New aperture photometry of QSO 0957+561; application to time delay and microlensing

Abstract

We present a re-reduction of archival CCD frames of the doubly imaged quasar 0957+561 using a new photometry code. Aperture photometry with corrections for both cross contamination between the quasar images and galaxy contamination is performed on about 2650 R-band images from a five year period (1992-1997). From the brightness data a time delay of 424.9 +/- 1.2 days is derived using two different statistical techniques. The amount of gravitational microlensing in the quasar light curves is briefly investigated, and we find unambiguous evidence of both long term and short term microlensing. We also note the unusual circumstance regarding time delay estimates for this gravitational lens. Estimates by different observers from different data sets or even with the same data sets give lag estimates differing by typically 8 days, and error bars of only a day or two. This probably indicates several complexities where the result of each estimate depends upon the details of the calculation.

arXiv comment14 pages, 16 figures (several in color)

References in corpus (12)

• 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
• BVRI photometry of QSO 0957+561A, B: Observations, new reduction method and time delay
• Around the Clock Observations of the Q0957+561 A,B Gravitationally Lensed Quasar II: Results for the second observing season
• Time delay in QSO 0957+561 from 1984-99 optical data
• New aperture photometry of QSO 0957+561; application to time delay and microlensing
• The 6 cm Light Curves of B0957+561, 1979-1994: New Features and Implications for the Time Delay
• A novel approach for extracting time-delays from lightcurves of lensed quasar images
• Short-timescale Fluctuations in the Difference Light Curves of QSO 0957+561A,B: Microlensing or Noise?
• Hourly Variability in Q0957+561
• Precision Photometry for Q0957+561 Images A and B

Cited by in corpus (21)

• The Hubble Constant from the Gravitational Lens B1608+656
• The STRong lensing Insights into the Dark Energy Survey (STRIDES) 2017/2018 follow-up campaign: Discovery of 10 lensed quasars and 10 quasar pairs
• Measuring Microlensing using Spectra of Multiply Lensed Quasars
• A Rapid Microlensing Event in the Q0957+561 A,B Gravitational Lens System
• New two-colour light curves of Q0957+561: time delays and the origin of intrinsic variations
• Time delay of SBS 0909+532
• New aperture photometry of QSO 0957+561; application to time delay and microlensing
• A New Microlensing Event in the Doubly-Imaged Quasar Q0957+561
• New database for a sample of optically bright lensed quasars in the northern hemisphere
• How accurate are the time delay estimates in gravitational lensing?
• Anomalous Fluctuations in Observations of Q0957+561 A,B: Smoking Gun of a Cosmic String?
• A Search for Host Galaxies of 24 Gamma-Ray Bursts
• Accretion Onto the Supermassive Black Hole in the High-redshift Radio-loud AGN 0957+561
• Revealing the structure of the lensed quasar Q 0957+561: I. Accretion disk size
• New VR magnification ratios of QSO 0957+561
• A 5.5-year robotic optical monitoring of Q0957+561: substructure in a non-local cD galaxy
• GLITP Optical Monitoring of QSO 0957+561: VR Light Curves and Variability
• Five nights of intensive R- and V-band photometry of QSO 0957+561A,B
• Revealing the nonlinear behaviour of the lensed quasar Q0957+561
• Spectroscopy and polarimetry of the gravitationally lensed quasar Q0957+561
• Kernel regression estimates of time delays between gravitationally lensed fluxes