Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Radio Wavelength Time Delay of Gravitational Lens 0957+561   The gravitational lens 0957+561 was monitored with the Very Large Array from
1979 to 1997. The 6 cm light curve data from 1995-1997 and the 4 cm data from
1990-1997 are reported here. At 4 cm, the intrinsic source variations occur
earlier and are twice as large as the corresponding variations at 6 cm. The
VLBI core and jet components have different magnification factors, leading to
different flux ratios for the varying and non-varying portions of the VLA light
curves. Using both the PRHQ and Dispersion statistical techniques, we
determined the time delay, core flux ratio, and excess non-varying B image flux
density. The fits were performed for the 4 cm 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 cm
and 4 cm 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. The unmodeled systematic effects may also corrupt light curves for
other lenses, and we caution that multiple events at multiple wavelengths may
be necessary to determine an accurate delay in any lens system. Now that
consensus has been reached regarding the time delay in the 0957+561 system, the
most pressing issue remaining for determining H_0 is a full understanding of
the mass distribution in the lens.

12
The categories of this paper are: nucl-th
37
The categories of this paper are: supr-con
7
The categories of this paper are: hep-th
1
The categories of this paper are: cs
13
The categories of this paper are: quant-ph
3
The categories of this paper are: physics
14
The categories of this paper are: math-ph
11
The categories of this paper are: hep-lat
25
The categories of this paper are: patt-sol
5
The categories of this paper are: gr-qc
8
The categories of this paper are: hep-ex
35
The categories of this paper are: mtrl-th
18
The categories of this paper are: econ
0
The categories of this paper are: hep-ph
22
The categories of this paper are: chao-dyn
29
The categories of this paper are: funct-an