Note: Original code by Michael T. Lam https://github.com/mtlam/FrequencyOptimizer Modified by Ryan S. Lynch

A python package for the optimal frequencies analysis (M. T. Lam et al in prep.) of pulsars

Requires: python 2.7 numpy scipy matplotlib

A class for describing pulsar noise parameters

Usage:

pn = PulsarNoise(name,alpha=1.6,dtd=None,dnud=None,taud=None,C1=1.16,I_0=18.0,DM=0.0,D=1.0,tauvar=None,Weffs=None,W50s=None,sigma_Js=None,P=None)

• alpha: Pulsar flux spectral index
• dtd: Scintillation timescale (s)
• dnud: Scintillation bandwidth (GHz)
• taud: Scattering timescale (us)
• C1: Coefficient relating dnud to taud (1.16 = uniform Kolmogorov medium)
• I_0: Pulsar flux density at 1 GHz
• DM: Dispersion measure (pc cm^-3)
• D: Distance (kpc)
• tauvar: Variation in scattering timescale (us)
• Weffs: Effective width, can be an array (us)
• W50s: Pulse full-width at half-maximum, can be an array (us)
• sigma_Js: Jitter for observation time T, can be an array (us) [note: T needs to be related to the TelescopeNoise class]

A class for describing galaxy parameters

Usage:

gn = GalacticNoise(beta=2.75,T_e=100.0,fillingfactor=0.2)

• beta: Galactic sky background spectral index
• T_e: electron temperature (for emission measure analysis, now defunct)
• fillingfactor: filling factor (for emission measure analysis, now defunct)

A class for describing telescope noise parameters

Usage:

tn = TelescopeNoise(gain,T_const,epsilon=0.08,pi_V=0.1,eta=0.0,pi_L=0.0,T=1800.0)

• gain: Telescope gain (K/Jy)
• T_const: Constant temperature (e.g. T_sys + T_CMB + ...)
• epsilon: Fractional gain error
• pi_V: Degree of circular polarization
• eta: Voltage cross-coupling coefficient
• pi_L: Degree of linear polarization
• T: Integration time (s)

A class for handling calculations

Usage:

freqopt = FrequencyOptimizer(psrnoise,galnoise,telnoise,numin=0.01,numax=10.0,dnu=0.05,nchan=100,log=False,nsteps=8,frac_bw=False,verbose=True,full_bandwidth=False,masks=None,levels=LEVELS,colors=COLORS,lws=LWS)
freqopt.calc() #calculate
freqopt.plot(filename="triplot.png",doshow=True,figsize=(8,6),save=True,minimum=None,points=None,colorbararrow=None) #plot/save figure
freqopt.save(filename) #save to .npz file

• psrnoise: Pulsar Noise object
• galnoise: Galaxy Noise object
• telnoise: Telescope Noise object
• numin: Lowest frequency to run (GHz)
• numax: Highest frequency to run (GHz)
• nsteps: Number of steps in the grid to run
• nchan: number of underlying frequency channels
• log: Run in log space
• frac_bw: Run in fractional bandwidth
• full_bandiwdth: enforce full bandwidth in calculations
• masks: mask frequencies [not fully implemented]
• levels: contour levels
• colors: contour colors
• lws: contour linewidths

For plotting:

• filename: filename
• doshow: show the plot
• figsize = figure size
• save: Save the figure
• minimum: Symbol to place over the minimum
• points: Place other points on the plot

galnoise = GalacticNoise()
telnoise = TelescopeNoise(gain=2.0,T_const=30)

NCHAN = 100
NSTEPS = 100
psrnoise = PulsarNoise("J1744-1134",alpha=1.49,taud=26.1e-3,I_0=4.888,DM=3.14,D=0.41,tauvar=12.2e-3,dtd=1272.2,Weffs=np.zeros(NCHAN)+511.0,W50s=np.zeros(NCHAN)+136.8,sigma_Js=np.zeros(NCHAN)+0.066,P=4.074545941439190)  #jitter upper limit

freqopt = FrequencyOptimizer(psrnoise,galnoise,telnoise,numin=0.1,numax=10.0,nchan=NCHAN,log=True,nsteps=NSTEPS)
freqopt.calc()
freqopt.plot("J1744-1134.png",doshow=False,minimum='k*',points=(1.3,1.2,'ko'))
freqopt.save("J1744-1134.npz")

Please cite this github page currently.