The variability and periods in the BL Lac AO 0235+164

AbstractVariability is one of the extreme observational properties of BL Lacertae objects. AO 0235+164 is a well studied BL Lac through the whole electro-magnetic wavebands, it is violently variable in the optical bands. In the present work, we show its optical R band photometric observations carried out during the period of Nov. 2006 to Dec. 2012 using the Ap6E CCD camera attached to the primary focus of the 70 cm meniscus telescope at Abastumani Observatory, Georgia. It shows a large variation of ΔR = 4.88 mag (14.20 - 19.08 mag) during our monitoring period. When periodicity analysis methods are adopted to its R observations from our Abastumani monitoring programme and those in the literature, the signs of some periods, P1 = 8.26 yr, P2 = 0.55 yr, P3 = 0.85 yr, P4 = 1.99 yr are found.

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Discovery of Five New X-ray–Selected BL Lacertae Objects and Three New Quasars

International Astronomical Union Colloquium ◽

10.1017/s025292110004063x ◽

1997 ◽

Vol 159 ◽

pp. 423-424

Author(s):

G.Z. Xie ◽

W. Brinkmann ◽

G.W. Cha ◽

S. Laurent-Muehleisen ◽

Y.H. Zhang ◽

...

Keyword(s):

Astronomical Observatory ◽

Bl Lacertae Objects ◽

Bl Lac Objects ◽

X Ray ◽

Bl Lacertae ◽

Bl Lac

Through combined ROSAT and VLA observations, we have identified 19 BL Lac/quasar candidates. In 1994 December, 1995 January and October, and 1996 January 1996, we obtained spectra of all 19 candidates using the 2.16-m telescope of Beijing Astronomical Observatory. The dispersion used is 195 Å mm−1, which yields a dispersion of about 4.65 Å pixel−1, and the wavelength coverage is 3500–7800 Å. Five of these objects are uniformly featureless, and we identify them as BL Lac objects. Three new quasars are also identified. Table 1 presents VLA positions and redshifts for the 5 new BL Lac objects and three new quasars. By checking them in the NASA/IPAC Extragalactic Database (NED) and Véron-Cetty & Véron’s (1993) Catalogue of Quasars and AGNs, and other recent reports about discovery of new BL Lac objects and quasars, we find that these sources are previously unreported.

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BL Lacertae objects as an evolutionary population

Symposium - International Astronomical Union ◽

10.1017/s0074180900153252 ◽

1986 ◽

Vol 119 ◽

pp. 491-492

Author(s):

A. Cavaliere ◽

E. Giallongo ◽

F. Vagnetti

Keyword(s):

Luminosity Function ◽

Bl Lacertae Objects ◽

Bl Lac Objects ◽

Bl Lacertae ◽

Bl Lac ◽

Bl Lacs

If the BL Lac Objects are active nuclei with a beamed component that is dominant when directed at us, their observed luminosity function must comprise a flat faint branch: N(L)dL ∝ L1+1/pdL with p=4.5 (Urry and Shafer 1984). If this is flatter than the LF NP(L) of the parent objects at equal observed L, then we expect the counts of BL Lacs to flatten out in turn at fluxes quite higher than the counts of the parents, even when both populations evolve strongly and uniformly with comparable timescales (Cavaliere, Giallongo and Vagnetti 1985).

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Optical Variability and Periodicity Analysis for Blazars. I. Light Curves for Radio‐selected BL Lacertae Objects

The Astrophysical Journal ◽

10.1086/308996 ◽

2000 ◽

Vol 537 (1) ◽

pp. 101-122 ◽

Cited By ~ 65

Author(s):

J. H. Fan ◽

R. G. Lin

Keyword(s):

Light Curves ◽

Optical Variability ◽

Bl Lacertae Objects ◽

Bl Lacertae ◽

Periodicity Analysis

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ASCAand Contemporaneous Ground‐based Observations of the BL Lacertae Objects 1749+096 and 2200+420 (BL Lac)

The Astrophysical Journal ◽

10.1086/307005 ◽

1999 ◽

Vol 515 (1) ◽

pp. 140-152 ◽

Cited By ~ 37

Author(s):

Rita M. Sambruna ◽

Gabriele Ghisellini ◽

Eric Hooper ◽

R. I. Kollgaard ◽

Joseph E. Pesce ◽

...

Keyword(s):

Bl Lacertae Objects ◽

Bl Lacertae ◽

Bl Lac

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The Character of the Optical Variability for the BL Lacertae Objects OJ 287

Symposium - International Astronomical Union ◽

10.1017/s0074180900140550 ◽

1989 ◽

Vol 134 ◽

pp. 116-117

Author(s):

H. Richard Miller ◽

Michael T. Carini

Keyword(s):

Time Scales ◽

Source Region ◽

Ccd Camera ◽

Seyfert Galaxies ◽

Convincing Evidence ◽

Rate Of Change ◽

Short Term ◽

Bl Lacertae Objects ◽

Bl Lacertae ◽

The Past

The BL Lacertae objects, OJ 287, has long been known to exhibit large amplitude variations on time scales as short as a few days. The time rate of change in brightness for these variations has been observed to be in excess of 1.0 mag. per day on several occasions. However, the nature of the optical variations on time scales significantly shorter than a day has not been well established, and in many cases the results have been controversial (Carrasco et al, 1985, Lawrence et al 1987, McHardy and Czerny, 1987). In order to address this problem, we have obtained observations of OJ 287 on four different nights during the past two years using the KPNO 0.9 meter telescope equipped with the direct CCD camera. Variations were detected for OJ 287 on each night with ranges of 0.05 mag. to 0.10 mag. The variations detected on 1986 November 9 are typical of those observed on each of the nights and is shown in Figure 1. A power spectrum analysis of the data was performed and no convincing evidence for the presence of any periodicity was found. Based on this analysis, the short term optical variations observed for OJ 287 have a very different character than the rapid x-ray flickering observed for Seyfert galaxies which have been characterized by 1/f - noise. Therefore, these observations would imply sizes for the source region 3 × 10−5 pc. If one assures that the underlying engine is a supermassive blackhole, then the time scales of the variability suggests masses for the blackhole of 107M⊙ – 108M⊙.

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The Rosat X-Ray Spectra of BL Lacertae Objects

Symposium - International Astronomical Union ◽

10.1017/s0074180900080761 ◽

1996 ◽

Vol 175 ◽

pp. 267-268

Author(s):

Paolo Padovani ◽

Paolo Giommi

Keyword(s):

Spectral Information ◽

Spectral Indices ◽

Bl Lacertae Objects ◽

X Ray ◽

Bl Lacertae ◽

Bl Lac ◽

Bl Lacs ◽

Selection Of

We have analyzed the X-ray spectra of all BL Lacs observed (as pointed or serendipitous sources) by ROSAT. Spectral indices were obtained from the hardness ratios given in the WGA catalogue, a large list of X-ray sources generated from all the ROSAT PSPC pointed observations. The selection of the objects was done by cross-correlating the first revision of the WGA catalogue with our recent catalogue of BL Lacs. This resulted in 163 observations of 85 distinct BL Lacs, which correspond to about half the confirmed BL Lacs presently known. This represents the largest number of BL Lacs for which homogeneous X-ray spectral information is available and the largest BL Lac sample ever studied at X-ray frequencies.

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Milliarcsecond Polarization Properties of Several BL Lacertae Objects

Symposium - International Astronomical Union ◽

10.1017/s0074180900134400 ◽

1988 ◽

Vol 129 ◽

pp. 167-168

Author(s):

D. C. Gabuzda ◽

D. H. Roberts ◽

J. F. C. Wardle ◽

L. F. Brown

Keyword(s):

The Other ◽

Bl Lacertae Objects ◽

Polarization Structure ◽

Preliminary Results ◽

Bl Lacertae ◽

The Core ◽

Bl Lac ◽

Core Components

We discuss the λ6 cm total intensity and polarization structures of a number of BL Lacertae objects at milliarcsecond resolution. 0235+164 was unresolved and weakly polarized at each of two epochs a year apart; each of the other objects displays structure in polarized flux. 0735+178 and 1749+096 can be adequately modeled by two or three point components—a “core” plus one or two “knots.” The core components were moderately polarized (≃ 5%), while “knots” may be polarized at 8% or more, consistent with these components being optically thin. Preliminary results for BL Lac indicate that the total intensity structure can be modeled well by a set of four gaussian components; the polarization structure is complex, but is dominated by the northernmost knot in the jet.

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