Around the Clock Observations of the Q0957+561 A,B Gravitationally Lensed Quasar II: Results for the second observing season

Abstract

We report on an observing campaign in March 2001 to monitor the brightness of the later arriving Q0957+561 B image in order to compare with the previously published brightness observations of the (first arriving) A image. The 12 participating observatories provided 3543 image frames which we have analyzed for brightness fluctuations. From our classical methods for time delay determination, we find a 417.09 +/- 0.07 day time delay which should be free of effects due to incomplete sampling. During the campaign period, the quasar brightness was relatively constant and only small fluctuations were found; we compare the structure function for the new data with structure function estimates for the 1995--6 epoch, and show that the structure function is statistically non-stationary. We also examine the data for any evidence of correlated fluctuations at zero lag. We discuss the limits to our ability to measure the cosmological time delay if the quasar's emitting surface is time resolved, as seems likely.

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References in corpus (9)

• A Structure for Quasars
• A Robust Determination of the Time Delay in 0957+561A,B and a Measurement of the Global Value of Hubble's Constant
• A Sharp Event in the Image a Light Curve of the Double Quasar 0957+561 and Prediction of the 1996 Image B Light Curve
• Improved Parameters and New Lensed Features for Q0957+561 from WFPC2 Imaging
• Time delay in QSO 0957+561 from 1984-99 optical data
• Measuring the Size of Quasar Broad-Line Clouds Through Time Delay Light-Curve Anomalies of Gravitational Lenses
• Hourly Variability in Q0957+561
• Precision Photometry for Q0957+561 Images A and B
• 'Round the Clock Observations of the Q0957+561 A,B Gravitationally Lensed Quasar

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