A Cold Neptune-Mass Planet OGLE-2007-BLG-368Lb: Cold Neptunes Are Common

Creators: Sumi, T.; Bennett, D. P.; Bond, I. A.; Udalski, A.; Batista, V.; Dominik, M.; Fouqué, P.; Kubas, D.; Gould, A.; Macintosh, B.; Cook, K.; Dong, S.; Skuljan, L.; Cassan, A.; Abe, F.; Botzler, C. S.; Fukui, A.; Furusawa, K.; Hearnshaw, J. B.; Itow, Y.; Kamiya, K.; Kilmartin, P. M.; Korpela, A.; Lin, W.; Ling, C. H.; Masuda, K.; Matsubara, Y.; Miyake, N.; Muraki, Y.; Nagaya, M.; Nagayama, T.; Ohnishi, K.; Okumura, T.; Perrott, Y. C.; Rattenbury, N.; Saito, To.; Sako, T.; Sullivan, D. J.; Sweatman, W. L.; Tristram, P. J.; Yock, P. C. M.; Beaulieu, J. P.; Cole, A.; Coutures, Ch.; Duran, M. F.; Greenhill, J.; Jablonski, F.; Marboeuf, U.; Martioli, E.; Pedretti, E.; Pejcha, O.; Rojo, P.; Albrow, M. D.; Brillant, S.; Bode, M.; Bramich, D. M.; Burgdorf, M. J.; Caldwell, J. A. R.; Calitz, H.; Corrales, E.; Dieters, S.; Prester, D. Dominis; Donatowicz, J.; Hill, K.; Hoffman, M.; Horne, K.; Jørgensen, U. G.; Kains, N.; Kane, S.; Marquette, J. B.; Martin, R.; Meintjes, P.; Menzies, J.; Pollard, K. R.; Sahu, K. C.; Snodgrass, C.; Steele, I.; Street, R.; Tsapras, Y.; Wambsganss, J.; Willams, A.; Zub, M.; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Soszyński, I.; Szewczyk, O.; Wyrzykowski, Ł.; Ulaczyk, K.; Allen, W.; Christie, G. W.; DePoy, D. L.; Gaudi, B. S.; Han, C.; Janczak, J.; Lee, C.-U.; McCormick, J.; Mallia, F.; Monard, B.; Natusch, T.; Park, B.-G.; Pogge, R. W.; Santallo, R.; MOA Collaboration; PLANET Collaboration; OGLE Collaboration; µFUN Collaboration

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Abstract

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] × 10^(-5) via gravitational microlensing. The planetary deviation was detected in real-time thanks to the high cadence of the Microlensing Observations in Astrophysics 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^(+0.21)_(–0.26) M_☉ and D_l = 5.9^(+0.9)_(–1.4) kpc, respectively, so the mass and separation of the planet are M_p = 20^(+7)_(–8) M_⊕ and a = 3.3^(+1.4)_(–0.8) AU, respectively. This discovery adds another cold Neptune-mass planet to the planetary sample discovered by microlensing, which now comprises four cold Neptune/super-Earths, five gas giant planets, and another sub-Saturn mass planet whose nature is unclear. The discovery of these 10 cold exoplanets by the microlensing method implies that the mass ratio function of cold exoplanets scales as dN_(pl)/d log q ∝ q^(–0.7±0.2) with a 95% confidence level upper limit of n < –0.35 (where dN_(pl)/d log q ∝ q^n). As microlensing is most sensitive to planets beyond the snow-line, this implies that Neptune-mass planets are at least three times more common than Jupiters in this region at the 95% confidence level.

Additional Information

© 2010 American Astronomical Society. Print publication: Issue 2 (2010 February 20); received 2009 December 7; accepted for publication 2010 January 4; published 2010 February 2. This work is supported by the grant JSPS18253002 and JSPS20340052 (MOA). T.S. was supported by MEXT Japan, Grant-in-Aid for Young Scientists (B), 18749004 and Grant-in-Aid for Scientific Research on Priority Areas, "Development of Extra-solar Planetary Science," 19015005. D.P.B.was supported by grants AST-0708890 from the NSF and NNX07AL71G from NASA. The OGLE project is partially supported by the Polish MNiSW grant N20303032/4275 to AU. Work by A.G. was supported by NSF grant AST-0757888. Work by B.S.G., A.G., and R.P. is supported by NASA grant NNG04GL51G Dave Warren provided financial support for Mt Canopus Observatory. C.H. was supported by Creative Research Initiative Program (2009-0081561) of National Research Foundation of Korea (CH). B.-G.P. and C.-U.L. were supported by the grant of Korea Astronomy and Space Science Institute.

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