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

¹ Instituto de Física y Astronomía, Universidad de Valparaíso, Gran Bretaña 1111, Playa Ancha, Valparaíso 2360102, Chile
² European Southern Observatory, Alonso de Cordova 3107, Santiago, Chile
³ Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
⁴ Department of Astrophysics/IMAPP, Radboud University, PO Box 9010 6500 GL Nijmegen, The Netherlands
⁵ Instituto de Física, Universidade Federal do Rio Grande do Sul, 91501-970 Porto Alegre, RS, Brazil
⁶ Isaac Newton Group of Telescopes (ING), Apto. 321, E-38700 Santa Cruz de la Palma, Canary Islands, Spain

^⋆ Corresponding author; larissa.amaral@postgrado.uv.cl

Received: 5 December 2024
Accepted: 10 January 2025

Abstract

In recent years, approximately 150 low-mass white dwarfs (WDs), typically with masses below 0.4 M_⊙, have been discovered. Observational evidence indicates that most of these low-mass WDs are in binary systems, supporting binary evolution scenarios as their 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, 16 objects were identified as being within the ZZ Ceti instability strip. Those objects were observed over multiple nights using high-speed photometry from the SOAR/Goodman and SMARTS-1 m telescopes. Our analysis led to the discovery of three new pulsating WDs: one pulsating ELM WD, 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 that shows a reflection effect.