S Noda

Publications (28)68.01 Total impact

• Article: Parallel computation of GA search for the artery shape determinants with CFD

  M Himeno, S Noda, K Fukasaku, R Himeno
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  ABSTRACT: We studied which factors play important role to determine the shape of arteries at the carotid artery bifurcation by performing multi-objective optimization with computation fluid dynamics (CFD) and the genetic algorithm (GA). To perform it, the most difficult problem is how to reduce turn-around time of the GA optimization with 3D unsteady computation of blood flow. We devised two levels of parallel computation method with the following features: level 1: parallel CFD computation with appropriate number of cores; level 2: parallel jobs generated by "master", which finds quickly available job cue and dispatches jobs, to reduce turn-around time. As a result, the turn-around time of one GA trial, which would have taken 462 days with one core, was reduced to less than two days on RIKEN supercomputer system, RICC, with 8192 cores. We performed a multi-objective optimization to minimize the maximum mean WSS and to minimize the sum of circumference for four different shapes and obtained a set of trade-off solutions for each shape. In addition, we found that the carotid bulb has the feature of the minimum local mean WSS and minimum local radius. We confirmed that our method is effective for examining determinants of artery shapes.
  IOP Conference Series Materials Science and Engineering 07/2010; 10(1):012131.
• Article: Microlensing Optical Depth toward the Galactic Bulge from Microlensing Observations in Astrophysics Group Observations during 2000 with Difference Image Analysis

  T. Sumi, F. Abe, I. A. Bond, R. J. Dodd, J. B. Hearnshaw, M. Honda, M. Honma, Y. Kan-ya, P. M. Kilmartin, K. Masuda, [......], Y. Saito, H. Sato, M. Sekiguchi, J. Skuljan, D. J. Sullivan, M. Takeuti, P. J. Tristram, S. Wilkinson, T. Yanagisawa, and P. C. M. Yock
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  ABSTRACT: We analyze the data of the gravitational microlensing survey carried out by the Microlensing Observations in Astrophysics (MOA) group during 2000 toward the Galactic bulge (GB). Our observations are designed to detect efficient high-magnification events with faint source stars and short-timescale events, by increasing the sampling rate up to ~6 times per night and using Difference Image Analysis (DIA). We detect 28 microlensing candidates in 12 GB fields corresponding to 16 deg2. We use Monte Carlo simulations to estimate our microlensing event detection efficiency, where we construct the I-band extinction map of our GB fields in order to find dereddened magnitudes. We find a systematic bias and large uncertainty in the measured value of the timescale tE,out in our simulations. They are associated with blending and unresolved sources, and are allowed for in our measurements. We compute an optical depth τ = 2.59 × 10-6 toward the GB for events with timescales 0.3 < tE < 200 days. We consider disk-disk lensing, and obtain an optical depth τbulge = 3.36 × 10-6[0.77/(1 - fdisk)] for the bulge component assuming a 23% stellar contribution from disk stars. These observed optical depths are consistent with previous measurements by the MACHO and OGLE groups, and still higher than those predicted by existing Galactic models. We present the timescale distribution of the observed events, and find there are no significant short events of a few days, in spite of our high detection efficiency for short-timescale events down to tE ~ 0.3 days. We find that half of all our detected events have high magnification (>10). These events are useful for studies of extrasolar planets.
  The Astrophysical Journal 12/2008; 591(1):204. · 6.02 Impact Factor
• Source

  Available from: Philip C. M. Yock

  Article: Multiple Outbursts of a Cataclysmic Variable in the Globular Cluster M22

  I. A. Bond, F. Abe, S. Eguchi, Y. Furuta, J. B. Hearnshaw, K. Kamiya, P. M. Kilmartin, Y. Kurata, K. Masuda, Y. Matsubara, [......], K. Okajima, N. J. Rattenbury, T. Sako, T. Sekiguchi, D. J. Sullivan, T. Sumi, P. J. Tristram, T. Yanagisawa, P. C. M. Yock, and (The MOA Collaboration
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  ABSTRACT: We present a 4 yr light curve of a cataclysmic variable in M22, based on an analysis of accumulated data from the Microlensing Observations in Astrophysics (MOA) microlensing survey. The position of the star coincides with that of a transient event observed by the Hubble Space Telescope (HST) in 1999, originally attributed to microlensing but later suspected to be a dwarf nova outburst. Two outburst episodes, one in 2002 and one in 2003, with ΔI ~ 3 are seen in the MOA data, thus confirming that the HST event was a dwarf nova outburst. The MOA and HST data show that this dwarf nova underwent at least three outburst episodes during 1999-2004. Further close monitoring of this event is encouraged, as future outburst episodes are expected.
  The Astrophysical Journal 12/2008; 620(2):L103. · 6.02 Impact Factor
• Source

  Available from: Philip C. M. Yock

  Article: OGLE 2003-BLG-235/MOA 2003-BLG-53: A Planetary Microlensing Event

  I. A. Bond, A. Udalski, M. Jaroszyński, N. J. Rattenbury, B. Paczyński, I. Soszyński, L. Wyrzykowski, M. K. Szymański, M. Kubiak, O. Szewczyk, [......], K. Okajima, T. Sako, T. Sekiguchi, D. J. Sullivan, T. Sumi, P. J. Tristram, T. Yanagisawa, P. C. M. Yock, and The MOA, OGLE Collaborations
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  ABSTRACT: We present observations of the unusual microlensing event OGLE 2003-BLG-235/MOA 2003-BLG-53. In this event, a short-duration (~7 days) low-amplitude deviation in the light curve due to a single-lens profile was observed in both the MOA (Microlensing Observations in Astrophysics) and OGLE (Optical Gravitational Lensing Experiment) survey observations. We find that the observed features of the light curve can only be reproduced using a binary microlensing model with an extreme (planetary) mass ratio of 0.0039 for the lensing system. If the lens system comprises a main-sequence primary, we infer that the secondary is a planet of about 1.5 Jupiter masses with an orbital radius of ~3 AU.
  The Astrophysical Journal 12/2008; 606(2):L155. · 6.02 Impact Factor
• Article: Observation of the Halo of the Edge-On Galaxy IC 5249

  F. Abe, I. A. Bond, B. S. Carter, R. J. Dodd, M. Fujimoto, J. B. Hearnshaw, M. Honda, J. Jugaku, S. Kabe, P. M. Kilmartin, [......], To. Saito, H. Sato, S. Sato, M. Sekiguchi, D. J. Sullivan, T. Sumi, Y. Watase, T. Yanagisawa, P. C. M. Yock, and M. Yoshizawa
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  ABSTRACT: Optical photometry and H I synthesis observations of the southern edge-on Sc/Sd galaxy IC 5249 are reported. The rotation curve rises linearly out to a radius of 7 kpc and then appears to flatten out at ~100 km s-1. The H I mass out to 24.5 kpc is ~6 × 109 M, or 10% of the total mass out to this radius. The color, central surface brightness, scale height, and scale length of the disk of IC 5249 are R - I ≈ 0.4, μ = 20.6 ± 0.1RC mag arcsec-2, 600 ± 40 pc, and 11 ± 2 kpc, respectively. Additional light to that predicted by an exponential disk is present at distances greater than 3 kpc from the disk. At 5 kpc the surface brightness is 27–28RC mag arcsec-2. The measured distribution of surface brightness is used to constrain the abundance of low-mass main-sequence stars in the halo of the galaxy. A halo made up entirely of main-sequence stars heavier than 0.13 M is excluded. We also find that less than 20% of the halo can be composed of main-sequence stars heavier than 0.30 M. Further observations are required to determine the rotation curve of IC 5249 to large radii and to determine precisely the abundance of low-mass main-sequence stars in the halo of the galaxy.
  The Astronomical Journal 12/2007; 118(1):261. · 4.03 Impact Factor
• Article: Candidate extrasolar planet transits discovered in the Microlensing Observations in Astrophysics‐I Galactic bulge data

  F. Abe, I. A. Bond, Y. Furuta, J. B. Hearnshaw, P. M. Kilmartin, Y. Kurata, K. Masuda, Y. Matsubara, Y. Muraki, S. Noda, K. Okajima, N. J. Rattenbury, T. Sako, D. J. Sullivan, T. Sumi, P. Tristram, J. N. Wood, T. Yanagisawa, P. C. M. Yock
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  ABSTRACT: We present the results of a search for candidate planetary transits using the Microlensing Observations in Astrophysics-I (MOA-I) microlensing survey data in the Galactic bulge. To achieve sufficient photometric precision, the analysis was confined to a selected subset of stars on selected images. Periodicities of light curves were found with a Box fitting Least Squares (BLS) procedure. This yielded 12 candidates. The derived radii of the candidates ranged from 1.7 to 3.2 RJ, consistent with interpretations in terms of blended binaries, late M dwarfs or strongly irradiated giant planets. Follow-up spectroscopic observations would be required to identify actual planets amongst the candidates by radial velocity variations. The results confirm that microlensing surveys provide an effective means for finding candidate planetary transits. It is anticipated that the recently commissioned MOA-II telescope will provide further candidates in the future.
  Monthly Notices of the Royal Astronomical Society 10/2005; 364(1):325 - 334. · 4.90 Impact Factor
• Source

  Available from: Philip C. M. Yock

  Article: Determination of stellar shape in microlensing event MOA 2002-BLG-33

  N. J. Rattenbury, F Abe, D. P. Bennett, I. A. Bond, J. J. Calitz, A. Claret, K. H. Cook, Y. Furuta, A. Gal-Yam, J. F. Glicenstein, [......], L. Philpott, S. H. Rhie, T Sako, D. J. Sullivan, T Sumi, D. M. Terndrup, P. J. Tristram, J. Wood, T Yanagisawa, P. C. M. Yock
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  ABSTRACT: We report a measurement of the shape of the source star in microlensing event MOA 2002-BLG-33. The lens for this event was a close binary whose centre-of-mass passed almost directly in front of the source star. At this time, the source star was closely bounded on all sides by a caustic of the lens. This allowed the oblateness of the source star to be constrained. We found that a/b = 1.02^{+0.04}_{-0.02} where a and b are its semi-major and semi-minor axes respectively. The angular resolution of this measurement is approximately 0.04 microarcsec. We also report HST images of the event that confirm a previous identification of the source star as an F8-G2 turn-off main-sequence star.
  07/2005;
• Source

  Available from: Philip C. M. Yock

  Article: Search for low-mass exoplanets by gravitational microlensing at high magnification.

  F Abe, D P Bennett, I A Bond, S Eguchi, Y Furuta, J B Hearnshaw, K Kamiya, P M Kilmartin, Y Kurata, K Masuda, [......], D Maoz, E O Ofek, A Udalski, O Szewczyk, K Zebrun, I Soszynski, M K Szymanski, M Kubiak, G Pietrzynski, L Wyrzykowski
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  ABSTRACT: Observations of the gravitational microlensing event MOA 2003-BLG-32/OGLE 2003-BLG-219 are presented, for which the peak magnification was over 500, the highest yet reported. Continuous observations around the peak enabled a sensitive search for planets orbiting the lens star. No planets were detected. Planets 1.3 times heavier than Earth were excluded from more than 50% of the projected annular region from approximately 2.3 to 3.6 astronomical units surrounding the lens star, Uranus-mass planets were excluded from 0.9 to 8.7 astronomical units, and planets 1.3 times heavier than Saturn were excluded from 0.2 to 60 astronomical units. These are the largest regions of sensitivity yet achieved in searches for extrasolar planets orbiting any star.
  Science 09/2004; 305(5688):1264-6. · 31.20 Impact Factor
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  Available from: Kouji Ohnishi

  Article: Observational properties of red variables in the LMC

  M. Takeuti, S. Noda, F. Abe, I. A. Bond, R. J. Dodd, J. B. Hearnshaw, M. Honda, M. Honma, J. Jugaku, Y. Kan-Ya, [......], To. Saito, H. Sato, M. Sekiguchi, J. Skuljan, D. J. Sullivan, T. Sumi, R. Yamada, T. Yanagisawa, P. C. M. Yock, M. Yoshizawa
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  ABSTRACT: More than 4000 stars observed in both MOA and DENIS projects showing periodic or quasi periodic light curves are studied. Almost all Mira stars are located on the classical period luminosity relation, and the multiplicity of the period luminosity relation is confirmed for small amplitude stars. The color magnitude diagrams based on the MOA red band, Rm, and KS constructed for the sequences, form a single strip with small successive shifts.
  04/2004; 310:332.
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  Available from: Philip C. M. Yock

  Article: OGLE 2003-BLG-235/MOA 2003-BLG-53: A planetary microlensing event

  I. A. Bond, A. Udalski, M. Jaroszynski, N. J. Rattenbury, B. Paczynski, I. Soszynski, L. Wyrzykowski, M. K. Szymanski, M. Kubiak, O. Szewczyk, [......], Y. Muraki, S Noda, K. Okajima, T Sako, T Sekiguchi, D. J. Sullivan, T Sumi, P. J. Tristram, T Yanagisawa, P. C. M. Yock
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  ABSTRACT: We present observations of the unusual microlensing event OGLE 2003-BLG-235/MOA 2003-BLG-53. In this event a short duration (~7 days) low amplitude deviation in the light curve due a single lens profile was observed in both the MOA and OGLE survey observations. We find that the observed features of the light curve can only be reproduced using a binary microlensing model with an extreme (planetary) mass ratio of 0.0039 +/- (11, 07) for the lensing system. If the lens system comprises a main sequence primary, we infer that the secondary is a planet of about 1.5 Jupiter masses with an orbital radius of ~3 AU. Comment: 13 pages, 3 colour figures. To appear in Astrophysical Journal Letters (May 2004)
  04/2004;
• Article: Study of variable stars in the MOA data base: long‐period red variables in the Large Magellanic Cloud – II. Multiplicity of the period–luminosity relation

  S. Noda, M. Takeuti, F. Abe, I. A. Bond, R. J. Dodd, J. B. Hearnshaw, M. Honda, M. Honma, J. Jugaku, Y. Kan-ya, [......], Y. Saito, H. Sato, M. Sekiguchi, J. Skuljan, D. J. Sullivan, T. Sumi, R. Yamada, T. Yanagisawa, P. C. M. Yock, M. Yoshizawa
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  ABSTRACT: Data for 4.4 million stars from the Microlensing Observations in Astrophysics (MOA) project are compared with the near-infrared data of the Deep Near Infrared Southern Sky Survey (DENIS). More than 4000 stars observed in both projects show a quite periodic light curve. Among them, a number of stars are likely eclipsing variables, and the others seem to be pulsating stars. The KS magnitudes of these red variables are in the range 10–12.5 but a minor clump at KS≈ 12.2 mag is also found. The multiplicity of the period–luminosity relation is confirmed, but most of the regular, large-amplitude variables are found on the relation established for the Mira stars. We study the properties of the variables on the colour–magnitude diagram constructed with the MOA red band Rm and KS of DENIS. Multiplicity of the period–luminosity relation is briefly discussed in relation to the excitation mechanism of red pulsating variables.
  Monthly Notices of the Royal Astronomical Society 02/2004; 348(4):1120 - 1134. · 4.90 Impact Factor
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  Available from: Philip C. M. Yock

  Article: MOA 2003-BLG-37: A Bulge Jerk-Parallax Microlens Degeneracy

  B. -G. Park, D. L. DePoy, B. S. Gaudi, A. Gould, C Han, R. W. Pogge, F Abe, D. P. Bennett, I. A. Bond, S Eguchi, [......], S Noda, K. Okajima, N. J. Rattenbury, T Sako, T Sekiguchi, D. J. Sullivan, T Sumi, P. J. Tristram, T Yanagisawa, P. C. M. Yock
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  ABSTRACT: We analyze the Galactic bulge microlensing event MOA-2003-BLG-37. Although the Einstein timescale is relatively short, t_e=43 days, the lightcurve displays deviations consistent with parallax effects due to the Earth's accelerated motion. We show that the chi^2 surface has four distinct local minima that are induced by the ``jerk-parallax'' degeneracy, with pairs of solutions having projected Einstein radii, \tilde r_e = 1.76 AU and 1.28 AU, respectively. This is the second event displaying such a degeneracy and the first toward the Galactic bulge. For both events, the jerk-parallax formalism accurately describes the offsets between the different solutions, giving hope that when extra solutions exist in future events, they can easily be found. However, the morphologies of the chi^2 surfaces for the two events are quite different, implying that much remains to be understood about this degeneracy. Comment: 19 pages, 3 figures, 1 table, ApJ, in press, 1 July 2004
  01/2004;
• Article: Photometry of eclipsing binary stars in the large and Small magellanic clouds

  G. P. Bayne, S. C. Besier, I. Bond, J. B. Hearnshaw, M Honda, P. M. Kilmartin, Y. Muraki, S Noda, K. R. Pollard, J. D. Pritchard, M Sekiguchi, T Sumi, M. Takeuti, W. Tobin, T Yanagisawa
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  ABSTRACT: Se han obtenido curvas de luz para tres binarias eclipsantes en las Nubes de Magallanes mediante fotometra CCD uVJIC. Uno de los objetos en la GNM, MACHO*05:36:48.7
  Revista Mexicana de Astronomía y Astrofísica. 01/2004;
• Source

  Available from: Philip C. M. Yock

  Article: Probing the atmosphere of a solar-like star by galactic microlensing at high magnification

  F Abe, D. P. Bennett, I. A. Bond, J. J. Calitz, A. Claret, K. H. Cook, Y. Furuta, A. Gal-Yam, J. F. Glicenstein, J. B. Hearnshaw, [......], L. Philpott, N. J. Rattenbury, S. H. Rhie, T Sako, D. J. Sullivan, T Sumi, D. M. Terndrup, P. J. Tristram, T Yanagisawa, P. C. M. Yock
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  ABSTRACT: We report a measurement of limb darkening of a solar-like star in the very high magnification microlensing event MOA 2002-BLG-33. A 15 hour deviation from the light curve profile expected for a single lens was monitored intensively in V and I passbands by five telescopes spanning the globe. Our modelling of the light curve showed the lens to be a close binary system whose centre-of-mass passed almost directly in front of the source star. The source star was identified as an F8-G2 main sequence turn-off star. The measured stellar profiles agree with current stellar atmosphere theory to within ~4% in two passbands. The effective angular resolution of the measurements is <1 micro-arcsec. These are the first limb darkening measurements obtained by microlensing for a Solar-like star. Comment: Accepted for publication in A&A Letters. 5 pages, 2 embedded colour ps figures plus 1 jpg figure. Version with all figures embedded available from: http://www.roe.ac.uk/~iab/moa33paper/
  10/2003;
• Source

  Available from: Berto Monard

  Article: The Nature of V359 Centauri Revealed: New Long-Period SU UMa-Type Dwarf Nova

  T Kato, R. Stubbings, P. Nelson, R. Santallo, R. Ishioka, M Uemura, T Sumi, Y. Muraki, P. Kilmartin, I. Bond, S Noda, P. Yock, J. B. Hearnshaw, B. Monard, H Yamaoka
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  ABSTRACT: We detected four outbursts of V359 Cen (possible nova discovered in 1939) between 1999 and 2002. Time-resolved CCD photometry during two outbursts (1999 and 2002) revealed that V359 Cen is actually a long-period SU UMa-type dwarf nova with a mean superhump period of 0.08092(1) d. We identified its supercycle length as 307-397 d. This secure identification of the superhump period precludes the previously supposed possibility that V359 Cen could be related to a WZ Sge-type system with a long persistence of late superhumps. The outburst characteristics of V359 Cen are, however, rather unusual in its low occurrence of normal outbursts. Comment: 8 pages, 10 figures, to appear in Astronomy and Astrophysics
  09/2002;
• Source

  Available from: Kouji Ohnishi

  Article: Microlensing optical depth towards the Galactic bulge from MOA observations during 2000 with Difference Image Analysis

  T Sumi, F Abe, I. A. Bond, R. J. Dodd, J. B. Hearnshaw, M Honda, M Honma, Y. Kan-ya, P. M. Kilmartin, K Masuda, [......], Y Saito, H Sato, M Sekiguchi, J. Skuljan, D. J. Sullivan, M. Takeuti, P. J. Tristram, S. Wilkinson, T Yanagisawa, P. C. M. Yock
  [show abstract] [hide abstract]
  ABSTRACT: We analyze the data of the gravitational microlensing survey carried out by by the MOA group during 2000 towards the Galactic Bulge (GB). Our observations are designed to detect efficiently high magnification events with faint source stars and short timescale events, by increasing the the sampling rate up to 6 times per night and using Difference Image Analysis (DIA). We detect 28 microlensing candidates in 12 GB fields corresponding to 16 deg^2. We use Monte Carlo simulations to estimate our microlensing event detection efficiency, where we construct the I-band extinction map of our GB fields in order to find dereddened magnitudes. We find a systematic bias and large uncertainty in the measured value of the timescale $t_{\rm Eout}$ in our simulations. They are associated with blending and unresolved sources, and are allowed for in our measurements. We compute an optical depth tau = 2.59_{-0.64}^{+0.84} \times 10^{-6} towards the GB for events with timescales 0.3<t_E<200 days. We consider disk-disk lensing, and obtain an optical depth tau_{bulge} = 3.36_{-0.81}^{+1.11} \times 10^{-6}[0.77/(1-f_{disk})] for the bulge component assuming a 23% stellar contribution from disk stars. These observed optical depths are consistent with previous measurements by the MACHO and OGLE groups, and still higher than those predicted by existing Galactic models. We present the timescale distribution of the observed events, and find there are no significant short events of a few days, in spite of our high detection efficiency for short timescale events down to t_E = 0.3 days. We find that half of all our detected events have high magnification (>10). These events are useful for studies of extra-solar planets. Comment: 65 pages and 30 figures, accepted for publication in ApJ. A systematic bias and uncertainty in the optical depth measurement has been quantified by simulations
  07/2002;
• Article: Study by MOA of extrasolar planets in gravitational microlensing events of high magnification

  I. A. Bond, N. J. Rattenbury, J. Skuljan, F. Abe, R. J. Dodd, J. B. Hearnshaw, M. Honda, J. Jugaku, P. M. Kilmartin, A. Marles, [......], H. Sato, M. Sekiguchi, D. J. Sullivan, T. Sumi, M. Takeuti, Y. Watase, S. Wilkinson, R. Yamada, T. Yanagisawa, P. C. M. Yock
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  ABSTRACT: A search for extrasolar planets was carried out in three gravitational microlensing events of high magnification, MACHO 98–BLG–35, MACHO 99–LMC–2 and OGLE 00–BUL–12. Photometry was derived from observational images by the MOA and OGLE groups using an image subtraction technique. For MACHO 98–BLG–35, additional photometry derived from the MPS and PLANET groups was included. Planetary modelling of the three events was carried out in a supercluster computing environment. The estimated probability for explaining the data on MACHO 98–BLG–35 without a planet is <1 per cent. The best planetary model has a planet of mass ∼(0.4–1.5)×MEarth at a projected radius of either ∼1.5 or ∼2.3 au. We show how multiplanet models can be applied to the data. We calculate exclusion regions for the three events and find that Jupiter-mass planets can be excluded with projected radii from as wide as about 30 au to as close as around 0.5 au for MACHO 98–BLG–35 and OGLE 00–BUL–12. For MACHO 99–LMC–2, the exclusion region extends out to around 10 au and constitutes the first limit placed on a planetary companion to an extragalactic star. We derive a particularly high peak magnification of ∼160 for OGLE 00–BUL–12. We discuss the detectability of planets with masses as low as Mercury in this and similar events.
  Monthly Notices of the Royal Astronomical Society 05/2002; 333(1):71 - 83. · 4.90 Impact Factor
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  Available from: Kouji Ohnishi

  Article: Study of variable stars in the MOA data base: long-period red variables in the Large Magellanic Cloud

  S Noda, M. Takeuti, F Abe, I. A. Bond, R. J. Dodd, J. B. Hearnshaw, M Honda, M Honma, J. Jugaku, S. Kabe, [......], M Sekiguchi, J. Skuljan, D. J. Sullivan, T Sumi, Y. Watase, S. Wilkinson, R Yamada, T Yanagisawa, P. C. M. Yock, M Yoshizawa
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  ABSTRACT: One hundred and forty six long-period red variable stars in the Large Magellanic Cloud (LMC) from the three year MOA project database were analysed. A careful periodic analysis was performed on these stars and a catalogue of their magnitudes, colours, periods and amplitudes is presented. We convert our blue and red magnitudes to $K$ band values using 19 oxygen-rich stars. A group of red short-period stars separated from the Mira sequence has been found on a (log P, K) diagram. They are located at the short period side of the Mira sequence consistent with the work of Wood and Sebo (1996). There are two interpretations for such stars; a difference in pulsation mode or a difference in chemical composition. We investigated the properties of these stars together with their colour, amplitude and periodicity. We conclude that they have small amplitudes and less regular variability. They are likely to be higher mode pulsators. A large scatter has been also found on the long period side of the (log P, K) diagram. This is possibly a systematic spread given that the blue band of our photometric system covers both standard B and V bands and affects carbon-rich stars. Comment: 19 pages, 19 figures, accepted for publication in MNRAS
  11/2001;
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  Available from: Philip C. M. Yock

  Article: Improving the Prospects for Detecting Extrasolar Planets in Gravitational Microlensing in 2002

  I. A. Bond, F Abe, R. J. Dodd, J. B. Hearnshaw, P. M. Kilmartin, K Masuda, Y Matsubara, Y. Muraki, S Noda, O. K. L. Petterson, [......], To. Saito, Y Saito, T Sako, J. Skuljan, D. J. Sullivan, T Sumi, S. Wilkinson, R Yamada, T Yanagisawa, P. C. M. Yock
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  ABSTRACT: Gravitational microlensing events of high magnification have been shown to be promising targets for detecting extrasolar planets. However, only a few events of high magnification have been found using conventional survey techniques. Here we demonstrate that high magnification events can be readily found in microlensing surveys using a strategy that combines high frequency sampling of target fields with online difference imaging analysis. We present 10 microlensing events with peak magnifications greater than 40 that were detected in real-time towards the Galactic Bulge during 2001 by MOA. We show that Earth mass planets can be detected in future events such as these through intensive follow-up observations around the event peaks. We report this result with urgency as a similar number of such events are expected in 2002. Comment: 11 pages, 3 embedded ps figures including 2 colour, revised version accepted by MNRAS
  11/2001;
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  Available from: Kouji Ohnishi

  Article: Study by MOA of extra-solar planets in gravitational microlensing events of high magnification

  I. A. Bond, N. J. Rattenbury, J. Skuljan, F Abe, R. J. Dodd, J. B. Hearnshaw, M Honda, J. Jugaku, P. M. Kilmartin, A. Marles, [......], H Sato, M Sekiguchi, D. J. Sullivan, T Sumi, M. Takeuti, Y. Watase, S. Wilkinson, R Yamada, T Yanagisawa, P. C. M. Yock
  [show abstract] [hide abstract]
  ABSTRACT: A search for extra-solar planets was carried out in three gravitational microlensing events of high magnification, MACHO 98-BLG-35, MACHO 99-LMC-2, and OGLE 00-BUL-12. Photometry was derived from observational images by the MOA and OGLE groups using an image subtraction technique. For MACHO 98-BLG-35, additional photometry derived from the MPS and PLANET groups was included. Planetary modeling of the three events was carried out in a super-cluster computing environment. The estimated probability for explaining the data on MACHO 98-BLG-35 without a planet is <1%. The best planetary model has a planet of mass ~(0.4-1.5) X 10^-5 M_Earth at a projected radius of either ~1.5 or ~2.3 AU. We show how multi-planet models can be applied to the data. We calculated exclusion regions for the three events and found that Jupiter-mass planets can be excluded with projected radii from as wide as about 30 AU to as close as around 0.5 AU for MACHO 98-BLG-35 and OGLE 00-BUL-12. For MACHO 99-LMC-2, the exclusion region extends out to around 10 AU and constitutes the first limit placed on a planetary companion to an extragalactic star. We derive a particularly high peak magnification of ~160 for OGLE 00-BUL-12. We discuss the detectability of planets with masses as low as Mercury in this and similar events. Comment: 14 pages, 16 embedded postscript figures, 3 PNG figures, revised version accepted by MNRAS
  02/2001;