The optical variability of steep-spectrum radio quasars in the SDSS stripe 82 region

Gu, Minfeng; Ai, Yong

doi:10.1051/0004-6361/201117467

Cited by 14 publications

(11 citation statements)

References 71 publications

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“…Gu et al 2006;Hu et al 2006). However, Gu & Ai (2011) found this color behavior for only one object in a sample of 29…”

Section: Color Behaviormentioning

confidence: 92%

Six-Year Optical Monitoring of the Bl Lacertae Object 1es 0806+52.4

Man

Zhang

et al. 2014

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We present the results of the first systematic long-term multi-color optical monitoring of the BL Lacertae object 1ES 0806+52.4. The monitoring was performed in multiple passbands with a 60/90 cm Schmidt telescope from December 2005 to February 2011. The overall brightness of this object decreased from 2005 December to 2008 December, and regained after that. A sharp outburst probably occurred around the end of our monitoring program. Overlapped on the long-term trend are some short-term small-amplitude oscillations. No intranight variability was found in the object, which is in accord with the historical observations before 2005. By investigating the color behavior, we found strong bluer-when-brighter chromatism for the long-term variability of 1ES 0806+52.4.The total amplitudes at the c, i, and o bands are 1.18, 1.12, and 1.02 mags, respectively. The amplitudes tend to increase toward shorter wavelength, which may be the major cause of bluer-when-brighter. Such bluer-when-brighter is also found in other blazars like S5 0716+714, OJ 287, etc. The hard X-ray data collected from the Swift/BAT archive was correlated with our optical data. No positive result was found, the reason of which may be that the hard X-ray flux is a combination of the synchrotron and inverse Compton emission but with different timescales and cadences under the leptonic Synchrotron-Self-Compton (SSC) model.

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“…Gu et al 2006;Hu et al 2006). However, Gu & Ai (2011) found this color behavior for only one object in a sample of 29…”

Section: Color Behaviormentioning

confidence: 92%

Six-Year Optical Monitoring of the Bl Lacertae Object 1es 0806+52.4

Man

Zhang

et al. 2014

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“…The mechanism of BWB was simulated and attributed to the difference of the amplitudes and cadences at different wavelengths (Dai et al 2011). For FSRQs, both BWB and redder-when-brighter trend can be found, and it is hard to conclude which dominates (Gu & Ai 2011;Gu et al 2006;Hu et al 2006).…”

Section: Color Behavior and Spectral Hysteresismentioning

confidence: 99%

Simultaneous optical monitoring of BL Lacertae object S5 0716+714 with high temporal resolution

Man¹,

Zhang²,

Wu³

et al. 2016

Mon. Not. R. Astron. Soc.

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We have monitored the BL Lacertae object S5 0716+714 simultaneously in the B, R and I bands on three nights in November 2014. The average time resolution is quite high (73s, 34s, 58s for the filters B, R and I), which can help us trace the profile of the variation and search for the short inter-band time delay. Intra-day variability was about 0.1 mag on the first two nights and more than 0.3 mag on the third. A bluerwhen-brighter color behavior was found. An clear loop path can be seen on the colormagnitude diagram of the third night, revealing possible time delays between variations at high and low energies. It is the first time that the intra-day spectral hysteresis loop has been found so obviously in the optical band. We used the interpolated crosscorrelation function method to further confirm the time delay and calculated the values of lag between light curves at different wavelengths on each night. On the third night, variations in the R and B bands is approximately 1.5 minutes lagging behind the I band. Such optical time delay is probably due to the interplay of different processes of electrons in the jet of the blazar.

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“…Our sample of eighteen SSRQs consists of five SSRQs in Gu & Ai (2011a) and thirteen SSRQs in Gu & Ai (2011b). The initial quasar sample was selected as those quasars in both the SDSS DR7 quasar catalog (Schneider et al 2010) (u, g, r, i, z) magnitudes have typical errors of about 0.03 mag.…”

Section: Samplementioning

confidence: 99%

“…We define a quasar to be an SSRQ according to its radio spectral index α r > 0.5. Finally, five SSRQs with single FIRST counterpart to within 1 arcmin of the SDSS positions were presented in Gu & Ai (2011a), while thirteen SSRQs with multiple FIRST counterparts were listed in Gu & Ai (2011b). To have the radio spectral information, we decided to consider only the sources with a radio counterpart in both 1.4 and 4.85 GHz radio images.…”

Section: Samplementioning

confidence: 99%

“…The source sample is listed in Table 1, in which the black hole mass and the Eddington ratio from Gu & Ai (2011b) are shown. In calculating the Eddington ratio, the bolometric luminosity is estimated as L Bol = 10 L BLR (Netzer 1990), in which the broad line region (BLR) luminosity L BLR is derived following Celotti et al (1997) by scaling the strong broad emission lines Hβ, Mg II, and C IV to the quasar template spectrum of Francis et al (1991), in which Lyα is used as a flux reference of 100.…”

Section: Samplementioning

confidence: 99%

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The ultraviolet/optical variability of steep-spectrum radio quasars: the change in accretion rate?

2013

A&A

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Context. The steep-spectrum radio quasars (SSRQs) are powerful radio sources, with thermal emission from accretion disk and jet nonthermal emission both likely contributing to the ultraviolet (UV)/optical luminosity; however, the former may play a dominant role. Since the UV/optical variability of SSRQs has been poorly studied, little is known about the mechanism of their variability. Aims. We investigate the mechanism of the UV/optical variability of SSRQs. Methods. A sample of eighteen SSRQs was established in SDSS Stripe 82 region in our previous works, in which the flux and spectral variability were studied. In this work, we construct the flux-flux diagram using SDSS u and i multi-epoch data for these eighteen SSRQs. The standard accretion disk model is used to fit the flux-flux variations, in order to explore the variability mechanism. Results. The model fit to flux-flux diagram are tuned with fixed black hole mass and varying accretion rate. We find that the flux-flux diagram of all our SSRQs can be qualitatively described by the standard accretion disk model with a change in the accretion rate. Although nonthermal jet power-law emission can also qualitatively reproduce the variability, the reasonable accretion rates and black hole masses required to fit the flux-flux variations suggest that a disk emission with variable accretion rate is a plausible description of the data.

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The optical variability of steep-spectrum radio quasars in the SDSS stripe 82 region

Cited by 14 publications

References 71 publications

Six-Year Optical Monitoring of the Bl Lacertae Object 1es 0806+52.4

Six-Year Optical Monitoring of the Bl Lacertae Object 1es 0806+52.4

Simultaneous optical monitoring of BL Lacertae object S5 0716+714 with high temporal resolution

The ultraviolet/optical variability of steep-spectrum radio quasars: the change in accretion rate?

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