Hasil untuk "astro-ph.SR"

R. B. Astro, Yulius Saprianus Dala Ngapa, S. Toda et al.

Pulau Flores yang terletak di Provinsi Nusa Tenggara Timur memiliki potensi EBT yang cukup beragam, antara lain panas bumi, air, angin, matahari, hingga arus laut. Penelitian ini bertujuan untuk menjabarkan potensi air di Flores serta sistem kerja pembangkit listrik ramah lingkungan yang memanfaatkan air sebagai sumber energi. Hasil penelitian ini dapat dimanfaatkan sebagai sumber belajar terkait potensi energi air di pulau Flores dan pemanfaatannya sebagai sumber energi listrik bersih (green energy). Penelitian ini dilaksanakan dengan metode studi literatur. Pulau Flores termasuk daerah beriklim kering dengan curah hujan yang minim dengan potensi air tergolong kecil, sehingga potensi energi air lebih tepat digunakan sebagai sumber energi listrik dengan daya menengah (PLTM) dan kecil (PLTMH). Potensi air yang tersedia juga mampu ditingkatkan dengan sistem cascade. Pada PLTM/MH energi potensial air diubah menjadi energi kinetik di dalam pipa pesat, selajutnya energi kinetik diubah menjadi energi mekanik berupa putaran poros turbin, dan terakhir energi mekanik dikonversi menjadi energi listrik oleh generator. Beberapa pembangkit listrik yang ada di pulau Flores antara lain PLTM Ndungga, PLTMH Ogi, dan PLTMH Wae Roa, PLTMH Waigarit, dan PLTMH Sita. Selain itu terdapat pula penelitian lain terkait potensi energi air di Flores yang masih dalam tahap penelitian awal dan lanjutan. Pada pengoperasiannya PLTM/MH terbukti menekan laju konsumsi bahan bakar fosil. PLTMH juga sangat memungkinkan untuk diterapkan pada daerah-daerah di Flores dan NTT umumnya yang terpencil dan jauh dari jaringan listrik PLN.

Marco Carraro, Morris Antonello, L. Tonin et al.

R. Moeller, G. Reitz, Zuofeng Li et al.

M. Lock, M. Høyer, S. Bydder et al.

L. Vanzi, J. Chacón, K. Hełminiak et al.

Astro Teller

F. Lascaux, E. Masciadri, S. Hagelin

In two recent papers, the mesoscale model Meso-NH, jointly with the Astro-Meso-NH package, has been validated at Dome C, Antarctica, for the characterization of optical turbulence. It has been shown that the meteorological parameters (temperature and wind speed, on which the optical turbulence depends) as well as the C2N profiles above Dome C were correctly reproduced statistically. The three most important derived parameters that characterize the optical turbulence above the Internal Antarctic Plateau – the surface-layer thickness, the seeing in the free atmosphere and the seeing in the total atmosphere – were shown to be in very good agreement with observations. Validation of C2N has been performed using all the measurements of the optical turbulence vertical distribution obtained in winter so far. In this paper, in order to investigate the ability of the model to discriminate between different turbulence conditions for site testing, we extend the study to two other potential astronomical sites in Antarctica: Dome A and South Pole, which we expect to be characterized by different turbulence conditions. The optical turbulence has been calculated above these two sites for the same 15 nights studied for Dome C and a comparison between the three sites has been performed. The ability of the Meso-NH model to discriminate between different types of optical turbulence behaviour is confirmed, and it is evident that the three sites considered have different characteristics as regards the seeing and the surface-layer thickness.

Astro Teller, M. Veloso

J. Williamson, P. Dunscombe, M. Sharpe et al.

L. Maunula, P. Klemola, A. Kauppinen et al.

A. Marconi, M. Pistore, P. Traverso

A. Pellizzoni, M. Pilia, A. Possenti et al.

Astro-rivelatore Gamma ad Immagini LEggero (AGILE) is a small gamma-ray astronomy satellite mission of the Italian Space Agency dedicated to high-energy astrophysics launched in 2007 April. Its ∼ 1 μs absolute time tagging capability coupled with a good sensitivity in the 30 MeV–30 GeV range, with simultaneous X-ray monitoring in the 18–60 keV band, makes it perfectly suited for the study of gamma-ray pulsars following up on the Compton Gamma Ray Observatory/EGRET heritage. In this paper, we present the first AGILE timing results on the known gamma-ray pulsars Vela, Crab, Geminga, and B1706 − 44. The data were collected from 2007 July to 2008 April, exploiting the mission Science Verification Phase, the Instrument Timing Calibration, and the early Observing Pointing Program. Thanks to its large field of view, AGILE collected a large number of gamma-ray photons from these pulsars (∼ 10,000 pulsed counts for Vela) in only few months of observations. The coupling of AGILE timing capabilities, simultaneous radio/X-ray monitoring, and new tools aimed at precise photon phasing, also exploiting timing noise correction, unveiled new interesting features at the submillisecond level in the pulsars' high-energy light curves.

Andrew Ogilvie, J. Allport, Michael Hannah et al.

Celestial Mechanics, V. Brumberg, N. D. Astrometry et al.

S. McCloskey, M. Tao, C. Rose et al.

L. Kuchinski, W. Freedman, B. Madore et al.

We have undertaken an imaging survey of 34 nearby galaxies in far-ultraviolet (FUV, ∼1500 Å) and optical (UBVRI) passbands to characterize galaxy morphology as a function of wavelength. This sample, which includes a range of classical Hubble types from elliptical to irregular, with emphasis on spirals at low inclination angle, provides a valuable database for comparison with images of high-z galaxies whose FUV light is redshifted into the optical and near-infrared bands. Ultraviolet data are from the Ultraviolet Imaging Telescope (UIT) Astro-2 mission. We present images and surface brightness profiles for each galaxy, and we discuss the wavelength dependence of morphology for different Hubble types in the context of understanding high-z objects. In general, the dominance of young stars in the FUV produces the patchy appearance of a morphological type later than that inferred from optical images. Prominent rings and circumnuclear star formation regions are clearly evident in FUV images of spirals, while bulges, bars, and old, red stellar disks are faint to invisible at these short wavelengths. However, the magnitude of the change in apparent morphology ranges from dramatic in early-type spirals with prominent optical bulges to slight in late-type spirals and irregulars, in which young stars dominate both the UV and optical emission. Starburst galaxies with centrally concentrated, symmetric bursts display an apparent "E/S0" structure in the FUV, while starbursts associated with rings or mergers produce a peculiar morphology. We briefly discuss the inadequacy of the optically defined Hubble sequence in describing FUV galaxy images and estimating morphological k-corrections, and we suggest some directions for future research with this data set.

Michael W. Kattan, P. Fearn, Steven A. Leibel et al.

F. Critz

Tadayuki Takahashi, K. Makishima, Y. Fukazawa et al.

M. Buyyounouski, A. Hanlon, D. Eisenberg et al.