# The Sloan Digital Sky Survey Reverberation Mapping Project: Improving Lag Detection with an Extended Multi-Year Baseline

## TL;DR

This study shows that extended multi-year light curves significantly improve the detection of quasar lag times, especially for long or previously undetectable lags, enhancing reverberation mapping at high redshift.

## Contribution

It demonstrates the advantages of longer observational baselines for detecting quasar lags, highlighting improvements over shorter datasets and informing future survey strategies.

## Key findings

- Extended data enables detection of longer lags.
- Long-term monitoring improves lag recovery accuracy.
- Multiple broad line lags can be measured in the same object.

## Abstract

We investigate the effects of extended multi-year light curves (9-year photometry and 5-year spectroscopy) on the detection of time lags between the continuum variability and broad-line response of quasars at z>~1.5, and compare with the results using 4-year photometry+spectroscopy presented in a companion paper. We demonstrate the benefits of the extended light curves in three cases: (1) lags that are too long to be detected by the shorter-duration data but can be detected with the extended data; (2) lags that are recovered by the extended light curves but missed in the shorter-duration data due to insufficient light curve quality; and (3) lags for different broad line species in the same object. These examples demonstrate the importance of long-term monitoring for reverberation mapping to detect lags for luminous quasars at high-redshift, and the expected performance of the final dataset from the Sloan Digital Sky Survey Reverberation Mapping project that will have 11-year photometric and 7-year spectroscopic baselines.