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121.
R. G. Gratton G. Bonanno P. Bruno A. CalÍ R. U. Claudi R. Cosentino S. Desidera F. Diego G. Farisato G. Martorana M. Rebeschini S. Scuderi 《Experimental Astronomy》2001,12(2):107-143
SARG is a cross dispersed echelle spectrograph in operation since late spring 2000 at the Italian Telescopio Nazionale Galileo
(TNG) 3.5 m telescope, La Palma. SARG offers both single object and long slit (up to 26 arcsec) observing modes covering a
spectral range from λ = 0.37 up to1 μm, with resolution ranging from R = 29,000 up to R = 164,000. Cross dispersion is provided by means of a selection of four grisms; interference filters may be used for the
long slit mode (up to 26 arcsec). A dioptric camera images the cross dispersed spectra onto a mosaic of two 2048 × 4096 EEV
CCDs (pixel size: 13.5 μm) allowing complete spectral coverage at all resolving power for λ < 0.8 μm. In order to reach a
high wavelength calibration precision an iodine-absorbing cell is provided. A Distributed Active Temperature Control System
(DATCS) maintains constant the temperature of all spectrograph components at a preset value. Early results show that SARG
works according to original specifications in terms of wavelength coverage, efficiency (measured peak efficiency is about
13%),resolution (maximum resolution R = 164,000 using a 0.3 arcsec slit, R ∼144,000 using an image slicer), and stability (preliminary estimates of radial velocity accuracy is ∼3 m/s using the iodine
cell and ±150 m/s without the iodine cell).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
122.
A recently developed near infrared high speed photometer intended for lunar oc-cultation studies is described. The primary scientific objective is to reach milli arc second levels of angular resolution so that circumstellar structure of the occulted sources can be resolved. Near infrared sky brightness close to the lunar limb is also studied. Angular diameter derived from the observed occultation of IRC +20169 is presented and system performance discussed. 相似文献
123.
124.
125.
A. R. King K. Schenker U. Kolb M. B. Davies 《Monthly notices of the Royal Astronomical Society》2001,321(2):327-332
We show that the usual picture of supersoft X-ray binary evolution as driven by conservative thermal time-scale mass transfer cannot explain the short orbital periods of RX J0537.7–7034 (3.5 h) and 1E 0035.4–7230 (4.1 h). Non-conservative evolution may produce such periods, but requires very significant mass loss, and is highly constrained. 相似文献
126.
127.
Matthias R. Aellig Alan J. Lazarus Justin C. Kasper Keith W. Ogilvie 《Astrophysics and Space Science》2001,277(1-2):305-307
The Triana PlasMag Faraday Cup (FC) will be able to determine speed, flow angles, temperature, and density of the main solar
wind ion species with a time resolution of better than one second. Thus, the Triana PlasMag FC will enable resolution of spatial
structures as small as a few hundred kilometers as the structures convect past the spacecraft. Under typical solar wind conditions,
that size is comparable to a few proton gyroradii.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
128.
Dryer M. Fry C.D. Sun W. Deehr C. Smith Z. Akasofu S.-I. Andrews M.D. 《Solar physics》2001,204(1-2):265-284
Prediction of solar-generated disturbances and their three-dimensional propagation through interplanetary space continues
to present a vitally important operational space weather forecasting objective. This paper presents the first successful real-time
prediction of a series of major heliospheric shock waves at Earth, including the one from the 14 July 2000 (`Bastille Day')
flare. An ensemble of three models and their predictions were distributed to a world-wide group of interested scientists as
part of an informal Internet space weather forecast research program. Two of the models, STOA (Shock Time of Arrival) and
ISPM (Interplanetary Shock Propagation Model), presently in operation by the US Air Force Weather Agency, provided predictions
of shock arrival time (SAT) that were, respectively, 0.5 hours after and 3.7 hours before the observed arrival. The third
model, HAFv.2 (Hakamada–Akasofu–Fry version 2.0) predicted a time 0.3 hours after the observed shock arrival time (14:37 UT,
15 July 2000). Of primary interest to this study is the third model, firstly in terms of its capability of propagating shocks
through non-uniform solar wind conditions, and secondly, in terms of its ability to integrate multiple solar events and display
them graphically along with the background solar wind. This latter capability was brought to bear on ten real-time-reported
flares, some with CMEs (coronal mass ejections) that took place as companions to the Bastille flare during the period 7–15
July 2000. Some limited statistics are given regarding the three models' shock arrival prediction capability at Earth, as
an extension of our earlier studies with this three model ensemble in the prediction of SAT. HAFv.2, however, was able to
describe not only the ten events and their interaction as measured at Earth, but also at the spacecraft NEAR (orbiting the
asteroid, Eros, at 1.8 AU), and CASSINI (en route, at 4.0 AU, to Saturn). Several important points are noted: (1) this epoch
represents a small statistical sample that should be expanded; and (2) the three models, based on theory, empiricism, and
simulations represent the state of the art that should presage a similar community process. This paper was presented earlier
as an Invited Talk at the American Geophysical Union Fall Meeting, December 14–19, 2000, in San Francisco, CA, U.S.A.toward
space weather objectives in the Sun-Earth domain.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1014200719867 相似文献
129.
C.J. Mooney W.R.J. Rolleston F.P. Keenan P.L. Dufton D.L. Pollacco H.R. Magee 《Monthly notices of the Royal Astronomical Society》2001,326(3):1101-1109
We present a model-atmosphere analysis for the bright ( V ∼13) star ZNG-1, in the globular cluster M10. From high-resolution ( R ∼40 000) optical spectra we confirm ZNG-1 to be a post-asymptotic giant branch (post-AGB) star. The derived atmospheric parameters are T eff =26 500±1000 K and log g =3.6±0.2 dex . A differential abundance analysis reveals a chemical composition typical of hot post-AGB objects, with ZNG-1 being generally metal poor, although helium is approximately solar. The most interesting feature is the large carbon underabundance of more than 1.3 dex. This carbon deficiency, along with an observed nitrogen enhancement relative to other elements, may suggest that ZNG-1 evolved off the AGB before the third dredge-up occurred. Also, iron depletions observed in other similar stars suggest that gas–dust fractionation in the AGB progenitor could be responsible for the observed composition of these objects. However, we need not invoke either scenario since the chemical composition of ZNG-1 is in good agreement with abundances found for a Population II star of the same metallicity. 相似文献
130.
K. C. WELTEN K. NISHIIZUMI J. MASARIK M. W. CAFFEE A. J. T. JULL S. E. KLANDRUD R. WIELER 《Meteoritics & planetary science》2001,36(2):301-317
Abstract— We measured the concentrations of 10Be, 26Al, 36Cl, 41Ca and 14C in the metal and/or stone fractions of 27 Antarctic chondrites from Frontier Mountain (FRO), including two large H‐chondrite showers. To estimate the pre‐atmospheric size of the two showers, we determined the contribution of neutron‐capture produced 36Cl (half‐life = 3.01 times 105 years) and 41Ca (1.04 times 105 years) in the stone fraction. The measured activities of neutron‐capture 36Cl and 41Ca, as well as spallation produced 10Be and 26Al, were compared with Monte Carlo‐based model calculations. The largest shower, FRO 90174, includes eight fragments with an average terrestrial age of (100 ± 30) × 103 years; the neutron‐capture saturation activities extend to 27 dpm/kg stone for 36Cl and 19 dpm/kg stone for 41Ca. The concentrations of spallation produced 10Be, 26Al and 36Cl constrain the radius (R) to 80–100 cm, while the neutron‐capture 41Ca activities indicate that the samples originated from the outer 25 cm. With a pre‐atmospheric radius of 80–100 cm, FRO 90174 is among the largest of the Antarctic stony meteorites. The large pre‐atmospheric size supports our hypothesis that at least 50 of the ~150 classified H5/H6‐chondrites from the Frontier Mountain stranding area belong to this single fall; this hypothesis does not entirely account for the high H/L ratio at Frontier Mountain. The smaller shower, FRO 90001, includes four fragments with an average terrestrial age of (40 ± 10) × 103 years; they contain small contributions of neutron‐capture 36Cl, but no excess of 41Ca. FRO 90001 experienced a complex exposure history with high shielding conditions in the first stage (150 < R < 300 cm) and much lower shielding in the second stage (R < 30 cm), the latter starting ~1.0 million years (Ma) ago. Based on the measured 10Be/21Ne and 26Al/21Ne ratios, the cosmic‐ray exposure ages of the two showers are 7.2 ± 0.5 Ma for FRO 90174 and 8 ± 1 Ma for FRO 90001. These ages coincide with the well‐established H‐chondrite peak and corroborate the observation that the exposure age distribution of FRO H‐chondrites is similar to that of non‐Antarctic falls. In addition, we found that corrections for neutron‐capture 36Ar (from decay of 36Cl) result in concordant 21Ne and 38Ar exposure ages. 相似文献