Astronomy & Astrophysics

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$\begin{figure} \par\includegraphics[width=8.8cm,clip]{AA7567f1.eps}\end{figure}$ Figure 1: Left - The basic components of a microquasar: an accreting compact object (a neutron star or a stellar-mass black hole), a donor star, and radio emitting relativistic jets. Right - The basic components of a classical (slow) X-ray pulsar: an accreting neutron star with a very strong magnetic field ( $\ge$ 1012 G) emitting X-rays at the polar caps. A millisecond X-ray pulsar ( $B~{\protect \la}~10^{8}$ G) could switch between a microquasar and an X-ray pulsar scenario, depending on the accretion mass rate (see Sect. 3.3). Figure not drawn to scale.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{AA7567f2.eps}\end{figure}$ Figure 2: Flowchart for the jet formation process. We show here the parallelism between the presence of a jet and the X-ray states cycle. The X-ray state names are mentioned for both, BH and NS XRBs. In the case of neutron stars the distinction between atoll- and Z-type sources (see Sect. 3.2) is made: IS = Island State / HB = Horizontal Branch, NB = Normal Branch, BS = Banana State / FB = Flaring Branch.
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{AA7567f3.eps}\end{figure}$ Figure 3: 3D plot of the Alfvén radius normalised to the stellar radius ( $R_{\rm A}/R_*$ ). The intersection between the function and the $R_{\rm A}/R_*= 1$ plane indicates the combination of the magnetic field and the mass accretion rate values for which plasma pressure, $P_{\rm p}$ , and magnetic field pressure, $P_{\rm B}$ , balance each other at the surface of the star. This ensures that the initial condition for jet formation ( $P_{\rm B} < P_{\rm p}$ ) is fulfilled over the whole accretion disk. A zoom of this region is shown at the bottom of the figure.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{AA7567f4.eps}\end{figure}$ Figure 4: Schwarzschild-BH XRBs: imposing the basic condition $R_{\rm A}/R_{\rm LSO}= 1$ we obtain a relation between the magnetic field strength at the last stable orbit (LSO = $6GM_{\bullet }/c^2$ ) and the mass accretion rate for different values of the BH mass. Radiative efficiency for a Schwarzschild BH is $\eta = 0.06$ . The $B_{\rm Eddington}$ curve is the upper limit for the magnetic field strength that corresponds to a mass accretion rate equal to the Eddington critical rate.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{AA7567f5.eps}\end{figure}$ Figure 5: Kerr-BH XRBs: imposing the basic condition $R_{\rm A}/R_{\rm LSO}= 1$ we obtain a relation between the magnetic field strength at the innermost possible stable orbit (LSO = $GM_{\bullet }/c^2$ ) and the mass accretion rate for different values of the BH mass. Radiative efficiency for a Kerr-BH is $\eta = 0.4$ . The $B_{\rm Eddington}$ curve is the same as in Fig. 4.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{AA7567f6.eps}\end{figure}$ Figure 6: Supermassive BHs: using Eqs. (3) and (4) we obtain by standard scaling a relation between the magnetic field strength at the last stable orbit and the mass accretion rate for different values of the mass of supermassive BHs. The cases of Schwarzschild and Kerr BHs are considered here with solid and dashed lines respectively. The $B_{\rm Eddington}$ curve is the same as in Fig. 4.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{AA7567f5.eps}\end{figure}$	Figure 5: Kerr-BH XRBs: imposing the basic condition $R_{\rm A}/R_{\rm LSO}= 1$ we obtain a relation between the magnetic field strength at the innermost possible stable orbit (LSO = $GM_{\bullet }/c^2$ ) and the mass accretion rate for different values of the BH mass. Radiative efficiency for a Kerr-BH is $\eta = 0.4$ . The $B_{\rm Eddington}$ curve is the same as in Fig. 4.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{AA7567f6.eps}\end{figure}$	Figure 6: Supermassive BHs: using Eqs. (3) and (4) we obtain by standard scaling a relation between the magnetic field strength at the last stable orbit and the mass accretion rate for different values of the mass of supermassive BHs. The cases of Schwarzschild and Kerr BHs are considered here with solid and dashed lines respectively. The $B_{\rm Eddington}$ curve is the same as in Fig. 4.
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