New clues to jet launching: The inner disks in radio loud quasars may be more stable

Cai, Z. M.; Sun, Yanchun; Wang, Junxian; Zhu, Fei-Fan; Gu, Wei‐Min; Yuan, Feng

doi:10.1007/s11433-018-9330-4

Cited by 17 publications

(12 citation statements)

References 68 publications

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“…Through comparing the composite spectra of EVQs at various states, we find that EVQs follow the general "bluer-when-brighter" pattern widely seen in quasars and AGNs (e.g. Cutri et al 1985;Wamsteker et al 1990;Clavel et al 1991;Giveon et al 1999;Webb & Malkan 2000;Trevese & Vagnetti 2001;Vanden Berk et al 2004;Wilhite et al 2005b;Meusinger et al 2010;Sakata et al 2011;Schmidt et al 2012;Bian et al 2012;Zuo et al 2012;Sun et al 2014;Ruan et al 2014;Cai et al 2016;Guo & Gu 2016;Cai et al 2019;Guo et al 2020a). The color variation is actually also visible in Fig.…”

Section: The "Bluer-when-brighter" Patternmentioning

confidence: 74%

Extreme Variability Quasars in Their Various States. I: The sample selection and composite SDSS spectra

Ren,

Wang,

Cai

et al. 2021

Preprint

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Extremely variable quasars (EVQs) are a population of sources showing large optical photometric variability revealed by time-domain surveys. The physical origin of such extreme variability is yet unclear. In this first paper of a series, we construct the largest-ever sample of 14,012 EVQs using photometric data spanning over > 15 years from SDSS and Pan-STARRS1. We divide them into five sub-samples according to the relative brightness of an EVQ during SDSS spectroscopic observation compared to the mean brightness from photometric observations. Corresponding control samples of normal quasars are built with matched redshift, bolometric luminosity and supermassive black hole mass. We obtain the composite SDSS spectra of EVQs in various states and their corresponding control samples. We find EVQs exhibit clearly bluer (redder) SDSS spectra during bright (dim) states, consistent with the "bluer-when-brighter" trend widely seen in normal quasars. We further find the line EWs of broad Mg II, C IV and [O III] (but not broad Hβ which is yet puzzling) gradually decreases from dim state to bright state, similar to the so-called intrinsic Baldwin effect commonly seen in normal AGNs. Meanwhile, EVQs have systematically larger line EWs compared with the control samples. We also see that EVQs exhibit subtle excess in the very broad line component compared with control samples. Possible explanations for the discoveries are discussed. Our findings support the hypothesis that EVQs are in the tail of a broad distribution of quasar properties, but not a distinct population.

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Section: The "Bluer-when-brighter" Patternmentioning

confidence: 74%

Extreme Variability Quasars in Their Various States. I: The sample selection and composite SDSS spectra

Ren,

Wang,

Cai

et al. 2021

Preprint

Self Cite

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“…Except for the most radio-loud group that might be contaminated by jet emission in the optical/UV band, the variability amplitudes of moderately radio-loud quasars are slightly (but significantly) smaller than those of radio-nondetected quasars (with controlled black-hole mass, luminosity, and Eddington ratio). Cai et al (2019) also suggest that the UV-emitting inner accretion flows of RLQs are stabilized (relative to those of RQQs) by the jet-launching magnetic field.…”

Section: The X-ray Variability Of Rlqsmentioning

confidence: 89%

The X-ray spectral and variability properties of typical radio-loud quasars

Zhu,

Timlin,

Brandt

2021

Preprint

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We present X-ray spectral and long-term variability analyses of an unbiased sample of 361 optically selected radio-loud quasars (RLQs) utilizing sensitive serendipitous X-ray data from the Chandra and XMM-Newton archives. The spectral and temporal properties of RLQs are compared with those of radio-quiet quasars (RQQs) matched in 𝐿 2500Å and 𝑧. The median power-law photon index (Γ) of RLQs is 1.84 +0.01 −0.01 , which is close to that of matched RQQs (1.90 +0.02 −0.01 ). No significant correlations between Γ and radio-loudness, 𝐿 x /𝐿 x,rqq (the X-ray luminosity over that expected from the 𝐿 x -𝐿 uv relation for RQQs), redshift, or Eddington ratio are found for our RLQs. The stacked X-ray spectra of our RLQs show strong iron-line emission and a possible Compton-reflection hump. The intrinsic X-ray variability amplitude is ≈ 40% for RLQs on timescales of months-to-years in the rest frame, which is somewhat smaller than for the matched RQQs (≈ 60%) on similar timescales, perhaps due to the larger black-hole masses and lower Eddington ratios in our RLQ sample. The X-ray spectral and variability results for our RLQs generally support the idea that the X-ray emission of typical RLQs is dominated by the disk/corona, as is also indicated by a recent luminosity correlation study.

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“…Theoretically, disc thermal fluctuating models (Dexter & Agol 2011;Cai et al 2016Cai et al , 2018Cai et al , 2019Cai et al , 2020 associate the multi-wavelength variability to magnetic turbulence in the accretion disc. Note such fluctuation models indeed predict bluer averaged EUV SEDs than the standard thin disk model without temperature fluctuation, and the stronger turbulence the bluer the mean SED (see Fig.…”

Section: Discussionmentioning

confidence: 99%

More variable quasars have stronger emission lines

Kang,

Wang,

Cai

et al. 2021

Preprint

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The UV/optical variation, likely driven by accretion disc turbulence, is a defining characteristic of type 1 active galactic nuclei (AGNs) and quasars. In this work we investigate an interesting consequence of such turbulence using quasars in SDSS Stripe 82 for which the measurements of the UV/optical variability amplitude are available from ∼ 10 years long light curves. We discover positive correlations between UV/optical variability amplitude σ rms and equivalent widths of CIV, Mg II and [OIII]5007 emission lines. Such correlations remain statistically robust through partial correlation analyses, i.e., after controlling the effects of other variables including bolometric luminosity, central supermassive black hole mass, Eddington ratio and redshift. This, for the first time, indicates a causal link between disc turbulence and emission line production. We propose two potential underlying mechanisms both of which may be involved: 1) quasars with stronger disc turbulence have on average bluer/harder broadband SED, an expected effect of the disc thermal fluctuation model; 2) stronger disc turbulence could lead to launch of emission line regions with larger covering factors.

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New clues to jet launching: The inner disks in radio loud quasars may be more stable

Cited by 17 publications

References 68 publications

Extreme Variability Quasars in Their Various States. I: The sample selection and composite SDSS spectra

Extreme Variability Quasars in Their Various States. I: The sample selection and composite SDSS spectra

The X-ray spectral and variability properties of typical radio-loud quasars

More variable quasars have stronger emission lines

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