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

TL;DR

This study identified three new pulsating low-mass white dwarfs and three binary systems through high-speed photometry, enhancing understanding of their formation and variability in the context of binary evolution.

Contribution

It presents the first comprehensive search for variable low-mass white dwarfs, discovering new pulsators and binary systems, expanding the known population and characteristics of these objects.

Findings

Discovered three new pulsating white dwarfs.

Identified three binary systems with ellipsoidal and reflection effects.

Enhanced understanding of low-mass WD variability and binary evolution.

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.