Chemical Evolution of Blue Compact Galaxies

Based on a sample of 72 Blue Compact Galaxies (BCGs) observed with the 2.16m telescope of the National Astronomical Observatories, Chinese Academy of Sciences (NAOC) and about 4000 strong emission line galaxies from the Sloan Digital Sky Survey, we analyzed their chemical evolution history using the revised chemical evolution model of Larsen et al. Our sample covers a much larger metallicity range (7.2 < 12 log(O/H) < 9.0). We found that, in order to reproduce the observed abundance pattern and gas fraction over the whole metallicity range, a relatively continuous star formation history is needed for high metallicity galaxies, while assuming a series of instantaneous bursts with long quiescent periods (some Gyrs) for low metallicity galaxies. Model calculations also show that only the closed-box model is capable of reproducing the observational data over the whole metallicity range. Models that consider the ordinary winds and/or inflow can only fit the observations in the low metallicity range, and a model with enriched wind cannot fit the data in the whole metallicity range. This implies that the current adopted simple wind and inflow models are not applicable to massive galaxies, where the underlying physics of galactic winds or inflow could be more complicated.     

一米望远镜低色散光谱仪试验

本文介绍了云南天文台一米望远镜附属的一台低色散光谱仪实验装置,介绍了该装置的设计原理、系统结构参数及试观测情况,并讨论了存在的问题和解决问题的设想。我们已用该装置观测到19m左右的具有大红移的类星体光谱。该类低色散光谱仪,将为我国星系研究工作者提供实测条件。     

Soft X—ray Properties of Ultraluminous IRAS Galaxies

We report on the results of cross-correlation of a sample of 903 Utraluminous IRAS galaxies (ULIRGs) with the ROSAT-All Sky Survey Bright Source Catalogue and the ROSAT archived pointing observations. The sample of ULIRGs has been compiled from the recently released PSCz redshift survey. In total,35 ULIRGs are securely detected by the ROSAT All-Sky Survey and pointing observations, five of which are blazars. The statistical properties of these sources in the soft X-ray band are determined and compared with their properties on other wavebands. We find that the ratio of the soft X-ray to the far-infrared flux spans about five orders of magnitude and reaches values of about unity. This ratio is a good indicator of the main energy source of ULIRGs. Those with soft X-ray to far-infrared flux exceeding 0.01 are probably powered by accretion onto central supermassive black holes while those with ratios smaller than 0.001 are probably powered by starbursts or other heating processes, or are Compton thick sources. Some ULIRGs have energy contributions from both. This ratio is low for most ULIRGs and hyperluminous infrared galaxies, which explains their low detection rate by ROSAT and ASCA.We also find that some ULIRGs have a similar soft X-ray luminosity vs. temperature relation to that for groups of galaxies and elliptical galaxies,suggesting a common origin of these systems. Our study also reveals a tight correlation between the hardness ratio and the soft X-ray luminosity for Seyfert 1s/QSOs.     

The irregular variable KU Her: The light and period variations

We present CCD photometric observations of the slow irregular type variable KU Her. We have also used observations from the ASAS Database and the AAVSO International Database. The V-band observations span eight years from August of 2002 to September of 2010. The length and density of the data enable us to look for variations on time scales ranging from days to years. The V-band observations of KU Her are analysed to derive periodicity. This analysis was an approach to find the fundamental periods of the variability of KU Her. Analysis of the KU Her light variation indicates a complex combination of different periods. Five main and three harmonic periods are identified. In addition to the period analysis, we present the colour variations of the star.     

A CCD OBSERVATIONAL METHOD TO DETERMINE PRECISELY THE BARYCENTRICPOSITIONS OF THE OUTER PLANETS(SATURN-NEPTUNE)

This paper presents a new method to determine precisely the barycentric positions of the outer planets(Saturn - Neptune)by optical observations. It requires the CCD observations from a long focal distance telescope which is used to observe a planet and its satellites and ones from a meridian circle when it works in a CCD drift scanning manner. The key part of the method is tested by the observations with 1 meter telescope of Yunnan Observatory. The result shows that the new method is feasible to carry out.     

The Historical Re-Brightening and Distance Recheck of SN 1006

We presume the re-brightening of SN 1006 in AD 1016 as recorded in the ancient Chinese literature to be true and the re-brightening was caused by the encounter either of photons or the shock wave from the SN outburst with the circumstellar thin envelope mate- rials. Based on these considerations, and combining the observational results on the optical proper motion of the N-W limb and the radio observations of the other parts of the supernova remnant G327.6 14.5, we re-determine the distance to SN 1006. For the photon-encounter model, the average radius of the envelope material would be 10ly; and for the shock wave- encounter model, the radius would be about 1 ly. We then set up four equations to solve for the distance of the SN, the initial shock speed, the expansion index for two different parts of the supernova remnant, and the real original radius of the thin envelope nebula. It is indicated that only the case of photon-encounter will lead to a reasonable result. We derived a distance of 5074ly (1.56kpc), an original shock expansion velocity of 0.071c, an expansion index of 0.72 for the N-W limb of the SNR, and 0.76 for the other parts . We deem that the SNR evolution is still in the stage of reverse shock.     

Mode identification from time-resolved spectroscopy of the pulsating white dwarf G29‐38

We have used time-resolved spectroscopy to measure the colour dependence of pulsation amplitudes in the DAV white dwarf G29-38. Model atmospheres predict that mode amplitudes should change with wavelength in a manner that depends on the spherical harmonic degree ℓ of the mode. This dependence arises from the convolution of mode geometry with wavelength-dependent limb darkening. Our analysis of the six largest normal modes detected in Keck observations of G29-38 reveals one mode with a colour dependence different from the other five, permitting us to identify the ℓ-value of all six modes and to test the model predictions. The Keck observations also show pulsation amplitudes that are unexpectedly asymmetric within absorption lines. We show that these asymmetries arise from surface motions associated with the non-radial pulsations (which are discussed in detail in a companion paper). By incorporating surface velocity fields into line profile calculations, we are able to produce models that more closely resemble the observations.     

2005年上海天文台卫星激光测距观测报告

介绍了2005年上海天文台卫星激光测距观测站搬迁、联调工作和激光观测的概况。     

Milestones in the Observations of Cosmic Magnetic Fields

Magnetic fields are observed everywhere in the universe. In this review, we concentrate on the observational aspects of the magnetic fields of Galactic and extragalactic objects. Readers can follow the milestones in the observations of cosmic magnetic fields obtained from the most important tracers of magnetic fields, namely, the star-light polarization, the Zeeman effect, the rotation measures (RMs, hereafter) of extragalactic radio sources, the pulsar RMs, radio polarization observations, as well as the newly implemented sub-mm and mm polarization capabilities. The magnetic field of the Galaxy was first discovered in 1949 by optical polarization observations. The local magnetic fields within one or two kpc have been well delineated by starlight polarization data. The polarization observations of diffuse Galactic radio background emission in 1962 confirmed unequivocally the existence of a Galactic magnetic field. The bulk of the present information about the magnetic fields in the Galaxy comes from anal     

Solar Impulsive Hard X-Ray Emission and Two-Stage Electron Acceleration

Heating and acceleration of electrons in solar impulsive hard X-ray (HXR) flares are studied according to the two-stage acceleration model developed by Zhang for solar 3He-rich events. It is shown that electrostatic H-cyclotron waves can be excited at a parallel phase velocity less than about the electron thermal velocity and thus can significantly heat the electrons (up to 40 MK) through Landau resonance. The preheated electrons with velocities above a threshold are further accelerated to high energies in the flare-acceleration process. The flare-produced electron spectrum is obtained and shown to be thermal at low energies and power law at high energies. In the non-thermal energy range, the spectrum can be double power law if the spectral power index is energy dependent or related. The electron energy spectrum obtained by this study agrees quantitatively with the result derived from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) HXR observations in the flare of 2002 July 23. The total flux and energy flux of electrons accelerated in the solar flare also agree with the measurements.     

On the Evolution of the Apparent Size of Gamma-Ray Burst Remnants

The remnants of two gamma-ray bursts, GRB 030329 and GRB 041227, have been resolved by Very Long Baseline Interferometry observations. The radio counterparts were observed to expand with time. These observations provide an important way to test the dynamics of the standard fireball model. We show that the observed size evolution of these two events cannot be explained by a simple jet model, rather, it can be satisfactorily explained by the two-component jet model. It strongly hints that gamma-ray burst ejecta may have complicated structures.     

GPS无线电掩星数据处理系统

GPS无线电掩星技术能提供高精度、高分辨率、全球覆盖的地球电离层和中性层大气剖面。它具有全天候、低费用、无系统长期漂移等优点。从1995年4月至1997年3月,首次GPS／MET试验的成功显示了GPS掩星技术对监测全球大气能够发挥重要的作用,从而成为当前空间探测技术的研究热点之一。该文主要叙述了无线电掩星技术的数据处理系统的有关情况,并介绍了美国UCAR的掩星数据处理系统CDAAC的概况,可作为我国开展无线电掩星计划有关工作的借鉴。     

Historical Evidence for the Birth of the Newly Discovered Pulsar PSR J1833-1034

Stimulated by the recent discovery of PSR J1833-1034 in SNR G21.5-0.9 and its age parameters presented by two groups of discovery, we demonstrate that the PSR J1833-1034 was born 2053 years ago from a supernova explosion, the BC 48 guest star observed in the Western Han (Early Han) Dynasty by ancient Chinese. Based on a detailed analysis of the Chinese ancient record of the BC 48 guest star and the new detected physical parameters of PSR J1833-1034, agreements on the visual position, age and distance between PSR J1833-1034 and the BC 48 guest star are obtained. The initial period P0 of PSR J1833-1034 is now derived from its historical and current observed data without any other extra assumption on P0 itself, except that the factor PP is a constant in its evolution until now.     

CCD联合平差方法及其初步实例检验

在常规照相天体测量工作中 ,对暗天体的定位是采用逐级定标星过渡的方法实现的。由于星表系统差和局部差的存在 ,最终定位结果可能包含难以把握的误差积累。在CCD小视场观测情况下时常难以找到足够数量的定标星。鉴于此 ,推导了CCD观测联合平差方法的严格矢量表达式 ,以期通过共同星的过渡 ,实现大天区统一平差。原理上此方法可实现相对于河外天体的定位 ,以削弱星表系统差和局部差对定位结果的影响。讨论了CCD联合平差方法实现中的问题 ,包括底片常数模型选择、切点位置改正、共同星的较差改正和法方程解算方法等 ,并分析了具体的处理措施。用实例初步检验了CCD联合平差方法的效果 ,表明通过对多张CCD观测的联合平差 ,可以削弱单张CCD观测参考星数目过少、单张CCD观测参考星分布不均、个别参考星存在位置偏差和局部区域参考星存在系统性位置偏差等不利因素对归算结果的影响 ,进而达到扩大视场和提高归算精度的目的     

Photoelectric photometry of eclipsing binary V375 cassiopeiae

Some 604 photoelectric BV observations of the eclipsing binary V375 Cas were obtained at Beijing Observatory from August to November 1982. Photometric solution was carried out using the Wilson-Devinney program for the BV light curves. The system is found to be a semidetached binary in which the less massive component fills its Roche lobe and the more massive component nearly does so. It is very similar to RZ Dra. This very interesting system is important for the understanding of the evolution of close binaries.     

Distribution of Helical Properties of Solar Magnetic Fields

We summarize studies of helical properties of solar magnetic fields such as current helicity and twist of magnetic fields in solar active regions (ARs), that are observational tracers of the alpha-effect in the solar convective zone (SCZ). Information on their spatial distribution is obtained by analysis of systematic mag-netographic observations of active regions taken at Huairou Solar Observing Station of National Astronomical Observatories of Chinese Academy of Sciences. The main property is that the tracers of the alpha-effect are antisymmetric about the solar equator. Identifying longitudinal migration of active regions with their individual rotation rates and taking into account the internal differential rotation law within the SCZ known from helioseismology, we deduce the distribution of the effect over depth. We have found evidence that the alpha-effect changes its value and sign near the bottom of the SCZ, and this is in accord with the theoretical studies and numerical simulations. We discuss     

Molecular Gas Distribution around the Supernova Remnant G40.5-0.5

The distribution of dense molecular gas around the supernova remnant G40.5-0.5 has been investigated by radio spectroscopic observations in the CO (J = 1-0) transition. The molecular gas is found to extend over the entire region of G40.5-0.5. A molecular shell, with a diameter of - 26', coincides with the ionized gas as revealed by the cm-radio observations. This coincidence, along with the velocity discontinuity following the shell, provides direct evidence for interaction between the ionized gas and the dense molecular gas. No clear evidence for cosmic-ray acceleration can be identified from this SNR as previously suggested, due to positional uncertainty in relating the SNR shell defined by CO to the EGRET gamma-ray sources, GRO J1904 06, from the gamma-ray observations.     

Measuring the Fundamental Parameters of Hot Hydrogen－Rich White Dwarfs

This review considers the observations of hot, hydrogen-rich white dwarf stars, with particular reference to measurements of temperature, surface gravity and composition. Spectroscopic data from a variety of wavelength ranges are required for this work and, in particular, the important contributions from optical, ultraviolet and extreme ultraviolet studies are discussed. Using the values of Tefr and log g determined for an individual white dwarf, estimates of mass and radius might be derived from the theoretical mass-radius relation. The issue of the accuracy of the theoretical mass-radius calculations and the prospects for making empirical tests using observational data are outlined.     

Measuring the Fundamental Parameters of Hot Hydrogen- Rich White Dwarfs

This review considers the observations of hot, hydrogen-rich white dwarf stars, with particular reference to measurements of temperature, surface gravity and composition. Spectroscopic data from a variety of wavelength ranges are required for this work and, in particular, the important contributions from optical, ultraviolet and extreme ultraviolet studies are discussed. Using the values of Teff and log g determined for an individual white dwarf, estimates of mass and radius might be derived from the theoretical mass-radius relation. The issue of the accuracy of the theoretical mass-radius calculations and the prospects for making empirical tests using observational data are outlined.