γ噪Blazar天体短时标光变的寄主星系影响

利用云南天文台1m光学望远镜2000～2001年对3个GeV和/或TeV γ噪Blazar天体的观测,发现γ噪类星体PKS 1510-089在R波段有一个光变时标为41min的星等变化为2.0mag的剧烈光变,这是迄今为止我们所观测到的变幅最大的一个γ噪Blazar天体短时标光变.对此光变,可估计限制光变辐射模型的一些参数,如辐射区半径R、多普勒因子δ以及吸积转化效率η等.η=59.6的值强烈预示着相对论聚束效应可较好解释γ噪Blazar天体的辐射机制.我们仔细考察了大气视宁度对光变的影响.发现对1ES 2344+514,观测到的光变与当地大气视宁度有一个弱相关,结果表明,对光变参数较小(C＜5)的光变,大气视宁度引起的假光变的贡献较大,需要选择较严格的光变判据.     

小行星(58)Concordia测光研究

小行星基本物理参量(周期、形状、自转)对于理解小行星起源、演化和碰撞具有重要意义.利用测光手段可以获得小行星的光变曲线,通过光变曲线可以确定小行星基本参数.利用云南天文台1 m望远镜在2000和2015年对小行星(58) Concordia进行观测,结合前人测光观测数据,通过凸面体光变曲线反演模型获得该小行星的周期、形状和轴指向.(58) Concordia的恒星周期为9.894541 h,在黄道坐标系下,极轴指向为λ_1=15.3?±0.7?,β_1=-4.2?±2.6?,另外一组解为λ_2=195.9?±1.0?,β_2=4.8?±1.2?.     

基于Jurkevich法CygX-1光变周期特性研究

针对天文观测数据不等间隔的特点,利用Jurkevich方法对黑洞候选体x射线双星CygX-1近16年的RossiX-rayTimingExplorer（RXTE）All-SkyMonitor（ASM）数据进行了频谱分析,并结合Kidger周期存在可信度的判据,发现CygX-1存在363±11．5d的光变周期,但没有发现420d的光变周期,而且150d的光变周期可能仅仅是51±1．4d光变周期的观测表象。     

基于Jurkevich法Cyg X-1光变周期特性研究

针对天文观测数据不等间隔的特点,利用Jurkevich方法对黑洞候选体X射线双星Cyg X-1近16年的Rossi X-ray Timing Explorer(RXTE)All-Sky Monitor(ASM)数据进行了频谱分析,并结合Kidger周期存在可信度的判据,发现Cyg X-1存在363±11.5 d的光变周期,但没有发现420 d的光变周期,而且150 d的光变周期可能仅仅是51±1.4 d光变周期的观测表象。     

利用MUSIC算法分析BL Lac天体S5 0716+714光变周期

将基于多重信号分类的MUSIC谱估计算法引入BL Lac天体光变周期分析中.给出了MUSIC算法的基本原理,利用模拟信号检测了算法的频谱分辨率.从大量文献中收集了BL Lac天体S5 0716+714光学V、R、I 3个波段从1994年到2008年的有效观测数据,用MUSIC算法和平均周期图算法分别计算了它们的光变周期,发现存在两个主要光变周期:一个是(3.33±0.08)yr的周期,另一个是(1.24±0.01)yr的周期.对这两种算法的周期估计性能进行了比较,结果表明,MUSIC谱估计算法对样本长度要求较低,具有良好的分辨特性和抗噪声能力,能提高在样本长度较短情况下光变周期分析的准确性.     

小行星(26)Proserpina的测光观测和建模研究

2011年12月到2012年2月期间对小行星(26)Proserpina进行了时序测光观测,获得其自转的会合周期为p=(13.107±0.002)h.结合历史测光数据,采用光变曲线凸壳反演方法对其自转状态和形状进行反演研究,并提出采用Bootstrap方法对反演参数进行误差估计.测定出(26)Proserpina是一个逆转的小行星,其极轴指向解为λ1=90.8?±1.4?,β1=-53.1?±3.2?和λ2=259.3?±2.2?,β2=-62.0?±2.0?;测定其自转的恒星周期为(13.109777±3.8×10-6)h;并基于两个极轴解反演出互为镜像的凸壳形状模型.     

活动星系核初探

观测表明,在IE0317+186、Mark421、ON+231、BL Lae等四个BL Lae天体中,都具有大振幅、短时标的激烈光变。在本文中,我们论证了如果把这种现象解释为中心黑洞的吸积盘不稳定性,那么,利用光度时标、光变曲线的最大值及最小值就可以估计出其中心致密天体的质量及辐射区域的大小。     

伽马射线暴的光度-光变复杂度关系

伽马射线暴的光变复杂度是描述其光变曲线复杂程度的物理量.由已知红移的伽马射线暴,Reichart等人发现其光变复杂度与各向同性光度之间有正相关性(LαVα,α在1.77～3.5之间),即光变越复杂,光度越高.此相关性类似于造父变星的周光关系,可用来估计伽马暴的距离和红移.调研、分析了各种光变复杂度的定义、算法和光变复杂度-各向同性光度关系的拟合结果,最后对光变复杂度和光度之间的关系做了总结和展望.     

激变变星3种周期振荡现象 的观测研究进展

激变变星(Cataclysmic Variables, CV)的典型特性是其存在3种周期振荡现象,周期振荡指准周期性的光度快速变化.按光变时标由短到长, CV的周期振荡可分为矮新星振荡、长周期矮新星振荡和准周期振荡.对3种不同振荡在观测上的特征以及在不同亚型CV中的表现进行了介绍,并阐述了可能产生3种周期振荡的物理机制.这些振荡现象为人们研究白矮星的吸积和几何提供了丰富的信息和线索.     

对Archer发现的17颗变星的光电观测

在1984年2—3月,用美国McDonald天文台91cm反射镜的UBV测光系统和云南天文台35厘米反射镜V色测光系统,对Archer 1959年在后发座用照相方法发现的24颗变(双)星中的17颗进行了观测研究,全部没有大于0~m.07的光变,其中12颗的连续观测时间长于半个周期以上,因而至少它们不是原定周期和变幅的那种变星。其他5颗或Archer未给周期,或观测复盖不够半个周期,未能肯定。最后给出这些星和比较星的星等和色指数。     

First lightcurve observations and rotation of minor planet 127 Johanna

Photoelectric observations of the minor planet 127 Johanna were made in the UBV (RI)_c photometric system during its apparition in 1991 at the Piszkéstetõ mountain-station of Konkoly Observatory from August to December, when it showed a brightness variation with an amplitude of about 0.2 magnitude. The derived H, G values in the two-parameter magnitude system in V are 8.459 ± 0.013 and 0.114 ± 0.020, respectively. The determined V linear phase coefficient is of 0.036 ± 0.001 (mag/deg). The value of G and the observed values of color indices (U-B), (B-V) confirm that this asteroid belongs to the C taxonomic class as it was previously classified. The estimated effective diameter is between 96 and 118 km if the assumed V geometric albedo is of 0.06 and 0.04, respectively. The available data suggest a pure principal axis rotation mode. The mean synodic rotational period of the asteroid 127 Johanna is 6.94 ± 0.29 h. The uncertainty is due to the changing of aspect geometry. This value of the synodic rotation period means that this asteroid has an intermediate rotation period. The sense of rotation is prograde as indicated by the temporal evolution of the time derivative of the ecliptic longitude of the phase angle bisector as well as with the increasing synodic period of rotation during the same interval (October/November and December in 1991). The composite lightcurves created for short arc time data reveal structures with breakings and linear portions in V; this fact and the Fourier coefficients indicate a probably irregularly shaped body. There are slight indications that the B-V is redder close to the brightness minimum and the V-R_c is redder at the brightness maximum, and the periodic behavior cannot be proved in V-I_c. The less full rotational phase coverage of the observational data is insufficient to construct a shape model. The accurate pole orientation obviously cannot be determined using one opposition lightcurve data only. Further observations are required to get a more accurate knowledge of the physical parameters of this asteroid. For this purpose, a good opportunity to perform observations arose in December 1996, when this asteroid was in opposition at the northernmost declination.     

1580 Betulia: An unusual asteroid with an extraordinary lightcurve

Results of UBV photometry and polarimetry of 1580 Betulia during its 1976 apparition are presented. The synodic period of rotation is found to be 6.130 hr. The linear phase coefficient and absolute magnitude of the primary maximum in V are 0.032 mag/deg and 14.88, respectively. No color variations with rotation or solar phase angle detected, the mean colors being B?V = 0.66 and U?B = 0.24. Betulia's lightcurve is unique among asteroids studied to date in that it displays three maxima and three minima within one rotational cycle, indicative of a region of greater roughness and/or a dark spot on one of its broad faces. Polarization results indicate a low albedo and a mean diameter of about 7 km, establishing Betulia as the first C type asteroid to be found among the Mars crossers. A model accounting for most features of Betulia's lightcurve is given by a prolate spheroid rotating about one of its shorter axes having an axis ratio of 1:1.21 with a major topographic feature on one of its broad faces.     

Photometric lightcurves and pole determination of 433 Eros

Fourteen photometric lightcurves of 433 Eros were made at the Astronomical Observatory of Torino during the 1974–75 close passage. The absolute magnitude of the primary maximum (10^m78), the phase coefficient (0.023 mag/degree), the synodic and sidereal period of rotation (0^d.21956 and 0^d.21959, respectively) and the ecliptic coordinates of the pole (λ = 17°, β = 10°) were deduced.     

Nature of the small main belt Asteroid 3169 Ostro

We present a set of rotational lightcurve measurements of the small main belt Asteroid 3169 Ostro. Our observations reveal an unambiguous, double-peaked rotational lightcurve with a peak-to-peak variation up to 1.2±0.05 mag and a synodic period of 6.509±0.001 h. From the large flux variation and the overall shape of the lightcurves, we suggest that 3169 Ostro could be a tightly bound binary or a contact binary, similar to the Trojan Asteroid 624 Hektor. A shape model of this system is proposed on the assumption that 3169 Ostro is a Roche binary described by a pair of homogeneous elongated bodies, with a size ratio of 0.87, in hydrostatic equilibrium and in circular synchronous motion around each other. The direction of the spin axis is determined modulo 180° by its J2000 ecliptic coordinates λ₀=50±10°, β₀=±54±5°. The binary interpretation and the pole solution adequately fit the earlier photometric observations made in 1986 and 1988. However, additional supporting lightcurves are highly desirable especially in the next mutual events occurrence of 2008 and 2009 in order to remove the pole ambiguity and to confirm unambiguously the binary nature of 3169 Ostro.     

Another view of synodic solar rotation

Adding the angular velocity of sidereal solar rotation and the apparent rotational effect of the Earth's revolution vectorially, a new synodic solar rotation vector has been obtained. The sidereal and synodic solar rotation axes (and equators) are separated. Using the known parameters of the Earth's orbital motion, the synodic rotation angular velocity and the inclination of the synodic equator, the corresponding sidereal rotation parameters have been calculated (ω₁ = 2.915 × 10^#X2212;6 rad s^#X2212;1 and i ₁ = 6.076). Various linear rotational velocities at the solar globe are briefly described.     

Photoelectric photometry of asteroids 9 Metis, 18 Melpomene, 60 Echo, 116 Sirona, 230 Athamantis, 694 Ekard,and 1984 KD

Photoelectric observations of seven asteroids were made from Gila Observatory between October 14, 1983, and June 21, 1984. The following synodic rotational periods and amplitudes are reported: 9 Metis, P = 5.04 hr, ΔM = 0.05; 18 Melpomene, P = 11.570 hr, ΔM = 0.22; 60 Echo, P = 25.208 hr, ΔM = 0.22; 116 Sirona, P = 12.028 hr, ΔM = 0.42; 230 Athamantis, P = 23.99 hr, ΔM > 0.20; 694 Ekard, P = 5.925 hr, ΔM = 0.50; 1984 KD, P = 1.97 hr, ΔM = 0.26. The rotational periods reported for asteroid 60 Echo, 116 Sirona, 694 Ekard, and 1984 KD represent completely new results. The synodic rotational period reported for asteroid 1984 KD is tentative and is based largely upon the observations of a single night. The reported synodic periods of the remaining six asteroids are based upon a minimum of 3 nights of photometric observations.     

The relation between the synodic and sidereal rotation period of the Sun

The relation between the synodic and sidereal rotation period of the Sun for an arbitrary date of observation is derived taking into account details of the Earth's motion. The transformation procedure between the synodic (apparent) and sidereal rotation period presented here can be performed without using the annual ephemerides.     

Exact analytic solutions for the rotation of an axially symmetric rigid body subjected to a constant torque

New exact analytic solutions are introduced for the rotational motion of a rigid body having two equal principal moments of inertia and subjected to an external torque which is constant in magnitude. In particular, the solutions are obtained for the following cases: (1) Torque parallel to the symmetry axis and arbitrary initial angular velocity; (2) Torque perpendicular to the symmetry axis and such that the torque is rotating at a constant rate about the symmetry axis, and arbitrary initial angular velocity; (3) Torque and initial angular velocity perpendicular to the symmetry axis, with the torque being fixed with the body. In addition to the solutions for these three forced cases, an original solution is introduced for the case of torque-free motion, which is simpler than the classical solution as regards its derivation and uses the rotation matrix in order to describe the body orientation. This paper builds upon the recently discovered exact solution for the motion of a rigid body with a spherical ellipsoid of inertia. In particular, by following Hestenes’ theory, the rotational motion of an axially symmetric rigid body is seen at any instant in time as the combination of the motion of a “virtual” spherical body with respect to the inertial frame and the motion of the axially symmetric body with respect to this “virtual” body. The kinematic solutions are presented in terms of the rotation matrix. The newly found exact analytic solutions are valid for any motion time length and rotation amplitude. The present paper adds further elements to the small set of special cases for which an exact solution of the rotational motion of a rigid body exists.     

Worldwide photometry and lightcurve observations of 16 Psyche during the 1975–1976 apparition

We present 26 lightcurves of 16 Psyche from 1975 and 1976. The synodic period during this apparition was 4^h.1958. Combining photometric data from this opposition with those from previous apparitions allowed us to derive a mean phase coefficient in V of 0.026 ± 0.002 mag/deg and to establish that Psyche's absolute V₀ magnitude and rotational amplitude vary with aspect; at 90° aspect, V₀(1, 0) = 6.27 ± 0.05 and the lightcurve amplitude is 0.30 mag, while at 0° or 180° aspect, V₀(1, 0) = 6.02 ± 0.02 and the amplitude is ?0.03 mag. This behavior is accounted for if, to first order, Psyche's shape is that of a triaxial ellipsoid with axial ratios near 5:4:3. Colors at zero phase are U-B = 0.26 ± 0.01 and B-V = 0.71 ± 0.01. Color phase coefficients are <0.001 mag/deg in U-B and 0.0010 ± 0.0004 mag/deg in B-V.     

Rotational shear near the solar surface as a probe for subphotospheric magnetic fields

Helioseismology revealed an increase in the rotation rate with depth just beneath the solar surface. The relative magnitude of the radial shear is almost constant with latitude. This rotational state can be interpreted as a consequence of two conditions characteristic of the near-surface convection: the smallness of convective turnover time in comparison with the rotation period and absence of a horizontal preferred direction of convection anisotropy. The latter condition is violated in the presence of a magnetic field. This raises the question of whether the subphotospheric fields can be probed with measurements of near-surface rotational shear. The shear is shown to be weakly sensitive to magnetic fields but can serve as a probe for sufficiently strong fields of the order of one kilogauss. It is suggested that the radial differential rotation in extended convective envelopes of red giants is of the same origin as the near-surface rotational shear of the Sun.