We present the first upper limit on gravitational wave (GW) backgrounds at an unexplored frequency of 0.2 Hz using a torsion-bar antenna (TOBA). A TOBA was proposed to search for low-frequency GWs. We have developed a small-scaled TOBA and successfully found Ωgw(f)<4.3×1017 at 0.2Hz as demonstration of the TOBA's capabilities, where Ωgw(f) is the GW energy density per logarithmic frequency interval in units of the closure density. Our result is the first nonintegrated limit to bridge the gap between the LIGO band (around 100Hz) and the Cassini band (10-6-10 -4Hz).
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