Five New Post-main-sequence Debris Disks with Gaseous Emission

Abstract

Observations of debris disks, the products of the collisional evolution of rocky planetesimals, can be used to trace planetary activity across a wide range of stellar types. The most common end points of stellar evolution are no exception, as debris disks have been observed around several dozen white dwarf stars. But instead of planetary formation, post-main-sequence debris disks are a signpost of planetary destruction, resulting in compact debris disks from the tidal disruption of remnant planetesimals. In this work, we present the discovery of five new debris disks around white dwarf stars with gaseous debris in emission. All five systems exhibit excess infrared radiation from dusty debris, emission lines from gaseous debris, and atmospheric absorption features indicating ongoing accretion of metal-rich debris. In four of the systems, we detect multiple metal species in emission, some of which occur at strengths and transitions previously unseen in debris disks around white dwarf stars. Our first year of spectroscopic follow-up hints at strong variability in the emission lines that can be studied in the future, expanding the range of phenomena these post-main-sequence debris disks exhibit.

Velocity-imaging the rapidly precessing planetary disc around the white dwarf HE 1349–2305 using Doppler tomography

“…The gaseous emission profiles encode velocity information within the disc which provides insight into its dynamical structure. Longterm observations of the Ca triplet profiles show similar morphological variations of the emission profiles (Gänsicke et al 2008;Melis et al 2010;Wilson et al 2015;Manser et al 2016b;Dennihy et al 2020b;Gentile Fusillo et al 2021), which have been wellmodelled for the disc around SDSS J122859.93+104032.9 (hereafter SDSS J1228+1040) using Doppler tomography (Marsh & Horne 1988;Manser et al 2016a). This modelling showed that the observed variability can be reproduced by the precession of a fixed, asymmetric intensity pattern in the disc on a period of 27 yr.…”

“…The candidate emission feature detected in the 5169 Å Fe region also changes in morphology between the two epochs, where the red-shifted component of the profile contracts to shorter wavelengths, corresponding to smaller velocities. We note that this region has also been shown to host 5167 Å, 5173 Å, and 5184 Å Mg emission for some gaseous debris discs (see Melis et al 2020;Dennihy et al 2020b;Gentile Fusillo et al 2021). The potential O emission feature appears to share the red-dominated asymmetry of the Ca triplet.…”

“…If the emission generated by a single planetesimal is proportional in strength to the total emission from the gaseous component of the disc, then it would be more efficient to observe gaseous debris discs with emission features comparable in strength to those at SDSS J1228+1040. Melis et al (2020), Dennihy et al (2020b) and Gentile Fusillo et al ( 2021) recently reported the combined detection of 14 new gaseous debris discs (for a total of 21 gaseous debris disc systems), five of which -SDSS J0006+2858, WD 0347+1624, WD 0611-6931, WD J0846+5703, and WD J2133+2428, show strong Ca triplet emission. Furthermore, the morphology of the emission profiles of WD 0347+1624 appears to vary on a time-scale of 2 -3 yrs; similar to HE 1349-2305 and indicative of the precession of the debris disc.…”

A catalogue of white dwarfs in Gaia EDR3

“…This rare polluting element is extremely difficult to detect in hotter white dwarfs and could be the signpost of accretion of the crust of a planetary object (Hollands et al 2021). More discoveries related to planetary systems around white dwarfs enabled by Gaia included WD J0914+1914, a peculiar white dwarf in the process of evaporating a Neptune-like exoplanet (Gänsicke et al 2019), and the 14 newly identified white dwarfs with gaseous debris from rocky planetesimals (Dennihy et al 2020;Melis et al 2020;Gentile Fusillo et al 2021), which brought the number of such systems known from seven to 21.…”

First detection of a disk free of volatile elements around a young A-type star: A possible sign of collisions between rocky planets

“…To the best of our knowledge this spectrum with strong emission lines from refractory elements, but completely lacking emission from volatile species is unique within the group of young stars. However, similar spectra are seen in rare instances in a completely different class of stars: metal-polluted white dwarfs (Gänsicke et al 2006;Wilson et al 2014;Manser et al 2016;Dennihy et al 2020;Melis et al 2020;Gentile Fusillo et al 2021). Similar to HD 152384, these rare emission line systems also exhibit excess infrared emission in their SED caused by the presence of circumstellar dust.…”