Improving the prospects for detecting extrasolar planets in gravitational microlensing events 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  N. J.Rattenbury  M.Reid  To.Saito  Y.Saito  T.Sako  J.Skuljan  D. J.Sullivan  T.Sumi  S.Wilkinson  R.Yamada  T.Yanagisawa  P. C. M.Yock 《Monthly notices of the Royal Astronomical Society》2002,331(2):L19-L23

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 on-line 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 the Microlensing Observations in Astrophysics (MOA) project. 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.  相似文献   

A search for collision orbits in the free-fall three-body problem I. Numerical procedure     

Kiyotaka Tanikawa  Hiroaki Umehara  Hiroshi Abe 《Celestial Mechanics and Dynamical Astronomy》1995,62(4):335-362

A numerical procedure is devised to find binary collision orbits in the free-fall three-body problem. Applying this procedure, families of binary collision orbits are found and a sequence of triple collision orbits are positioned. A property of sets of binary collision orbits which is convenient to search triple collision orbits is found. Important numerical results are formulated and summarized in the final section.  相似文献   

Concentration level of dissolved cadmium and its variation in surface seawater of Urasoko Bay,Ishigaki Island     

Kazuo Abe 《Journal of Oceanography》2007,63(2):341-347

From April 2005 to March 2006, the concentration of dissolved cadmium (Cd) was monitored in the surface seawater of Urasoko Bay, which is in a subtropical area of the North Pacific Ocean and is surrounded by a well-developed fringing reef. During this period, the observed salinity and Cd concentrations varied in a range of approximately 16–34.5 and 4.8–77.8 pM, respectively. The concentration range of Cd obtained in this study was considered to be too low to damage the coral species, and its variation throughout the year did not show any seasonality and was not connected with climate data. The Cd-salinity plot for all the data in the salinity range over 26 showed apparent non-conservative behavior, which suggests a possible irregular input of Cd from a solid phase through streams and groundwater, release from bottom sediments, and atmospheric deposition into the bay.  相似文献   

Recolonization of the Krakataus by Hymenoptera and Isoptera (Insecta)     

Seiki Yamane Dr.  Takuya Abe Dr.  Junichi Yukawa Dr. 《GeoJournal》1992,28(2):213-218

The aculeate and isopteran fauna was surveyed in 1982 on the Krakatau islands, all the biota of which had been exterminated by the great eruption in 1883.The pattern of colonization of these insects (wasps, bees and termites) and the present state of their faunas are discussed based upon our 1982 survey and those made earlier. Species numbers varied only slightly between the four islands in spite of their differing sizes. This may be because the islands are situated close to each other and most of the aculeates prefer open sites rather than forests.The species/time curve for the Aculeata as a whole was still rising in 1982. However, in some groups flattening of the curve had occurred, and a comparison of species number in social wasps and bees, for example, between Java, Krakatau and Sumatra suggested the occurrence of supersaturation. Cumulative species numbers was distinctly larger than actual number in the three most recent surveys showing that several species must have become extinct in each intersurvey period. Species turnover associated with habitat changes may have occurred for the whole island group and on particular islands.Analysis of the colour pattern of the Krakatau populations of certain species with different geographical races on Java and Sumatra showed that the Javan elements have a slight preponderance over the Sumatran ones on the Krakataus.Some examples of faunal disharmony were found; the most remarkable was the almost complete lack of species of swarm-founding social wasps and bees, and of ground-nesting termites probably reflecting their poor dispersal ability across the sea barrier.  相似文献   

Effect of nutrient release from sea floor on Si:P ratio in the Buzen-Kai,western Seto Inland Sea,in summer     

Kazuo Abe  Mutsumi Tsujino  Norihisa Nakagawa  Katsuyuki Abo 《Journal of Oceanography》2015,71(2):221-227

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Apodized Lyot coronagraph for SPHERE/VLT: II. Laboratory tests and performance     

G��raldine Guerri  Jean-Baptiste Daban  Sylvie Robbe-Dubois  Richard Douet  Lyu Abe  Jacques Baudrand  Marcel Carbillet  Anthony Boccaletti  Philippe Bendjoya  Carole Gouvret  Farrokh Vakili 《Experimental Astronomy》2011,30(1):59-81

SPHERE (which stands for Spectro-Polarimetric High-contrast Exoplanet REsearch) is a second-generation Very Large Telescope (VLT) instrument dedicated to high-contrast direct imaging of exoplanets whose first-light is scheduled for 2011. Within this complex instrument one of the central components is the apodized Lyot coronagraph (ALC). The principal aim of this paper is to report the first laboratory experiment of the ALC designed for the SPHERE instrument. The performance and sensitivity of the optical configuration was first numerically studied with an end-to-end approach (see the results in paper I subtitled ??Detailed numerical study??). Made confident by the results, we then tested a prototype on an infrared coronagraphic bench. We measured the transmission profiles of the apodizer prototype and the coronagraphic performance of the apodized Lyot coronagraph in Y, J, and H bands. The coronagraph sensitivity to lateral and longitudinal misalignments of its three main components (apodizer, coronagraphic mask and Lyot stop) was finally studied in H band. We can conclude that the prototype meets the SPHERE technical requirements for coronagraphy.  相似文献   

Experimental comparison of support vector machines with random forests for hyperspectral image land cover classification   总被引：1，自引：0，他引：1  

B T Abe  O O Olugbara  T Marwala 《Journal of Earth System Science》2014,123(4):779-790

The performances of regular support vector machines and random forests are experimentally compared for hyperspectral imaging land cover classification. Special characteristics of hyperspectral imaging dataset present diverse processing problems to be resolved under robust mathematical formalisms such as image classification. As a result, pixel purity index algorithm is used to obtain endmember spectral responses from Indiana pine hyperspectral image dataset. The generalized reduced gradient optimization algorithm is thereafter executed on the research data to estimate fractional abundances in the hyperspectral image and thereby obtain the numeric values for land cover classification. The Waikato environment for knowledge analysis (WEKA) data mining framework is selected as a tool to carry out the classification process by using support vector machines and random forests classifiers. Results show that performance of support vector machines is comparable to that of random forests. This study makes a positive contribution to the problem of land cover classification by exploring generalized reduced gradient method, support vector machines, and random forests to improve producer accuracy and overall classification accuracy. The performance comparison of these classifiers is valuable for a decision maker to consider tradeoffs in method accuracy versus method complexity.  相似文献   

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  K. Masuda  Y. Matsubara  Y. Muraki  T. Nakamura  G. Nankivell  S. Noda  C. Noguchi  K. Ohnishi  M. Reid  To. Saito  H. Sato  M. Sekiguchi  D. J. Sullivan  T. Sumi  M. Takeuti  Y. Watase  S. Wilkinson  R. Yamada  T. Yanagisawa  P. C. M. Yock 《Monthly notices of the Royal Astronomical Society》2002,333(1):71-83

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)× M _Earth 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.  相似文献   

Spin Temperature of Ammonia Determined from NH2 in Comet C/2001 A2 (LINEAR)     

Kawakita  Hideyo  Watanabe  Jun-Ichi  FUSE  Tetsuharu  Furusho  Reiko  Abe  Shinsuke 《Earth, Moon, and Planets》2002,90(1-4):371-379

The ortho-to-para ratio (OPR) of a cometary molecule is one of primordial character in comets. The OPR which is characterized by a spin temperature, is thought to reflect the formation conditions of the molecule. In this paper we show the high-dispersion spectrum of cometary NH₂ in Comet C/2001 A2 (LINEAR), from which the OPR of NH₂ is determined based on the fluorescence excitation model. Since the NH₂ is a photodissociation product of cometary ammonia, we applied the permutation group theory to the whole reaction system (i.e. the photodissociation reaction of ammonia to NH₂ and H) in order to derive the OPR of ammonia from that of NH₂. The derived OPR of ammonia is 1.12 ± 0.03 in Comet C/2001 A2 (LINEAR). This value corresponds to a spin temperature of 30⁺³ _-2 K. If this reflects the temperature where the comet formed in the protosolar nebula, our result indicates that thiscomet was formed in the region of the giant planets between Jupiter and Neptune.  相似文献   

Sylvite and halite on particles recovered from 25143 Itokawa: A preliminary report     

T. Noguchi  M. Kimura  T. Hashimoto  M. Konno  T. Nakamura  M. E. Zolensky  A. Tsuchiyama  T. Matsumoto  J. Matsuno  R. Okazaki  M. Uesugi  Y. Karouji  T. Yada  Y. Ishibashi  K. Shirai  M. Abe  T. Okada 《Meteoritics & planetary science》2014,49(7):1305-1314

We observed cross sectional ultra‐thin sections near the surface of 12 particles recovered from the S‐type asteroid Itokawa by the Hayabusa spacecraft in 2010, using spherical aberration–corrected STEM and conventional TEM. Although their mineralogy is almost identical to the equilibrated LL chondrites and therefore basically anhydrous, micrometer‐to‐submicrometer‐sized sylvite was identified on the surface of Itokawa particle RA‐QD02‐0034. Separately, micrometer‐sized halite was also identified on the surface of Itokawa particle RA‐QD02‐0129. Detailed inspection of the sample processing procedures at the JAXA's Planetary Materials Sample Curation Facility and textural observation of the sylvite and halite indicate that they were clearly present on two Itokawa particles before they were removed from Clean Chamber #2 at JAXA. However, there is no direct evidence for their extraterrestrial origin at present. If the sylvite and halite are extraterrestrial, their presence suggests that they may be more abundant on the surface of S‐type asteroids than previously thought.  相似文献