A recently released XMM-Newton note revealed a significant calibration issue between nuclear spectroscopic telescope array(NuSTAR)and XMM-Newton European Photon Imaging Camera(EPIC)and provided an empirical correction...A recently released XMM-Newton note revealed a significant calibration issue between nuclear spectroscopic telescope array(NuSTAR)and XMM-Newton European Photon Imaging Camera(EPIC)and provided an empirical correction to the EPIC effective area.To quantify the bias caused by the calibration issue in the joint analysis of XMM-NuSTAR spectra and verify the effectiveness of the correction,in this work,we perform joint-fitting of the NuSTAR and EPIC-pn spectra for a large sample of 104 observation pairs of 44 X-ray bright active galactic nuclei(AGN).The spectra were extracted after requiring perfect simultaneity between the XMM-Newton and NuSTAR exposures(merging good time intervals(GTIs)from two missions)to avoid bias due to the rapid spectral variability of the AGN.Before the correction,the EPIC-pn spectra are systematically harder than the corresponding NuSTAR spectra by■subsequently yielding significantly underestimated cutoff energy E_(cut)and the strength of reflection component R when performing joint-fitting.We confirm that the correction is highly effective and can commendably erase the discrepancy in best-fitΓ,E_(cut),and R.We thus urge the community to apply the correction when joint-fitting XMM-NuSTAR spectra,but note that the correction is limited to 3–12 keV and therefore not applicable when the soft X-ray band data are included.Besides,we show that as merging GTIs from two missions would cause severe loss of NuSTAR net exposure time,in many cases,joint-fitting yields no advantage compared with utilizing NuSTAR data alone.Finally,We present a technical note on filtering periods of high background flares for XMM-Newton EPIC-pn exposures in the small window(SW)mode.展开更多
AT2019 wey is a new galactic X-ray binary that was first discovered as an optical transient by the Asteroid Terrestrial-impact Last Alert System(ATLAS)on December 7,2019.AT2019 wey consists of a black hole candidate a...AT2019 wey is a new galactic X-ray binary that was first discovered as an optical transient by the Asteroid Terrestrial-impact Last Alert System(ATLAS)on December 7,2019.AT2019 wey consists of a black hole candidate as well as a low-mass companion star(M_(star)≤1.0 M_(■))and is likely to have a short orbital period(P_(orb)≤16h).Although AT2019 wey began activation in the X-ray band on March 8,2020,it did not enter the soft state during almost the entire outburst.In this study,we present a detailed spectral analysis of AT2019 wey in the low/hard state during its X-ray outburst on the basis of Nuclear Spectroscopic Telescope Array(Nu S T AR)observations.We obtain tight constraints on several of its important physical parameters by applying the state of the art relxill relativistic reflection model family.In particular,we determine that the measured inner radius of the accretion disk is most likely to have extended to the innermost stable circular orbit(ISCO)radius,i.e.,R_(in)=1.38^(+0.23)_(-0.16)R_(ISCO).Hence,assuming R_(in)=R_(ISCO),we find the spin of AT2019 wey to be a*~0.97,which is close to the extreme and an inner disk inclination angle of i~22°.Additionally,according to our adopted models,AT2019 wey tends to have a relatively high iron abundance of AFe~5A_(Fe,■)and a high disk ionization state of logξ~3.4.展开更多
One ultraluminous X-ray source in M82 has recently been identified as an accreting neutron star （named NuSTAR J095551＋6940.8）. It has a super-Eddington luminosity and is spinning up. An aged magnetar is more likely...One ultraluminous X-ray source in M82 has recently been identified as an accreting neutron star （named NuSTAR J095551＋6940.8）. It has a super-Eddington luminosity and is spinning up. An aged magnetar is more likely to be a low magnetic field magnetar. An accreting low magnetic field magnetar may explain both the super- Eddington luminosity and the rotational behavior of this source. Considering the effect of beaming, the spin-up rate is understandable using the traditional form of accretion torque. The transient nature and spectral properties of M82 X-2 are discussed. The theoretical range of periods for accreting magnetars is provided. Three observational appearances of accreting magnetars are summarized.展开更多
基金supported by the National Natural Science Foundation of China(12033006,12192221,123B2042).
文摘A recently released XMM-Newton note revealed a significant calibration issue between nuclear spectroscopic telescope array(NuSTAR)and XMM-Newton European Photon Imaging Camera(EPIC)and provided an empirical correction to the EPIC effective area.To quantify the bias caused by the calibration issue in the joint analysis of XMM-NuSTAR spectra and verify the effectiveness of the correction,in this work,we perform joint-fitting of the NuSTAR and EPIC-pn spectra for a large sample of 104 observation pairs of 44 X-ray bright active galactic nuclei(AGN).The spectra were extracted after requiring perfect simultaneity between the XMM-Newton and NuSTAR exposures(merging good time intervals(GTIs)from two missions)to avoid bias due to the rapid spectral variability of the AGN.Before the correction,the EPIC-pn spectra are systematically harder than the corresponding NuSTAR spectra by■subsequently yielding significantly underestimated cutoff energy E_(cut)and the strength of reflection component R when performing joint-fitting.We confirm that the correction is highly effective and can commendably erase the discrepancy in best-fitΓ,E_(cut),and R.We thus urge the community to apply the correction when joint-fitting XMM-NuSTAR spectra,but note that the correction is limited to 3–12 keV and therefore not applicable when the soft X-ray band data are included.Besides,we show that as merging GTIs from two missions would cause severe loss of NuSTAR net exposure time,in many cases,joint-fitting yields no advantage compared with utilizing NuSTAR data alone.Finally,We present a technical note on filtering periods of high background flares for XMM-Newton EPIC-pn exposures in the small window(SW)mode.
基金supported by the National Program on Key Research and Development Project(Grant No.2016YFA0400804)the National Natural Science Foundation of China(Grant No.U1838114)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB23040100)。
文摘AT2019 wey is a new galactic X-ray binary that was first discovered as an optical transient by the Asteroid Terrestrial-impact Last Alert System(ATLAS)on December 7,2019.AT2019 wey consists of a black hole candidate as well as a low-mass companion star(M_(star)≤1.0 M_(■))and is likely to have a short orbital period(P_(orb)≤16h).Although AT2019 wey began activation in the X-ray band on March 8,2020,it did not enter the soft state during almost the entire outburst.In this study,we present a detailed spectral analysis of AT2019 wey in the low/hard state during its X-ray outburst on the basis of Nuclear Spectroscopic Telescope Array(Nu S T AR)observations.We obtain tight constraints on several of its important physical parameters by applying the state of the art relxill relativistic reflection model family.In particular,we determine that the measured inner radius of the accretion disk is most likely to have extended to the innermost stable circular orbit(ISCO)radius,i.e.,R_(in)=1.38^(+0.23)_(-0.16)R_(ISCO).Hence,assuming R_(in)=R_(ISCO),we find the spin of AT2019 wey to be a*~0.97,which is close to the extreme and an inner disk inclination angle of i~22°.Additionally,according to our adopted models,AT2019 wey tends to have a relatively high iron abundance of AFe~5A_(Fe,■)and a high disk ionization state of logξ~3.4.
基金Supported by the National Natural Science Foundation of China
文摘One ultraluminous X-ray source in M82 has recently been identified as an accreting neutron star （named NuSTAR J095551＋6940.8）. It has a super-Eddington luminosity and is spinning up. An aged magnetar is more likely to be a low magnetic field magnetar. An accreting low magnetic field magnetar may explain both the super- Eddington luminosity and the rotational behavior of this source. Considering the effect of beaming, the spin-up rate is understandable using the traditional form of accretion torque. The transient nature and spectral properties of M82 X-2 are discussed. The theoretical range of periods for accreting magnetars is provided. Three observational appearances of accreting magnetars are summarized.
