The Changing-Look Quasar Mrk 590 is Awakening

TL;DR

The paper reports on the reawakening of the changing-look quasar Mrk 590, showing increased UV brightness and emission lines, indicating episodic accretion rather than obscuration as the cause of its variability.

Contribution

It provides new multiwavelength observations demonstrating the re-emergence of broad emission lines and soft excess, challenging previous explanations of changing-look AGN behavior.

Findings

Mrk 590's UV continuum and broad MgII line have brightened significantly.

The soft X-ray excess re-emerged, linked to UV via warm Comptonization.

Fe K-alpha variability suggests a reprocessing region within 10 light years.

Abstract

Mrk 590 was originally classified as a Seyfert 1 galaxy, but then it underwent dramatic changes: the nuclear luminosity dropped by over two orders of magnitude and the broad emission lines all but disappeared from the optical spectrum. Here we present followup observations to the original discovery and characterization of this "changing look" active galactic nucleus (AGN). The new Chandra and HST observations from 2014 show that Mrk 590 is awakening, changing its appearance again. While the source continues to be in a low state, its soft excess has re-emerged, though not to the previous level. The UV continuum is brighter by more than a factor of two and the broad MgII emission line is present, indicating that the ionizing continuum is also brightening. These observations suggest that the soft excess is not due to reprocessed hard X-ray emission. Instead, it is connected to the UV continuum through warm Comptonization. Variability of the Fe K-alpha emission lines suggests that the reprocessing region is within about 10 light years or 3 pc of the central source. The AGN type change is neither due to obscuration, nor due to one-way evolution from type-1 to type-2, as suggested in literature, but may be related to episodic accretion events.