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971.
Preliminary data are presented on seven “special” objects found in low-dispersion spectral plates of the FBS survey. The first
object, FBS 0250+167, is found to be a class M7 dwarf with a high proper motion (∼5.130 arcsec/year) lying about 3 pc from
the sun. Three of the objects, with spectra of classes M8–M9, are suspected of being long-period Mirids with large mass losses
and surrounded by dense clouds. The three remaining objects have very short low-dispersion spectra on the FBS survey plates
(clearly they are non stellar objects) and are of interest for later detailed study.
__________
Translated from Astrofizika, Vol. 50, No. 1, pp. 73–85 (February 2007). 相似文献
972.
Jun-Fang Zhu Xin Wu Da-Zhu Ma 《中国天文和天体物理学报》2007,7(4):601-610
Newtonian core-shell systems, as limiting cases of relativistic core-shell models under the two conditions of weak field and slow motion, could account for massive circumstellar dust shells and rings around certain types of star remnants. Because this kind of systems have Hamiltonians that can be split into a main part and a small perturbing part, a good choice of the numerical tool is the pseudo 8th order symplectic integrator of Laskar & Robutel, and, to match the symplectic calculations, a good choice of chaos indicator is the fast Lyapunov indicator (FLI) with two nearby trajectories proposed by Wu, Huang & Zhang. Numerical results show that the FLI is very powerful when describing not only the transition from regular motion to chaos but also the global structure of the phase space of the system. 相似文献
973.
974.
975.
976.
S. A. Sim D. N. Sauer F. K. Röpke W. Hillebrandt 《Monthly notices of the Royal Astronomical Society》2007,378(1):2-12
We compare observations of the high-redshift galaxy population to the predictions of the galaxy formation model of Croton et al. and De Lucia & Blaizot. This model, implemented on the Millennium Simulation of the concordance Lambda cold dark matter cosmogony, introduces 'radio mode' feedback from the central galaxies of groups and clusters in order to obtain quantitative agreement with the luminosity, colour, morphology and clustering properties of the present-day galaxy population. Here we construct deep light cone surveys in order to compare model predictions to the observed counts and redshift distributions of distant galaxies, as well as to their inferred luminosity and mass functions out to redshift 5. With the exception of the mass functions, all these properties are sensitive to modelling of dust obscuration. A simple but plausible treatment agrees moderately well with most of the data. The predicted abundance of relatively massive (∼ M * ) galaxies appears systematically high at high redshift, suggesting that such galaxies assemble earlier in this model than in the real Universe. An independent galaxy formation model implemented on the same simulation matches the observed mass functions slightly better, so the discrepancy probably reflects incomplete or inaccurate galaxy formation physics rather than problems with the underlying cosmogony. 相似文献
977.
978.
Wynn C. G. Ho 《Monthly notices of the Royal Astronomical Society》2007,380(1):71-77
RX J1856.5−3754 is one of the brightest, nearby isolated neutron stars (NSs), and considerable observational resources have been devoted to its study. In previous work, we found that our latest models of a magnetic, hydrogen atmosphere match well the entire spectrum, from X-rays to optical (with best-fitting NS radius R ≈ 14 km, gravitational redshift z g ∼ 0.2 , and magnetic field B ≈ 4 × 1012 G). A remaining puzzle is the non-detection of rotational modulation of the X-ray emission, despite extensive searches. The situation changed recently with XMM–Newton observations that uncovered 7-s pulsations at the level. By comparing the predictions of our model (which includes simple dipolar-like surface distributions of magnetic field and temperature) with the observed brightness variations, we are able to constrain the geometry of RX J1856.5−3754, with one angle <6° and the other angle , though the solutions are not definitive, given the observational and model uncertainties. These angles indicate a close alignment between the rotation and the magnetic axes or between the rotation axis and the observer. We discuss our results in the context of RX J1856.5−3754 being a normal radio pulsar and a candidate for observation by future X-ray polarization missions such as Constellation-X or XEUS . 相似文献
979.
980.
Rosemary A. Mardling 《Monthly notices of the Royal Astronomical Society》2007,382(4):1768-1790