Analytical growth tracks of planetary cores for four combinations of the accretion viscosity α, the pebble Stokes number St (set to be equal to α), and the ratioof radial pebble-to-gas flux rates ξ. Protoplanets are started at either 5 or 25 AU and with a starting mass of 0.01 M_E. The pebble isolation mass is indicated for two values of the turbulent viscosity α_v, assumed here to be 0.1 times the accretion viscosity α. The proportionality between the migration rate and the mass results in all growth tracks turning nearly horizontal before reaching their maximal mass at r = 0.