We have developed a fully automated dynamic calorimeter, which can measure the dynamic specific heat of a liquid or solid sample as a function of frequency over the range of six decades 0.01 Hz-10 kHz. The shape of a solid sample can be either wire or planar. At low frequencies, the measured quantity corresponds to the usual static specific heat. With this probe, one can study the slow dynamics occurring in condensed matter systems.

We experimentally investigate the periodic vortex shedding dynamics in a highly oblate Bose-Einstein condensate using a moving penetrable Gaussian obstacle. The shedding frequency fv is measured as a function of the obstacle velocity v and characterized by a linear relationship of fv=a(v-vc) with vc being the critical velocity. The proportionality constant a is linearly decreased with a decrease in the obstacle strength, whereas vc approaches the speed of sound. When the obstacle size increases, both a and vc are decreased. We discuss a possible association of a with the Strouhal number in the context of universal shedding dynamics of a superfluid. The critical vortex shedding is further investigated for an oscillating obstacle and found to be consistent with the measured fv . When the obstacle's maximum velocity exceeds vc but its oscillation amplitude is not large enough to create a vortex dipole, we observe that vortices are generated in the low-density boundary region of the trapped condensate, which is attributed to the phonon emission from the oscillating obstacle.

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