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تسجيل مستخدم جديدMultiwavelength Observations of the Black Hole Candidate XTE J1550-564 during the 2000 Outburst
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R. K. Jain
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We report optical, infrared, and X-ray light curves for the outburst, in 2000, of the black hole candidate XTE J1550-564. We find that the start of the outburst in the H and V bands precedes that seen in the RXTE All Sky Monitor by 11.5 +/- 0.9 and 8.8 +/- 0.6 days, respectively; a similar delay has been observed in two other systems. About 50 days after the primary maxima in the VIH light curves, we find secondary maxima, most prominently in H. This secondary peak is absent in the X-ray light curve, but coincides with a transition to the low/hard state. We suggest that this secondary peak may be due to non-thermal emission associated with the formation of a jet.
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We study hard states of the black-hole binary XTE J1550--564 during its 2000 outburst. In order to explain those states at their highest luminosities, $Lsim 10%$ of the Eddington luminosity, $L_{rm E}$, we propose a specific hot accretion flow model.
We point out that the highest values of the hard-state $L$ are substantially above the $L$ an advection-dominated accretion flow (ADAF) can produce, $sim 0.4alpha^2 L_{rm E}$, which is only $sim (3$--$4)%L_{rm E}$ even for $alpha$ as high as 0.3. On the other hand, we successfully explain the hard states with $Lsim (4$--$10)%$ using the luminous hot accretion flow (LHAF) model. As $10%L_{rm E}$ is also roughly the highest luminosity an LHAF can produce, such an agreement between the predicted and observed highest luminosities provides by itself strong support for this model. Then, we study multi-waveband spectral variability during the 2000 outburst. In addition to the primary maxima in the optical light curves, secondary maxima were detected after the transition from the very high state to the hard state. We show that the secondary maxima are well modeled by synchrotron emission from a jet formed during the state transition. We argue that the absence of the corresponding secondary peak in the X-ray light curve indicates that the X-ray jet emission, regardless of its radiative process, synchrotron or its Comptonization, is not important in the hard state compared to the emission from the accretion flow.
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