Markarian 590 Shows State Transition Linking Active Galactic Nuclei to X-ray Binaries
Astronomers analyzing a decade of Swift telescope observations of the active galaxy Markarian 590 have documented a clear spectral state transition tied to its recent 'changing look' event. The galaxy's X-ray loudness parameter traced a V-shaped evolution with Eddington ratio, with a statistically significant break at roughly 2% of the Eddington limit, mirroring thresholds seen in population studies of changing look quasars. The findings suggest that the accretion physics governing supermassive black holes in AGN may be broadly analogous to those in stellar-mass X-ray binaries, offering a rare time-resolved case study.
Using multi-band Swift observations spanning roughly a decade, researchers led by B. Palit and colleagues captured Markarian 590 undergoing a pronounced accretion state transition associated with its changing look event. The X-ray loudness parameter α_ox exhibited a V-shaped dependence on Eddington ratio, with a statistically significant break at an Eddington fraction of 0.021 ± 0.008, consistent with thresholds found in broader population studies of changing look quasars. Independent UV and X-ray Eddington ratio tracers corroborated this, each showing breaks near an Eddington fraction of ~0.004. The galaxy evolved through distinct accretion phases: from a faint, hard X-ray dominated state through a flaring phase and into a bright UV/soft X-ray dominated phase, with variability on month-, year-, and decade-long timescales. The team interprets this as a transition from a truncated accretion disk with a dominant hot corona at low accretion rates to an inward-extending disk with enhanced UV emission and a warm Comptonizing layer at higher rates. The overall transition timescale is shorter than classical viscous timescales but broadly consistent with propagating thermal fronts in the disk. A declining radio-to-X-ray luminosity ratio with increasing Eddington fraction further supports growing disk dominance over the corona, reinforcing the analogy with X-ray binary state transitions.
What's missing
The paper is a preprint submitted to arXiv and has not yet undergone peer review, so its conclusions remain provisional. The physical mechanism driving the thermal front propagation on observed timescales shorter than classical viscous expectations is not definitively established.
What different sources said
- arXiv astro-phCenter
The Millimeter/X-ray Relation in Rapidly Accreting Supermassive Black Holes at $z < 0.16$
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