News
Signposts of Remnant Planetary Systems
In June 2024, a manuscript led by graduate student and BUWD member Joseph Guidry (Guidry, Hermes, De et al. 2024) took a look at infrared variability of white dwarfs as seen over many years from NASA's Wide-field Infrared Survey Explorer (WISE) space telescope, discovering dozens of new infrared-variable white dwarfs that are likely to be host to remnant planetary systems. Some white dwarfs with planetary systems host dusty debris that causes an infrared excess, and collisions within the debris disks often cause infrared variability. The manuscript has been accepted in The Astrophysical Journal.
Dr. Tyler Heintz
Massive congratulations to Dr. Tyler Heintz, who successfully defended his PhD dissertation on Tuesday July 23, 2024! Tyler has been at BU throughout the entire history of the BUWD research group, and has become expert in the reliability of white dwarf cosmochronology (age-dating white dwarf stars).
EuroWD Conference, July 2024
Three members of the BU White Dwarf group attended the 23rd European Workshop on White Dwarfs, held in July 2024 in Barcelona. We will be hosting the 24th meeting in Summer 2026 in Boston!
Testing Ages Using Spectroscopy of White Dwarfs
In May 2024, a manuscript led by graduate student and BUWD member Tyler Heintz (Heintz, Hermes, Tremblay et al. 2024) announced the most detailed test of white dwarf ages measured from spectroscopic fits in wide WD+WD binaries. By comparing the age estimates of wide pairs of stars that should have both been born at the same time, using fits using both photometry and spectroscopy, Tyler provided one of the most reliable tests of current age-dating methods of white dwarf stars. This work shows that photometry + parallax (distance) measurements returns more reliable results for fainter white dwarfs. It also finds further evidence of a significant merger fraction among wide WD+WD binaries, where roughly 20% are inconsistent with a monotonically increasing initial-final mass relation. The manuscript has been published in The Astrophysical Journal.
Gaia’s Light Curve Prospects
In April 2024, a manuscript led by former BU undergraduate student and BUWD member Maya Steen (Steen, Hermes, Guidry et al. 2024) detailed one of the first systematic analyses of Gaia DR3 multi-epoch light curves, this focused on white dwarfs. Roughly 1300 candidate white dwarfs have Gaia light curves (spanning roughly 1000 days with visits roughly every 44 days). Even with that sparse sampling, Maya (who is now a graduate student at New Mexico State University) showed that periodicities as short as minutes can be detected from the Gaia light curves alone! We discover 86 new objects from the 105 target sample, including pulsating, spotted, and binary white dwarfs, and even a new 68.4 min eclipsing cataclysmic variable. The manuscript has been published in The Astrophysical Journal.
JWST directly images two giant planet candidates
In January 2024, a manuscript led by Susan Mullally from Space Telescope Science Institute and including members of the BUWD group (Mullally et al. 2024) announced that JWST has directly images giant planet candidates around two metal-polluted white dwarf stars. The two planet candidates (JWST/MIRI images shown above) are consistent with 1-7 Jupiter-mass planets on orbits that would have been similar to Jupiter or Saturn in our solar system before the host star lost mass to become a white dwarf. JWST has improved our sensitivity to such planets by an order of magnitude. If confirmed to move with the white dwarf (although unlikely, in each case the point source could be a background galaxy), these would be the oldest directly imaged exoplanets ever found, and would be direct evidence that giant planets like Jupiter survive the evolution of their host star. Because they orbit white dwarf stars, we can get reasonable estimates on their ages: WD1202-232b is likely close in age to our Sun (~5 billion years old), and WD2105−82b is between 1.4-2.4 Gyr. Some nice press coverage of the discovery was published by Science Magazine as well as Universe Today. The manuscript has been accepted in The Astrophysical Journal Letters.
USRA Distinguished Undergraduate award
Former BU White Dwarf researcher Madi VanWyngarden, who worked with us in Summer 2021 and helped with our discovery of many new pulsating white dwarfs in TESS, has recently been honored with a 2023 Universities Space Research Association (USRA) Distinguished Undergraduate Award. Madi is one of only five recipients of this year's award, and the first ever from Boston University!
A 23-min binary in TESS
In November 2023, a manuscript led by Matthew Green from the Max-Planck-Institut für Astronomie in Heidelberg, Germany and including members of the BUWD group (Green, Hermes, Barlow et al. 2023) announced the discovery of the shortest-period binary system yet found by NASA's Transiting Exoplanet Survey Satellite (TESS)! Although TESS is tuned to finding transiting exoplanets, we used the facility to discover a pair of stars orbiting one other roughly every 23 minutes, one of the brightest (and closest) AM CVn binaries ever found. This is the second system we have recently found from TESS that will be detectable in gravitational wave radiation when we launch space-based interferometers in the coming decades. The manuscript has been accepted for publication in the Monthly Notices of the Royal Astronomical Society.
TESS’s first gravitational wave source
In August 2023, a manuscript led by James Munday from the University of Warwick and including members of the BUWD group (Munday, Tremblay, Hermes, et al. 2023) announced the discovery of an eclipsing, 47.19-min double-white-dwarf binary first identified by NASA's Transiting Exoplanet Survey Satellite. The pair of stars are massive enough (0.40 and 0.28 solar masses) and close enough (separated by roughly the distance from the Earth to the Moon) that they are an extremely strong source of gravitational radiation, ripples in the fabric of space. The system is likely the first binary identified by the TESS mission that will in the future have its gravitational wave radiation directly detected by the LISA space mission. The manuscript has been published in the Monthly Notices of the Royal Astronomical Society.
A two-faced white dwarf
In July 2023, a manuscript led by Ilaria Caiazzo from Caltech and including members of the BUWD group was published in Nature announcing the discovery of an enigmatic new star: a white dwarf that is entirely composed of hydrogen on one side and helium on the other. Every 15 minutes the star rotates once on its axis, showing both its hydrogen and helium faces; we nicknamed the star "Janus" after Roman mythology. We believe the chemical stratification is likely related to a small magnetic field and a very thin layer of hydrogen on the star, but it remains a relatively unsolved problem. The discovery was published in the July 19 2023 issue of Nature and included press coverage from Sky & Telescope, The Guardian, and Space.com.