NuSTAR Discovery of Dead Quasar Engine in Arp 187

Kohei Ichikawa, Taiki Kawamuro, Megumi Shidatsu, Claudio Ricci, Hyun Jin Bae, Kenta Matsuoka, Jaejin Shin, Yoshiki Toba, Junko Ueda, Yoshihiro Ueda

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


Recent active galactic nucleus (AGN) and quasar surveys have revealed a population showing rapid AGN luminosity variability by a factor of ∼10. Here we present the most drastic AGN luminosity decline by a factor of g 103 constrained by a NuSTAR X-ray observation of the nearby galaxy Arp 187, which is a promising "dead" quasar whose current activity seems quiet but whose past activity of erg s-1 is still observable at a large scale by its light echo. The obtained upper bound of the X-ray luminosity is , corresponding to , indicating an inactive central engine. Even if a putative torus model with cm-2 is assumed, the strong upper bound still holds with or . Given the expected size of the narrow-line region, this luminosity decrease by a factor of gap 103 must have occurred within ≲104 yr. This extremely rapid luminosity/accretion shutdown is puzzling, and it requires one burst-like accretion mechanism producing a clear outer boundary for an accretion disk. We raise two possible scenarios realizing such an accretion mechanism: a mass accretion (1) by the tidal disruption of a molecular cloud and/or (2) by the gas depletion as a result of vigorous nuclear star formation after rapid mass inflow to the central engine.

Original languageEnglish
Article numberL13
JournalAstrophysical Journal Letters
Issue number1
Publication statusPublished - 2019 Sept 20

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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