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Abstract The supermassive black holes (M_BH∼ 10⁶–10¹⁰M_⊙) that power luminous active galactic nuclei (AGNs), i.e., quasars, generally show a correlation between thermal disk emission in the ultraviolet (UV) and coronal emission in hard X-rays. In contrast, some “massive” black holes (mBHs;M_BH∼ 10⁵–10⁶M_⊙) in low-mass galaxies present curious X-ray properties with coronal radiative output up to 100× weaker than expected. To examine this issue, we present a pilot study incorporating Very Large Array radio observations of a sample of 18 high-accretion-rate (Eddington ratiosL_bol/L_Edd> 0.1), mBH-powered AGNs (M_BH∼ 10⁶M_⊙) with Chandra X-ray coverage. Empirical correlations previously revealed in samples of radio-quiet, high-Eddington AGNs indicate that the radio–X-ray luminosity ratio,L_R/L_X, is approximately constant. Through multiwavelength analysis, we instead find that the X-ray-weaker mBHs in our sample tend toward larger values ofL_R/L_Xeven though they remain radio-quiet per their optical–UV properties. This trend results in a tentative but highly intriguing correlation betweenL_R/L_Xand X-ray weakness, which we argue is consistent with a scenario in which X-rays may be preferentially obscured from our line of sight by a “slim” accretion disk. We compare this observation to weak emission-line quasars (AGNs with exceptionally weak broad-line emission and a significant X-ray-weak fraction) and conclude by suggesting that our results may offer a new observational signature for finding high-accretion-rate AGNs. 

Abstract We present the rest-frame ultraviolet−optical spectral properties of 65 broad absorption line (BAL) quasars from the Gemini Near Infrared Spectrograph−Distant Quasar Survey (GNIRS-DQS). These properties are compared with those of 195 non-BAL quasars from GNIRS-DQS in order to identify the drivers for the appearance of BALs in quasar spectra. In particular, we compare equivalent widths and velocity widths, as well as velocity offsets from systemic redshifts, of principal emission lines. In spite of the differences between their rest-frame ultraviolet spectra, we find that luminous BAL quasars are generally indistinguishable from their non-BAL counterparts in the rest-frame optical band at redshifts 1.55 ≲z≲ 3.50. We do not find any correlation between BAL trough properties and the Hβ-based supermassive black hole masses and normalized accretion rates in our sample. Considering the Sloan Digital Sky Survey quasar sample, which includes the GNIRS-DQS sample, we find that a monochromatic luminosity at rest-frame 2500 Å of ≳10⁴⁵erg s⁻¹is a necessary condition for launching BAL outflows in quasars. We compare our findings with other BAL quasar samples and discuss the roles that accretion rate and orientation play in the appearance of BAL troughs in quasar spectra.