High Velocity Circumstellar Gas Orbiting a White Dwarf Star

TL;DR

This paper reports the discovery of broad, gaseous circumstellar absorption features around a second white dwarf, WD J0234-0406, indicating the presence of orbiting gas and dust, with notable differences from the previously studied WD 1145+017.

Contribution

First detection of broad circumstellar gas absorption features around WD J0234-0406, expanding understanding of white dwarf circumstellar environments.

Findings

Broad gaseous absorption lines from multiple ions detected.

No rapid brightness variations observed in WD J0234-0406.

Infrared excess indicates circumstellar dust presence.

Abstract

Numerous white dwarf stars are known to be orbited by disks of gas and dust. To date, broad, about 300 km s-1 wide, gaseous circumstellar absorption features have only been reported for the already iconic WD 1145+017, where one is witnessing the breakup of an extrasolar asteroid in real time. We report here the discovery of absorption from circumstellar gas around a second white dwarf (WD J0234-0406) with similarly broad features. The observed lines are carried by ions of Ca, Cr, Fe, Ti, Mg, Mn, Na, O, Si, Sc, Sr, Ti, and V. In addition, deep, non-photospheric lines of Si IV are seen in the ultraviolet; we compare these with Si IV lines previously seen in the ultraviolet spectra of various other white dwarfs. The apparent broadband flux of WD 1145+017 is known to change often and rapidly as chunks of the asteroid pass between the star and Earth. No such variations are seen in the brightness of WD J0234-0406. In addition, while the strength/structure of circumstellar absorption features at WD 1145+017 has changed dramatically with time, nothing similar is seen at WD J0234-0406. Excess infrared emission at WD J0234-0406 indicates the presence of circumstellar dust particles.