Two New White Dwarfs With Variable Magnetic Balmer Emission Lines

TL;DR

This paper reports the discovery of two new magnetic white dwarfs with variable Balmer emission lines, expanding the known DAHe class and revealing magnetic field fluctuations linked to stellar rotation.

Contribution

It introduces two new DAHe white dwarfs exhibiting variable magnetic fields, providing insights into magnetic activity and emission variability in this rare stellar class.

Findings

Discovered two new DAHe white dwarfs with variable magnetic fields.

Observed magnetic field fluctuations over stellar rotation periods.

Expanded the DAHe class to at least five known objects.

Abstract

We report the discovery of two apparently isolated stellar remnants that exhibit rotationally modulated magnetic Balmer emission, adding to the emerging DAHe class of white dwarf stars. While the previously discovered members of this class show Zeeman-split triplet emission features corresponding to single magnetic field strengths, these two new objects exhibit significant fluctuations in their apparent magnetic field strengths with variability phase. The Zeeman-split hydrogen emission lines in LP $705{-}64$ broaden from $9.4$ MG to $22.2$ MG over an apparent spin period of $72.629$ minutes. Similarly, WD J$143019.29{-}562358.33$ varies from $5.8$ MG to $8.9$ MG over its apparent $86.394$-minute rotation period. This brings the DAHe class of white dwarfs to at least five objects, all with effective temperatures within $500$ K of $8000$ K and masses ranging from $0.65{-}0.83\,M_{\odot}$.