Author: JJ Hermes

Rotation in shrapnel from a supernova

In June 2021 work led by researchers in the BU White Dwarf group discovered that the partly burnt runaway star LP 40-365 (also known as GD 492) rotates every 8.9 hours using archival data from the Transiting Exoplanet Survey Satellite (TESS) and the Hubble Space Telescope (HST). This relatively long rotation period likes adds more […]

Debris orbiting a white dwarf every 9.9 hours

In June 2021, collaborators from all over the world led by UT-Austin graduate student Zach Vanderbosch characterized the orbital period of transiting debris around a new white dwarf: ZTF J0328−1219. The debris shows repeating dips that are stable from night-to-night and repeat every 9.937 hr (shown in the figure above over several nights), as well […]

Untangling mysterious emission in some cool white dwarfs

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 […]

More transiting debris found in ZTF

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 […]

Planetary debris transiting a second white dwarf

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 […]

Seeing the interiors of massive A stars with TESS

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 […]

A puzzling, fast-spinning white dwarf with emission

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 […]

Pulsations & eclipses in a white dwarf

In March 2020, collaborators led by Steven Parsons at the University of Sheffield published in Nature Astronomy the first pulsating white dwarf ever found in a binary system that also exhibits eclipses. Having both pulsations and eclipses in this low-mass (0.325 solar-mass) white dwarf will put some exceptional constraints on the star. We already know […]

An old failed star

Collaborators, led by PhD student ZJ Zhang at the University of Hawaii, have discovered a bound pair of stars that serve as an exciting benchmark: one is a T4 (

A class of supernova survivors

Group members and collaborators have discovered a new class of zombie stars that are likely the shattered remnants of thermonuclear supernova that did not fully disrupt the white dwarf! Led by Roberto Raddi at Dr.Karl-Remeis-Sternwarte Bamberg, we have now published at least three more members of this new class of star named after the prototype […]