* Astronomy

Title: A Cold Neptune-Mass Planet OGLE-2007-BLG-368Lb: Cold Neptunes Are Common
Authors: T. Sumi, D.P. Bennett, I.A. Bond, A. Udalski, V. Batista, M. Dominik, P. Fouqué, D. Kubas, A. Gould, B. Macintosh, K. Cook, S. Dong, L. Skuljan, A. Cassan, The MOA Collaboration: F. Abe, C.S. Botzler, A. Fukui, K. Furusawa, J.B. Hearnshaw, Y. Itow, K. Kamiya, P.M. Kilmartin, A. Korpela, W. Lin, C.H. Ling, K. Masuda, Y. Matsubara, N. Miyake, Y. Muraki, M. Nagaya, T. Nagayama, K. Ohnishi, T. Okumura, Y.C. Perrott, N. Rattenbury, To. Saito, T. Sako, D.J. Sullivan, W.L. Sweatman, P., P.C.M. Yock, The PLANET Collaboration: J.P. Beaulieu, A. Cole, Ch. Coutures, M.F. Duran, J. Greenhill, F. Jablonski, U. Marboeuf, E. Martioli, E. Pedretti, O. Pejcha, P. Rojo, M.D. Albrow, S. Brillant, M. Bode, D.M. Bramich, M.J. Burgdorf, J.A.R. Caldwell, H. Calitz, E. Corrales, S. Dieters, D. Dominis Prester,
J. Donatowicz, K. Hill, M. Hoffman, K. Horne, U.G. J, N. Kains, S. Kane, J.B. Marquette, R. Martin, P. Meintjes, J. Menzies, K.R. Pollard, K.C. Sahu, C. Snodgrass, I. Steele, R. Street, Y. Tsapras, J. Wambsganss, A. Williams, M. Zub, The OGLE Collaboration: M.K. Szyma, M. Kubiak, G. Pietrzy, I. Soszy, O. Szewczyk, K. Ulaczyk, The $\mu$FUN Collaboration: W. Allen, G.W. Christie, D.L. DePoy, B.S. Gaudi, C. Han, J. Janczak, C.-U. Lee, J. McCormick, F. Mallia, B. Monard, T. Natusch, B.-G. Park, R.W. Pogge, R. Santallo
et al. (42 additional authors not shown)

We present the discovery of a Neptune-mass planet OGLE-2007-BLG-368Lb with a planet-star mass ratio of q=[9.5 ±2.1] x10^{-5} via gravitational microlensing. The planetary deviation was detected in real-time thanks to the high cadence of the MOA survey, real-time light curve monitoring and intensive follow-up observations. A Bayesian analysis returns the stellar mass and distance at M_l = 0.64_{-0.26}^{+0.21} M_\sun and D_l = 5.9_{-1.4}^{+0.9} kpc, respectively, so the mass and separation of the planet are M_p = 20_{-8}^{+7} M_\oplus and a = 3.3_{-0.8}^{+1.4} AU, respectively. This discovery adds another cold Neptune-mass planet to the planetary sample discovered by microlensing, which now comprise four cold Neptune/Super-Earths, five gas giant planets, and another sub-Saturn mass planet that could be a cold Neptune or Super-Earth. The discovery of these ten cold exoplanets by the microlensing method implies that the mass function of cold exoplanets scales as \Psi(q) \propto q^{-1.7+/- 0.2} with a 95% confidence level upper limit of n < -1.35 (where \Psi(q) \propto q^n). The microlensing sensitivity region is largely beyond the snow-line, so this implies that Neptune-mass planets are at least three times more common than Jupiters, beyond the snow-line at the 95% confidence level.

Read more (615kb, PDF)