Long-term optical spectra variability of BL Lacertae object OJ 287

Zheng, Y. G.; Zhang, X.; Bi, X. W.; Hao, J. M.; Zhang, H. J.

doi:10.1111/j.1365-2966.2008.12761.x

Cited by 31 publications

(13 citation statements)

References 61 publications

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“…We have considered two fits to the corrected points: a power-law fit with spectral index of α = −0.4 ± 0.17 and a bremsstrahlung fit with temperature T = 3 +6 −2 × 10 5 K. The power-law fit would imply a spectrum which is flatter than the normal spectrum by ∆α ∼ 0.4 units. Such flattening of the spectrum at high brightness has been previously observed in other outbursts (Zheng et al 2008, Tavecchio et al 2010) even though by a smaller amount. In normal flares of OJ287 the whole spectrum up to optical-UV is raised, while the inverse Compton scattering in the relativistic jet raises the X-ray flux correspondingly (Seta et al 2009).…”

Section: Outburst Spectral Energy Distributionsupporting

confidence: 71%

On the masses of OJ287 black holes

Valtonen¹,

Ciprini²,

Lehto

2012

Monthly Notices of the Royal Astronomical Society

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Two multifrequency campaigns were carried out on OJ287 in 2005: in April when it was in its pre-outburst state, and in November, during the main 12 yr cycle outburst. The wavelength coverage was from radio to X-rays. In the optical-to-UV range the differential spectrum between the observations has a bremsstrahlung spectral shape, consistent with gas at $3 \times 10^{5}K$ temperature. Our result supports the hydrogen column density of the OJ287 host galaxy of $\sim9.3\times 10^{20} cm^{-2}$, the average value found by Gosh & Soundararajaperumal. The $3 \times 10^{5}K$ bremsstrahlung radiation was predicted in the binary black hole model of OJ287, and it arises from a hot bubble of gas which is torn off the accretion disc by the impact of the secondary. As this radiation is not Doppler boosted, the brightness of the outburst provides an estimate for the mass of the secondary black hole, $\sim1.4\times10^{8}$ solar mass. In order to estimate the mass of the primary black hole, we ask what is the minimum mass ratio in a binary system which allows the stability of the accretion disc. By using particle simulations, we find that the ratio is $\sim1.3\times10^{2}$. This makes the minimum mass of the primary $\sim1.8\times10^{10}$ solar mass, in agreement with the mass determined from the orbit solution, $1.84 \times 10^{10}$ solar mass. With this mass value and the measured K-magnitude of the bulge of the host galaxy of OJ287, the system lies almost exactly on the previously established correlation in the black hole mass vs. K-magnitude diagramme. It supports the extension of this correlation to brighter magnitudes and to more massive black holes than has been done previously.Comment: to appear in Mon.Not.R.Astron.So

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Section: Outburst Spectral Energy Distributionsupporting

confidence: 71%

On the masses of OJ287 black holes

Valtonen¹,

Ciprini²,

Lehto

2012

Monthly Notices of the Royal Astronomical Society

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“…2 m . Zheng et al (2008) found that flux variations are associated with the color variations on long-term timescales. Then the color variations may be related with the active state of the object.…”

Section: Relation Of Color and Magnitudementioning

confidence: 99%

Multi-Color Optical Monitoring of MRK 501 From 2010 to 2015

Xiong¹,

Zhang²,

Zhang³

et al. 2016

ApJS

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We have monitored the BL Lac object Mrk 501 in the optical V, R, and I bands from 2010 to 2015. For Mrk 501, the presence of a strong host galaxy component can affect the results of photometry. After subtracting the host galaxy contributions, the source shows intraday and long-term variabilities for optical flux and color indices. The average variability amplitudes of the V, R, and I bands are 22.05%, 22.25%, and 23.82%, respectively, and the value of the duty cycle is 14.87%. A minimal variability timescale of 106 minutes is detected. No significant time lag between the V and I bands is found on one night. The bluer-when-brighter (BWB) trend is dominant for Mrk 501 on intermediate, short, and intraday timescales, which supports the shock-in-jet model. For the long timescale, Mrk 501, in different states, can have different BWB trends. The corresponding results for non-correcting host galaxy contributions are also presented.

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“…In Fig. 4, we show the observed time lag between 100-400 MeV and > 400 MeV with the discrete correlation function (DCF; Edelson & Krolik 1988;Zheng et al 2008). As can be seen that observed light curves do not show a significant time lag.…”

Section: Variability Profilementioning

confidence: 99%

Modelling the γ-ray variability of 3C 273

Zheng

Zhang

Huang

et al. 2013

Monthly Notices of the Royal Astronomical Society

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We investigate MeV-GeV γ-ray outbursts in 3C 273 in the frame of a time-dependent one-zone synchrotron self-Compton (SSC) model. In this model, electrons are accelerated to extra-relativistic energy through the stochastic particle acceleration and evolve with the time, nonthermal photons are produced by both synchrotron and inverse Compton scattering of synchrotron photons. Moreover, nonthermal photons during a quiescent are produced by the relativistic electrons in the steady state and those during a outburst are produced by the electrons whose injection rate is changed at some time interval. We apply the model to two exceptionally luminous γ-ray outbursts observed by the Fermi-LAT from 3C 273 in September, 2009 and obtain the multi-wavelength spectra during the quiescent and during the outburst states, respectively. Our results show that the time-dependent properties of outbursts can be reproduced by adopting the appropriate injection rate function of the electron population.

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Long-term optical spectra variability of BL Lacertae object OJ 287

Cited by 31 publications

References 61 publications

On the masses of OJ287 black holes

On the masses of OJ287 black holes

Multi-Color Optical Monitoring of MRK 501 From 2010 to 2015

Modelling the γ-ray variability of 3C 273

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