Searching for new variable white dwarfs: The discovery of the three new pulsating and three new binary systems

Abstract

In recent years, approximately 150 low-mass white dwarfs (WDs), typically with masses below 0.4 solar masses, have been discovered. Observational evidence indicates that most of these low-mass WDs are found in binary systems, supporting binary evolution scenarios as the primary formation pathway. A few extremely low-mass (ELM) WDs in this population have also been found to be pulsationally variable. In this work, we present a comprehensive analysis aimed at identifying new variable low-mass WDs. From our candidate selection, we observed 16 objects identified within the ZZ Ceti instability strip. These objects were observed over multiple nights using high-speed photometry from the SOAR/Goodman and SMARTS-1m telescopes. Our analysis led to the discovery of three new pulsating WDs: one pulsating ELM, one low-mass WD, and one ZZ Ceti star. Additionally, we identified three objects in binary systems: two with ellipsoidal variations in their light curves, one of which is likely a pre-ELM star, and a third showing a reflection effect.