2008/05/30 by D. P. Bennett, I. A. Bond, A. Udalski +55
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Brown dwarf #Einstein radius #Exoplanet #Galaxy #Gamma-ray bursts and supernovae #Gravitational lens #Gravitational microlensing #Light curve #Mass ratio #Physics #Planet #Planetary mass #Planetary system #RADIUS #Star formation #Stars #Stellar mass #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/589940
Accepted for publication in the Astrophysical Journal. Scheduled for the Sept. 1, 2008 issue
arxiv created 2008/05/30 · openalex publication_date 2008/08/26 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We report the detection of an extrasolar planet of mass ratio q ∼ 2 × 10 −4 in microlensing event MOA-2007-BLG-192. The best-fit microlensing model shows both the microlensing parallax and finite source effects, and these can be combined to obtain the lens masses of M = 0.060 + 0.028 −0.021 M ☉ for the primary and m = 3.3 + 4.9 −1.6 M ⊕ for the planet. However, the observational coverage of the planetary deviation is sparse and incomplete, and the radius of the source was estimated without the benefit of a source star color measurement. As a result, the 2 σ limits on the mass ratio and finite source measurements are weak. Nevertheless, the microlensing parallax signal clearly favors a substellar mass planetary host, and the measurement of finite source effects in the light curve supports this conclusion. Adaptive optics images taken with the Very Large Telescope (VLT) NACO instrument are consistent with a lens star that is either a brown dwarf or a star at the bottom of the main sequence. Follow-up VLT and/or Hubble Space Telescope ( HST ) observations will either confirm that the primary is a brown dwarf or detect the low-mass lens star and enable a precise determination of its mass. In either case, the lens star, MOA-2007-BLG-192L, is the lowest mass primary known to have a companion with a planetary mass ratio, and the planet, MOA-2007-BLG-192Lb, is probably the lowest mass exoplanet found to date, aside from the lowest mass pulsar planet.