A Low-Mass Planet with a Possible Sub-Stellar-Mass Host in Microlensing Event MOA-2007-BLG-192
Abstract
We report the detection of an extrasolar planet of mass ratio q ~ 2 x 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_sun for the primary and m = 3.3 (+4.9 -1.6) M_earth 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-sigma limits on the mass ratio and finite source measurements are weak. Nevertheless, the microlensing parallax signal clearly favors a sub-stellar 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.
Cite
@article{arxiv.0806.0025,
title = {A Low-Mass Planet with a Possible Sub-Stellar-Mass Host in Microlensing Event MOA-2007-BLG-192},
author = {D. P. Bennett and I. A. Bond and A. Udalski and T. Sumi and F. Abe and A. Fukui and K. Furusawa and J. B. Hearnshaw and S. Holderness and Y. Itow and K. Kamiya and A. V. Korpela and P. M. Kilmartin and W. Lin and C. H. Ling and K. Masuda and Y. Matsubara and N. Miyake and Y. Muraki and M. Nagaya and T. Okumura and K. Ohnishi and Y. C. Perrott and N. J. Rattenbury and T. Sako and To. Saito and S. Sato and L. Skuljan and D. J. Sullivan and W. L. Sweatman and P. J. Tristram and P. C. M. Yock and M. Kubiak and M. K. Szymanski and G. Pietrzynski and I. Soszynski and O. Szewczyk and L. Wyrzykowski and K. Ulaczyk and V. Batista and J. P. Beaulieu and S. Brillant and A. Cassan and P. Fouque and P. Kervella and D. Kubas and J. B. Marquette},
journal= {arXiv preprint arXiv:0806.0025},
year = {2009}
}
Comments
Accepted for publication in the Astrophysical Journal. Scheduled for the Sept. 1, 2008 issue