Follow-up Studies of the Pulsating Magnetic White Dwarf SDSS J142625.71+575218.3

TL;DR

This study provides detailed photometric and spectroscopic analysis of the magnetic white dwarf SDSS J142625.71+575218.3, confirming pulsational origins of its luminosity variations and identifying a new periodicity.

Contribution

It offers the first detection of a new periodicity in the star and conclusively rules out the binary activity hypothesis, supporting pulsational instability as the cause.

Findings

Discovery of a new 319.720 s periodicity.

Radial velocity analysis rules out binary hypothesis.

Luminosity variations caused by g-mode pulsations.

Abstract

We present a follow-up analysis of the unique magnetic luminosity-variable carbon-atmosphere white dwarf SDSS J142625.71+575218.3. This includes the results of some 106.4 h of integrated light photometry which have revealed, among other things, the presence of a new periodicity at 319.720 s which is not harmonically related to the dominant oscillation (417.707 s) previously known in that star. Using our photometry and available spectroscopy, we consider the suggestion made by Montgomery et al. (2008) that the luminosity variations in SDSS J142625.71+575218.3 may not be caused by pulsational instabilities, but rather by photometric activity in a carbon-transferring analog of AM CVn. This includes a detailed search for possible radial velocity variations due to rapid orbital motion on the basis of MMT spectroscopy. At the end of the exercise, we unequivocally rule out the interacting binary hypothesis and conclude instead that, indeed, the luminosity variations are caused by g-mode pulsations as in other pulsating white dwarfs. This is in line with the preferred possibility put forward by Montgomery et al. (2008).