We present the results of a 7–12 GHz phased-array study of the Galactic center magnetar J1745 - 2900 with the Karl G. Jansky Very Large Array ( VLA ) .
Using data from two 6.5 hour observations from September 2014 , we find that the average profile is comprised of several distinct components at these epochs and is stable over \sim day timescales and \sim GHz frequencies .
Comparison with additional phased VLA data at 8.7 GHz shows significant profile changes on longer timescales .
The average profile at 7–12 GHz is dominated by the jitter of relatively narrow pulses .
The pulses in each of the four main profile components seen in September 2014 are uncorrelated in phase and amplitude , though there is a small but significant correlation in the occurrence of pulses in two of the profile components .
Using the brightest pulses , we measure the dispersion and scattering parameters of J1745 - 2900 .
A joint fit of 38 pulses gives a 10 GHz pulse broadening time of \tau _ { sc, 10 } = 0.09 \pm 0.03 ~ { } ms and a dispersion measure of { DM } = 1760 ^ { +2.4 } _ { -1.3 } ~ { } { pc~ { } cm } ^ { -3 } .
Both of these results are consistent with previous measurements , which suggests that the scattering and dispersion measure of J1745 - 2900 may be stable on timescales of several years .