467,525 research outputs found

    A Principal Component Analysis of the 3B Gamma-Ray Burst Data

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    We have carried out a principal component analysis for 625 gamma-ray bursts in the BATSE 3B catalog for which non-zero values exist for the nine measured variables. This shows that only two out of the three basic quantities of duration, peak flux and fluence are independent, even if this relation is strongly affected by instrumental effects, and these two account for 91.6% of the total information content. The next most important variable is the fluence in the fourth energy channel (at energies above 320 keV). This has a larger variance and is less correlated with the fluences in the remaining three channels than the latter correlate among themselves. Thus a separate consideration of the fourth channel, and increased attention on the related hardness ratio H43H43 appears useful for future studies. The analysis gives the weights for the individual measurements needed to define a single duration, peak flux and fluence. It also shows that, in logarithmic variables, the hardness ratio H32H32 is significantly correlated with peak flux, while H43H43 is significantly anticorrelated with peak flux. The principal component analysis provides a potentially useful tool for estimating the improvement in information content to be achieved by considering alternative variables or performing various corrections on available measurementsComment: Ap.J., accepted 12/9/97; revised version contains a new appendix, somewhat expanded discussion; latex, aaspp4, 15 page

    Multicomponent binary spreading process

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    I investigate numerically the phase transitions of two-component generalizations of binary spreading processes in one dimension. In these models pair annihilation: AA->0, BB->0, explicit particle diffusion and binary pair production processes compete with each other. Several versions with spatially different productions have been explored and shown that for the cases: 2A->3A, 2B->3B and 2A->2AB, 2B->2BA a phase transition occurs at zero production rate (σ=0\sigma=0), that belongs to the class of N-component, asymmetric branching and annihilating random walks, characterized by the order parameter exponent β=2\beta=2. In the model with particle production: AB->ABA, BA-> BAB a phase transition point can be located at σc=0.3253\sigma_c=0.3253 that belongs to the class of the one-component binary spreading processes.Comment: 5 pages, 5 figure

    Discovery of a Young L Dwarf Binary, SDSS J224953.47+004404.6AB

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    We report discovery of a young 0.32" L dwarf binary, SDSS J2249+0044AB, found as the result of a Keck LGSAO imaging survey of young field brown dwarfs. Weak K, Na, and FeH features as well as strong VO absorption in the integrated-light J-band spectrum indicate a young age for the system. From spatially resolved K-band spectra we determine spectral types of L3 and L5 for components A and B, respectively. SDSS J2249+0044A is spectrally very similar to G196-3B, an L3 companion to a young M2.5 field dwarf. Thus, we adopt 100 Myr (the age estimate of the G196-3 system) as the age of SDSS J2249+0044AB, but ages of 12-790 Myr are possible. By comparison to G196-3B, we estimate a distance to SDSS J2249+0044AB of 54 +- 16 pc and infer a projected separation of 17 +- 5 AU for the binary. Comparison of the luminosities to evolutionary models at an age of 100 Myr yields masses of 0.029 and 0.022 Msun for SDSS J2249+0044A and B, respectively. Over the possible ages of the system (12-790 Myr), the mass of SDSS J2249+0044A could range from 0.011 to 0.070 Msun and the mass of SDSS J2249+0044B could range from 0.009 to 0.065 Msun. Evolutionary models predict that either component could be burning deuterium, which could result in a mass ratio as low as 0.4, or alternatively, a reversal in the luminosities of the binary. We find a likely proper motion companion, GSC 00568-01752, which lies 48.9" away (2600 AU) and has SDSS+2MASS colors consistent with an early M dwarf. The photometric distance to GSC 00568-01752 is 53 +- 15 pc, in agreement with our distance estimate for SDSS J2249+0044AB. The space motion of SDSS J2249+0044AB shows no obvious coincidence with known young moving groups. The unusually red near-IR colors, young age, and low masses of the binary make it an important template for studying planetary-mass objects found by direct imaging surveys.Comment: revised, accepted versio

    The TWA 3 Young Triple System: Orbits, Disks, Evolution

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    We have characterized the spectroscopic orbit of the TWA 3A binary and provide preliminary families of probable solutions for the TWA 3A visual orbit as well as for the wide TWA 3A--B orbit. TWA 3 is a hierarchical triple located at 34 pc in the \sim10 Myr old TW Hya association. The wide component separation is 1."55; the close pair was first identified as a possible binary almost 20 years ago. We initially identified the 35-day period orbital solution using high-resolution infrared spectroscopy which angularly resolved the A and B components. We then refined the preliminary orbit by combining the infrared data with a re-analysis of our high-resolution optical spectroscopy. The orbital period from the combined spectroscopic solution is \sim35 days, the eccentricity is \sim0.63, and the mass ratio is \sim0.84; although this high mass ratio would suggest that optical spectroscopy alone should be sufficient to identify the orbital solution, the presence of the tertiary B component likely introduced confusion in the blended optical spectra. Using millimeter imaging from the literature, we also estimate the inclinations of the stellar orbital planes with respect to the TWA 3A circumbinary disk inclination and find that all three planes are likely misaligned by at least \sim30 degrees. The TWA 3A spectroscopic binary components have spectral types of M4.0 and M4.5; TWA 3B is an M3. We speculate that the system formed as a triple, is bound, and that its properties were shaped by dynamical interactions between the inclined orbits and disk.Comment: Accepted to Ap

    Neurospora tetrasperma helper strains using the E gene

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    In N. crassa, strains with an inactive mating type allele are available that can be used as one component of a forced heterokaryon, serving as a helper to shelter a second component that is infertile or otherwise disadvantaged because of some recessive trait (Griffiths and DeLange 1978 Genetics 88:239-254; Perkins 1984 Neurospora Newsl. 31:41-42). am1 ad-3B cyh-1 (FGSC 4564), which is heterokaryon- compatible with both A and a mating types in Oak Ridge background (het-C, -d, -e), has been especially useful. When such a phenotypically wild-type heterokaryon is used as one parent in a cross, the helper nuclei do not participate sexually and all progeny are parented by the disadvantaged component. Heterokaryons with the helper are also useful for stock preservation, assuring survival of genotypes that would otherwise be difficult to maintain

    Compilation, design tests: Energetic particles Satellite S-3 including design tests for S-3A, S-3B and S-3C

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    A compilation of engineering design tests which were conducted in support of the Energetic Particle Satellite S-3, S-3A, and S-3b programs. The purpose for conducting the tests was to determine the adequacy and reliability of the Energetic Particles Series of satellites designs. The various tests consisted of: (1) moments of inertia, (2) functional reliability, (3) component and structural integrity, (4) initiators and explosives tests, and (5) acceptance tests
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