The time-delay of the gravitationally lensed double quasar UM 673

TL;DR

This paper discusses the impact of a broken filter on quasar monitoring data, leading to unreliable original analysis and conclusions about the gravitationally lensed double quasar UM 673.

Contribution

The paper highlights the importance of data quality verification in gravitational lensing studies and reports the withdrawal of previous findings due to instrumental issues.

Findings

Data affected by filter malfunction was unreliable

Original analysis and conclusions are invalid

Emphasizes need for data validation in astrophysical observations

Abstract

The paper has been withdrawn because double checking and comparison with other data sets after the original submission showed that a broken R-band filter at the Maidanak telescope had affected our quasar monitoring observations in the years 2004 and 2005. They had led to partially spurious measurements, hence our original analysis and conclusions are not reliable.