Long-term photometric variations in the candidate white-dwarf pulsar AR Scorpii from K2, CRTS, and ASAS-SN observations

TL;DR

This study analyzes long-term photometric data of the white-dwarf pulsar AR Scorpii, revealing stable orbital modulation over 78 days and gradual waveform changes over years, providing insights into its variable behavior.

Contribution

It presents the first long-term comparison of K2 and survey data, showing orbital waveform stability and gradual evolution, advancing understanding of AR Sco's variability.

Findings

Orbital modulation stable over 78 days in K2 data.

Detected aperiodic deviations with ~2% amplitude.

Orbital maximum shifted to earlier phases between 2005 and 2010.

Abstract

We analyze long-cadence Kepler K2 observations of AR Sco from 2014, along with survey photometry obtained between 2005 and 2016 by the Catalina Real-Time Sky Survey and the All-Sky Automated Survey for Supernovae. The K2 data show the orbital modulation to have been fairly stable during the 78 days of observations, but we detect aperiodic deviations from the average waveform with an amplitude of ~2% on a timescale of a few days. A comparison of the K2 data with the survey photometry reveals that the orbital waveform gradually changed between 2005 and 2010, with the orbital maximum shifting to earlier phases. We compare these photometric variations with proposed models of this unusual system.