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Astron. Astrophys. 362, L53-L56 (2000)

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4. Discussion

The the properties of the outburst of XTE J2012+381 are very similar to those of the X-ray Novae that have been associated with black hole candidates. It has a FRED (fast-rise-exponential-decay) light curve, with secondary maxima, as is typical for X-ray transients (Chen, Shrader & Livio 1997).

The spectrum of the source can be well described by standard two-component model which is typical for black hole candidate X-ray binaries (Tanaka & Lewin 1995). The evolution of the energy spectrum of XTE J2012+381 can be characterized as a gradual increase of the contribution of the soft thermal component as the overall X-ray flux decreases.

Our calculations show that the value of model parameter [FORMULA], inferred from the soft spectral component approximation is nearly constant during the decay phase of the outburst (Table 2) in general agreement with earlier results of Zhang et al. 1998. However we believe that it is premature to assume a constant radius of inner accretion disk during the outburst.  2

The PDS of XTE J2012+381 is also very typical for the VHS of black hole candidates with dominant soft spectral component. The energy dependence of the fractional rms provided another hint at the universal correlation between the amplitude of the variability and relative strength of the hard spectral component.

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© European Southern Observatory (ESO) 2000

Online publication: October 30, 2000