As many as 50% of otherwise pristine white dwarf H or He photospheres show evidence of metal contamination resembling bulk-Earth composition. These metals are thought to accrete onto the surface of the white dwarf from a debris disk composed of the tidally disrupted remnants of the dead star’s planetary system. Dusty debris necessarily passes close enough to the white dwarf to sublimate, yet only a fraction of a percent of white dwarfs will have detectable Doppler-broadened CaIItriplet emission indicative of a gaseous component of the debris disk. Until recently only 7 white dwarfs with both dusty and gaseous debris disks were known. Between 2020-2021, that number tripled, opening the door for detailed study of these systems as a class. Using the Goodman Spectrograph on the SOAR telescope, we have monitored 25 known gaseous debris disk and candidate systems, obtaining multiple epochs of many. In the two most well-studied systems, emission profiles vary in time, consistent with a stable pattern of disk emission that precesses. In-depth monitoring of a new system, SDSS J0347+1624, reveals a more dynamic disk, where the model of a fixed pattern of emission precessing fails. Preliminary findings from observations at all monitored systems suggest the majority of gaseous debris disks are actually not consistent with a stable pattern of precessing emission, and instead are host to circumstellar environments with complex dynamics, casting the two most well-studied systems as the exception rather than the rule. Observations also indicate that almost all systems considered in this work have at least part, if not all, of the gaseous debris disk inside of the dusty disk.

Phillips Hall room 277, or at the zoom link below.

Ryan Hegedus is inviting you to a scheduled Zoom meeting.

Topic: Ryan Hegedus’ Defense

Time: Oct 24, 2022 03:00 PM Eastern Time (US and Canada)

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https://unc.zoom.us/j/97655959725

Meeting ID: 976 5595 9725