A New Class of Large-amplitude Radial-mode Hot Subdwarf Pulsators

Thomas Kupfer, Evan B. Bauer, Kevin B. Burdge, Eric C. Bellm, Lars Bildsten, Jim Fuller, J. J. Hermes, Shrinivas R. Kulkarni, Thomas A. Prince, Jan Van Roestel, Richard Dekany, Dmitry A. Duev, Michael Feeney, Matteo Giomi, Matthew J. Graham, Stephen Kaye, Russ R. Laher, Frank J. Masci, Michael Porter, Reed RiddleDavid L. Shupe, Roger M. Smith, Maayane T. Soumagnac, Paula Szkody, Charlotte Ward

Research output: Contribution to journalArticlepeer-review


Using high-cadence observations from the Zwicky Transient Facility at low Galactic latitudes, we have discovered a new class of pulsating, hot compact stars. We have found four candidates, exhibiting blue colors (g - r ≤ -0.1 mag), pulsation amplitudes of >5%, and pulsation periods of 200-475 s. Fourier transforms of the light curves show only one dominant frequency. Phase-resolved spectroscopy for three objects reveals significant radial velocity, T eff, and variations over the pulsation cycle, which are consistent with large-amplitude radial oscillations. The mean T eff and for these stars are consistent with hot subdwarf B (sdB) effective temperatures and surface gravities. We calculate evolutionary tracks using MESA and adiabatic pulsations using GYRE for low-mass, helium-core pre-white dwarfs (pre-WDs) and low-mass helium-burning stars. Comparison of low-order radial oscillation mode periods with the observed pulsation periods show better agreement with the pre-WD models. Therefore, we suggest that these new pulsators and blue large-amplitude pulsators (BLAPs) could be members of the same class of pulsators, composed of young ≈0.25-0.35 M o helium-core pre-WDs.

Original languageEnglish
Article numberL35
Number of pages6
JournalAstrophysical Journal Letters
Issue number2
StatePublished - 20 Jun 2019


  • asteroseismology
  • stars: oscillations
  • stars: variables: general
  • white dwarfs

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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