The BU White Dwarf Group

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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 dwarf stars 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.

Emerging magnetism in white dwarfs

By JJ HermesAugust 24th, 2023
A look at two of the Hydrogen Balmer lines in the white dwarf LP 705-64 showing Zeeman-split emission at photomtric minimum (top) and maximum (bottom) as seen from the 4.3-m SOAR telescope (credit Reding et al. 2023).

The BUWD group continues observational efforts to understand the emergence of strong magnetic fields in white dwarf stars as they cool down with age. In June 2023, BUWD group members helped in the discovery of two new stars with variable, strongly magnetic Balmer emission lines corresponding to surface magnetic fields more than 5 MG (more 5 million times stronger than in the Sun, see figure above); that work by Reding, Hermes, Clemens et al. was accepted for publication in a June 2023 issue of the Astrophysical Journal. Group members have also shown that at least some of these white dwarfs with Balmer emission lines do not necessarily have very strong magnetic fields, with some <0.05 MG; that work by Elms et al. is published in the Monthly Notices of the Royal Astronomical Society. Very recently, BUWD group members have helped show that the spot sizes on these magnetic stars cannot be composed of simple single spots; that work by Farihi, Hermes, Littlefair et al. is accepted and published in an October 2023 issue of the Monthly Notices of the Royal Astronomical Society.

A hidden white dwarf found

By JJ HermesSeptember 23rd, 2022
Changes in the arrival time of pulsations (top) of the 342-s pulsation period in the stripped red giant BPM 36430, along with residuals after subtracting the best-fitting sinusoid from the data (bottom). The data reveal that this stripped red giant is being orbited by an unseen, cool, white dwarf that is at least 42% as massive as the Sun (credit Smith et al. 2022).

In September 2022, a manuscript led by undergraduate student at High Point University, Bryce Smith, and including members of the BUWD group has been published (Smith, Barlow, Rosenthal, Hermes & Schaffenroth 2022), which announces the discovery of an unseen, cool white dwarf using the stable pulsations of a stripped red giant star. This work implements the same timing method used to find the first exoplanets around a pulsar --- looking for light-travel-time changes in an object with a steady pulsation period. The discovery was confirmed with spectroscopy showing the star really is wobbling from an unseen companion. The pulsation-timing changes were first discovered by a high-school student working with the BUWD group, Ben Rosenthal, who joined us as a RISE intern in July 2021; Ben is now an undergraduate at Yale University. The work has been accepted for publication in the Astrophysical Journal; a short thread on the discovery can be found here.

Empirically testing WD ages

By JJ HermesAugust 6th, 2022

In June 2022, a manuscript led by BUWD graduate student Tyler Heintz was accepted for publication that empirically tested the reliability of white dwarf stars as age indicators. This extensive work was funded by the NSF and used more than 1250 widely separated (>100 au) pairs of white dwarfs to quantify how accurate their ages are. On the whole, white dwarf ages agree to at least 25% using only existing survey data, but we can do better! We also found that roughly 21-36% of the wide WD+WD binaries had a more massive white dwarf that was hotter than the less massive white dwarf -- so up to 1/3 of WD+WD may have arisen from merged triples! The work has been accepted for publication in the Astrophysical Journal; a short thread on the discovery can be found here.

Planetary bodies observed for first time in habitable zone of dead star

By JJ HermesMarch 24th, 2022
An artist's impression of the white dwarf star WD1054-226 orbited by clouds of planetary debris and a possible major planet in the habitable zone. (credit Mark A. Garlick /

In February 2022, a manuscript led by Jay Farihi from University College London and including members of the BUWD group (Farihi, Hermes, Marsh, et al. 2022) announced the discovery of a remarkable white dwarf that hosts the first planetary debris found in the habitable zone of a retired solar system. The white dwarf, WD1054-226, started out its life like the Sun, but has since evolved through its giant phase and is now a retired white dwarf star. The debris orbits the white dwarf every 25 hours, and features persistent structures in the transit light curve that are most simply explained by a more massive unseen object, in the same way that structures in the rings of Saturn are caused by orbital resonances with moons and moonlets. The discovery was covered by BBC News, NewScientist, Newsweek,, and IFLScience. A nice thread on Twitter by Corey S. Powell summarizes some of the most interesting figures from the manuscript, published in MNRAS.