Constraining Spins of SMBHs from TeV Variability

Yan-Rong Li (IHEP)

Ye-Fei Yuan (USTC), Jian-Min Wang (IHEP)Jian-Cheng Wang (YNAO), Shu Zhang (IHEP)

2009.4.28

Refs: Wang, J. -M. , Li, Y. -R. et al. 2008, ApJ, 676, L109 Li, Y.-R. et al. 2009, ApJ in press

Outline

I. Introduction: TeV variability in

M87

II. Constraints of Pair Production

III. ADAFs/RIAFs in M87

IV. Optical Depth to ~TeV photons

V. Summary

I. Introduction

A radio galaxy at 16Mpc with

Mbh=3.0×109M⊙ (Macchetto et al

1996, Harms et al. 1994)

Inclination of jet: 30° (Bicknell et al.

1996)

Variability time scale:Aharonian et al 2006, ScienceHESS

M87

I. IntroductionThe characteristic size,

Size: 20Rg

The possible source of the TeV-rays is the nucleus of M87 itself (Aharonian et al. 2006) .

emission mechanism: Levinson 2000, Neronov & Aharonian 2007, Rieger & Aharonian 2008

Question: how do TeV photons escape?

II Constraints of Pair Production

Pair production processes

II. Constraints of Pair Production

TeV photons are used as a tracer to probe the radiation fields around BHs

II. Constraints of Pair Production

Radiation field: accretion rate and spin

orientation: 30°

BH mass: Mbh=3.0×109M⊙

accretion rate?

spin?

Only fitting SED is not enough!

• Supplementing TeV constraints relax the degeneration of the spin and the accretion rate.

III. ADAFs/RIAFs in M87

SED shows: ADAFs/RIAFs is working due to the absence of Big Blue Bump

Radio: VLBI (0.1″), IR: Gemini (460″),

Optical: HST (22″), X-ray: Chandra (500″) (see Di Matteo et al. 2003, Wang et al. 2008)

III. ADAFs/RIAFs in M87

Fully GR ADAFs/RIAFs model (Manmoto 2000)

Radiation Processes Synchrotron Inverse Compton Scattering Bremsstrahlung

III. ADAFs/RIAFs in M87

Free Parameters : spin : accretion rate : viscoisty : magnetic : viscous dissipation that heats

electrons : the observation angle.

have typical value from physical model.

Spectral fit To reduce the freedom, fix , adjust

.

III. ADAFs/RIAFs in M87

(data see Di Matteo et al. 2003, Wang et al. 2008)

III. ADAFs/RIAFs in M87

(data see Di Matteo et al. 2003, Wang et al. 2008 add HST observation from Sparks et al. 1996, Maoz et al. 2005 )

IV. Optical Depth to TeV Photons

Ray tracing

IV. Optical Depth to TeV Photons

IV. Optical Depth to TeV Photons

IV. Optical Depth to TeV Photons

IV. Optical Depth to TeV Photons

To avoid being optically thick to 10TeV photons, the spin of SMBH in M87 should be

a>0.8

V. Summary

We use fully GR solutions of

ADAFs/RIAFs.

We use the GR time-space to

calculate the optical depth.

The SMBH in M87 is spinning fast.

V. Summary

The TeV variability can be used to probe the

innermost regions around the central black

hole and allows us to disentangle the spin

from other parameters in modeling the

continuum spectrum.

Future H.E.S.S. (phase II) observations may

reveal the TeV variability of M87-like sources.