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861.
����CCDС�ߴ������Ӧ�ü������� 总被引:3,自引:0,他引:3
????????CCD??????????????С????????????巽???? ???????????????????????CCD?????????????????????С???????????;????ò?????????????????????? 相似文献
862.
Be/X-ray binaries are systems formed by a massive Be star and a magnetized neutron star, usually in an eccentric orbit. The
Be star has strong equatorial winds occasionally forming a circumstellar disk. When the neutron star intersects the disk the
accretion rate dramatically increases and a transient accretion disk can be formed around the compact object. This disk can
last longer than a single orbit in the case of major outbursts. If the disk rotates faster than the neutron star, the Cheng-Ruderman
mechanism can produce a current of relativistic protons that would impact onto the disk surface, producing gamma-rays from
neutral pion decays and initiating electromagnetic cascades inside the disk. In this paper we present calculations of the
evolution of the disk parameters during both major and minor X-ray events, and we discuss the generation of gamma-ray emission
at different energies within a variety of models that include both screened and unscreened disks. 相似文献
863.
We present a comparative analysis of 5 GHz VLA and 200 ks Chandra ACIS-I image. In the 5 GHz image the familiar jet and much weaker counterjet are seen, which bend as the jet propagates towards
the hotspots. Furthermore, where the lobe detected in 5 GHz emission starts to interact with the jet, we see that the jet
“threads”. In the 0.2–10 keV X-ray image we do not detect the jet, but do detect a relic of the counterjet. 相似文献
864.
Jiang-Hua Wu Xiang-Tao He Yang Chen Wolfgang Voges National Astronomical Observatories Chinese Academy of Sciences Beijing jhwu Department of Astronomy Beijing Normal University Beijing Max-Planck-Institut fur Extraterrestrische Physik D- Garching Germany 《中国天文和天体物理学报》2003,(5)
We report the discovery of five Narrow-Line Seyfert 1 galaxies (NLSls) identified from the ROSAT All-Sky Survey bright sources. One of them has a quasar-like luminosity and two, including the quasar-like one, have close companions and/or show interacting features. We calculate the central black hole masses and Eddington ratios for the five NLSls. In combination with the objects of Kaspi et al., we find that NLSls have smaller central black hole masses and higher accretion rate than normal Seyfert 1s. 相似文献
865.
Cui-Lian Zhu Jia-Long WangNational Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2003,3(6):563-568
We present a verification of the short-term predictions of solar Xray bursts for the maximum phase (2000-2001) of Solar Cycle 23, issued by two prediction centers. The results are that the rate of correct predictions is about equal for RWC-China and WWA; the rate of too high predictions is greater for RWC-China than for WWA, while the rate of too low predictions is smaller for RWC-China than for WWA. 相似文献
866.
J. Hawreliak J. Colvin J. Eggert D. H. Kalantar H. E. Lorenzana S. Pollaine K. Rosolankova B. A. Remington J. Stölken J. S. Wark 《Astrophysics and Space Science》2007,307(1-3):285-289
X-ray diffraction is a widely used technique for measuring the crystal structure of a compressed material. Recently, short
pulse x-ray sources have been used to measure the crystal structure in-situ while a sample is being dynamically loaded. To
reach the ultra high pressures that are unattainable in static experiments at temperatures lower than using shock techniques,
shockless quasi-isentropic compression is required. Shockless compression has been demonstrated as a successful means of accessing
high pressures. The National Ignition Facility (NIF), which will begin doing high pressure material science in 2010, it should
be possible to reach over 2 TPa quasi-isentropically. This paper outlines how x-ray diffraction could be used to study the
crystal structure in laser driven, shocklessly compressed targets the same way it has been used in shock compressed samples.
A simulation of a shockless laser driven iron is used to generate simulated diffraction signals, and recent experimental results
are presented. 相似文献
867.
We compared the microwave bursts with short timescale fine structure observed at 2.84 GHZ at Beijing Astronomical Observatory with the hard X-ry bursts (HXB) observed by the YOHKOH satellite during the period 1991 Oct–1992 Dec, and found that of the 20 microwave events, 12 had HXB counterparts. For the typical event of 1992-06-07, we analyzed the common quasi-period oscillations on the order of 102 s and calculated the parameters of the source region, together with a brief discussion. 相似文献
868.
The energy and angular distribution of electrons as a function of column densities initially for monoenergetic and monodirectional
electron beams and incidence angles of 0‡, 30‡ and 60‡ have been studied by combining small angle scattering using analytical
treatment with large angle collisions using Monte Carlo calculations. Using these distributions, X-ray and EUV-line flux have
been studied as a function of column density. It is observed that the line flux increases with the increase in column density,
becoming significant at intermediate column densities where the electron energies and angular distributions have a non-Maxwellian
nature. 相似文献
869.
Ni Chen-ping 《Chinese Astronomy and Astrophysics》1990,14(4):422-428
The supernova exploded at the boundary of a dense molecular cloud in a diffuse gas. The eastern half of the shock wave entered the diffuse gas and is now in the stage of adiabatic expansion, forming the observed semicircular remnant; the western half entered the dense cloud, moved at a much slower speed and is now in the pressure-driven snowplow phase, the radiation it emits is in the uv, and is completely absorbed by the interstellar gas along the line of sight. 相似文献
870.
S.?V.?Molkov A.?M.?Cherepashchuk A.?A.?Lutovinov M.?G.?Revnivtsev K.?A.?Postnov R.?A.?Sunyaev 《Astronomy Letters》2004,30(8):534-539
We analyze the images of the Sagittarius Arm tangent obtained with the IBIS telescope of the INTEGRAL observatory in the energy range 18–120 keV during its observations in the spring of 2003. We detected 28 sources at a statistically significant level with fluxes above 1.4 mCrab in the energy range 18–60 keV. Of these sources, 16 were previously identified as binaries of various classes in our Galaxy, 3 were identified as extragalactic objects, 2 were identified as pulsars in supernova remnants, and 7 sources were of an unknown nature. These observations revealed three new sources. A statistically significant flux in the energy range 60–120 keV was recorded from 13 sources. 相似文献