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We present a spectral and timing analysis of the newly reported GalacticX-ray transient Swift J1658.2-4242 observed by NuSTAR and Swift. The broad-bandX-ray continuum is typical of a black hole binary in the bright hard state,with a photon index of $\Gamma=1.63\pm0.02$ and a low coronal temperature of$kT_{\rm e}=22\pm1$ keV, corresponding to a low spectral cutoff wellconstrained by NuSTAR. Spectral modeling of the relativistic disk reflectionfeatures, consisting of a broad Fe K$\alpha$ line and the Compton reflectionhump, reveals that the black hole is rapidly spinning with the spin parameterof $a^{*}>0.96$, and the inner accretion disk is viewed at a high inclinationangle of $i=64^{+2}_{-3}{^\circ}$ (statistical errors, 90% confidence). Thehigh inclination is independently confirmed by dips in the light curves, whichcan be explained by absorbing material located near the disk plane temporarilyobscuring the central region. In addition, we detect an absorption line in theNuSTAR spectra centered at $7.03^{+0.04}_{-0.03}$ keV. If associated withionized Fe K absorption lines, this provides evidence for the presence ofoutflowing material in the low/hard state of a black hole binary candidate. Atiming analysis shows the presence of a type-C QPO in the power spectrum, withthe frequency increasing from $\sim0.14$ Hz to $\sim0.21$ Hz during the singleNuSTAR exposure. Our analysis reveals that Swift J1658.2-4242 displayscharacteristics typical for a black hole binary that is viewed at a highinclination angle, making it a good system for studying the accretion geometryin black hole binaries.

The Hard State of the Highly Absorbed High Inclination Black Hole Binary Candidate Swift J1658.2-4242 Observed by NuSTAR and Swift