jet: Leptonic relativistic jet model

This is the single zone, leptonic relativistic jet code of Ghisellini & Tavecchio (2009), hereafter GT09, as used in Ghisellini et al. (2010), coded up by Gardner & Done (2017). Please reference all of these papers if you use this model in xspec.

The default parameters reproduce the mean FSRQ spectrum in G10 (except that the synchrotron self absorption cutoff is at a lower frequency) The spectrum longward of this cutoff is assumed to have a flat spectrum in L$_{\nu }$, as appropriate for the sum of self-absorbed components further down the jet.

par1	mass, black hole mass in solar masses
par2	Dco, COMOVING distance - as in optxagnf!
par3	logL/LEdd, log (accretion power / Eddington luminosity)

Parameter 3 is the DISC luminosity, for external Comptonization. THIS IS SET TO ZERO for $\log{L/L_{Edd}} < -2$ as the accretion flow is assumed to make a transition to an Advection dominated state. For $\log{L/L_{Edd}} \geq -2$ the disc luminosity is set by the black hole mass and $L/L_{Edd}$ so $L_{disc} = 1.3\times 10^{38} MBH (L/L_{Edd})$. The peak temperature of the disc is set by equation 1 in GT09 i.e. black hole spin has no effect.

Parameters 4-7 determine the physical parameters of the jet and its boost

par4	thetaobs, inclination angle (deg) between the jet axis and line of sight
par5	BulkG, bulk lorentz factor of the jet
par6	phi, angular size scale (radians) of the jet acceleration region as seen from the black hole - all this does is relate the jet acceleration region size scale $r_{diss}$ to its height above the black hole via $r_{diss} = \phi \times z_{diss}$
par7	zdiss, distance from the black hole of the jet dissipation region (this corresponds to $R_{diss}$ in G10: it is renamed to zdiss to show explictly that this is a vertical distance. Also, units are $R_g = GM/c^2$ instead of $R_s = 2GM/c^2$ as used in G10)

Parameters 8-14 are all in the jet frame

par8	B, Magnetic field in the jet (Gauss)
par9	logPrel, log of the power injected in relativisitic particles (ergs/s)
par10	gmininj, minimum lorentz factor of the injected electrons
par11	gbreak, lorentz factor of the break in injected electron distribution
par12	gmax, maximum lorentz factor
par13	s1, injected index of the electron distribution below the break
par14	s2, injected index of the electron distribution above the break
par15	z, cosmological redshift corresponding to the comoving distance of parameter 2
norm	MUST BE FIXED AT UNITY as the jet spectrum normalisation is set by the relativisitic particle power.

The code works on its own energy grid, from 107 Hz to 1028 Hz. It calculates the total spectrum, summing up the synchrotron emission, together with the self-Compton, EC disc, EC X-ray corona, EC BLR, EC X-ray reflection from BLR and EC torus components, using the seed photon densities assumed in GT09. These individual components can be written out individually (see e.g. Kynoch et al. (2017)), by editing the code and uncommenting out lines which write(2,*). This produces file fort.2 in the directory where xspec is being run.

The individual seed photon densities within the jet can likewise be extracted from the code by uncommenting lines which write(3,*). Perhaps more useful is the self consistent electron distribution, N$_\gamma$, which can be written out by uncommenting out lines which write(908,*) - writing to file 908.

The code writes out to the screen the components of jet power in the observers frame:

Pr	radiation
Pb	magnetic field
Pe	kinetic power in electrons
Pp	kinetic power in protons (assuming one cold proton per electron)
Pj	total jet power, the sum of all the above

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Last modified: Friday, 23-Aug-2024 13:20:40 EDT