XMM and NuSTAR observations of an optically quiescent quasar

Abstract

Optically quiescent quasars (OQQs) represent a recently systematized class of infrared-luminous active galactic nuclei (AGNs) that have galaxy-like optical continua. They may represent an interesting, brief phase in the AGN life cycle, e.g., either cocooned within high-covering-factor media or indicative of recent triggering, though their nature remains unclear. Here, we present the first targeted simultaneous X-ray observations of an OQQ, our previously identified prototype, SDSS J075139.06+402811.2 at z = 0.587. The source is significantly detected over 0.5–16 keV with XMM-Newton and NuSTAR, unambiguously confirming the presence of current accretion activity. Spectral modeling yields an intrinsic luminosity L_{2–10 keV} ≈ 4.4 × 10⁴³ erg s⁻¹, well within the AGN regime, but underluminous relative to its infrared power. It is lightly obscured, with log N_H [cm⁻²] ≈ 22.

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Identifiers

ORCID for Claire Louise Greenwell: orcid.org/0000-0002-7719-5809

ORCID for Poshak Gandhi: orcid.org/0000-0003-3105-2615

ORCID for Peter Gregory Boorman: orcid.org/0000-0001-9379-4716

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