Abstract
ABSTRACT Broad Balmer emission lines in active galactic nuclei (AGN) may display dramatic changes in amplitude, even disappearance and re-appearance in some sources. As a nearby galaxy at a redshift of z = 0.0264, Mrk 590 suffered such a cycle of Seyfert type changes between 2006 and 2017. Over the last 50 yr, Mrk 590 also underwent a powerful continuum outburst and a slow fading from X-rays to radio wavelengths with a peak bolometric luminosity reaching about 10 per cent of the Eddington luminosity. To track its past accretion and ejection activity, we performed very long baseline interferometry (VLBI) observations with the European VLBI Network (EVN) at 1.6 GHz in 2015. The EVN observations reveal a faint (∼1.7 mJy) radio jet extending up to ∼2.8 mas (projected scale ∼1.4 pc) toward north, and probably resulting from the very intensive AGN activity. To date, such a parsec-scale jet is rarely seen in the known changing-look AGN. The finding of the faint jet provides further strong support for variable accretion as the origin of the type changes in Mrk 590.
Highlights
Variations of the mass-accretion rate may give rise to different classes of emission-line nuclei of galaxies (e.g. Elitzur et al 2014; Noda & Done 2018). This scenario has been further supported by the findings of some optical changing-look active galactic nuclei (AGN) that cannot be explained as a consequence of variable absorption, e.g. the Seyfert galaxies Mrk 590 (Denney et al 2014) and Mrk 1018 (McElroy et al 2016; Noda & Done 2018), and the quasar SDSS J015957.64+003310.5 (LaMassa et al 2015)
A few large samples of changing-look AGN have been selected (e.g. Runco et al 2016; MacLeod et al 2016; Yang et al 2018). If these dramatic type changes are mainly due to variations of the ionising continuum luminosity, changing-look AGN would play a key role in probing the complex accretion-ejection activity (e.g. Yuan & Narayan 2014; Noda & Done 2018) of super massive black holes (SMBHs)
To search for potential faint jet activity launched by the accreting SMBH during and after the outburst, we performed deep very long baseline interferometry (VLBI) observations of Mrk 590 with the European VLBI Network (EVN)
Summary
Variations of the mass-accretion rate may give rise to different classes of emission-line nuclei of galaxies (e.g. Elitzur et al 2014; Noda & Done 2018). A few large samples of changing-look AGN have been selected (e.g. Runco et al 2016; MacLeod et al 2016; Yang et al 2018) If these dramatic type changes are mainly due to variations of the ionising continuum luminosity, changing-look AGN would play a key role in probing the complex accretion-ejection activity VLBI observations of a few SMBHs accreting close to or above the Eddington accretion rate reveal significant pc-scale jet activities while with faint radio cores To search for potential faint jet activity launched by the accreting SMBH during and after the outburst, we performed deep very long baseline interferometry (VLBI) observations of Mrk 590 with the European VLBI Network (EVN). The VLBI images have a scale of 0.5 pc mas−1
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