Leptonic relativistic jet model.

NOTE: This model is now in the Xspec release and this page is superceded by the Xspec manual

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 our synchrotron self absorption cutoff is at a lower frequency) The spectrum longward of this cutoff is assumed to have a flat spectrum in Lv, as appropriate for the sum of self-absorbed components further down the jet.

1  =   mass, black hole mass in solar masses
2  =   Dco, COMOVING distance - as in optxagnf!
3  =   logL/LEdd, log (accretion power / Eddington luminosity)

this is the DISC luminosity, for external Comptonisation. THIS IS SET TO ZERO for log L/LEdd < -2 as the accretion flow is assumed to make a transition to an Advection dominated state. For log L/LEdd ≥ -2 the disc luminosity is set by the black hole mass and L/LEdd so Ldisc=1.3x1038 MBH (L/LEdd). 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

4  =   thetaobs, inclination angle (deg) between the jet axis and line of sight
5  =   BulkG, bulk lorentz factor of the jet
6  =   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 rdiss
             to its height above the black hole via rdiss=phi x zdiss
7  =   zdiss, distance from the black hole of the jet dissipation region (this corresponds to Rdiss in G10: we have renamed it to zdiss to show explictly that this
             is a vertical distance. Also, we use units of Rg=GM/c2 instead of Rs=2GM/c2 as used in G10)

parameters 8-14 are all in the jet frame

8  =   B, Magnetic field in the jet (Gauss)
9  =   logPrel, log of the power injected in relativisitic particles (ergs/s)
10  =   gmininj, minimum lorentz factor of the injected electrons
11  =   gbreak, lorentz factor of the break in injected electron distribution
12  =   gmax, maximum lorentz factor
13  =   s1, injected index of the electron distribution below the break
14  =   s2, injected index of the electron distribution above the break
15  =   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. Kynock 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, Nγ, 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

To install as an XSPEC local model download the source code and model description file.

Keith Arnaud, Lab. for High Energy Astrophysics, NASA/Goddard Space Flight Center

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Last modified: Tuesday, 14-Feb-2023 16:41:49 EST