摘要:An international bimonthly journal, founded in 2001 as a continuation of Acta Astrophysica Sinica (founded in 1981, ISSN 0253-2379). The Chinese Journal of Astronomy and Astrophysics(ISSN 1009-9271) is published for the Chinese Astronomical Society and the National Astronomical Observatories of Chinese Academy of Sciences by the Science Press in Beijing.
摘要:We present the orbits of ten visual binary stars: WDS 01015+6922, WDS 01424– 0645, WDS 01461+6349, WDS 04374–0951, WDS 04478+5318, WDS 05255–0033, WDS 05491+6248, WDS 06404+4058, WDS 07479–1212, and WDS 18384+0850. We have also determined their masses, dynamical parallaxes and ephemerides.
摘要:Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) is one of the major on-going national large scientific projects in China.Active optics is a key technology for the LAMOST with which the thin-mirror active optics and segmented-mirror active optics are tied in. A pre-calibration method considering all active forces and displacements specially for LAMOST has been developed in early 2004. We give a detailed mathematical derivation and calculation including numerical simulation and computer program realization of the pre-calibration method of LAMOST open-loop control for the third-order aspherical aberration. We have also carried out calculations on the application of the pre-calibration method and the parameters of actuator design in LAMOST active optics in observation mode, including estimations of the actuator ranges,the interval of active optics correction and the ranges and trends of load changes on all the actuators during LAMOST tracking a given star.
摘要:A Gamma-ray burst (GRB) is generally believed to be a jet with a small opening angle, this opening angle is usually derived with the afterglow light curve break time using an analytical method. Here we show that the method is not accurate. Using the set of equations of hydrodynamic evolution with the sideways expansion at the local sound speed derived by previous authors and the observed light curve break times, we numerically derive the initial opening angles. Then the collimation-corrected energies (Eγ) for a sample of GRBs are calculated. They are found to show a wide spread, suggesting that the previously declared clustering by some authors may not exist. Also, the Epeak -Eγ relation, claimed by some other authors (Epeak is the spectral peak energy), is found still to hold, with a slightly stronger correlation.
摘要:We present a quantitative estimate of the relativistic corrections to the thermal SZ power spectrum produced by the energetic electrons in massive clusters. The corrections are well within 10% for current experiments with working frequencies below v < 100 GHz, but become non-negligible at high frequencies v >350 GHz. Moreover, the corrections appear to be slightly smaller at higher e or smaller angular scales. We conclude that there is no need to include the relativistic corrections in the theoretical study of the SZ power spectrum especially at low frequencies unless the SZ power spectrum is used for precision cosmology.
摘要:We report the discovery of five Narrow-Line Seyfert 1 galaxies (NLS1s)identified from the ROSAT All-Sky Survey bright sources. One of them has a quasarlike luminosity and two, including the quasar-like one, have close companions and/or show interacting features. We calculate the central black hole masses and Eddington ratios for the five NLSls. In combination with the objects of Kaspi et al., we find that NLSls have smaller central black hole masses and higher accretion rate than normal Seyfert 1s.
摘要:New methanol maser lines at 72 → 63A-(86.6GHz) and 72 → 63A+(86.9GHz) together with two candidate methanol maser lines at 72 → 81A-(80.99GHz) and 72 → 81A+(111.29GHz) have been detected in W3(OH). We use a pumping mechanism,i.e.,methanol masers without population inversion,to explain the formation of weak methanol masers of 72 → 81A+ and 72 → 81A-. We explain well why the line-shape of the transition 72 → 81A+ is not typical. A similar argument can be applied to the Λ-type level system 72A-,63A-and 81A-,as well as to the 72 → 81A-80.99GHz masers.
摘要:We report on time-resolved spectroscopic observations of the SU Ursae Majorisdwarf nova, YZ Cnc for over 11 h on two nights during its 2002 January superoutburst. The spectra on the first day only showed absorption-line profiles, while on the second day the lines showed 'W' profiles with blue and red troughs.The radial velocity curve of the absorption troughs and emission peaks of Hβ has an amplitude of 49 ± 10 km s-1 and a phase offset of -0.07 ± 0.04, which are very similar to those measured in quiescence. However, the γ velocity deviates strongly from the systemic velocity measured in quiescence, by some ±60 km s-1.Large shifts of ~70 km s-1 in the orbital-averaged velocity and ~0.09 in the phase are also found in our observations. All these features can be well explained by a precessing, eccentric disk.
摘要:A brief description of the NAO coude echelle spectrograph mounted on the 2.16 m telescope at Xinglong station is given. This echelle spectrograph is located at the coudé focus with a prism cross disperser. The echelle image covers the spectral region from 330 to 1100 nm displayed in 80 spectral orders in one exposure through two light beams. With a slit height of 2mm, spectral orders are separated by 15 to 23 pixels in blue region and by 7 to 19 pixels in red region. Alternatively, two additional resolution modes corresponding to different focal length cameras with resolving power R 16000, 170 000 in the blue beam and R = 13000, 170 000 in the red beam could be provided by this spectrograph. The bias, dark, wavelength calibration, flat field and science exposure are described in details. The limiting magnitude for 1 hour exposure with an S/N ratio of 100 scales to V = 9.5 in the red path and to V = 7.2 in the blue path.
摘要:We present UB Visurface photometry over a 20.5'× 20.5' area of the latetype spiral galaxy NGC 300.We have derived isophotal maps,surface brightness profiles,ellipticity profiles,position angle profiles,and color profiles.By merging ourI-band measurements with those of Boker et al.Based on Hubble Space Telescope observations,we have obtained combinedI-band surface brightness profiles for the region 0.02″< r < 500″ and have decomposed the profiles into three components:a nucleus,a bulge,and an exponential disk.
摘要:The role of T50 in classifying gamma-ray bursts(GRBs)is investigated.We take T50 = 0.Ts as the line of division and find that some bursts belonging to the class of long bursts defined by T90 ≥ 2s now become short bursts(sample 1),while some belonging to the class of short bursts defined by T90 < 2 s now become long bursts(sample 2).We study how these sources are affected by the two methods of classification and find the change of classes of sample 1 is due to some peculiar properties of the light curves.Based on their characters,most of the bursts of sample 1 should be taken as short bursts.
摘要:We compile a sample of 11 Fanaroff-Riley type I Radio Galaxies(FR-I RGs)with multi-wavelength observations to address the dynamic behavior of jets in these objects.Optical images acquired by the Hubble Space Telescope(HST)are carefully analyzed.The method and reduction procedure are described in detail. Unresolved optical cores emerge after having properly removed starlight from the host galaxies in eight of the FR-I RGs,of which five are new identifications.Broad band spectral properties of these newly identified compact cores are compared with that previously found in FR-I RGs,as well as the low-energy-peaked BL Lac objects. The similarity between them argues for the same non-thermal synchrotron origin. Well-resolved optical jets with knotty morphologies are found in three FR-I RGs in our sample,namely 3C 15,3C 66B and B20755+37.The optical counterparts to the inner radio/X-ray jets are identified and a clear one-to-one correspondence between the optical,radio and X-ray knots is found.The structure and information on the optical jets are discussed.Physical parameters such as the knots position,flux and size are also presented.Detailed comparison between the multi-wavelength data and radiative and dynamic models of jet will be made in a forthcoming paper.
摘要:Convincing evidence for a past interaction between the two rich clusters A399 and A401 was recently found in the X-ray imaging observations. We examine the structure and dynamics of this pair of galaxy clusters. A mixture-modeling algorithm was applied to obtain a robust partition into two clusters, which allowed us to discuss the virial mass and velocity distribution of each cluster. Assuming that these two clusters follow a linear orbit and they have once experienced a close encounter, we model the binary cluster as a two-body system. As a result, four gravitationally bound solutions are obtained. The recent X-ray observations seem to favor a scenario in which the two clusters with a true separation of 5.4h-1 Mpc are currently expanding at 583 km s-1along a direction with a projection angle of 67.5°, and they will reach a maximum extent of 5.65 h-1 Mpc in about 1.0 h-1 Gyr.