Improved Detection Rates for Close Binaries Via Astrometric Observations of Gravitational Microlensing Events

In addition to constructing a Galactic matter mass function free from the bias induced by the hydrogen-burning limit, gravitational microlensing allows one to construct a mass function which is less affected by the problem of unresolved binaries (Gaudi & Gould). However, even with the method of microlensing, the photometric detection of binaries is limited to binary systems with relatively large separations of $b\gtrsim 0.4$ of their combined Einstein ring radius, and thus the mass function is still not totally free from the problem of unresolved binaries. In this paper, we show that by detecting distortions of the astrometric ellipse of a microlensing event with high precision instruments such as the {\it Space Interferometry Mission}, one can detect close binaries at a much higher rate than by the photometric method. We find that by astrometrically observing microlensing events, $\sim 50$ of binaries with separations of $0.1r_{\rm E}$ can be detected with the detection threshold of 3%. The proposed astrometric method is especially efficient at detecting very close binaries. With a detection threshold of 3% and a rate of 10%, one can astrometrically detect binaries with separations down to $\sim 0.01r_{\rm E}$.Comment: total 14 pages, including 5 Figures and no Table (For figure 1, please send a request mail to [email protected]), accepted to ApJ (Vol 525, 000), updated versio

Second Backbend in the Mass A ~ 180 Region

Within the framework of selfconsistent cranked Hartree-Fock- Bogoliubov theory(one-dimensional) we predict second backbend in the yrast line of Os-182 at $I \approx 40$, which is even sharper than the first one observed experimentally at $I \approx 14$. Around such a high spin the structure becomes multi-quasiparticle type, but the main source of this strong discontinuity is a sudden large alignment of i_13/2 proton orbitals along the rotation axis followed soon by the alignment of j_15/2 neutron orbitals. This leads to drastic structural changes at such high spins. When experimentally confirmed, this will be observed for the first time in this mass region, and will be at the highest spin so far.Comment: 13 pages, 4 ps figure

Probing the Mass Fraction of MACHOs in Extragalactic Halos

Current microlensing searches calibrate the mass fraction of the Milky Way halo which is in the form of Massive Compact Halo Objects (MACHOs). We show that surveys like the Sloan Digital Sky Survey (SDSS) can probe the same quantity in halos of distant galaxies. Microlensing of background quasars by MACHOs in intervening galaxies would distort the equivalent width distribution of the quasar emission lines by an amplitude that depends on the projected quasar-galaxy separation. For a statistical sample of detectable at the >2sigma level out to a quasar-galaxy impact parameter of several tens of kpc, as long as extragalactic halos are made of MACHOs. Detection of this signal would test whether the MACHO fraction inferred for the Milky-Way halo is typical of other galaxies.Comment: 12 pages, 2 figures, submitted to ApJ Letter

A New Channel for the Detection of Planetary Systems Through Microlensing: I. Isolated Events Due to Planet Lenses

We propose and evaluate the feasibility of a new strategy to search for planets via microlensing. This new strategy is designed to detect planets in "wide" orbits, i.e., with orbital separation, $a$ greater than $\sim 1.5 R_E$. Planets in wide orbits may provide the dominant channel for the microlensing discovery of planets, particularly low-mass (e.g., Earth-mass) planets. This paper concentrates on events in which a single planet serves as a lens, leading to an isolated event of short duration. We point out that a distribution of events due to lensing by stars with wide-orbit planets is necessarily accompanied by a distribution of shorter- duration events. The fraction of events in the latter distribution is proportional to the average value of $\sqrt{q}$, where $q$ is the ratio between \pl and stellar masses. The position of the peak or peaks also provides a measure of the mass ratios typical of planetary systems. We study detection strategies that can optimize our ability to discover isolated short-duration events due to lensing by planets, and find that monitoring employing sensitive photometry is particularly useful. If planetary systems similar to our own are common, even modest changes in detection strategy should lead to the discovery of a few isolated events of short duration every year. We therefore also address the issue of the contamination due to stellar populations of any microlensing signal due to low-mass MACHOs. We describe how, even for isolated events of short duration, it will be possible to test the hypothesis that the lens was a planet instead of a low-mass MACHO, if the central star of the planetary system contributes a measurable fraction of the baseline flux.Comment: 37 pages, 6 figure. To be published in the Astrophysical Journal. This is part one of a series of papers on microlensing by planetary systems containing wide-orbit planets; the series represents a reorganization and extension of astro-ph/971101

Level density and level density parameter in medium heavy nuclei including thermal and quantal fluctuation effects

In a realistic application of the SPA + RPA theory for calculation of the nuclear level densities we find that quantal fluctuation corrections (RPA) are important even up to temperature $T = 2.0$ $MeV$. This leads to a good agreement between calculated numbers and the available experimental data for $^{104}Pd$ and $^{114}Sn$, particularly the excitation energy ($E^*$) dependence. Furthermore, we also argue that $a=S^2/4E^*$ is the only correct definition of the level density parameter in the present context which is also consistent with the Bethe like level density formula

Occurrence of parasites in selected fish species in Gandoman Lagoon, Iran

This study was carried out to investigate occurrence of parasite in selected cyprinid fish species in Gandoman Lagoon, in the vicinity of Gandoman City, Chaharmahal & Bakhtyari Province. A total of 90 fish specimens including Cyprinus carpio, Carassius auratus gibelio, Capoeta aculeata , C.damascina, Chondrostoma regium and Alburnus alburnus from Gandoman were examined during spring and summer 2007. Ten species of parasites were found, including Ichthyophthirius multifiliis, Trichodina sp. (Cilliophora), Myxobolus musayevi, Myxobolus sp. (Myxozoa), Dactylogyrus extensus, D.lenkorani (Monogenea), Diplostomum spathaceum, Tylodelphys clavata (Digenea). Argulus foliaceus and Lernea cyprinacea (Crustaceans). 77.7% of fishes were infected to parasites and 22.3 % did not show any infection. Chondrostoma regium and Alburnus alburnus are reported as new hosts for D. extensus

Bird Responses to Habitat Change in the Karst Area of Bantimurung Bulusaraung National Park

Birds are useful bioindicators to habitat changes. This study aims to determine the responses of birds to habitat change at Maros-Pangkep karst area, Bantimurung-Bulusaraung National Park. The research was carried out in three disturbance degrees (core-zone, wilderness-zone, and the community-gardens), which represents minimal, middle, and high interference level. A modified square-line method was used to observe vegetation of bird habitat. Point count method was used to observe bird population. Data of the bird habitat vegetation was analyzed using vegetation density. The difference of vegetation composition was analyzed using Sorensen-similarity index. Data of the bird was analyzed using abundance, and indexes of Shannon-Weinner diversity, Simpson dominance, Pielou evenness, and Margalef species richness. Significant differences between the number of the individual bird were tested using one-way ANOVA, Tukey-Bonferroni test. The results showed that birds living in karst were sensitive to habitat changes. Birds responded through reducing the number of individuals and species, shifting the species of bird that has high importance value index from low tolerance species to high tolerance species. Birds also responded by shifting the feeding guild that has high important value index from frugivore to frugivore-insectivore and then to granivore, decreasing the number of bird species with large body size, reducing the number of bird species that need a special location to build nest. Considering that Maros-Pangkep Karst has vital roles, scientific values, and biodiversity richness, it is necessary to involve all stakeholders to maintain its sustainability, including the establishment of entire Maros-Pangkep Karst area as the karst-landscape area

Destriping of Polarized Data in a CMB Mission with a Circular Scanning Strategy

A major problem in Cosmic Microwave Background (CMB) anisotropy mapping, especially in a total-power mode, is the presence of low-frequency noise in the data streams. If unproperly processed, such low-frequency noise leads to striping in the maps. To deal with this problem, solutions have already been found for mapping the CMB temperature fluctuations but no solution has yet been proposed for the measurement of CMB polarization. Complications arise due to the scan-dependent orientation of the measured polarization. In this paper, we investigate a method for building temperature and polarization maps free of striping effects in the case of a circular scanning strategy mission such as that of the Planck satellite

Colour-singlet strangelets at finite temperature

Considering massless $u$ and $d$ quarks, and massive (150 MeV) $s$ quarks in a bag with the bag pressure constant $B^{1/4} = 145$ MeV, a colour-singlet grand canonical partition function is constructed for temperatures $T = 1-30$ MeV. Then the stability of finite size strangelets is studied minimizing the free energy as a function of the radius of the bag. The colour-singlet restriction has several profound effects when compared to colour unprojected case: (1) Now bulk energy per baryon is increased by about $250$ MeV making the strange quark matter unbound. (2) The shell structures are more pronounced (deeper). (3) Positions of the shell closure are shifted to lower $A$-values, the first deepest one occuring at $A=2$, famous $H$-particle ! (4) The shell structure at $A=2$ vanishes only at $T\sim 30$ MeV, though for higher $A$-values it happens so at $T\sim 20$ MeV.Comment: Revtex file(8 pages)+6 figures(ps files) available on request from first Autho