目录
图像
上传图像
DSS Images Other Images
相关文章
X-rays from the radio-quiet quasar PG 1407+265: relativistic jet or accretion disc emission?
We present two XMM-Newton observations of the luminous (Lx> 1046ergs-1), radio-quiet quasar PG 1407+265,separated by 11 months. The data indicate two distinct states: a highlyvariable, bright state (first epoch); and a quiescent, low-flux one(second epoch). During the low-flux state the spectrum is consistentwith a single, unabsorbed power law. However, during the brighter statea highly variable, steep component is statistically required.Contemporaneous ultraviolet data from the Optical Monitor allow anestimate of the optical-to-X-ray spectral index (αox),which appears typical of radio-quiet quasars during the low-flux state,but extremely flat during the high-flux state. The XMM-Newton data canbe described as originating from a combination of jet and accretion discprocesses, in which the (relativistic) X-ray jet only worksintermittently. The scenario could help to describe some of thecomplexities seen in the broad-band spectral energy distribution of PG1407+265, such as weak high-ionization emission lines, strong FeII,unbeamed continuum and the weak radio emission relative to the optical.
| The Tokyo PMC catalog 90-93: Catalog of positions of 6649 stars observed in 1990 through 1993 with Tokyo photoelectric meridian circle
The sixth annual catalog of the Tokyo Photoelectric Meridian Circle(PMC) is presented for 6649 stars which were observed at least two timesin January 1990 through March 1993. The mean positions of the starsobserved are given in the catalog at the corresponding mean epochs ofobservations of individual stars. The coordinates of the catalog arebased on the FK5 system, and referred to the equinox and equator ofJ2000.0. The mean local deviations of the observed positions from theFK5 catalog positions are constructed for the basic FK5 stars to comparewith those of the Tokyo PMC Catalog 89 and preliminary Hipparcos resultsof H30.
|
提交文章
相关链接
提交链接
下列团体成员
|
观测天体数据
目录:
|
