A study of the photometric variability of the peculiar magnetic white dwarf WD1953-011

TL;DR

This study investigates the photometric and spectroscopic variability of the magnetic white dwarf WD1953-011, revealing a correlation between magnetic structures and dark spots, and refining the star's rotational period.

Contribution

It provides new simultaneous photometric and spectroscopic observations, models the magnetic and thermal surface features, and refines the star's rotational period.

Findings

Variability with a 1.45-day period linked to magnetic structures.

Dark spots and magnetic regions are spatially overlapping.

Refined the star's rotational period and characterized surface inhomogeneities.

Abstract

We present and interpret simultaneous new photometric and spectroscopic observations of the peculiar magnetic white dwarf WD1953-011. The flux in the V-band filter and intensity of the Balmer spectral lines demonstrate variability with the rotation period of about 1.45 days. According to previous studies, this variability can be explained by the presence of a dark spot having a magnetic nature, analogous to a sunspot. Motivated by this idea, we examine possible physical relationships between the suggested dark spot and the strong-field magnetic structure (magnetic "spot", or "tube") recently identified on the surface of this star. Comparing the rotationally-modulated flux with the variable spectral observables related to the magnetic "spot" we establish their correlation, and therefore their physical relationship. Modeling the variable photometric flux assuming that it is associated with temperature variations in the stellar photosphere, we argue that the strong-field area and dark, low-temperature spot are comparable in size and located at the same latitudes, essentially overlapping each other with a possible slight longitudinal shift. In this paper we also present a new, improved value of the star's rotational period and constrain the characteristics of the thermal inhomogeneity over the degenerate's surface.