1. On the X-ray origin in Quiescent Black Hole X-ray Binaries Hui Zhang ( 张惠 ) Shanghai Astronomical Observatory, Chinese Academy of Sciences Collaborators: Feng Yuan (SHAO) Wei Cui (Purdue University) Wei Cui (Purdue University) Gabor Pszota (Purdue University) Gabor Pszota (Purdue University)

2. Outline 1.Introduction: (a)observation of Black hole X-ray binary (a)observation of Black hole X-ray binary (b) theoretical model: Coupled accretion-Jet (b) theoretical model: Coupled accretion-Jet 2. Prediction of Yuan & Cui for quiescent state 3.X-ray Observation results of three sources in quiescent state sources in quiescent state 4.Our modeling results

3. What is black hole X-ray binary?  More than 40 black hole X-ray binaries and their candidates have been found in our Galaxy.  They are in the quiescent state in most of their life.  When the accretion rate increases, some instability mechanism happen, then outburst occurs, going through various states

4. Models for various Spectral states Esin et al. 1997, ApJ

5. Spectral states in black hole binaries Quiescent State: Quiescent State: - Large transient radius; - very low luminosity, L x ~10 30.5 -10 33.5 erg/s ; - power law spectrum photon index  =1.5~2.1; - Jet is thought to be exist Hard State: Hard State: - power law spectrum >80% (2-20keV) - power law spectrum photon index  =1.4~2.1 - strong varibility (QPO) - strong radio emission (Jet exist) SPL/Very High State/Intermediate State : SPL/Very High State/Intermediate State : - power law spectrum photon index  >2.4 - power law component>20% (2-20keV)and QPO - power law component>50% (2-20keV) and no QPO - radio flare at HS  VHS High Soft State (Thermal Dominant State): High Soft State (Thermal Dominant State): - disk component>75%(2-20keV) - no QPO or QPO is toot weak to be detected - very weak radio emission and no Jet exist - power law spectrum photon index  =2.1~4.8 Done, C. 2007, A&ARv

6. Coupled Accretion-Jet Models SSD: Opt/UV ADAF: X-ray, Opt/UV Jet: Radio, infrared

7. Coupled Accretion-Jet Models Standard thin disk (SSD):  Standard thin disk (SSD): -geometrical thin, optical thick - T  r -3/4 -multicolor black body spectrum Advection Dominated Accretion Flow (ADAF):  Advection Dominated Accretion Flow (ADAF): -geometrical thick, optical thin -Compton scattering, synchrotron, bremsstrahlung -strong advection, low emission efficiency -double high temperature plasma Jet model:  Jet model: -internal shock -power law distribution of electron -synchrotron emission dominated

8. ADAF-Jet Models for hard state Yuan, Cui & Narayan, 2005, ApJ Success in hard state of XTE J1118+480! SSD ADAF Jet

9. Radio/X-ray correlation Gallo et al. 2003, MNRAS, 344 L R ~L X 0.7

10. Yuan & Cui 2005 prediction 1. When the accretion rate decreases, the correlation between the radio and X-ray still exist, but when the luminosity lower than a certain critical value, the correlation will change and become more steeper than before. Because L acc,x  M 2, L Jet,x  M. So most of the X-ray comes from Jet in quiescent state. 2.Because jet radiation dominates below this critical luminosity, the spectrum of X-ray is a power law.  

11. The change of the radio—X-ray correlation from hard to quiescent states The critical luminosity : Yuan & Cui 2005,ApJ L crit ~(10 -5 ~10 -6 )L Edd

12. Recent new study result: Yuan & Cui 2005 also predicted: Recently, Wrobel, Terashima & Ho 2008 studied two quiesent LLAGN in NGC 4621 and NGC 4697, they found the observed radio luminosity is within a factor of 3 of the predicted value (based on L x ~10 -9 L Edd and the relation above).

13. XMM/Newton Observation of Quiescent Sources XTE J1550-564GRO J1655-40 We observed two black hole X-ray binaries XTE J1550-564 and GRO J1655-40 V404 Cyg for long time by XMM-Newton. We also analysed V404 Cyg from archival data.

14. Jet SSD ADAF Modeling results (GRO J1655-40)

15. Jet SSD ADAF Modeling results (V404Cyg)

16. Jet SSD ADAF Modeling results (XTE J1550-564)

17. Conclusion In quiescent black hole X-ray binaries, the X-ray emission originates from Jet ! Jet model can fit all the X-ray spectrum of these three sources, but for XTE J1550-564, It can also be modeled by ADAF. Because the spectrum of ADAF is curved at low accretion rate, however, the spectrum of Jet is power-law.