Chromatic delay models

[abhisrkckl]

PINT should have variable-index chromatic delay models

1. Taylor series representation (like DispersionDM) - Chromatic delay similar to dispersion delay #1616
2. Piecewise representation (like DMX) - WIP: Piecewise-constant chromatic variations (CMX) #1777
3. Fourier series representation (like DMWaveX) - Fourier series representation of chromatic noise (CMWaveX) #1802
4. Fourier GP representation (like PLDMNoise) - Powerlaw chromatic noise GP model (PLChromNoise) #1797
5. Chromatic events (e.g. for J1713+0747)

[abhisrkckl]

The chromatic exponential dip parameters for J1713+0747 look like this:

EXPEP_1        54764.272428904194001       
EXPEP_2        57500.886666587524999       
EXPPH_1        1.6641670367524487e-06      
EXPPH_2        2.1964077367938582999e-06   
EXPTAU_1       112.00425959054773          
EXPTAU_2       26.57155879530331           
EXPINDEX_1     -1.9148109887274356         
EXPINDEX_2     -1.5060816448307765999

[abhisrkckl]

The chromatic noise parameters look like this:

TNChromAmp -12.9681
TNChromGam 1.36311
TNChromIdx 4
TNChromC 40

[abhisrkckl]

TNChromIdx is already part of ChromaticCM.