BRIGHTNESS VARIATIONS OF Mg Ib BRIGHT FEATURES     

Dara  H.C.  Koutchmy  S.  Zachariadis  Th.G.  Alissandrakis  C.E. 《Solar physics》2001,198(2):313-324

We study the temporal intensity variations of Mgib bright features and investigate the corresponding Hα velocity pattern. The network bright features are well visible in the continuum, in images averaged over the duration of the observations (130 min). We detected `flashing' bright features, which appear and disappear within two to five minutes, while the rest of the bright features undergo small variations of either their shape and/or their intensity. A power spectrum analysis reveals a 10-min oscillation for approximately half of the stable bright features. The 5-min oscillations are detected mainly at the network boundaries, where stable bright features are located, while 3-min oscillations coincide with few bright features, but are also quite intense inside the network cells. The majority of bright features are associated with Hα downflows. The downflow is very intense at the location of `flashing' bright features.  相似文献   

A Colliding-Winds Interpretation of the U Orbital Variation of the Symbiotic Binary AG Pegasi     

N. Tomov  M. Tomova 《Astrophysics and Space Science》2001,278(3):311-317

The photometric U orbital variations of the symbiotic binary AG Peg, caused by occultation of a bright gaseous region by the M giant in this system, are used to determine the geometry of this region whose existence is explained in the framework of the colliding winds model. The emission of the bright region varies and a particular value of its mean density of 2–3 10¹⁰ cm^-3 has been derived. The causes for the irregular variations of the light in the orbital minimum and maximum are discussed. It is also obtained, when the mass-loss rate of the hot companion of the system decreases to about 5 10^-10 Ms _⊙ yr^-1, this bright region will disappear. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Trigger conditions and effective areas of imaging air Cherenkov telescopes (Astroparticle Physics 6 (1996) 77)     

C. Khler  G. Hermann  W. Hofmann  A. Konopelko  A. Plyasheshnikov 《Astroparticle Physics》1997,6(3-4):423

  相似文献   

Chromospheric evolution and the flare activity of super-active region NOAA 6555     

C. Debi Prasad  Ashok Ambastha  Nandita Srivastava  Sushanta C. Tripathy  Mona J. Hagyard 《Journal of Astrophysics and Astronomy》1997,18(1):39-55

Super-active region NOAA 6555 was highly flare productive during the period March 21st–27th, 1991 of its disk passage. We have st udied its chromospheric activity using high spatial resolution Hα filtergrams taken at Udaipur along with MSFC vector magnetograms. A possible relationship of flare productivity and the variation in shear has been explored. Flares were generally seen in those subareas of the active region which possessed closed magnetic field configuration, whereas only minor flares and/or surges occurred in subareas showing open magnetic field configuration. Physical mechanisms responsible for the observed surges are also discussed.  相似文献   

富碳拱星IRC＋10216和CIT6的CO J=1—0转动谱的观测     

裴春传  陈亚峰 《紫金山天文台台刊》1997,16(4):226-231

使用中国科学院紫金山天文台青海站13.7米射电望远镜于1996年12月至1997年1月对富碳拱星IRC 10216和CIT6的CO J=1-0跃迁(115GHz)进行了观测。在观测谱线的基础上得到了IRC 10216的视向速度和膨胀速度分别为一26.1km s~(-1)和14.8km s~(-1),CIT6的视向速度和膨胀速度分别为0.6km s~(-1)和13.8kms~(-1)。并对望远镜的射束及指向精度进行了研究。  相似文献   

Kinematics of Gas and Stars in 20 Disc Galaxies     

J.C. Vega Beltrán  W.W. Zeilinger  A. Pizzella  E.M. Corsini  F. Bertola  J.G. Funes  J.E. Beckman 《Astrophysics and Space Science》2001,276(2-4):1201-1210

In this paper we present the kinematics of the gas and/or the stars of a sample of 20 disc galaxies. We investigate whether there is any relation between the kinematics of the gas and stars and the classical morphological type of the galaxies in the sample. We deduce that, in most of the late-type spirals we have studied, the stars and the ionized gas are moving with virtually circular velocity, except when the spectroscopic slit crosses a bar region. On the other hand, we found in the central parts of early-type disc galaxies a wider variety of different behaviour of stars and gas. We find many possible factors that complicate the classification of the kinematical properties of the galaxies by their morphological type: the presence of counter-rotations (star vs. stars or star vs. gas), misalignment between the different kinematic components present in the galaxy, the presence of a bar structure and its orientation with respect to the line of nodes of the galaxy, and interactions and mergers or external accretion processes are some of the problems we find in the study of the kinematics of a galaxy.  相似文献   

VALIDATION - ANOTHER PERSPECTIVE   总被引：1，自引：0，他引：1  

C. McCombie  I. McKinley 《Ground water》1993,31(4):530-531

  相似文献   

Brightness Variation and Proper Motions of Three Objects in the Cygnus Region     

H. A. Harutyunian  N. D. Melikian 《Astrophysics》2001,44(3):352-358

The results of an investigation of three peculiar objects in the Cygnus region are given. One of them was already known to be a Herbig-Haro object. In accordance with its observational characteristics, the second object is, in all probability, a T Tauri star. The physical character of the last object is not yet entirely clear, but from the properties of its emission in the near infrared range it is probably also a T Tauri star. The proper motions of the objects have been measured. It is shown that all three objects are members of a tight system of the Trapezium type and evidently are the results of the successive fragmentation of an original protostellar body.  相似文献   

CCD Polarimetric Imaging Of Comet Hale-Bopp (C/1995 O1)     

E. Hadamcik  A. C. Levassuer-Regourd  J. B. Renard 《Earth, Moon, and Planets》1997,78(1-3):365-371

Polarimetric observations of the light scattered by dust have been carried out at Pic-du-Midi Observatory with the 2 m telescope in June and September–October 1996, and at Haute-Provence Observatory with the 0.80 m telescope in April 1997. They cover a total number of 11 nights and a large (6.9°–47.7°) phase angle range. The spatial resolution allows to underline structures in the coma, as well in the brightness images as in the polarization maps, with a correlation between the regions of bright structures and the regions of higher polarization. A clear difference appears between the sunward and antisunward side, with higher polarization on the antisunward side. The phase angle coverage allows us to obtain a polarimetric phase curve for the whole coma and to compare it with other cometary phase curves. The degree of polarization is higher for Hale-Bopp than for the comets previously observed. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The SuperCOSMOS Sky Survey – III. Astrometry     

N.C. Hambly  A.C. Davenhall  M.J. Irwin  H.T. MacGillivray 《Monthly notices of the Royal Astronomical Society》2001,326(4):1315-1327

In this, the third in a series of three papers concerning the SuperCOSMOS Sky Survey, we describe the astrometric properties of the data base. We describe the algorithms employed in the derivation of the astrometric parameters of the data, and demonstrate their accuracies by comparison with external data sets using the first release of data, the South Galactic Cap survey. We show that the celestial coordinates, which are tied to the International Celestial Reference Frame via the Tycho–2 reference catalogue, are accurate to better than ±0.2 arcsec at J , R ∼19,18 , rising to ±0.3 arcsec at J , R ∼22,21 , with positional-dependent systematic effects from bright to faint magnitudes at the ∼0.1-arcsec level. The proper motion measurements are shown to be accurate to typically ±10 mas yr⁻¹ at J , R ∼19,18 , rising to ±50 mas yr⁻¹ at J , R ∼22,21 , and are tied to zero using the extragalactic reference frame. We show that the zero-point errors in the proper motions are ≤1 mas yr⁻¹ for R >17 , and are no larger than ∼10 mas yr⁻¹ for R <17 mas yr⁻¹ .  相似文献