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We utilize recent NuSTAR observations (co-added depth $\approx55$-120 ks) ofPG $1001+054$, PG $1254+047$, and PHL 1811 to constrain their hard X-ray($\gtrsim5$ keV) weakness and spectral shapes, and thus to investigate thenature of their extreme X-ray weakness. These quasars showed very weak softX-ray emission, and they were proposed to be intrinsically X-ray weak, with theX-ray coronae producing weak continuum emission relative to their optical/UVemission. However, the new observations suggest an alternative explanation. TheNuSTAR 3-24 keV spectral shapes for PG $1001+054$ and PHL 1811 are likely flat(effective power-law photon indices $\Gamma_{\rm eff}=1.0^{+0.5}_{-0.6}$ and$\Gamma_{\rm eff}=1.4^{+0.8}_{-0.7}$, respectively), while the shape is nominalfor PG $1254+047$ ($\Gamma_{\rm eff}=1.8\pm0.3$). PG $1001+054$ and PHL 1811are significantly weak at hard X-ray energies (by factors of $\approx26$-74 atrest-frame 8 keV) compared to the expectations from their optical/UV emission,while PG $1254+047$ is only hard X-ray weak by a factor of $\approx3$. Wesuggest that X-ray obscuration is present in all three quasars. We proposethat, as an alternative to the intrinsic X-ray weakness + X-ray obscurationscenario, the soft and hard X-ray weakness of these quasars can be uniformlyexplained under an obscuration-only scenario. This model provides adequatedescriptions of the multi-epoch soft and hard X-ray data of these quasars, withvariable column density and leaked fraction of the partial-covering absorber.We suggest that the absorber is the clumpy dust-free wind launched from theaccretion disk. These quasars probably have super-Eddington accretion ratesthat drive powerful and high-density winds.

NuSTAR Observations of Intrinsically X-ray Weak Quasar Candidates: An Obscuration-Only Scenario