X-rays from Quiescent Black Holes: Accretion

or Jet Powered? Wei Cui

Purdue UniversityCollaborators: Gabor Pszota, Purdue University Feng Yuan, Shanghai Astronomical Observatory Hui Zhang, Shanghai Astronomical Observatory

Stellar-Mass Black Holes21 dynamically determined BH X-ray binaries

about 2 dozens more BH candidatesOnly 4 are persistent X-ray sources

all with OB secondary starsTransients constitute the majority

nearly all with late-type secondary stars

Outbursts

Spectral States

Xue, Wu, & Cui 2008

XTE J1550-564

Low-Hard State

Jet: radio, IRCold accretion flow:IR, optical, UV, soft X-ray

Hot accretion flow:optical, UV, X-ray

Yuan, Cui, & Narayn 2005

Modeling Low-Hard State

Jet

Non-thermalelectronsin accretionflows

Thin disk

ADAF

Yuan, Cui, & Narayan 2005Yuan, Cui, & Narayn 2005

Extrapolation to Quiescence

The shape of X-ray spectra deviates from a power law in

the quiescent state.

Yuan & Cui 2005

XMM-Newton ObservationsGRO J1655-40: 185 ks, Fx = 5.8 x 10-14 erg s-1 cm-2

in two segments, separated by about 1 month

XTE J1550-40: 59 ks, Fx = 4.9 x 10-14 erg s-1 cm-2

but severely contaminatedV404 Cyg: 40 ks, Fx = 40 x 10-14 erg s-1 cm-2

archival observation

Quiescent X-ray Spectra

Pszota et al. 2008

Can AFAF Fit?

Pszota et al. 2008

ConclusionsThe observed X-ray spectra of GRO J1655-60 and V404 Cyg in the quiescent state deviate strongly from the expectation of ADAF models.

The power-law shape of the X-ray spectra can be explained by a dominant jet contribution.

The case of XTE J1550-564 is still ambiguous, as limited by the statistics of the data. Pszota et al. 2008, MNRAS

Another Test

Yuan & Cui 2005