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81.
K. A. Wills M. Das A. Pedlar T. W. B. Muxlow T. G. Robinson 《Monthly notices of the Royal Astronomical Society》2000,316(1):33-48
We present VLA A-array 21-cm atomic hydrogen (H i ) absorption observed against the central region of the starburst galaxy M82 with an angular resolution of ∼1.3 arcsec (≃20 pc). These observations, together with MERLIN H i absorption measurements, are compared with the molecular (CO) and ionized ([Ne ii ]) gas distributions and are used to constrain the dynamics and structure of the ionized, neutral and molecular gas in this starburst.
A position–velocity diagram of the H i distribution reveals an unusual 'hole' feature which, when previously observed in CO, has been interpreted as an expanding superbubble contained within a ring of gas in solid body rotation. However, we interpret this feature as a signature of a nearly edge-on barred galaxy. In addition, we note that the CO, H i and [Ne ii ] position–velocity diagrams reveal two main velocity gradients, and we interpret these as gas moving on x1 - and x2 -orbits within a bar potential. We find the best fit to the data to be produced using a bar potential with a flat rotation curve velocity v b =140 km s−1 and a total length of 1 kpc, a non-axisymmetry parameter q =0.9, an angular velocity of the bar Ωb =217 km s−1 arcsec−1 , a core radius R c =25 pc, an inclination angle i =80° and a projected angle between the bar and the major axis of the galaxy φ '=4°. We also discuss the orientation of the disc and bar in M82. 相似文献
A position–velocity diagram of the H i distribution reveals an unusual 'hole' feature which, when previously observed in CO, has been interpreted as an expanding superbubble contained within a ring of gas in solid body rotation. However, we interpret this feature as a signature of a nearly edge-on barred galaxy. In addition, we note that the CO, H i and [Ne ii ] position–velocity diagrams reveal two main velocity gradients, and we interpret these as gas moving on x
82.
We investigate the evolution of rotation period and spindown age of a pulsar whose surface magnetic field undergoes a phase
of growth. Application of these results to the Crab pulsar strongly indicates that its parameters cannot be accounted for
by the field growth theories. 相似文献
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88.
A wide-field time-series CCD photometric survey of variable stars in the field of the open cluster NGC 2168 was carried out using the BATC Schmidt telescope. In total 13 new variable stars are discovered with three W UMa systems, one EA type and two EB type eclipsing binaries (one of them could be a W UMa system), and seven pulsating stars including three candidates of δScuti stars. 相似文献
89.
Hui-Rong Ji Qi-Jun Pu Yi-Hua Yan Yu-Ying Liu Zhi-Jun Chen Cheng-Ming Tan Cong-Ling Cheng De-Bang Lao Shu-Ke Li Zhi-Qiang Wang Min-Hong Yu Jian-Nong Liu Li-Kang Zhang Ji-Yong Gao National Astronomical Observatories Chinese Academy of Sciences Beijing Hebei Semiconductor Research Institute Shijiazhuang 《中国天文和天体物理学报》2005,5(4):433-441
An improved Solar Radio Spectrometer working at 1.10-2.06 GHz with much improved spectral and temporal resolution, has been accomplished by the National Astronomical Observatories and Hebei Semiconductor Research Institute, based on an old spectrometer at 1-2 GHz. The new spectrometer has a spectral resolution of 4 MHz and a temporal resolution of 5ms, with an instantaneous detectable range from 0.02 to 10 times of the quiet Sun flux. It can measure both left and right circular polarization with an accuracy of 10% in degree of polarization. Some results of preliminary observations that could not be recorded by the old spectrometer at 1-2 GHz are presented. 相似文献
90.
Shin'ichirou Yoshida † Shigeyuki Karino Shijun Yoshida Yoshiharu Eriguchi 《Monthly notices of the Royal Astronomical Society》2000,316(1):L1-L4
The first results of numerical analysis of classical r-modes of rapidly rotating compressible stellar models are reported. The full set of linear perturbation equations of rotating stars in Newtonian gravity is solved numerically without the slow rotation approximation. A critical curve of gravitational wave emission induced instability, which restricts the rotational frequencies of hot young neutron stars, is obtained. Taking the standard cooling mechanisms of neutron stars into account, we also show the 'evolutionary curves' along which neutron stars are supposed to evolve as cooling and spinning down proceed. Rotational frequencies of 1.4-M⊙ stars suffering from this instability decrease to around 100 Hz when the standard cooling mechanism of neutron stars is employed. This result confirms the results of other authors, who adopted the slow rotation approximation. 相似文献