GQ Lup B visible and near-infrared photometric analysis

Christian Mardis, Bruce Macintosh, Travis Barman

Research output: Contribution to journalArticle

16 Scopus citations


We have reanalyzed archival HST and Subaru data of the recently discovered planetary mass companion (PMC) GQ Lup B. With these we produce the first R- and I-band photometry of the companion and fit a radius and effective temperature using detailed model atmospheres. We find an effective temperature of 2335 ± 100 K, a radius of 0.38 ± 0.05 Ṙ, and a luminosity of log (L/L) = -2.42 ± 0.07 (at 140 pc). Since we fit wavelengths that span most of the emitted radiation from GQ Lup, this luminosity estimate is robust, with uncertainty dominated by the distance uncertainty (± 50 pc). The radius obtained for 140 pc (0.38 R ̇) is significantly larger than the one originally derived and larger than model predictions. The mass of the object is much more model-dependent than the radiative properties, but for the Gaia dusty models we find a mass between 10MJup and 20MJup, in the range of the brown dwarf and PMC deuterium-burning boundary. Assuming a distance of 140 pc, observations fit to 1 σ the Baraffe evolution model for an ∼15M Jup brown dwarf. Additionally, the F606W photometric band is significantly overluminous compared to model predictions and other brown dwarfs. Such overluminosity could be explained by a bright Hα emission from chromospheric activity, interaction with another undetected companion, or accretion. Assuming that GQ Lup B has a bright Ha emission line, its Ha emission strength is 10-1.71±0.10Lbol, significantly larger than field late-type dwarfs. GQ Lup B might be strongly accreting and might still be in its formation phase.

Original languageEnglish (US)
Pages (from-to)L151-L154
JournalAstrophysical Journal
Issue number2 II
StatePublished - Jan 10 2007
Externally publishedYes


  • Planetary systems
  • Stars: imaging
  • Stars: low-mass, brown dwarfs
  • Stars: pre-main-sequence
  • Techniques: photometric

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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