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The NASA/GSFC network is currently experiencing intermittent issues that affect our services. We are working on it and apologize for the inconvenience.
The offline tool hark (also on github) can be used to find and download data from the cloud.

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srcut: synchrotron spectrum, cutoff power law

srcut describes the synchrotron spectrum from an exponentially cut off power-law distribution of electrons in a homogeneous magnetic field. This spectrum is itself a power-law, rolling off more slowly than exponential in photon energies. Though more realistic than a power-law, it is highly oversimplified, but does give the maximally curved physically plausible spectrum and can be used to set limits on maximum accelerated-electron energies even in remnants whose X-rays are thermal. See Reynolds & Keohane (1999) and Reynolds (1998). Note that the radio spectral index and flux can be obtained from Green's Catalogue for galactic SNRs.

par1 alpha: radio spectral index
par2 break Hz: approximately the frequency at which the flux has dropped by a factor of 10 from a straight power law.
norm 1 GHz flux (Jy)