The BU White Dwarf Group
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.
Paper Cakes at BU
Paper Cake is a great tradition our group has mugged from astronomers at the University of Warwick. During Paper Cake, you are encouraged to bake a cake and share it along with a discussion of a new paper posted to arXiv. Here is a celebration of a recent BUWD paper on 6 Mar 2026!
White Dwarf Envelopes and Gravitational Redshifts
In March 2026, a manuscript led by graduate student and BUWD member Stefan Arseneau (Arseneau, Hermes, Camisassa, Raddi & Bauer 2026) was accepted laying the foundations to constrain the envelope structure of white dwarfs using gravitational redshifts. The hydrogen envelope mass in most white dwarfs is poorly constrained but critically affects the inferred masses and cooling age of these stars. This work combines precise gravitational redshifts and Gaia-inferred radii for nearly 500 objects to measure the mass–radius relation. The results favor evolutionary models with thick, mass-dependent hydrogen envelopes (e.g., MIST). The manuscript has been accepted in The Astrophysical Journal.
Delayed Q Branch White Dwarfs Lack Strong Magnetism
In February 2026, a manuscript led by graduate student and BUWD member Lou Baya Ould Rouis (Ould Rouis, Hermes, Guidry et al. 2026) was accepted which we hope will change the way we think about some white dwarf merger remnants. Ultramassive white dwarfs in the Gaia "Q branch" exhibit multi-Gyr cooling delays, likely linked to merger origins, but our volume-limited spectroscopic study within 100 pc reveals unexpected trends in composition and rotation of the most delayed Q branch white dwarfs. Contrary to expectations for merger products, the most delayed objects show little magnetism or rotational variability. We also add new detections of pulsations in DAQ white dwarfs which suggest a possible extension of the DAV instability strip to hotter, thin-hydrogen atmospheres. The manuscript has been accepted in The Astrophysical Journal.
Transits (that vanish) around a white dwarf every 4.97 hr
In August 2025, a manuscript led by graduate student and BUWD member Joseph Guidry (Guidry, Vanderbosch, Hermes et al. 2025) was accepted which announced the discovery of deep, irregular, periodic transits from rocky exoplanetary debris towards the white dwarf ZTF J1944+4557. This retired star dims by more than 30% roughly every five hours, as clumps of debris block off light from the white dwarf. For the first time we have also observed transits around a white dwarf completely stop, and completely return roughly a year later, giving us a new laboratory to watch how shattered rocks evolve around dead stars. The manuscript has been accepted in The Astrophysical Journal.
Gravitational redshift bias in white dwarf spectra
In August 2025, a manuscript led by graduate student and BUWD member Stefan Arseneau (Arseneau, Hermes, Zakamska et al. 2025) was accepted which showed that substantial biases (5-15 km/s) exist in low-resolution radial velocity measurements, indicating that all the physics of line formation in high-density plasmas is not fully accounted for in state-of-the-art white dwarf model atmospheres. Using large samples from SDSS-V, we attempt to measure this bias and provide simple corrections for surveys like SDSS, DESI, and 4MOST. The manuscript has been accepted in The Astrophysical Journal.