TY - JOUR

T1 - Flares in the changing look AGN Mrk 590-I. The UV response to X-ray outbursts suggests a more complex reprocessing geometry than a standard disc

AU - Lawther, D.

AU - Vestergaard, M.

AU - Raimundo, S.

AU - Koay, J. Y.

AU - Peterson, B. M.

AU - Fan, X.

AU - Grupe, D.

AU - Mathur, S.

PY - 2023/1/9

Y1 - 2023/1/9

N2 - Mrk 590 is a known changing-look active galactic nuclei (AGNs) which almost turned off in 2012, and then in 2017 partially re-ignited into a repeat flaring state, unusual for an AGN. Our Swift observations since 2013 allow us to characterize the accretion-generated emission and its reprocessing in the central engine of a changing-look AGN. The X-ray and UV variability amplitudes are higher than those typically observed in 'steady-state' AGN at similar moderate accretion rates; instead, the variability is similar to that of highly accreting AGN. The unusually strong X-ray to UV correlation suggests that the UV-emitting region is directly illuminated by X-ray outbursts. We find evidence that the X-rays are reprocessed by two UV components, with the dominant one at similar to 3 d and a faint additional reprocessor at near-zero lag. However, we exclude a significant contribution from diffuse broad line region continuum, known to contribute for bonafide AGN. A near-zero lag is expected for a standard 'lamp-post' disc reprocessing model with a driving continuum source near the black hole. That the overall UV response is dominated by the similar to 3-d lagged component suggests a complicated reprocessing geometry, with most of the UV continuum not produced in a compact disc, as also found in recent studies of NGC 5548 and NGC 4151. None the less, the observed flares display characteristic time-scales of similar to 100 rest-frame days, consistent with the expected thermal time-scale in an accretion disc.

AB - Mrk 590 is a known changing-look active galactic nuclei (AGNs) which almost turned off in 2012, and then in 2017 partially re-ignited into a repeat flaring state, unusual for an AGN. Our Swift observations since 2013 allow us to characterize the accretion-generated emission and its reprocessing in the central engine of a changing-look AGN. The X-ray and UV variability amplitudes are higher than those typically observed in 'steady-state' AGN at similar moderate accretion rates; instead, the variability is similar to that of highly accreting AGN. The unusually strong X-ray to UV correlation suggests that the UV-emitting region is directly illuminated by X-ray outbursts. We find evidence that the X-rays are reprocessed by two UV components, with the dominant one at similar to 3 d and a faint additional reprocessor at near-zero lag. However, we exclude a significant contribution from diffuse broad line region continuum, known to contribute for bonafide AGN. A near-zero lag is expected for a standard 'lamp-post' disc reprocessing model with a driving continuum source near the black hole. That the overall UV response is dominated by the similar to 3-d lagged component suggests a complicated reprocessing geometry, with most of the UV continuum not produced in a compact disc, as also found in recent studies of NGC 5548 and NGC 4151. None the less, the observed flares display characteristic time-scales of similar to 100 rest-frame days, consistent with the expected thermal time-scale in an accretion disc.

KW - galaxies: active

KW - galaxies: Seyfert

KW - ACTIVE GALACTIC NUCLEI

KW - RADIUS-LUMINOSITY RELATIONSHIP

KW - OPTICAL CONTINUUM EMISSION

KW - VARIABILITY TIME-SCALE

KW - DIGITAL SKY SURVEY

KW - ACCRETION DISK

KW - SPACE TELESCOPE

KW - LOOK AGN

KW - THERMAL REVERBERATION

KW - BLACK-HOLES

U2 - 10.1093/mnras/stac3515

DO - 10.1093/mnras/stac3515

M3 - Journal article

VL - 519

SP - 3903

EP - 3922

JO - Royal Astronomical Society. Monthly Notices

JF - Royal Astronomical Society. Monthly Notices

SN - 0035-8711

IS - 3

ER -