Black Hole Spin via Continuum Fitting and the Role of Spin in Powering Transient Jets (1303.1583v2)

Abstract: The spins of ten stellar black holes have been measured using the continuum-fitting method. These black holes are located in two distinct classes of X-ray binary systems, one that is persistently X-ray bright and another that is transient. Both the persistent and transient black holes remain for long periods in a state where their spectra are dominated by a thermal accretion disk component. The spin of a black hole of known mass and distance can be measured by fitting this thermal continuum spectrum to the thin-disk model of Novikov and Thorne; the key fit parameter is the radius of the inner edge of the black hole's accretion disk. Strong observational and theoretical evidence links the inner-disk radius to the radius of the innermost stable circular orbit, which is trivially related to the dimensionless spin parameter a_* of the black hole (|a_| < 1). The ten spins that have so far been measured by this continuum-fitting method range widely from a_ \approx 0 to a_* > 0.95. The robustness of the method is demonstrated by the dozens or hundreds of independent and consistent measurements of spin that have been obtained for several black holes, and through careful consideration of many sources of systematic error. Among the results discussed is a dichotomy between the transient and persistent black holes; the latter have higher spins and larger masses. Also discussed is recently discovered evidence in the transient sources for a correlation between the power of ballistic jets and black hole spin.

• The paper demonstrates that the continuum-fitting method reliably measures black hole spin by analyzing the thermal spectra of accretion disks.
• It presents spin measurements for ten stellar black holes with values ranging from near-zero to over 0.95, underscoring methodological robustness.
• The study empirically links black hole spin to transient jet power, supporting theoretical models based on the Penrose process and Blandford-Znajek mechanism.

Insights into Black Hole Spin Measurement and Jet Power Correlation

The academic paper, "Black Hole Spin via Continuum Fitting and the Role of Spin in Powering Transient Jets," authored by Jeffrey E. McClintock, Ramesh Narayan, and James F. Steiner, provides an in-depth analysis of black hole spin measurements using the continuum-fitting method, and explores the correlation between black hole spin and the power of transient jets. This analysis is crucial for understanding the physics underpinning black holes and their interaction with the surrounding environment, particularly within the context of X-ray binary systems.

The paper begins with a review of the continuum-fitting method, which is employed to measure the spin of stellar black holes. This method utilizes the thin accretion disk model developed by Novikov and Thorne (NT model) to interpret the thermal spectrum emitted by the accretion disk. The key parameter derived from this model is the innermost stable circular orbit (ISCO), which is directly related to the dimensionless spin parameter, $a_*$. The spins of ten stellar black holes have been measured using this method, showing a wide range from $a_* \approx 0$ to $a_* > 0.95$.

A significant contribution of this paper is the robust demonstration of the continuum-fitting method's reliability. Through hundreds of independent measurements, corroborated by strong observational evidence and GRMHD simulations, the NT model's assumptions, particularly the zero-torque condition at the ISCO, have been validated despite minor systematic errors. However, the method hinges on accurate estimates of the mass $M$, accretion disk inclination $i$, and distance $D$, with observational errors in these parameters primarily dominating the error budget for $a_*$.

The analysis further distinguishes between two classes of black holes in X-ray binaries: persistent systems, typically associated with high black hole spins and substantial masses, and transient systems, displaying a broader range of spins. Interestingly, the spins of persistent black holes, such as those found in Cyg X-1, M33 X-7, and LMC X-1, are found to be high and are likely natal, suggesting minimal accretive spin-up.

The paper also explores the intriguing correlation between black hole spin and the power of ballistic jets, a phenomenon that had been elusive for many years. The authors provide empirical evidence that the radio luminosity, used as a proxy for jet kinetic energy in microquasars, shows a strong correlation with black hole spin measured via the continuum-fitting method. This correlation, spanning three orders of magnitude in radio power, aligns well with theoretical predictions that invoke the Penrose process and the Blandford-Znajek mechanism, which leverage the rotational energy of black holes to power such jets.

In conclusion, the continuum-fitting method has proven to be a robust and valuable tool for measuring black hole spins, facilitating advances in our understanding of their astrophysical processes. The demonstrated correlation between spin and jet power underscores the importance of spin as a fundamental parameter in black hole physics. Future research prospects include improving the precision of spin measurements, expanding the sample of measured black holes, and furthering our understanding of the mechanisms behind jet production. Such studies hold the potential to refine our theoretical models of accretion physics and provide insight into the enigmatic nature of black holes in the cosmos.