Recurring Planetary Debris Transits and Circumstellar Gas around White Dwarf ZTF J0328$-$1219

TL;DR

This study confirms ZTF J0328-1219 as a white dwarf with transiting planetary debris, revealing multiple orbital periods, dynamic dust behavior, and circumstellar gas, advancing understanding of planetary disintegration around white dwarfs.

Contribution

It provides new observational evidence of multiple debris clumps with distinct orbital periods and circumstellar gas features, enhancing knowledge of planetary debris dynamics around white dwarfs.

Findings

Detected two significant debris orbital periods at 9.937 and 11.2 hours.

Observed dynamic changes in debris transit structures over various timescales.

Identified circumstellar Na D absorption features indicating gas around the white dwarf.

Abstract

We present follow-up photometry and spectroscopy of ZTF J0328$-$1219 strengthening its status as a white dwarf exhibiting transiting planetary debris. Using TESS and Zwicky Transient Facility photometry, along with follow-up high speed photometry from various observatories, we find evidence for two significant periods of variability at 9.937 and 11.2 hr. We interpret these as most likely the orbital periods of different debris clumps. Changes in the detailed dip structures within the light curves are observed on nightly, weekly, and monthly timescales, reminiscent of the dynamic behavior observed in the first white dwarf discovered to harbor a disintegrating asteroid, WD 1145+017. We fit previously published spectroscopy along with broadband photometry to obtain new atmospheric parameters for the white dwarf, with $M_{\star} = 0.731 \pm 0.023\,M_{\odot}$, $T_{\mathrm{eff}} = 7630 \pm 140\,$K, and $\mathrm{[Ca/He]}=-9.55\pm0.12$. With new high-resolution spectroscopy, we detect prominent and narrow Na D absorption features likely of circumstellar origin, with velocities $21.4\pm1.0$ km s$^{-1}$ blue-shifted relative to atmospheric lines. We attribute the periodically modulated photometric signal to dusty effluents from small orbiting bodies such as asteroids or comets, but are unable to identify the most likely material that is being sublimated, or otherwise ejected, as the environmental temperatures range from roughly 400K to 600K.