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SUB-SATURN PLANET MOA-2008-BLG-310Lb: LIKELY TO BE IN THE GALACTIC BULGE
Janczak, Julia,Fukui, A.,Dong, Subo,Monard, L. A. G.,Kozłowski, Szymon,Gould, A.,Beaulieu, J. P.,Kubas, Daniel,Marquette, J. B.,Sumi, T.,Bond, I. A.,Bennett, D. P.,Abe, F.,Furusawa, K.,Hearnshaw, J. B IOP Publishing 2010 The Astrophysical journal Vol.711 No.2
<P>We report the detection of sub-Saturn-mass planet MOA-2008-BLG-310Lb and argue that it is the strongest candidate yet for a bulge planet. Deviations from the single-lens fit are smoothed out by finite-source effects and therefore are not immediately apparent from the light curve. Nevertheless, we find that a model in which the primary has a planetary companion is favored over the single-lens model by Delta chi(2) similar to 880 for an additional 3 degrees of freedom. Detailed analysis yields a planet/star mass ratio q = (3.3 +/- 0.3) x 10(-4) and an angular separation between the planet and star within 10% of the angular Einstein radius. The small angular Einstein radius, theta(E) = 0.155 theta 0.011 mas, constrains the distance to the lens to be D(L) > 6.0 kpc if it is a star (M(L) > 0.08 M(circle dot)). This is the only microlensing exoplanet host discovered so far that must be in the bulge if it is a star. By analyzing VLT NACO adaptive optics images taken near the baseline of the event, we detect additional blended light that is aligned to within 130 mas of the lensed source. This light is plausibly from the lens, but could also be due to a companion to the lens or source, or possibly an unassociated star. If the blended light is indeed due to the lens, we can estimate the mass of the lens, M(L) = 0.67 +/- 0.14 M(circle dot), planet mass m = 74 +/- 17 M(circle plus), and projected separation between the planet and host, 1.25 +/- 0.10 AU, putting it right on the 'snow line.' If not, then the planet has lower mass, is closer to its host and is colder. To distinguish among these possibilities on reasonable timescales would require obtaining Hubble Space Telescope images almost immediately, before the source-lens relative motion of mu = 5 mas yr(-1) causes them to separate substantially.</P>
BINARY MICROLENSING EVENT OGLE-2009-BLG-020 GIVES VERIFIABLE MASS, DISTANCE, AND ORBIT PREDICTIONS
Skowron, J.,Udalski, A.,Gould, A.,Dong, Subo,Monard, L. A. G.,Han, C.,Nelson, C. R.,McCormick, J.,Moorhouse, D.,Thornley, G.,Maury, A.,Bramich, D. M.,Greenhill, J.,Kozłowski, S.,Bond, I.,Poleski, R.,W IOP Publishing 2011 The Astrophysical journal Vol.738 No.1
<P>We present the first example of binary microlensing for which the parameter measurements can be verified (or contradicted) by future Doppler observations. This test is made possible by a confluence of two relatively unusual circumstances. First, the binary lens is bright enough (I = 15.6) to permit Doppler measurements. Second, we measure not only the usual seven binary-lens parameters, but also the 'microlens parallax' (which yields the binary mass) and two components of the instantaneous orbital velocity. Thus, we measure, effectively, six 'Kepler+1' parameters (two instantaneous positions, two instantaneous velocities, the binary total mass, and the mass ratio). Since Doppler observations of the brighter binary component determine five Kepler parameters (period, velocity amplitude, eccentricity, phase, and position of periapsis), while the same spectroscopy yields the mass of the primary, the combined Doppler + microlensing observations would be overconstrained by 6 + (5 + 1) - (7 + 1) = 4 degrees of freedom. This makes possible an extremely strong test of the microlensing solution. We also introduce a uniform microlensing notation for single and binary lenses, define conventions, summarize all known microlensing degeneracies, and extend a set of parameters to describe full Keplerian motion of the binary lenses.</P>
DISCOVERY AND MASS MEASUREMENTS OF A COLD, 10 EARTH MASS PLANET AND ITS HOST STAR
Muraki, Y.,Han, C.,Bennett, D. P.,Suzuki, D.,Monard, L. A. G.,Street, R.,Jorgensen, U. G.,Kundurthy, P.,Skowron, J.,Becker, A. C.,Albrow, M. D.,Fouqué,, P.,Heyrovský,, D.,Barry, R. K.,Beau IOP Publishing 2011 The Astrophysical journal Vol.741 No.1
<P>We present the discovery and mass measurement of the cold, low-mass planet MOA-2009-BLG-266Lb, performed with the gravitational microlensing method. This planet has a mass of m(p) = 10.4 +/- 1.7 M-circle plus and orbits a star of mass M-star = 0.56 +/- 0.09 M-circle dot at a semimajor axis of a = 3.2(-0.5)(+1.9) AU and an orbital period of P = 7.6(-1.5)(+7.7) yrs. The planet and host star mass measurements are enabled by the measurement of the microlensing parallax effect, which is seen primarily in the light curve distortion due to the orbital motion of the Earth. But the analysis also demonstrates the capability to measure the microlensing parallax with the Deep Impact (or EPOXI) spacecraft in a heliocentric orbit. The planet mass and orbital distance are similar to predictions for the critical core mass needed to accrete a substantial gaseous envelope, and thus may indicate that this planet is a 'failed' gas giant. This and future microlensing detections will test planet formation theory predictions regarding the prevalence and masses of such planets.</P>
Han, C.,Hwang, K.-H.,Kim, D.,Udalski, A.,Abe, F.,Monard, L. A. B.,McCormick, J.,Szymań,ski, M. K.,Kubiak, M.,Pietrzyń,ski, G.,Soszyń,ski, I.,Szewczyk, O.,Wyrzykowski, Ł.,Ulaczyk, K.,Bon IOP Publishing 2009 The Astrophysical journal Vol.705 No.2
<P>To improve the planet detection efficiency, current planetary microlensing experiments are focused on high-magnification events searching for planetary signals near the peak of lensing light curves. However, it is known that signals from those induced by binary companions. In this paper, we analyze the light curves of microlensing events OGLE-2007-BLG-137/MOA-2007-BLG-091, OGLE-2007-BLG-355/MOA-2007-BLG-278, and MOA-2007- BLG-199/OGLE-2007-BLG-419, for all of which exhibit short-term perturbations near the peaks of the light curves. From detailed modeling of the light curves, we find that the perturbations of the events are caused by binary companions rather than planets. From a close examination of the light curves combined with the underlying physical geometry of the lens system obtained from modeling, we find that the short timescale caustic-crossing feature occurring at a low or a moderate base magnification with an additional secondary perturbation is a typical feature of binary-lens events and thus can be used for the discrimination between the binary and planetary interpretations.</P>
Im, Myungshin,Choi, Changsu,Yoon, Sung-Chul,Kim, Jae-Woo,Ehgamberdiev, Shuhrat A.,Monard, Libert A. G.,Sung, Hyun-Il IOP Publishing 2015 The Astrophysical journal Supplement series Vol.221 No.1
<P>The main progenitor candidates of Type Ia supernovae (SNe Ia) are white dwarfs in binary systems where the companion star is another white dwarf (double degenerate (DD) system) or a less-evolved, non-degenerate star with R-* greater than or similar to 0.1 R-circle dot (single degenerate system). However, no direct observational evidence exists to tell us which progenitor system is more common. Recent studies suggest that the light curve of a supernova shortly after its explosion can be used to set a limit on the progenitor size, R-*. Here, we report high-cadence monitoring observations of SN 2015F, a normal SN Ia in the galaxy NGC 2442, starting about 84 days before the first light time. Using our daily cadence data, we capture the emergence of the radioactively powered light curve; more importantly, with >97.4% confidence, we detect possible dim precursor emission that appears roughly 1.5 days before the rise of the radioactively powered emission. The signal is consistent with theoretical expectations for a progenitor system involving a companion star with R-* similar or equal to 0.1-1 R-circle dot or a prompt explosion of a DD system, but is inconsistent with the typically invoked size of a white dwarf progenitor of R-* similar to 0.01 R-circle dot. Upper limits on the precursor emission also constrain the progenitor size to be R-* less than or similar to 0.1 R-circle dot with a companion star size of R-* less than or similar to 1.0 R-circle dot, excluding a very large companion star in the progenitor system. Additionally, we find that the distance to SN 2015F is 23.9 +/- 0.4 Mpc.</P>
MOA-2013-BLG-220Lb: MASSIVE PLANETARY COMPANION TO GALACTIC-DISK HOST
Yee, J. C.,Han, C.,Gould, A.,Skowron, J.,Bond, I. A.,Udalski, A.,Hundertmark, M.,Monard, L. A. G.,Porritt, I.,Nelson, P.,Bozza, V.,Albrow, M. D.,Choi, J.-Y.,Christie, G. W.,DePoy, D. L.,Gaudi, B. S.,H IOP Publishing 2014 The Astrophysical journal Vol.790 No.1
<P>We report the discovery of MOA-2013-BLG-220Lb, which has a super-Jupiter mass ratio q = 3.01 +/- 0.02 x 10(-3) relative to its host. The proper motion, mu = 12.5 +/- 1 mas yr(-1), is one of the highest for microlensing planets yet discovered, implying that it will be possible to separately resolve the host within similar to 7 yr. Two separate lines of evidence imply that the planet and host are in the Galactic disk. The planet could have been detected and characterized purely with follow-up data, which has important implications for microlensing surveys, both current and into the Large Synoptic Survey Telescope (LSST) era.</P>
Yee, J. C.,Udalski, A.,Sumi, T.,Dong, Subo,Kozłowski, S.,Bird, J. C.,Cole, A.,Higgins, D.,McCormick, J.,Monard, L. A. G.,Polishook, D.,Shporer, A.,Spector, O.,Szymań,ski, M. K.,Kubiak, M.,Pietrzy IOP Publishing 2009 The Astrophysical journal Vol.703 No.2
<P>We analyze the extreme high-magnification microlensing event OGLE-2008-BLG-279, which peaked at a maximum magnification of A similar to 1600 on 2008 May 30. The peak of this event exhibits both finite-source effects and terrestrial parallax, from which we determine the mass of the lens, M-l = 0.64 +/- 0.10 M-circle dot, and its distance, D-l = 4.0 +/- 0.6 kpc. We rule out Jupiter-mass planetary companions to the lens star for projected separations in the range 0.5-20 AU. More generally, we find that this event was sensitive to planets with masses as small as 0.2 M-circle dot similar or equal to 2 (MMars) with projected separations near the Einstein ring (similar to 3 AU).</P>