The BU White Dwarf Group

Boston Skyline

Welcome to the home page of the BU White Dwarf group, headquartered a few blocks from Fenway Park in Boston, MA, USA.

Our research focuses on white dwarfs and their connection to the endpoints of stars, binary, and planetary systems. Our work is supported by Boston University, the Institute for Astrophysical Research, the National Aeronautics and Space Administration (NASA), the National Science Foundation (NSF), and the Massachusetts Space Grant Consortium.


Recent news and group updates:
Research updates can be found below and on the news page.

Untangling mysterious emission in some cool white dwarfs

By JJ HermesMarch 18th, 2021

In March 2021 work led by University College London graduate student Nik Walters was accepted to MNRAS analyzing GD 356, the prototype of a new class of just four white dwarfs that exhibit Balmer emission lines despite being apparently isolated stars. Here we provide strong evidence that this emission is not the result of a current generated by a close-in rocky planet; instead, this process may reveal a new phase of white dwarf evolution. This work includes multiple BUWD group researchers, as well as data collected remotely during the COVID-19 pandemic from BU's 1.8-meter Perkins Telescope Observatory, which helped rule out large spin-period changes in this rapidly rotating white dwarf.

More transiting debris found in ZTF

By JJ HermesMarch 18th, 2021
Seven different white dwarf stars showing evidence of dimming from transiting debris, on long (left) and short (right) timescales (credit Guidry et al. 2021).

In December 2020 work led by UT-Austin undergraduate student Joseph Guidry and collaborators was posted to arXiv announcing up to five new white dwarfs showing transiting debris from the Zwicky Transient Facility (ZTF), more than tripling the number of such systems known! That work was accepted for publication in March 2021 and will appear soon in ApJ, and includes spectroscopy from the Lowell Discovery Telescope confirming that at least one of the white dwarfs with transiting debris is also heavily polluted by rocky debris. A thread can be found here on Twitter: https://twitter.com/jotajotahermes/status/1334144180231266312?s=20 as well as a thread on how we used Gaia's empirical uncertainties to select variable stars located here: https://twitter.com/jotajotahermes/status/1334509064596893701?s=20

Planetary debris transiting a second white dwarf

By JJ HermesNovember 28th, 2020
An artist's impression of a an asteroid breaking apart (credit NASA/JPL-Caltech).

In July 2020, collaborators led by PhD student Zachary Vanderbosch at the University of Texas at Austin have published in The Astrophysical Journal only the second white dwarf known to show transits from an asteroid or planetesimal that got too close to its retired host star. The transits recur roughly every 100 days as the cloud of debris passes in front of the white dwarf. A thread first announcing the submitted paper is here, https://twitter.com/jotajotahermes/status/1166521382336913408, and the system continues to provide interesting surprises, including a deep new transit in November 2020: https://twitter.com/jotajotahermes/status/1326235133297520642

Seeing the interiors of massive A stars with TESS

By JJ HermesNovember 28th, 2020

Collaborators led by Tim Bedding at the University of Sydney published in Nature in May 2020 exciting new results from NASA's TESS mission that are some of the first convincing identifications of the oscillations of a class of massive A stars that pulsate, named after the prototype star delta Scuti. The 2-minute cadence of TESS has finally allowed astronomers to identify the pulsations in delta Scuti stars, especially those that are young. Besides a NASA press release and a Nature News & Views for more general audiences, a thread contextualizing the discovery is here: https://twitter.com/danxhuber/status/1260630021250494470

A puzzling, fast-spinning white dwarf with emission

By JJ HermesNovember 28th, 2020
An artist's impression of a strongly magnetic white dwarf (credit ESO/L. Cal├žada).

In May 2020, collaborators led by PhD student Josh Reding at the University of North Carolina at Chapel Hill published in The Astrophysical Journal the fastest-rotating, isolated white dwarf. The star spins on its axis every 317 seconds, and is only the second white dwarf to show Balmer emission lines -- the origin of this emission is still puzzling, and could be connected to the induction of a current from a close-in rocky planet. A thread detailing this highly magnetic stellar remnant is here: https://twitter.com/jotajotahermes/status/1242792338751205376