Weak Merging Scenario of CLASH Cluster A209

We study the structural and dynamical properties of A209 based on Chandra and XMM-Newton observations.We obtain detailed temperature,pressure,and entropy maps with the contour binning method,and find a hot region in the NW direction.The X-ray brightness residual map and corresponding temperature profiles reveal a possible shock front in the NW direction and a cold front feature in the SE direction.Combined with the galaxy luminosity density map we propose a weak merger scenario.A young sub-cluster passing from the SE to NW direction could explain the optical subpeak,the intracluster medium temperature map,the X-ray surface brightness excess,and the X-ray peak offset together.

The Year-scale X-Ray Variations in the Core of M87

The analysis of light variation of M87 can help us understand the disk evolution.In the past decade,M87 has experienced several short-term light variabilities related to flares.We also find that there are year-scale X-ray variations in the core of M87.Their light variability properties are similar to clumpy-ADAF.By re-analyzing 56Chandra observations from 2007 to 2019,we distinguish the“non-flaring state”from“flaring state”in the light variability.After removing flaring state data,we identify four gas clumps in the nucleus and all of them can be well fitted by the clumpy-ADAF model.The average mass accretion rate is~0.16M⊙yr^(-1).We analyze the photon index(Γ)-flux(2-10 keV)correlation between the non-flaring state and flaring state.For the non-flaring states,the flux is inversely proportional to the photon index.For the flaring states,we find no obvious correlation between the two parameters.In addition,we find that the flare always occurs at a high mass accretion rate,and after the luminosity of the flare reaches the peak,it will be accompanied by a sudden decrease in luminosity.Our results can be explained as that the energy released by magnetic reconnection destroys the structure of the accretion disk,thus the luminosity decreases rapidly and returns to normal levels thereafter.

A Deprojection Analysis of Abell 1650 with XMM-Newton

We revisit the XMM-Newton observation of the galaxy cluster Abell 1650 with a deprojection technique. We find that the radial deprojected spectra of Abell 1650 can be marginally fitted by a single-temperature model. In order to study the properties of the central gas, we fit the spectra of the central two regions with a two- temperature model. The fits then become significantly better and the cool gas about 1～2 keV can be connected with the gas cooling. Fitting the central spectrum （r≤1′） by using a cooling flow model with an isothermal component yields a small mass deposition rate of 10-7^＋11 M. yr^-1, while the standard cooling flow model can not fit this spectrum satisfactorily except that there exists a cut-off temperature having a level of about 3 keV. From the isothermal model we derive the deprojected electron density profile ne（r）, and then together with the deprojected temperature profile the total mass and gas mass fraction of cluster are also determined. We compare the properties of Abell 1650 with those of Abell 1835 （a large cooling flow cluster） and some other clusters, to explore the difference in properties between large and small cooling flow cluster, and what causes the difference in the cooling flow of different clusters. It has been shown that Abell 1835 has a steeper potential well and thus a higher electron density and a lower temperature in its center, indicating that the shape of the gravitational potential well in central region determines the cooling flow rates of clusters. We calculate the potential, internal and radiated energies of these two clusters, and find that the gas energies in both clusters are conserved during the collapsing stage.

The YSZ,Planck - YSZ,XMM scaling relation and its difference between cool-core and non-cool-core clusters

We construct a sample of 70 clusters using data from XMM-Newton and Planck to investigate the YSZ,Planck-YSZ,XMM scaling relation and the cool-core influences on this relation.YSZ,XMM is calculated by accurately de-projected temperature and electron number density profiles derived from XMMNewton.YSZ,Planckis the latest Planck data restricted to our precise X-ray cluster size θ500.To study the cool-core influences on the YSZ,Planck-YSZ,XMM scaling relation,we apply two criteria,namely the limits of central cooling time and classic mass deposition rate,to distinguish cool-core clusters(CCCs) from non-cool-core clusters(NCCCs).We also use YSZ,Planckfrom other papers,which are derived from different methods,to confirm our results.The intercept and slope of the YSZ,Planck-YSZ,XMM scaling relation are A =-0.86 ± 0.30 and B = 0.83 ± 0.06 respectively.The intrinsic scatter is σins= 0.14 ± 0.03.The ratio of YSZ,Planck/YSZ,XMM is 1.03 ± 0.05,which is in excellent statistical agreement with unity.Discrepancies in the YSZ,Planck-YSZ,XMM scaling relation between CCCs and NCCCs are found in the observation.They are independent of the cool-core classification criteria and YSZ,Planckcalculation methods,although the discrepancies are more significant under the classification criteria of classic mass deposition rate.The intrinsic scatter of CCCs(0.04) is quite small compared to that of NCCCs(0.27).The ratio of YSZ,Planck/YSZ,XMM for CCCs is 0.89 ± 0.05,suggesting that CCCs’ YSZ,XMM may overestimate the Sunyaev-Zel’dovich(SZ)signal.By contrast,the ratio of YSZ,Planck/YSZ,XMM for NCCCs is 1.14 ± 0.12,which indicates that NCCCs’ YSZ,XMM may underestimate the SZ signal.

Timing analysis of the black hole candidate EXO 1846–031 with Insight-HXMT monitoring

We present the observational results from a detailed timing analysis of the black hole candidate EXO 1846-031 during its outburst in 2019 with the observations of Insight-HXMT,NICER and MAXI.This outburst can be classified roughly into four different states.Type-C quasi-periodic oscillations(QPOs)observed by NICER(about 0.1-6 Hz)and Insight-HXMT(about 0.7-8 Hz)are also reported in this work.Meanwhile,we study various physical quantities related to QPO frequency.The QPO rms-frequency relationship in the energy band 1-10 keV indicates that there is a turning pointing in frequency around2 Hz,which is similar to that of GRS 1915+105.A possible hypothesis for the relationship above may be related to the inclination of the source,which may require a high inclination to explain it.The relationships between QPO frequency and QPO rms,hardness,total fractional rms and count rate have also been found in other transient sources,which can indicate that the origin of type-C QPOs is non-thermal.

The performance of out-of-time events of the follow-up X-ray telescope onboard Einstein probe

Purpose:The purpose of this study is to investigate the performance of out-of-time events(OoT events)in the Follow-up X-ray Telescope(FXT)onboard the Einstein Probe.The OoT events,registered on the PN-CCD during its readout time,can provide information on the sources,e.g.,spectral indices,and diagnose the behavior of pile-up.Methods:In order to analyze the characteristics of OoT events,we simulated sources,each of which had been modeled using an absorbed power law combined with Gaussians,in different FXT modes and different luminosities.This allowed us to determine the OoT spectral indices and pile-up effect.Results:In the timing mode of FXT,the OoT events occupy a large proportion and the OoT correction must be done with the assumption that all photons originate from the source position on the CCD.While for some bright sources,the OoT events may be sufficient to derivate the source spectra,especially when pile-up occurs,particularly in the full frame mode and the partial window mode of FXT.Conclusion:We conclude that the OoT events can provide additional information about the celestial sources and can be used to estimate whether the pile-up occurs or not and the scope of pile-up.Furthermore,they can be also used to determine the new sources and improve the detection significance of a source.