GQ Lup B visible and near-infrared photometric analysis

Christian Mardis, Bruce Macintosh, Travis Barman

Research output: Contribution to journalArticlepeer-review

19 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


  • 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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