NGC 1566: analysis of the nuclear region from optical and near-infrared Integral Field Unit spectroscopy

Silva, Patrícia da; Steiner, J. E.; Menezes, R. B.

doi:10.1093/mnras/stx1458

Cited by 28 publications

(30 citation statements)

References 52 publications

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“…The narrow Fe Kα line intensity can change by a factor of 1.5 for the corresponding continuum variation within a time interval as short as four months. This allows us to put the material responsible for producing the narrow Fe Kα line at a distance scale to <0.1pc, comparable to the size of BLR which is ∼ 0.01pc inferred for NGC 1566 (Alloin et al 1985;da Silva et al 2017). The rapidly variable narrow Fe Kα line have also been reported in the AGN NGC 4151 (Zoghbi et al 2019), which can be explained as originating from the inner BLR.…”

Section: Response Of the Fe Kα Emission To The Longterm X-ray Continu...supporting

confidence: 60%

Response of the Fe K_alpha line emission to the X-ray continuum variability in the changing-look active galactic nucleus NGC 1566

Liang¹,

Shu²,

Wang³

et al. 2022

Preprint

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NGC 1566 is a changing look AGN known to exhibit recurrent X-ray outbursts with each lasting for several years. The most recent X-ray outburst is observed on 2018, with a substantial increase of 2-10 keV flux by a factor of ∼24 than the historical minimum. We re-analyze the XMM-Newton and NuSTAR observations covering the pre-outburst, outburst and post-outburst epochs, and confirm the discovery of the broad feature in the ∼5-7 keV band during the period of outburst that could be interpreted as a relativistic Fe Kα emission line. Our analysis suggests that its flux has increased in tandem with the 2-10 keV continuum, making it the second changing look AGN in which the broad Fe Kα line responds to the X-ray continuum variability. This behavior strongly supports the idea that X-rays originates in a corona above the accretion disk, and disk reflection produces the relativistic Fe Kα line. In addition, we find the response of narrow Fe Kα emission line to the changes in the X-ray continuum on a time-scale as short as four months, allowing to put the location of line-emitting region at <0.1 pc, comparable to the size of optical BLR. By comparing to the changing look AGN NGC 2992, the Fe Kα variation rate (the ratio of Fe Kα variation to luminosity variation) in NGC 1566 appears greater, which could be possibly explained by larger amount of gas or Fe abundance responsible for producing the Fe Kα line for the latter. The strength of variable broad Fe Kα line as well as the soft X-ray excess emission appears to be correlated with the accretion rate, which could be explained as due to the state transition associated with the changing-look phenomenon.

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Section: Response Of the Fe Kα Emission To The Longterm X-ray Continu...supporting

confidence: 60%

Response of the Fe K_alpha line emission to the X-ray continuum variability in the changing-look active galactic nucleus NGC 1566

Liang¹,

Shu²,

Wang³

et al. 2022

Preprint

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“…For example, the multiplet 42 lines of FeII are clearly seen superimposed on the [OIII] lines in our spectrum, but these were not detected in NGC 1566's low state (see fig. 10 in da Silva et al 2017).…”

Section: Optical Spectrum: New Resultsmentioning

confidence: 99%

“…The lag of the K band variability relative to J was however elsewhere found to be less than 20 days (Oknyanskij & Horne 2001). Alloin et al (1985) and da Silva et al (2017) found the broad line region upper limit radius to be 20 light-days and 15 light-days respectively. These values together with the IR time delays may be used to estimate the location of the inner edge of the dust torus (see e.g., Clavel et al 2000;Netzer 2015).…”

Section: Introductionmentioning

confidence: 98%

New changing look case in NGC 1566

Oknyansky

Winkler

Tsygankov

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We present a study of optical, UV and X-ray light curves of the nearby changing look active galactic nucleus in the galaxy NGC 1566 obtained with the Neil Gehrels Swift Observatory and the MASTER Global Robotic Network over the period 2007 -2018. We also report on our optical spectroscopy at the South African Astronomical Observatory with the 1.9-m telescope on the night 2018 August 2-3. A substantial increase in X-ray flux by 1.5 orders of magnitude was observed following the brightening in the UV and optical bands during the last year. After a maximum was reached at the beginning of 2018 July the fluxes in all bands decreased with some fluctuations. The amplitude of the flux variability is strongest in the X-ray band and decreases with increasing wavelength. Low-resolution spectra reveal a dramatic strengthening of the broad emission as well as high-ionization [FeX]6374Å lines. These lines were not detected so strongly in the past published spectra. The change in the type of the optical spectrum was accompanied by a significant change in the X-ray spectrum. All these facts confirm NGC 1566 to be a changing look Seyfert galaxy.

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“…These investigations of NGC 1566 have long history (see e.g. references at da Silva et al 2017; Oknyansky et al 2019b; Oknyansky et al 2020; Parker et al 2019). The NGC1566 is one of the brightest and nearest galaxies with active galactic nuclei (AGN) in the South Hemisphere.…”

Section: Introductionmentioning

confidence: 99%

Changing looks of the nucleus of the Seyfert galaxy NGC 1566 compared with other changing‐look AGNs

Oknyansky

2021

Astron Nachr

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We present results of a long-term optical, UV, and X-ray study of variability of the nearby changing-look (CL) Seyfert NGC 1566 which was observed with the Swift Observatory from 2007 to 2020. We summarize our previously published spectroscopic and photometric results and present new observations. We reported on the alteration in the spectral type of NGC 1566 in 2018 (REF1).Moreover, we focused on the exceptional postmaximum behavior after 2018 July, when all bands dropped with some fluctuations (REF2). We observed four significant re-brightenings in the postmaximum period. We have found differences in X-ray and UV/Optical variability. The L uv ∕L x ratio was decreased during 2018-2020. New postmaximum spectra covering the period November 31, 2018 to September 23, 2019 show dramatic changes compared to August 2, 2018, with fading of the broad lines and [Fe X] λ6374 until 2019 March (REF2). Effectively, two changing-look (CL) states were observed for this object: Changing to type 1.2 and then returning to the low state as a type 1.8 Sy. We suggest that the changes are mostly due to fluctuations in the energy generation. Variability properties of NGC1566 are compared with our results for other CL active galactic nuclei.

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NGC 1566: analysis of the nuclear region from optical and near-infrared Integral Field Unit spectroscopy

Cited by 28 publications

References 52 publications

Response of the Fe K_alpha line emission to the X-ray continuum variability in the changing-look active galactic nucleus NGC 1566

Response of the Fe K_alpha line emission to the X-ray continuum variability in the changing-look active galactic nucleus NGC 1566

New changing look case in NGC 1566

Changing looks of the nucleus of the Seyfert galaxy NGC 1566 compared with other changing‐look AGNs

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