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We present NuSTAR hard X-ray observations of two X-ray weak broad absorptionline (BAL) quasars, PG 1004+130 (radio loud) and PG 1700+518 (radio quiet).Many BAL quasars appear X-ray weak, probably due to absorption by the shieldinggas between the nucleus and the accretion-disk wind. The two targets are amongthe optically brightest BAL quasars, yet they are known to be significantlyX-ray weak at rest-frame 2-10 keV (16-120 times fainter than typical quasars).We would expect to obtain ~400-600 hard X-ray (>10 keV) photons with NuSTAR,provided that these photons are not significantly absorbed (NH<1E24 cm^{-2}).However, both BAL quasars are only detected in the softer NuSTAR bands (e.g.,4-20 keV) but not in its harder bands (e.g., 20-30 keV), suggesting that eitherthe shielding gas is highly Compton-thick or the two targets are intrinsicallyX-ray weak. We constrain the column densities for both to be NH~7E24 cm^{-2} ifthe weak hard X-ray emission is caused by obscuration from the shielding gas.We discuss a few possibilities for how PG 1004+130 could have Compton-thickshielding gas without strong Fe K? line emission; dilution from jet-linkedX-ray emission is one likely explanation. We also discuss the intrinsic X-rayweakness scenario based on a coronal-quenching model relevant to the shieldinggas and disk wind of BAL quasars. Motivated by our NuSTAR results, we perform aChandra stacking analysis with the Large Bright Quasar Survey BAL quasar sampleand place statistical constraints upon the fraction of intrinsically X-ray weakBAL quasars; this fraction is likely 17-40%.

Weak Hard X-ray Emission from Two Broad Absorption Line Quasars Observed with NuSTAR: Compton-thick Absorption or Intrinsic X-ray Weakness?