J/ApJ/510/64 Radio time delay of gravitational lens 0957+561 (Haarsma+, 1999)
The Radio Wavelength Time Delay of Gravitational Lens 0957+561
Haarsma D. B., Hewitt J. N., Lehar J., Burke B. F.
<Astrophys. J. 510, 64 (1999)>
=1999ApJ...510...64H 1999ApJ...510...64H
ADC_Keywords: Galaxies, radio; QSOs; Radio sources
Keywords: distance scale - gravitational lensing -
quasars: individual (0957+561) - radio continuum: stars
Abstract:
The gravitational lens 0957+561 was monitored with the Very Large
Array from 1979 to 1997. The 6 cm light-curve data from 1995 to 1997
and the 4cm data from 1990 to 1997 are reported here. At 4cm the
intrinsic source variations occur earlier and are twice as large as
the corresponding variations at 6cm. The VLBI core and jet components
have different magnification factors, leading to different flux ratios
for the varying and nonvarying portions of the VLA light curves. Using
both the Press, Rybicki, & Hewitt Q (1992ApJ...385..404P 1992ApJ...385..404P) and
dispersion statistical techniques, we determined the time delay, core
flux ratio, and excess nonvarying B image flux density. The fits were
performed for the 4 and 6 cm light curves, both individually and
jointly, and we used Gaussian Monte Carlo data to estimate 68%
statistical confidence levels. The delay estimates from each
individual wavelength were inconsistent given the formal
uncertainties, suggesting that there are unmodeled systematic errors
in the analysis. We roughly estimate the systematic uncertainty in the
joint result from the difference between the 6 and 4cm results,
giving 409±30 days for the PRHQ statistic and 397±20 days for the
dispersion statistic. These results are consistent with the current
optical time delay of 417±3 days, reconciling the long-standing
difference between the optical and radio light curves and between
different statistical analyses.
Objects:
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RA (2000) DE Designation(s)
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10 01 21 +55 53 56 QSO 0957+561 = 8C 0958+561
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 48 34 VLA 6 cm light-curve data
table2.dat 47 58 VLA 4 cm light-curve data
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Byte-by-byte Description of file: table*.dat
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Bytes Format Units Label Explanations
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2- 5 I4 yr Obs.Y Year of observation
7- 9 A3 "month" Obs.M Month of observation
11- 12 I2 d Obs.D Day of observation
17- 24 F8.2 --- JD-2440000 Julian date (-2,440,000.0) of observation
26- 31 A6 --- Config VLA configuration (1)
37- 41 F5.2 mJy AIm Flux density of the A image
43- 47 F5.2 mJy BIm Flux density of the B image
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Note (1): The VLA has four standard configurations (A, B, C, and D). The
notation AnB, BnC, and CnD represent hybrid configurations between the
standard configurations. The -- represents a transition between
the configurations given.
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History:
From the ApJ electronic edition.
References:
Haarsma+ 1997 (1997ApJ...479..102H 1997ApJ...479..102H)
Lahar+ 1992 (1992ApJ...384..453L 1992ApJ...384..453L)
(End) Greg Schwarz (AAS) 08-Feb-2000