2 results for Pietrzynski, G

  • 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 ?? 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 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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  • Microlens OGLE-2005-BLG-169 Implies That Cool Neptune-like Planets Are Common

    Gould, A; Udalski, A; An, D; Bennett, Diane; Zhou, Arui; Dong, S; Rattenbury, Nicholas; Gaudi, BS; Yock, Philip; Bond, IA; Christie, GW; Horne, K; Anderson, J; Stanek, J; DePloy, DL; Han, C; McCormick, J; Park, BG; Pogge, RW; Poindexter, SD; Soszynski, I; Szymanski, MK; Kubiak, M; Pietrzynski, G; Szewczyk, O; Wyrzykowski, L; Ulaczyk, K; Paczynski, B; Bramich, DM; Snodgrass, C; Steele, Ivan; Burgdorf, MJ; Bode, MF; Botzler, Christine; Mao, Sophin; Swaving, SC (2006)

    Journal article
    The University of Auckland Library

    We detect a Neptune mass ratio (q 8#10 5) planetary companion to the lens star in the extremely high magnification (A ??? 800) microlensing event OGLE-2005-BLG-169. If the parent is a main-sequence star, it has mass M ??? 0.5 M,, implying a planet mass of ???13 M and projected separation of ???2.7 AU. When intensely monitored over their peak, high-magnification events similar to OGLE-2005-BLG-169 have nearly complete sensitivity to Neptune mass ratio planets with projected separations of 0.6???1.6 Einstein radii, corresponding to 1.6???4.3 AU in the present case. Only two other such events were monitored well enough to detect Neptunes, and so this detection by itself suggests that Neptune mass ratio planets are common. Moreover, another Neptune was recently discovered at a similar distance from its parent star in a low-magnification event, which are more common but are individually much less sensitive to planets. Combining the two detections yields 90% upper and lower frequency limits fp0.38 0.31 over 0.22 just 0.4 decades of planet-star separation. In particular, f 1 16% at 90% confidence. The parent star hosts no Jupitermass companions with projected separations within a factor 5 of that of the detected planet. The lens-source relative proper motion is m ??? 7???10 mas yr 1, implying that if the lens is sufficiently bright, I 23.8, it will be detectable by the Hubble Space Telescope by 3 years after peak. This would permit a more precise estimate of the lens mass and distance and, so, the mass and projected separation of the planet. Analogs of OGLE-2005-BLG-169Lb orbiting nearby stars would be difficult to detect by other methods of planet detection, including radial velocities, transits, and astrometry.

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