possible implications and uses of the 0957+561A,B light curves.

Computational Intelligence in Astronomy – A Win-Win Situation

“…We stress that this method was able to sometimes outperform even methods that were used to generate the data sets themselves (Gaussian process or the Bayesian model of [13]). In terms of real data from Q0957+561, the best (smallest estimated error) time delay quotes were 417±3 [18] and 419.5±0.8 [6]. Our results were consistent with these findings.…”

“…In figure 3 we show an example of real optical data measured from Q0957+561. The optical fluxes observed from images A and B are given in the astronomical unit of magnitude (mag m), defined as m = −2.5 log 10 f , where f is the flux measured when observed through a green filter [18] (g-band). The measurement errors are shown as error bars.…”

“…Despite numerous claims, a universally agreed value for the time delay in the Q0957+561 system has not emerged [18,5]. Indeed, a major problem with time delay estimation in astrophysics literature has been that these estimates are routinely produced for individual quasars, for which we have no idea what the 'true' time delay is (e.g.…”

How accurate are the time delay estimates in gravitational lensing?

“…Haarsma et al (1997) reviews the various measurements, showing how various delays in the range of 300 to 1000 days have been claimed, from various data sets using different methods (Kochanek & Schechter 2004). In the early nineties, the quoted time delay values were either around 420 days (e.g., Falco et al 1991) or 540 days (e.g., Press et al 1992), culminating in a "definitive" measure of a time delay of 417 ± 3 days (Kundic et al 1997).…”

Where Does The Dark Matter Begin?

“…There are presently twelve lenses with published time delay measurements of varying accuracy: B0218+357 (Biggs et al 1999), RXJ0911+0551 (Hjorth et al 2002), FBQ0951+ 2635 (Jakobsson et al 2004), Q0957+561 (Kundić et al 1997), HE1104-1805 (Ofek & Maoz 2003), PG1115+080 (Schechter et al 1997), B1422+231 (Patnaik & Narasimha 2001), SBS1520+530 (Burud et al 2002b), B1600+434 (Burud et al 2000, Koopmans et al 2000, B1608+656 (Fassnacht et al 2002), PKS1830-211 (Lovell et al 1998) and HE2149-2745 (Burud et al 2002a). The interpretation of these delays is controversial (e.g.…”