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271.
We have used photometric images of ten barred galaxies in the B and I bands to infer the geometrical and dynamical parameters of their bars: Their length, (R
bar), their strengths, (S
b), and their corotation radii, (R
CR).These parameters have been obtained studying azimuthal profiles from the B and I band images of the galaxies. We find that R
CR is in all cases slightly larger than R
bar, with mean values close to 1.2 R
bar. We have also found a dependence of the ratio R
CR/R
bar on S
bar.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
272.
273.
Excitation of electron cyclotron waves and whistlers by reflected auroral electrons which possess a loss-cone distribution is investigated. Based on a given magnetic field and density model, the instability problem is studied over a broad region along the auroral field lines. This region covers altitudes ranging from one quarter of an Earth radius to five Earth radii. It is found that the growth rate is significant only in the region of low altitude, say below the source region of the auroral kilometric radiation. In the high altitude region the instability is insignificant either because of low refractive indices or because of small loss cone angles. 相似文献
274.
G. M. Tovmasyan R. Kh. Oganesyan R. A. Epremyan S. E. Nersesyan M. A. Mkrtchyan Yu. M. Khodzhayants M. N. Krmoyan A. L. Kashin D. Huguenin S. I. Serova Yu. V. Romanenko A. P. Aleksandrov V. G. Titov M. Kh. Manarov 《Astrophysics》1990,32(1):1-5
Byurakan Astrophysical Observatory; SKB Granit; Geneva Observatory; Flight Control Center. Translated from Astrofizika, Vol. 32, No. 1, p. 5–13, January–February, 1990. 相似文献
275.
276.
O. Hernandez † C. Carignan P. Amram L. Chemin O. Daigle 《Monthly notices of the Royal Astronomical Society》2005,360(4):1201-1230
We present the Hα gas kinematics of 21 representative barred spiral galaxies belonging to the BHαBAR sample. The galaxies were observed with FaNTOmM, a Fabry–Perot integral-field spectrometer, on three different telescopes. The three-dimensional data cubes were processed through a robust pipeline with the aim of providing the most homogeneous and accurate data set possible useful for further analysis. The data cubes were spatially binned to a constant signal-to-noise ratio, typically around 7. Maps of the monochromatic Hα emission line and of the velocity field were generated and the kinematical parameters were derived for the whole sample using tilted-ring models. The photometrical and kinematical parameters (position angle of the major axis, inclination, systemic velocity and kinematical centre) are in relative good agreement, except perhaps for the later-type spirals. 相似文献
277.
O. V. Verkhodanov V. V. Sokolov M. L. Khabibullina S. V. Karpov 《Astrophysical Bulletin》2010,65(3):238-249
We analyze the randomness of the sky distribution of cosmic gamma-ray bursts. These events are associated with massive galaxies,
spiral or elliptical, and therefore their positions should trace the large-scale structure, which, in turn, could show up
in the sky distribution of fluctuations of the cosmicmicrowave background (CMB). We test this hypothesis by mosaic correlation
mapping of the distributions of CMB peaks and burst positions, find the distribution of these two signals to be correlated,
and interpret this correlation as a possible systematic effect. 相似文献
278.
Leitzinger M Odert P Kulikov YN Lammer H Wuchterl G Penz T Guarcello MG Micela G Khodachenko ML Weingrill J Hanslmeier A Biernat HK Schneider J 《Planetary and Space Science》2011,59(13):1472-1481
We present thermal mass loss calculations over evolutionary time scales for the investigation if the smallest transiting rocky exoplanets CoRoT-7b (∼1.68REarth) and Kepler-10b (∼1.416REarth) could be remnants of an initially more massive hydrogen-rich gas giant or a hot Neptune-class exoplanet. We apply a thermal mass loss formula which yields results that are comparable to hydrodynamic loss models. Our approach considers the effect of the Roche lobe, realistic heating efficiencies and a radius scaling law derived from observations of hot Jupiters. We study the influence of the mean planetary density on the thermal mass loss by placing hypothetical exoplanets with the characteristics of Jupiter, Saturn, Neptune, and Uranus to the orbital location of CoRoT-7b at 0.017 AU and Kepler-10b at 0.01684 AU and assuming that these planets orbit a K- or G-type host star. Our findings indicate that hydrogen-rich gas giants within the mass domain of Saturn or Jupiter cannot thermally lose such an amount of mass that CoRoT-7b and Kepler-10b would result in a rocky residue. Moreover, our calculations show that the present time mass of both rocky exoplanets can be neither a result of evaporation of a hydrogen envelope of a “Hot Neptune” nor a “Hot Uranus”-class object. Depending on the initial density and mass, these planets most likely were always rocky planets which could lose a thin hydrogen envelope, but not cores of thermally evaporated initially much more massive and larger objects. 相似文献
279.
280.
Abramova D. Yu. Philippov S. V. Abramova L. M. 《Izvestiya Atmospheric and Oceanic Physics》2021,57(9):1021-1028
Izvestiya, Atmospheric and Oceanic Physics - Geomagnetic data measured by the CHAMP satellite have been used to construct the spatial distribution of the lithospheric magnetic anomaly field in the... 相似文献