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701.
We carried out a series of linear stability analyses of the radial and low-degree non-radial p modes for stellar models with initial masses of . The stellar models were computed by using convective overshoot distance , 0.25 and 0.40 H P . Our numerical results show that the β Cephei instability strip forms a horn-shaped region pointing upwards near the main sequence on the Hertzsprung–Russell diagram (HRD). The lower part of the instability strip for the radial modes join the zero-age main-sequence (ZAMS) at , while the top of the instability strip extends up to . The instability strip for the non-radial modes is even wider. The overall instability strip is dominated by the radial and non-radial fundamental modes. The first overtone (the radial-order index is also pulsationally unstable. We have shown that the β Cephei stability is almost independent of the overshoot parameter d over used for the stellar models, while it depends critically on the metal abundance. With decreasing metal abundance, the instability region shrinks and eventually disappears for . 相似文献
702.
A. Bhatnagar R. M. Jain J. T. Burkepile I. M. Chertok A. Magun H. Urbarz P. Zlobec 《Astrophysics and Space Science》1996,243(1):209-213
The powerful cosmic ray flare of Sept. 29, 1989 occurred behind the limb and was observed over a wide spectral range. The analysis of optical, radio, and other relevant data suggest two phases of energy release. After an impulsive phase a prolonged post eruption energy release occurred in an extended region of the corona following the eruption of a large coronal mass ejection (CME). This phase is responsible for numerous coronal and interplanetary phenomena including the ground-level increase of cosmic rays. 相似文献
703.
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
704.
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
705.
P. Cox 《Astrophysics and Space Science》1997,255(1-2):489-497
This review summarizes spectroscopic and imaging results obtained on board the Infrared Space Observatory (ISO) on well-known
planetary nebulae: the young nebula NGC 7027, and two fully evolved nearby nebulae, the Dumbbell and the Helix.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
706.
Almudena Alonso-Herrero Marcia J. Rieke George H. Rieke Douglas M. Kelly 《Astrophysics and Space Science》2001,276(2-4):1109-1120
The irregular galaxy M82 is known as the archetypal starburst galaxy. Its proximity (3.5 Mpc) makes this galaxy an ideal laboratory
for studying the properties of its starburst. The detailed morphology of the [FeII] 1.644 μm and emission Paα (at 1.87 μm) is revealed by the NICMOS images. The peak of the 2.2 μm continuum brightness(evolved population) lies very
close to the dynamical centre. Most of the Paα emission (which traces the young population) is distributed in a ring of star formation (with a `hole' lacking line emission
at the centre of the galaxy). These observations support the scenario in which the starburst in M82 is propagating outwards.
It has long been suggested that the [FeII] emission in starburst galaxies can be used as a measure of supernova (SN) activity.
M82 shows a large number of radio supernova remnants (SNRs), approximately 50, lying in the plane of the galaxy. The comparison
of the positions of the bright compact [FeII] emitting regions with the location of the radio SNRs shows that there is no one-to-one spatial correspondence between
the two emissions, suggesting that the radio and [FeII] emissions trace two populations of SNRs with different ages. Young
(a few hundred years) SNRs are best traced by their radio emission, whereas the [FeII] stage lasts for at least a few 104 yr. The compact [FeII] sources contribute only some 20 % of the total [FeII] emission observed in M82. However, much of the remaining unresolved
[FeII] emission in the plane of the galaxy may arise from SNRs that expanded and merged into a general interstellar medium
within a few 104 yr. Presumably, as much as 70% of the total extinction-corrected [FeII]1.644 μm in M82 is associated with SNRs. The extended
and diffuse [FeII] component in M82 seems to be related with the superwind above and below the disc of the galaxy.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
707.
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
708.
709.
VALIDATION - ANOTHER PERSPECTIVE 总被引:1,自引:0,他引:1
710.
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