[seminar] Astro Journal Club on November 9th

[Lana Ceraj]

Dear all,

this Wednesday on Astro Jorunal Club we'll be talking about rotating black
holes and their spectral signatures.

Journal Club starts at 3 p.m. (sharp) in the seminar room F-201 of the
Physics Department.


Presenter: Ana Babić

Title: Effects of spin on high-energy radiation from accreting black holes

Authors: M. O'Riordan, A. Pe'er, J.C. McKinney

Abstract:
Observations of jets in X-ray binaries show a correlation between radio
power and black hole spin. This correlation, if confirmed, points towards
the idea that relativistic jets may be powered by the rotational energy of
black holes.  In order to examine this further, we perform
general-relativistic radiative transport calculations on magnetically
arrested accretion flows, which are known to produce powerful jets via the
Blandford-Znajek (BZ) mechanism. We find that the X-ray and gamma-ray
emission strongly depend on spin and inclination angle. Surprisingly, the
high-energy power does not show the same dependence on spin as the BZ jet
power, but instead can be understood as a redshift effect. In particular,
photons observed perpendicular to the spin axis suffer little net redshift
until originating from close to the horizon. Such observers see deeper
into the hot, dense, highly-magnetized inner disk region. This effect is
largest for rapidly rotating black holes due to a combination of frame
dragging and decreasing horizon radius. While the X-ray emission is
dominated by the near horizon region, the near-infrared radiation
originates at larger radii. Therefore, the ratio of X-ray to near-infrared
power is an observational signature of black hole spin.

Link to the paper: https://arxiv.org/pdf/1607.01060v2.pdf

If you are willing to present a paper in our journal club, please contact
me via e-mail: lceraj at phy.hr

See you on Wednesday.

Cheers,
Lana