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Are type Ia supernovae reliable distance indicators Ia型超新星是可靠的距离指示器吗
Chinese Journal of Astronomy and Astrophysics Pub Date : 2007-10-01 DOI: 10.1088/1009-9271/7/5/05
L. Lü, Y. Qin, Fu-Wen Zhang
{"title":"Are type Ia supernovae reliable distance indicators","authors":"L. Lü, Y. Qin, Fu-Wen Zhang","doi":"10.1088/1009-9271/7/5/05","DOIUrl":"https://doi.org/10.1088/1009-9271/7/5/05","url":null,"abstract":"Recent applications of type Ia supernovae (SNe Ia) in cosmology have successfully revealed the accelerating expansion of the universe. However, as distance indicators used in measuring the expansion history of the universe and probing the nature of dark energy, these objects must pass more strict tests. We propose a K-S test to investigate if there exists any systematic bias when deriving the luminosity distances under the standard candle assumption. Two samples, one comprising 71 high-redshift SNe Ia and the other, 44 nearby ones, are used in our investigation. We find that it is likely there exists a bias in the adopted samples, which is probably caused by a systematic error, e.g. in the color parameter used in the luminosity calibration and a bias may be caused by the SN evolution or by varying properties of the dust surrounding the SNe Ia.","PeriodicalId":124495,"journal":{"name":"Chinese Journal of Astronomy and Astrophysics","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115337877","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
A Statistical Study of Rapid Sunspot Structure Change Associated with Flares 与耀斑相关的太阳黑子结构快速变化的统计研究
Chinese Journal of Astronomy and Astrophysics Pub Date : 2007-10-01 DOI: 10.1088/1009-9271/7/5/14
Wei-Zhong Chen, Chang Liu, Hui Song, N. Deng, Changyi Tan, Haimin Wang
{"title":"A Statistical Study of Rapid Sunspot Structure Change Associated with Flares","authors":"Wei-Zhong Chen, Chang Liu, Hui Song, N. Deng, Changyi Tan, Haimin Wang","doi":"10.1088/1009-9271/7/5/14","DOIUrl":"https://doi.org/10.1088/1009-9271/7/5/14","url":null,"abstract":"We reported recently some rapid changes of sunspot structure in white-light (WL) associated with major flares. We extend the study to smaller events and present here results of a statistical study of this phenomenon. In total, we investigate 403 events from 1998 May 9 to 2004 July 17, including 40 X-class, 174 M-class, and 189 C-class flares. By monitoring the structure of the flaring active regions using the WL observations from the Transition Region and Coronal Explorer (TRACE), we find that segments in the outer sunspot structure decayed rapidly right after many flares; and that, on the other hand, the central part of sunspots near the flare-associated magnetic neutral line became darkened. These rapid and permanent changes are evidenced in the time profiles of WL mean intensity and are not likely resulted from the flare emissions. Our study further shows that the outer sunspot structure decay as well as the central structure darkening are more likely to be detected in larger solar flares. For X-class flares, over 40% events show distinct sunspot structure change. For M- and C-class flares, this percentage drops to 17% and 10%, respectively. The results of this statistical study support our previously proposed reconnection picture, i.e., the flare-related magnetic fields evolve from a highly inclined to a more vertical configuration.","PeriodicalId":124495,"journal":{"name":"Chinese Journal of Astronomy and Astrophysics","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129081353","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 25
Stellar and HI Mass Functions Predicted by a Simple Preheating Galaxy Formation Model 用简单的预热星系形成模型预测恒星和HI质量函数
Chinese Journal of Astronomy and Astrophysics Pub Date : 2007-08-20 DOI: 10.1088/1009-9271/7/4/16
Zhijian Luo, C. Shu
{"title":"Stellar and HI Mass Functions Predicted by a Simple Preheating Galaxy Formation Model","authors":"Zhijian Luo, C. Shu","doi":"10.1088/1009-9271/7/4/16","DOIUrl":"https://doi.org/10.1088/1009-9271/7/4/16","url":null,"abstract":"According to the new preheating mechanism of galaxy formation suggested by Mo et al., we construct a simple model of formation of disk galaxies within the current paradigm of galaxy formation. It incorporates preheating, gas cooling, bulge formation and star formation. The predicted stellar and HI mass functions of galaxies are discussed and compared with the observations. It is found that our model can roughly match both the observed galaxy luminosity function and the observed HI-mass function.","PeriodicalId":124495,"journal":{"name":"Chinese Journal of Astronomy and Astrophysics","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116430459","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Rotation Periods of Nine ROSAT Selected Solar-Type Stars 九颗ROSAT选定的太阳型恒星的自转周期
Chinese Journal of Astronomy and Astrophysics Pub Date : 2007-08-20 DOI: 10.1088/1009-9271/7/4/11
L. Xing, Shuang-Yi Zhao, W. Su, Yan Shen, X. Zhang, Jianyan Wei
{"title":"Rotation Periods of Nine ROSAT Selected Solar-Type Stars","authors":"L. Xing, Shuang-Yi Zhao, W. Su, Yan Shen, X. Zhang, Jianyan Wei","doi":"10.1088/1009-9271/7/4/11","DOIUrl":"https://doi.org/10.1088/1009-9271/7/4/11","url":null,"abstract":"We monitored 16 X-ray selected young solar-type stars for light variation and found appreciable periodic light variability with amplitudes of a few hundredths of a magnitude in nine of the objects. Using the method of Phase Dispersion Minimization (PDM) and Fourier analysis (software PERIOD04), the rotation periods of these stars were determined from the photometric data. The rotation periods of all nine stars are shorter than about 3 days. It is suggested that, as with the Pleiades cluster, small amplitude light variations are quite common among young solar-type stars with rotation periods around 3 days or less. This gives further evidence for the spin up of solar-type stars predicted by models of angular momentum evolution of pre-main sequence stars.","PeriodicalId":124495,"journal":{"name":"Chinese Journal of Astronomy and Astrophysics","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116368295","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 4
Are Homologous Radio Bursts Driven by Solar Post-Flare Loops? 同源射电暴是由太阳耀斑后环驱动的吗?
Chinese Journal of Astronomy and Astrophysics Pub Date : 2007-08-01 DOI: 10.1088/1009-9271/7/4/02
Min Wang, R. Xie, Yihua Yan, Yu-ying Liu
{"title":"Are Homologous Radio Bursts Driven by Solar Post-Flare Loops?","authors":"Min Wang, R. Xie, Yihua Yan, Yu-ying Liu","doi":"10.1088/1009-9271/7/4/02","DOIUrl":"https://doi.org/10.1088/1009-9271/7/4/02","url":null,"abstract":"Three particularly complex radio bursts (2001 October 19, 2001 April 10 and 2003 October 26) obtained with the spectrometers (0.65-7.6GHz) at the National Astronomical Observatories, Chinese Academy of Sciences (NAOC, Beijing and Yunnan) and other instruments (NoRH, TRACE and SXT) are presented. They each have two groups of peaks occurring in different frequency ranges (broad-band microwave and narrow-band decimeter wavelengths). We stress that the second group of burst peaks that occurred in the late phase of the flares and associated with post-flare loops may be homologous radio bursts. We think that they are driven by the post-flare loops. In contrast to the time profiles of the radio bursts and the images of coronal magnetic polarities, we are able to find that the three events are caused by the active regions including main single-bipole magnetic structures, which are associated with multipole magnetic structures during the flare evolutions. In particular, we point out that the later decimetric radio bursts are possibly the radio counterparts of the homologous flares (called \"homologous radio bursts\" by us), which are also driven by the single-bipole magnetic structures. By examining the evolutions of the magnetic polarities of sources (17 GHz), we could presume that the drivers of the homologous radio bursts are new and/or recurring appearances/disappearances of the magnetic polarities of radio sources, and that the triggers are the magnetic reconnections of single-bipole configurations.","PeriodicalId":124495,"journal":{"name":"Chinese Journal of Astronomy and Astrophysics","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130846856","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
A New Feature Vector Using Selected Line Spectra for Pulsar Signal Bispectrum Characteristic Analysis and Recognition 基于选择谱线的脉冲星信号双谱特征分析与识别新方法
Chinese Journal of Astronomy and Astrophysics Pub Date : 2007-08-01 DOI: 10.1088/1009-9271/7/4/13
Zhen-hua Xie, Lu-ping Xu, Guang-ren Ni, Yan Wang
{"title":"A New Feature Vector Using Selected Line Spectra for Pulsar Signal Bispectrum Characteristic Analysis and Recognition","authors":"Zhen-hua Xie, Lu-ping Xu, Guang-ren Ni, Yan Wang","doi":"10.1088/1009-9271/7/4/13","DOIUrl":"https://doi.org/10.1088/1009-9271/7/4/13","url":null,"abstract":"Average pulse profiles of pulsar signals are analyzed using the bispectrum technique. The result shows that there are nonlinear phase couplings between the two frequency axes of the bispectrum charts, which indicate nonlinear factors in the generation and propagation of pulsar signals. Bispectra can be used as feature vectors of pulsar signals because of their being translation invariant. A one-dimension selected line spectrum algorithm for extracting pulsar signal characteristic is proposed. Compared with selected bispectra, the proposed selected line spectra have the maximum interclass separability measurements from the point of view of the whole one-dimension feature vector. Recognition experiments on several pulsar signals received at several frequency bands are carried out. The result shows that the selected line spectrum algorithm is suitable for extracting pulsar signal characteristics and has a good classification performance.","PeriodicalId":124495,"journal":{"name":"Chinese Journal of Astronomy and Astrophysics","volume":"129 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122309183","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 5
A Survey of Newtonian Core-Shell Systems with Pseudo High Order Symplectic Integrator and Fast Lyapunov Indicator 具有伪高阶辛积分器和快速Lyapunov指标的牛顿核壳系统研究
Chinese Journal of Astronomy and Astrophysics Pub Date : 2007-08-01 DOI: 10.1088/1009-9271/7/4/18
Jun-Fang Zhu, Xin Wu, D. Ma
{"title":"A Survey of Newtonian Core-Shell Systems with Pseudo High Order Symplectic Integrator and Fast Lyapunov Indicator","authors":"Jun-Fang Zhu, Xin Wu, D. Ma","doi":"10.1088/1009-9271/7/4/18","DOIUrl":"https://doi.org/10.1088/1009-9271/7/4/18","url":null,"abstract":"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.","PeriodicalId":124495,"journal":{"name":"Chinese Journal of Astronomy and Astrophysics","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131115267","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 2
X-Ray Afterglows of GRBs 050318 and 060124 and their External Shock Origin GRBs 050318和060124的x射线余辉及其外部激波来源
Chinese Journal of Astronomy and Astrophysics Pub Date : 2007-08-01 DOI: 10.1088/1009-9271/7/4/07
Jin Zhang, Y. Qin, Fu-Wen Zhang, Bin-Bin Zhang
{"title":"X-Ray Afterglows of GRBs 050318 and 060124 and their External Shock Origin","authors":"Jin Zhang, Y. Qin, Fu-Wen Zhang, Bin-Bin Zhang","doi":"10.1088/1009-9271/7/4/07","DOIUrl":"https://doi.org/10.1088/1009-9271/7/4/07","url":null,"abstract":"The observations with Swift X-ray telescope (XRT) challenge the conventional gamma-ray burst model in many aspects. The XRT light curves are generally composed of four consecutive segments, i.e., a steep decay segment, a shallow decay segment, a normal decay segment, a jet-like steep decay segment, and sometimes erratic flares as well. The physical origin of the X-ray emission is highly debatable. We focus here on the physical origin of the X-ray emissions of GRBs 050318 and 060124. We present the XRT light curves and spectra of the two bursts. The light curve decay slopes of the two bursts are normal, and their relations to the spectral indices are consistent with the prediction of the standard forward shock model. The multi-wavelength light curves at 0.5 keV, 1.0 keV, 2.0 keV and 4.0 keV can be reproduced by this model with an isotropic kinetic energy E-k = 2.2 x 10(52) erg, epsilon(e) = 0.04, epsilon(B) = 0.01 for GRB 050318 and E-k = 4.2 x 10(53) erg, epsilon(e) = 0.05, epsilon(B) = 0.01 for GRB 060124. These facts suggest that the normal decay phases of the X-rays for the two bursts are of the forward shock origin.","PeriodicalId":124495,"journal":{"name":"Chinese Journal of Astronomy and Astrophysics","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125212419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
A Statistical Analysis of Radio Pulsar Timing Noise 射电脉冲星定时噪声的统计分析
Chinese Journal of Astronomy and Astrophysics Pub Date : 2007-08-01 DOI: 10.1088/1009-9271/7/4/08
A. Chukwude
{"title":"A Statistical Analysis of Radio Pulsar Timing Noise","authors":"A. Chukwude","doi":"10.1088/1009-9271/7/4/08","DOIUrl":"https://doi.org/10.1088/1009-9271/7/4/08","url":null,"abstract":"We present an analysis of the timing observations on 27 radio pulsars, collected at Hartebeesthoek Radio Astronomy Observatory (HartRAO), with time spans ranging between ~ 9 and 14 yr. Our results show that the measured pulsar frequency second derivatives are non-stationary. Both the magnitude and the sign of the values depend upon the choice of epoch and data span. A simple statistical analysis of the observed second time derivative of the pulse frequency (obs) of a large sample of 391 (25 HartRAO and 366 Jodrell Bank Observatory) pulsars reveals that is only marginally correlated with both the pulsar spin-down rate () and the characteristic age (τc). We find correlation coefficients of ~ 0.20 and -0.30 between the measured braking indices and, respectively, and τc. This result reaffirms earlier conclusions that the braking indices of most radio pulsars, obtained through the standard timing technique, are strongly dominated by sustained random fluctuations in the observed pulse phase.","PeriodicalId":124495,"journal":{"name":"Chinese Journal of Astronomy and Astrophysics","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121299408","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 11
Measuring the Distance of VX Sagittarii with SiO Maser Proper Motions 用SiO脉泽固有运动测量人马座VX的距离
Chinese Journal of Astronomy and Astrophysics Pub Date : 2007-08-01 DOI: 10.1088/1009-9271/7/4/09
Xi Chen, Zhi-qiang Shen, Ye Xu
{"title":"Measuring the Distance of VX Sagittarii with SiO Maser Proper Motions","authors":"Xi Chen, Zhi-qiang Shen, Ye Xu","doi":"10.1088/1009-9271/7/4/09","DOIUrl":"https://doi.org/10.1088/1009-9271/7/4/09","url":null,"abstract":"We report on 43 GHz v=1, J=1–0 SiO maser proper motions in the circumstellar envelope of the M-type semi-regular variable star VX Sgr, observed by Very Long Baseline Array (VLBA) at 3 epochs during 1999 April–May. Applying the statistical parallax analysis to these proper motions, we estimated a distance of VX Sgr of 1.57±0.27 kpc, which is consistent with that based on the proper motions of H2O masers, or on the assumption that VX Sgr belongs to the Sgr OB1 association. At this distance, VX Sgr can be classified as a red supergiant. Comparing the statistical parallax method with those of model fitting and annual parallax, we think that the statistical parallax method may be a good way of estimating SiO maser distances at present.","PeriodicalId":124495,"journal":{"name":"Chinese Journal of Astronomy and Astrophysics","volume":"05 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127196074","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 15
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