The radiative mechanism of black hole X-ray transients （BHXTs） in their quiescent states （defined as the 2-10 keV X-ray luminosity ≤ 10^34 erg s-1） remains unclear. In this work, we investigate the quasi-simultan...The radiative mechanism of black hole X-ray transients （BHXTs） in their quiescent states （defined as the 2-10 keV X-ray luminosity ≤ 10^34 erg s-1） remains unclear. In this work, we investigate the quasi-simultaneous quiescent state spectrum （including radio, infrared, optical, ultraviolet and X-ray） of two BHXTs, A0620-00 and XTE J1118＋480. We find that these two sources can be well described by a coupled accretion - jet model. More specifically, most of the emission （radio up to infrared, and the X-ray waveband） comes from the collimated relativistic jet. Emission from hot accretion flow is totally insignificant, and it can only be observed in mid-infrared （the synchrotron peak）. Emission from the outer cold disk is only evident in the UV band. These results are consistent with our previous investigation on the quiescent state of V404 Cyg and confirm that the quiescent state is jet-dominated.展开更多
We study spectral and temporal properties of Galactic short orbital period transient black hole XTE J1118+480 during its 2005 outburst using archival data of RXTE PCA and HEXTE instruments in the combined energy range...We study spectral and temporal properties of Galactic short orbital period transient black hole XTE J1118+480 during its 2005 outburst using archival data of RXTE PCA and HEXTE instruments in the combined energy range of 3−100 keV.Spectral analysis with the physical two component advective flow(TCAF)model allows us to understand the accretion flow properties of the source.We found that this outburst of XTE J1118+480 is an unconventional outburst as the source was only in the hard state(HS).Our spectral analysis suggests that during the entire outburst,the source was highly dominated by the low angular momentum sub-Keplerian halo rate.Since the source was active in radio throughout the outburst,we make an effort to estimate X-ray contribution of jets to total observed X-ray emissions from the spectral analysis with the TCAF model.The total X-ray intensity shows a similar nature of evolution as that of radio and jet X-ray fluxes.This allowed us to define this‘outburst’also as a jet dominated‘outburst’.Total X-ray flux is also found to subside when jet activity disappears.Our detailed spectral analysis also indicated that although the source was only in the HS during the outburst,in the late declining phase the spectrum became slightly softer due to the slow rise in the Keplerian disk rate.展开更多
基金supported by the National Basic Research Program of China(973 Program,Grant 2014CB845800)the National Natural Science Foundation of China(Grant Nos.11203057,11103061,11133005 and 11121062)the Strategic Priority Research Program“The Emergence of Cosmological Structures”of the Chinese Academy of Sciences(Grant XDB09000000)
文摘The radiative mechanism of black hole X-ray transients （BHXTs） in their quiescent states （defined as the 2-10 keV X-ray luminosity ≤ 10^34 erg s-1） remains unclear. In this work, we investigate the quasi-simultaneous quiescent state spectrum （including radio, infrared, optical, ultraviolet and X-ray） of two BHXTs, A0620-00 and XTE J1118＋480. We find that these two sources can be well described by a coupled accretion - jet model. More specifically, most of the emission （radio up to infrared, and the X-ray waveband） comes from the collimated relativistic jet. Emission from hot accretion flow is totally insignificant, and it can only be observed in mid-infrared （the synchrotron peak）. Emission from the outer cold disk is only evident in the UV band. These results are consistent with our previous investigation on the quiescent state of V404 Cyg and confirm that the quiescent state is jet-dominated.
基金This work made use of PCA and HEXTE data of NASA’s RXTE satellite.Research of D.D.and S.K.C.is supported in part by the Higher Education Dept.of the Govt.of West Bengal,India.D.D.and S.K.C.also acknowledge partial support from ISRO sponsored RESPOND project(ISRO/RES/2/418/17-18)fund.D.C.and D.D.acknowledge support from DST/SERB sponsored Extra Mural Research project(EMR/2016/003918)+2 种基金fund.A.J.and D.D.acknowledge support from DST/GITA sponsored India-Taiwan collaborative project(GITA/DST/TWN/P-76/2017)fund.A.J.acknowledges CSIR SRF fellowship(09/904(0012)2K18 EMR-1)post-doctoral fellowship of PRL,Ahmedabad,India.K.C.acknowledges support from DST/INSPIRE fellowship(IF 170233).
文摘We study spectral and temporal properties of Galactic short orbital period transient black hole XTE J1118+480 during its 2005 outburst using archival data of RXTE PCA and HEXTE instruments in the combined energy range of 3−100 keV.Spectral analysis with the physical two component advective flow(TCAF)model allows us to understand the accretion flow properties of the source.We found that this outburst of XTE J1118+480 is an unconventional outburst as the source was only in the hard state(HS).Our spectral analysis suggests that during the entire outburst,the source was highly dominated by the low angular momentum sub-Keplerian halo rate.Since the source was active in radio throughout the outburst,we make an effort to estimate X-ray contribution of jets to total observed X-ray emissions from the spectral analysis with the TCAF model.The total X-ray intensity shows a similar nature of evolution as that of radio and jet X-ray fluxes.This allowed us to define this‘outburst’also as a jet dominated‘outburst’.Total X-ray flux is also found to subside when jet activity disappears.Our detailed spectral analysis also indicated that although the source was only in the HS during the outburst,in the late declining phase the spectrum became slightly softer due to the slow rise in the Keplerian disk rate.
