Photometric information on globular cluster stars from the Palomar Sky Survey prints     

V. Castellani  F. A. D'Antona  R. de Amicis  F. Smriglio 《Astrophysics and Space Science》1973,22(1):71-78

Photometric information that can be taken from the Palomar Sky Survey prints can be used to discriminate among the various evolutionary stages of stars that are members of globular clusters, as well as to obtain some idea of the HR diagram for vary faint stars. For a test case, it is shown that in a check analysis forM3 the known turn-off luminosity is given to within about 0.5 mag. The globular cluster NGC 5466 is examined and it is concluded that no turn-off occurs beforeP20 mag.  相似文献   

Physical conditions in the convective envelopes of stars     

Vittorio Castellani  Alvio Renzini 《Astrophysics and Space Science》1969,3(2):283-291

The physical conditions in the convective envelopes of Pop. II main-sequence stars are described with some detail. A particular care has been devoted to the effects due to the formation of hydrogen molecules and to the pressure ionization.

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Riassunto Vengono descritte in dettaglio le condizioni fisiche nelle zone convettive esterne delle stelle di sequenza principale di Popolazione II. In particolare vengono studiati gli effetti dovuti alla formazione della molecola dell'idrogeno ed alla ionizzazione per pressione.

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Overshooting of convective cores in helium-burning horizontal-branch stars     

V. Castellani  P. Giannone  A. Renzini 《Astrophysics and Space Science》1971,10(2):340-349

In helium-burning horizontal-branch stars, transformation of helium into carbon increases opacity in the convective core. Such a situation can drive an increase of the core-mass extension via the mixing by overshooting. The efficiency of this mechanism is investigated in order to obtain an indication of the time scale for the propagation of the convective boundary. Schwarzschild's criterion is shown to be fulfilled within a few percent at the innermost interface of the core boundary.

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Riassunto Nei primi stadi evolutivi di stelle di ramo orizzontale, la combustione di elio in carbonio aumenta l'opacità nel nucleo convettivo. Ne segue che il rimescolamento al bordo della convezione (overshooting) induce una progressiva instabilità convettiva negli strati contornanti il nucleo con conseguente incremento della massa del nucleo stesso. E' studiata l'efficienza di tale meccanismo al fine di ottenere indicazioni sui tempi scala caratteristici del processo di propagazione. Si mostra come il criterio di Schwarzschild risulti verificato entro qualche percento al bordo interno del nucleo convettivo.

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Observations of the temperature and polarization anisotropies with Boomerang 2003     

W.C. Jones  P.A.R. Ade  J.J. Bock  J.R. Bond  J. Borrill  A. Boscaleri  P. Cabella  C.R. Contaldi  B.P. Crill  P. de Bernardis  G. De Gasperis  A. de Oliveira-Costa  G. De Troia  G. Di Stefano  E. Hivon  A.H. Jaffe  T.S. Kisner  A.E. Lange  C.J. MacTavish  S. Masi  P.D. Mauskopf  A. Melchiorri  T.E. Montroy  P. Natoli  C.B. Netterfield  E. Pascale  F. Piacentini  D. Pogosyan  G. Polenta  S. Prunet  S. Ricciardi  G. Romeo  J.E. Ruhl  P. Santini  M. Tegmark  M. Veneziani  N. Vittorio   《New Astronomy Reviews》2006,50(11-12):945

The Boomerang experiment completed its final long duration balloon (LDB) flight over Antarctica in January 2003. The focal plane was upgraded to accommodate four sets of 145 GHz polarization sensitive bolometers (PSBs), identical to those to be flown on the Planck HFI instrument. Approximately, 195 hours of science observations were obtained during this flight, including 75 hours distributed over 1.84% of the sky and an additional 120 hours concentrated on a region covering 0.22% of the sky. We derive the angular power spectra of the cosmic microwave background (cmb) temperature and polarization anisotropies from these data. The temperature anisotropies are detected with high signal to noise on angular scales ranging from several degrees to 10 arcminutes. The curl-free (EE) component is detected at 4.8σ, and a two-sigma upper limit on the curl (BB) component of 8.6 μK² is obtained on scales corresponding to 0.5°. Both the temperature and polarization anisotropies are found to be consistent with a concordance ΛCDM cosmology that is seeded by adiabatic density perturbations. In addition to the cmb observations, Boomerang03 surveyed a 300 square degree region centered on the Galactic plane. These observations represent the first light for polarization sensitive bolometers, which are currently operational in two South-Pole based polarimeters, as well as Planck HFI, at frequencies ranging from 100 to 350 GHz (3 mm to 850 μm).  相似文献   

Origin of salt giants in abyssal serpentinite systems     

Scribano  Vittorio  Carbone  Serafina  Manuella  Fabio C.  Hovland  Martin  Rueslåtten  Håkon  Johnsen  Hans-K. 《International Journal of Earth Sciences》2017,106(7):2595-2608

International Journal of Earth Sciences - Worldwide marine salt deposits ranging over the entire geological record are generally considered climate-related evaporites, derived from the...  相似文献