Discovery of a magnetic white dwarf/probable brown dwarf short-period binary

Gary D. Schmidt, Paula Szkody, Nicole M. Silvestri, Michael C. Cushing, James Liebert, Paul S. Smith

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


The magnetic white dwarf SDSS J121209.31 +013627.7 exhibits a weak, narrow Ha emission line whose radial velocity and strength are modulated on a period of ∼90 minutes. Though indicative of irradiation on a nearby companion, no cool continuum component is evident in the optical spectrum, and IR photometry limits the absolute magnitude of the companion to MJ > 13.37. This is equivalent to an isolated L5 dwarf, with Teff < 1700 K. Consideration of possible evolutionary histories suggests that, until ∼0.6 Gyr ago, the brown dwarf orbited a ∼1.5 M⊙ main-sequence star with P ∼ 1 yr and a ∼ 1 AU, thus resembling many of the gaseous superplanets being found in extrasolar planet searches. Common-envelope evolution when the massive star left the main sequence reduced the period to only a few hours, and ensuing angular momentum loss has further degraded the orbit. The binary is ripe for additional observations aimed at better studying brown dwarfs and the effects of irradiation on their structure.

Original languageEnglish (US)
Pages (from-to)L173-L176
JournalAstrophysical Journal
Issue number2 II
StatePublished - Sep 10 2005
Externally publishedYes


  • Binaries: close
  • Brown dwarfs
  • Magnetic fields

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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