Behaviour of the Mg ii 2798 Å line over the full range of AGN variability

Homan, David; MacLeod, Chelsea L.; Lawrence, Andy; Ross, Nicholas P.; Bruce, Alastair

doi:10.1093/mnras/staa1467

Cited by 11 publications

(15 citation statements)

References 60 publications

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“…The time delay between the continuum variations and the response of the Mg II emission line has been already reported for radioquiet (Czerny et al 2019) and radio-loud objects (Nalewajko et al 2019). What is more the very recent results on the study of a large sample of extremely variable radio-quiet AGNs (Homan et al 2020) indicate that indeed the MgII line does respond to the continuum changes, although the scale of behaviour variability is very broad. In most of the studied AGNs the MgII line varies less than the continuum.…”

Section: Sdss (2001) Spectrum But the Mgiiλ2800mentioning

confidence: 99%

“…According to Guo et al (2019) the MgII line flux changes can be well explained as a photoionization response to extreme continuum variability. However, a wide range of possible responses among AGNs may indicate additional factors that affect the change in the MgII line (Popović, Kovačević-Dojčinović & Marčeta-Mandić 2019;Homan et al 2020;Yang et al 2020).…”

Section: Sdss (2001) Spectrum But the Mgiiλ2800mentioning

confidence: 99%

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Caltech-NRAO Stripe 82 Survey (CNSS). IV. The Birth of Radio-loud Quasar 013815+00

Kunert-Bajraszewska¹,

Wołowska²,

Mooley

et al. 2020

ApJ

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It is believed that the gas accretion onto the supermassive black holes (SMBHs) is the main process of powering its luminous emission, which occurs in optical, UV and X-ray regimes and less frequently in radio waves. The observational fact that only a few percent of quasars are radio-loud is still an unresolved issue concerning the understanding of the active galactic nucleus (AGN) population. Here we present a detection of a rapid transition from the radio-quiet to the radio-loud mode in quasar 013815+00 (z=0.94) which coincides with changes of its UV-optical continuum and the low ionization MgII broadline. We interpret this as an enhancement of accretion onto a central black hole of mass about 10 9 solar masses. As a consequence a new radio-loud AGN was born. Its spectral and morphological properties indicate that it went through the short gigahertz-peaked spectrum (GPS) phase at the beginning of its activity and has now stabilized its flux density at the level of a few mJy. The radio morphology of 013815+00 is very compact and we predict that with such short-term jet activity its development will be very slow. The observed luminosity changes of the accretion disk are shorter than the lifetime of the new radio phase in 013815+00.

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Section: Sdss (2001) Spectrum But the Mgiiλ2800mentioning

confidence: 99%

Section: Sdss (2001) Spectrum But the Mgiiλ2800mentioning

confidence: 99%

Caltech-NRAO Stripe 82 Survey (CNSS). IV. The Birth of Radio-loud Quasar 013815+00

Kunert-Bajraszewska¹,

Wołowska²,

Mooley

et al. 2020

ApJ

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“…Again focussing on quasars that show large changes in their optical light curves, Homan et al (2020) find that Mg II clearly does respond to the continuum. However, a key finding from Homan et al (2020) is that the degree of responsivity varies strikingly from one object to another. There are cases of Mg II changing by as much as the continuum, more than the continuum, or very little at all.…”

Section: Continuum and Line Changes: Comparisons To Recent Observationsmentioning

confidence: 91%

“…Using the same data set as MacLeod et al 2019, Homan et al (2020) investigate the responsiveness of the Mg II broad emission line doublet in AGN on time-scales of several years. Again focussing on quasars that show large changes in their optical light curves, Homan et al (2020) find that Mg II clearly does respond to the continuum. However, a key finding from Homan et al (2020) is that the degree of responsivity varies strikingly from one object to another.…”

Section: Continuum and Line Changes: Comparisons To Recent Observationsmentioning

confidence: 99%

“…CLQs to date have primarily been defined according to the (recombination) Balmer emission line properties with particular attention paid to the H β emission line, observed from optical spectroscopy. Recent works report on discoveries of Mg II changing-look AGN (Guo et al 2019;Homan et al 2020). However, current CLQ studies have primarily been at redshifts z < 1.…”

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confidence: 99%

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The first high-redshift changing-look quasars

Ross

Graham

Calderone

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We report on three redshift z > 2 quasars with dramatic changes in their C iv emission lines, the first sample of changing-look quasars (CLQs) at high redshift. This is also the first time the changing-look behaviour has been seen in a high-ionisation emission line. SDSS J1205+3422, J1638+2827, and J2228+2201 show interesting behaviour in their observed optical light curves, and subsequent spectroscopy shows significant changes in the C iv broad emission line, with both line collapse and emergence being displayed on rest-frame timescales of ∼240-1640 days. These are rapid changes, especially when considering virial black hole mass estimates of MBH > 109M⊙ for all three quasars. Continuum and emission line measurements from the three quasars show changes in the continuum-equivalent width plane with the CLQs seen to be on the edge of the full population distribution, and showing indications of an intrinsic Baldwin effect. We put these observations in context with recent state-change models, and note that even in their observed low-state, the C iv CLQs are generally above ∼5% in Eddington luminosity.

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The long-term broad-line responsivity in MKN 110

Homan

Lawrence

Ward

et al. 2022

Monthly Notices of the Royal Astronomical Society

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We examine the long-term history of the optical spectrum of the extremely variable Active Galactic Nucleus (AGN) MKN 110. By combining various archival data with new data, we cover an unprecedented long period of ∼30 years (1987 – 2019). We find that the He II λ4686 emission line changes by a factor of forty and varies more strongly than the optical continuum. Following Ferland et al. (2020), we take He II λ4686 as a proxy for the FUV continuum and compare the flux of several other line species against it. This comparison reveals a clear pattern, whereby lines respond close to linearly at low FUV fluxes, and saturate at high FUV fluxes. The saturation level of the response appears to depend on the excitation energy of the line species. In addition to this global pattern, we note changes among observational epochs, indicating a structural evolution in the broad line region (BLR). The line profiles in our spectra show an offset between the narrow and broad components of the He II λ4686 and Hβ lines. This offset shows a significant negative correlation with the FUV flux and a positive correlation with the line velocity width. Our analysis reveals a complex BLR response to a changing continuum. The clear presence of a non-responsive component of the broad lines indicates the existence of multiple contributions to the line emission. We find there are several kinematic models of the BLR and inner regions of the AGN that match our data.

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Behaviour of the Mg ii 2798 Å line over the full range of AGN variability

Cited by 11 publications

References 60 publications

Caltech-NRAO Stripe 82 Survey (CNSS). IV. The Birth of Radio-loud Quasar 013815+00

Caltech-NRAO Stripe 82 Survey (CNSS). IV. The Birth of Radio-loud Quasar 013815+00

The first high-redshift changing-look quasars

The long-term broad-line responsivity in MKN 110

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