3 results for Abe, F

  • Unbound or distant planetary mass population detected by gravitational microlensing

    Sumi, T; Kamiya, K; Bennett, DP; Bond, IA; Abe, F; Botzler, CS; Fukui, A; Furusawa, K; Hearnshaw, JB; Itow, Y; Kilmartin, PM; Korpela, A; Lin, W; Ling, CH; Masuda, K; Matsubara, Y; Miyake, N; Motomura, M; Muraki, Y; Nagaya, M; Nakamura, S; Ohnishi, K; Okumura, T; Perrott, YC; Rattenbury, Nicholas; Saito, T; Sako, T; Sullivan, DJ; Sweatman, WL; Tristram, PJ; Yock, Philip; Udalski, A; Szymański, MK; Kubiak, M; Pietrzyński, G; Poleski, R; SoszyAński, I; Wyrzykowski, Ł; Ulaczyk, K (2011)

    Journal article
    The University of Auckland Library

    Since 1995, more than 500 exoplanets have been detected using different techniques1,2, of which 12 were detected with gravitational microlensing3,4. Most of these are gravitationally bound to their host stars. There is some evidence of free-floating planetarymass objects in young star-forming regions5–8, but these objects are limited to massive objects of 3 to 15 Jupiter masses with large uncertainties in photometric mass estimates and their abundance. Here, we report the discovery of a population of unbound or distant Jupiter-mass objects, which are almost twice (1:8z1:7 {0:8) as common as main-sequence stars, based on two years of gravitational microlensing survey observations towards the Galactic Bulge. These planetary-mass objects have no host stars that can be detected within about ten astronomical units by gravitational microlensing. However, a comparison with constraints from direct imaging9 suggests that most of these planetary-mass objects are not bound to any host star. An abrupt change in the mass function at about one Jupiter mass favours the idea that their formation process is different from that of stars and brown dwarfs. They may have formed in proto-planetary disks and subsequently scattered into unbound or very distant orbits.

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  • A sub-Saturn mass planet, MOA-2009-BLG-319Lb

    Miyake, N; Sumi, T; Dong, S; Street, R; Mancini, L; Gould, A; Bennett, DP; Tsapras, Y; Yee, JC; Albrow, MD; Bond, IA; Fouqué, P; Browne, P; Han, C; Snodgrass, C; Finet, F; Furusawa, K; Harpsøe, K; Allen, W; Hundertmark, M; Freeman, M; Suzuk, D; Abe, F; Botzler, CS; Douchin, D; Fukui, A; Hayashi, F; Hearnshaw, JB; Hosaka, S; Itow, Y; Kamiya, K; Kilmartin, PM; Korpela, A; Lin, W; Ling, CH; Makita, S; Masuda, K; Matsubara, Y; Muraki, Y; Nagayama, T; Nishimoto, K; Ohnishi, K; Perrott, YC; Rattenbury, Nicholas; Saito, To; Skuljan, L; Sullivan, DJ; Sweatman, WL; Tristram, PJ; Wada, K; Yock, Philip; Bolt, G; Bos, M; Christie, GW; Depoy, DL; Drummond, J; Gal-Yam, A; Gaudi, BS; Gorbikov, E; Higgins, D; Hwang, K-H; Janczak, J; Kaspi, S; Lee, C-U; Koo, J-R; Kozllowski, S; Lee, Y; Mallia, F; Maury, A; Maoz, D; McCormick, J; Monard, LAG; Moorhouse, D; Muñoz, JA; Natusch, T; Ofek, EO; Pogge, RW; Polishook, D; Santallo, R; Shporer, A; Spector, O; Thornley, G; Allan, A; Bramich, DM; Horne, K; Kains, N; Steele, I; Bozza, V; Burgdorf, MJ; Calchi Novati, S; Dominik, M; Dreizler, S; Glitrup, M; Hessman, FV; Hinse, TC; Jørgensen, UG; Liebig, C; Maier, G; Mathiasen, M; Rahvar, S; Ricci, D; Scarpetta, G; Skottfelt, J; Southworth, J; Surdej, J; Wambsganss, J; Zimmer, F; Batista, V; Beaulieu, JP; Brillant, S; Cassan, A; Cole, A; Corrales, E; Coutures, Ch; Dieters, S; Greenhill, J; Kubas, D; Menzies, J (2011)

    Journal article
    The University of Auckland Library

    We report the gravitational microlensing discovery of a sub-Saturn mass planet, MOA-2009-BLG-319Lb, orbiting a K- or M-dwarf star in the inner Galactic disk or Galactic bulge. The high-cadence observations of the MOA-II survey discovered thismicrolensing event and enabled its identification as a high-magnification event approximately 24 hr prior to peak magnification. As a result, the planetary signal at the peak of this light curve was observed by 20 different telescopes, which is the largest number of telescopes to contribute to a planetary discovery to date. The microlensing model for this event indicates a planet–star mass ratio of q = (3.95 ± 0.02) × 10−4 and a separation of d = 0.97537 ± 0.00007 in units of the Einstein radius. A Bayesian analysis based on the measured Einstein radius crossing time, tE, and angular Einstein radius, θE, along with a standard Galactic model indicates a host star mass of ML = 0.38+0.34 −0.18M and a planet mass of Mp = 50+44 −24 M⊕, which is half the mass of Saturn. This analysis also yields a planet–star three-dimensional separation of a = 2.4+1.2 −0.6 AU and a distance to the planetary system of DL = 6.1+1.1 −1.2 kpc. This separation is ∼2 times the distance of the snow line, a separation similar to most of the other planets discovered by microlensing.

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  • A Low-Mass Planet with a Possible Sub-Stellar-Mass Host in Microlensing Event MOA-2007-BLG-192

    Bennett, Diane; Bond, IA; Udalski, A; Sumi, T; Abe, F; Fukui, A; Furusawa, K; Hearnshaw, JB; Holderness, Sharon; Itow, Y; Kamiya, K; Korpela, A; Kilmartin, PM; Lin, Wei-Ting; Ling, Chai; Masuda, K; Matsubara, Y; Miyake, N; Muraki, Y; Nagaya, M; Okumura, T; Ohnishi, K; Perrott, YC; Rattenbury, Nicholas; Sako, T; Saito, T; Sato, T; Skuljan, J; Sullivan, DJ; Sweatman, Winston; Tristram, PJ; Yock, Philip; Kubiak, M; Szymanski, MK; Pietrzynski, G; Soszynski, I; Szewczyk, O; Wyrzykowski, L; Ulaczyk, K; Batista, V; Beaulieu, JP; Brilliant, S; Cassan, A; Fouque, P; Kervella, P; Kubas, D; Marquette, JB (2008)

    Journal article
    The University of Auckland Library

    We report the detection of an extrasolar planet of mass ratio q 2 ; 10 4 in microlensing eventMOA-2007-BLG-192. The best-fit microlensing model shows both themicrolensing parallax and finite source effects, and these can be combined to obtain the lens masses of M ¼ 0:060þ0:028 0:021 M for the primary and m ¼ 3:3þ4:9 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 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 bottomof the main sequence. Follow-up VLTand/or Hubble Space Telescope (HST ) observationswill 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.

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