In the radiation-hydrodynamics model,the time lag and fractional root-mean-squared(rms) amplitude as a function of emitted photon energy should show a minimum on the normal branch oscillations.This has been seen in the Z-sources Cyg X-2 and GX 5-1.Here,using the observations from the Rossi X-ray Timing Explorer(RXTE),we study the energy dependence of normal branch QPOs in the peculiar Z-source Cir X-1.We discuss the results in the context of radiation-hydrodynamics and the Comptonization model.
QU JinLu1,LU Yu1,2,DING GuoQiang3,ZHANG Fan1,LEI YaJuan1 & LI ZhiBing1 1 Key Laboratory for Particle Astrophysics,Institute of High Energy Physics,Chinese Academy of Sciences,Beijing 100049,China
Based the Alfven wave oscillation model(AWOM) and relativistic precession model(RPM) for twin kHz QPOs,we estimate the emission positions of most detected kHz QPOs to be at r=18+/-3 km(R/15 km),except Cir X-1 at r-30+/-5 km(R/15 km).For the proposed Keplerian frequency as an upper limit to kHz QPO,the spin effects in Kerr Spacetime are discussed,which have about a 5%(2%) modification for that of the Schwarzchild case for the spin frequency of 1000(400) Hz.The application to the four typical QPO sources,Cir X-1,Sco X-1,SAX J1808.4-3658 and XTE 1807-294,is mentioned.
ZHANG ChengMin1,WEI YingChun1,YIN HongXing1,ZHAO YongHeng1,LEI YaJuan2,SONG LiMing2,ZHANG Fan2 & YAN Yan3 1 National Astronomical Observatories,Chinese Academy of Sciences,Beijing 100012,China
We have investigated the relation between the root mean square(rms) variability and the X-ray flux(rms-flux relation) of the Z source Cyg X-2,and as well the energy dependence based on the Rossi X-ray Timing Explorer(RXTE) observations.We currently focus on the horizontal branch(HB),due to the negative correlation in flux of the soft and the hard X-rays.The rms-flux correlation has energy dependence as follows:positive at hard X-rays(above 10 keV) but negative at soft X-rays(below 10 keV).This provides a feature different from the previous one,and may be suggestive of different origins of X-rays below and above 10 keV.Nevertheless,the overall spectrum can be well fitted with a model consisting of a blackbody and Comptonization components,but the fitting results do not reveal any features around 10 keV that could account for such a change in the rms-flux relation.
LI ZhiBing,LEI YaJuan,QU JinLu,ZHANG Shu & SONG LiMing Key Laboratory for Particle Astrophysics,Institute of High Energy Physics,Chinese Academy of Sciences(CAS),Beijing 100049,China
We present a new method for the analysis of Abell 1835 observed by XMM-Newton.The method is a combination of the Direct Demodulation technique and deprojection.We eliminate the effects of the point spread function(PSF) with the Direct Demodulation technique.We then use a traditional deprojection technique to study the properties of Abell 1835.Compared to only using a deprojection method,the central electron density derived from this method increases by 30%,while the temperature profile is similar.
WANG YuSa,JIA ShuMei & CHEN Yong Key Laboratory for Particle Astrophysics,Institute of High Energy Physics,Chinese Academy of Sciences,Beijing 100049,China
The spatial distributions of old neutron stars (NSs) with ages 109 to 1010 yr in our Galaxy are investigated by Monte Carlo simulation under two different initial random velocity models.It is found that the scale heights of the distribution increase with the Galactic radial distance.The location of the peak of the NS distribution is closer to the Galactic center than that of their progenitors.The results from our detailed numerical analysis reveal that there is resemblance between the simulated old NS distribution and the structure of the observed HI disk.
WEI YingChunZHANG ChengMinWU XinJiZHAO YongHengCHOU ChiKangLUO ALi
The evolutionary scenario of neutron star binaries is still an essential enigma in both stellar astrophysics and high energy astrophysics.In order to explore the scenario,we include the accumulation of data on the orbits and spins of compact binaries in multi-wavelength ranging from radio to X-ray,such as radio pulsar binaries,HMXBs,and LMXBs,filling them into the so called "Corbet Diagram" which initially investigated the period of orbit(Porb)～the period of spin(Pspin) correlation of HMXBs.We find that the evolutionary scenario comes more clearly and makes strong confirmation of the connection between LMXBs and radio pulsar binaries,predicted by the recycle process.However,the origins of radio pulsar binaries sre still unknown.Accretion Induced Collapse(AIP) process may be a mechanism which can explain the origin of the binary millisecond pulsars with relatively longer orbital periods.A correlation of P1/3orb～P-1spin of LMXBs and radio pulsar binaries may exist.
