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We present results for the first observed outburst from the transient X-raybinary source MAXI J0637-430. This study is based on eight observations fromthe Nuclear Spectroscopic Telescope Array (NuSTAR) and six observations fromthe Neil Gehrels Swift Observatory X-Ray Telescope (Swift/XRT) collected from2019 November 19 to 2020 April 26 as the 3-79 keV source flux declined from8.2e-10 to 1.4e-12 erg/cm^2/s. We see the source transition from a soft statewith a strong disk-blackbody component to a hard state dominated by a power-lawor thermal Comptonization component. NuSTAR provides the first reportedcoverage of MAXI J0637-430 above 10 keV, and these broadband spectra show thata two-component model does not provide an adequate description of the softstate spectrum. As such, we test whether blackbody emission from the plungingregion could explain the excess emission. As an alternative, we test areflection model that includes a physical Comptonization continuum. Finally, wealso test a spectral component based on reflection of a blackbody illuminationspectrum, which can be interpreted as a simple approximation to the reflectionproduced by returning disk radiation due to the bending of light by the stronggravity of the black hole. We discuss the physical implications of eachscenario and demonstrate the value of constraining the source distance.

Spectral and Timing Analysis of NuSTAR and Swift/XRT Observations of the X-Ray Transient MAXI J0637-430