Monitoring Quasar Colour Variability in Stripe 82

TL;DR

This study investigates the use of photometric monitoring of quasar colours in Stripe 82 to serve as an early warning system for detecting Broad Absorption Line (BAL) variability, which is crucial for understanding cloud dynamics near quasars.

Contribution

It introduces a method to analyze BAL and non-BAL quasar colour variability using time series photometry to predict spectroscopic variability events.

Findings

Photometric variability can precede spectroscopic changes in BAL quasars.

Stripe 82 data enables detailed analysis of quasar colour changes over time.

Potential for early detection of BAL variability events.

Abstract

Broad Absorption Line (BAL) trough variability is predominantly due to cloud motion transverse to our line of sight. The rate at which the variability occurs indicates the velocity of the cloud, which can provide constraints on the cloud's distance from the central source. This requires detailed spectroscopy during a variability event. Such spectra have proven elusive, suggesting either the timescale of variability is too short to be caught, or too long to notice until a sufficient amount of time has passed. Photometric monitoring of BAL quasar colours may potentially be used as an early warning system to trigger time resolved spectroscopic monitoring of BAL variability. Towards this end, we are analyzing both BAL and non-BAL colour variability using time series photometry from Stripe 82 in the Sloan Digital Sky Survey.