Abstract
Using 5 GHz radio luminosity at light-curve maximum as a proxy for jet power and black-hole spin measurements obtained via the continuum-fitting method, Narayan & McClintock (2012) presented the first direct evidence for a relationship between jet power and black hole spin for four transient black-hole binaries. We test and confirm their empirical relationship using a fifth source, H1743-322, whose spin was recently measured. We show that this relationship is consistent with Fe-line spin measurements provided that the black hole spin axis is assumed to be aligned with the binary angular momentum axis. We also show that, during a major outburst of a black hole transient, the system reasonably approximates an X-ray standard candle. We further show, using the standard synchrotron bubble model, that the radio luminosity at light-curve maximum is a good proxy for jet kinetic energy. Thus, the observed tight correlation between radio power and black hole spin indicates a strong underlying link between mechanical jet power and black hole spin. Using the fitted correlation between radio power and spin for the above five calibration sources, we predict the spins of six other black holes in X-ray/radio transient systems with low-mass companions. Remarkably, these predicted spins are all relatively low, especially when compared to the high measured spins of black holes in persistent, wind-fed systems with massive companions.
Highlights
Jets are observed in diverse astrophysical systems and by objects spanning a wide range of mass: protoplanetary disks around newly birthed stars, through white dwarfs, neutron stars, stellar-mass black holes, and up to the supermassive black holes that power active galactic nuclei (Livio 1999)
We sharply focus on one particular class of jets, namely, impulsive ballistic jets produced during the brightest phase of outbursting black hole transients
In Appendix A, we validate our “standard candle” assumption (NM12) by showing that during major outbursts the systems we consider reach a substantial fraction of their Eddington limit, and in Appendix B we describe a simple synchrotron bubble model and demonstrate that the radio synchrotron flux density at light-curve maximum is a reasonable proxy for jet kinetic power
Summary
Jets are observed in diverse astrophysical systems and by objects spanning a wide range of mass: protoplanetary disks around newly birthed stars, through white dwarfs, neutron stars, stellar-mass black holes, and up to the supermassive black holes that power active galactic nuclei (Livio 1999). We sharply focus on one particular class of jets, namely, impulsive ballistic jets produced during the brightest phase of outbursting black hole transients. This is an advantageous approach to the study of jets because black holes are the simplest astrophysical objects, and because, as we will show, the jets we consider are produced at very nearly the same (Eddingtonscaled) mass accretion rates. A typical system approaches its Eddington limit, and it approximates a standard candle, as we show in Appendix A
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