Rapid Evolution of the Gaseous Exoplanetary Debris Around the White Dwarf Star HE 1349--2305

TL;DR

This study presents a detailed spectroscopic monitoring of the gaseous debris around white dwarf HE 1349--2305, revealing rapid morphological changes that challenge existing models and suggest dynamic processes like density waves.

Contribution

It provides the first long-term spectroscopic dataset showing rapid evolution of gaseous debris, offering new insights into debris disk dynamics around white dwarfs.

Findings

Emission profile variations occur on 1-2 year timescales.

Rapid evolution likely incompatible with general relativistic precession.

Alternative explanations include propagation of density waves.

Abstract

Observations of heavy metal pollution in white dwarf stars indicate that metal-rich planetesimals are frequently scattered into star-grazing orbits, tidally disrupted, and accreted onto the white dwarf surface, offering direct insight into the dynamical evolution of post-main-sequence exoplanetary systems. Emission lines from the gaseous debris in the accretion disks of some of these systems show variations on timescales of decades, and have been interpreted as the general relativistic precession of recently formed, elliptical disk. Here we present a comprehensive spectroscopic monitoring campaign of the calcium infrared triplet emission in one system, HE 1349--2305, which shows morphological emission profile variations suggestive of a precessing, asymmetric intensity pattern. The emission profiles are shown to vary on a timescale of one to two years, which is an order of magnitude shorter than what has been observed in other similar systems. We demonstrate that this timescale is likely incompatible with general relativistic precession, and consider alternative explanations for the rapid evolution including the propagation of density waves within the gaseous debris. We conclude with recommendations for follow-up observations, and discuss how the rapid evolution of the gaseous debris in HE 1349--2305 could be leveraged to test theories of exoplanetary debris disk evolution around white dwarf stars.