SIMBAD references

2001ApJ...549L..77W - Astrophys. J., 549, L77-L80 (2001/March-1)

Slim-disk model for ultraluminous X-ray sources.


Abstract (from CDS):

The ultraluminous X-ray sources (ULXs) are unique in exhibiting moderately bright X-ray luminosities, LX∼1038-1040 ergs.s–1, and relatively high blackbody temperatures, Tin∼1.0-2.0 keV. From the constraint that LX cannot exceed the Eddington luminosity LE, we require relatively high black hole masses, M∼10-100 M; however, for such large masses the standard disk theory predicts lower blackbody temperatures, Tin<1.0 keV. To understand a cause of this puzzling fact, we carefully calculate the accretion flow structure shining at ~LE, fully taking into account the advective energy transport in the optically thick regime and the transonic nature of the flow. Our calculations show that at high accretion rate (M{dot}≳30LE/c2) an apparently compact region with a size of Rin≃(1-3)rg (with rg being the Schwarzschild radius) is shining with a blackbody temperature of Tin≃1.8(M/10 M)–1/4 keV even for the case of a nonrotating black hole. Furthermore, Rin decreases as M{dot} increases, contrary to the canonical belief that the inner edge of the disk is fixed at the radius of the marginally stable last circular orbit. Accordingly, the loci of a constant black hole mass on the H-R diagram (representing the relation between LX and Tin both on the logarithmic scales) are not straight but bent toward the lower M-direction in the frame of the standard disk relation.

We also plot the ASCA data of some ULXs on the same H-R diagram, finding that they all fall on the regions with relatively high masses, M∼10-30 M, and high accretion rates, M{dot}≳10LE/c2. Interestingly, IC 342 source 1, in particular, was observed to move along the constant M line (not constant Rin line) in our simulations. This provides firm evidence that at least some ULXs are shining at ≳LE and contain black holes with M≃10-100 M.

Abstract Copyright:

Journal keyword(s): Accretion, Accretion Disks - Black Hole Physics - X-Rays: Stars

CDS comments: NGC 1313 source A, B = [RSD93] A, B, M81 source X-6, X-8 = [F88] X-6, X-8, IC 342 source 1 = [FT87] IC 342 1

Simbad objects: 9

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