Photopolarimetric Monitoring of Blazars in the Optical and Near-Infrared Bands with the Kanata Telescope. I. Correlations between Flux, Color, and Polarization

We report on the correlation between the flux, color and polarization variations on time scales of days--months in blazars, and discuss their universal aspects. We performed monitoring of 42 blazars in the optical and near-infrared bands from 2008 to 2010 using TRISPEC attached to the "Kanata" 1.5-m telescope. We found that 28 blazars exhibited "bluer-when-brighter" trends in their whole or a part of time-series data sets. This corresponds to 88% of objects that were observed for >10 days. Thus, our observation unambiguously confirmed that the "bluer-when-brighter" trend is common in the emission from blazar jets. This trend was apparently generated by a variation component with a constant and relatively blue color and an underlying red component. Prominent short-term flares on time scales of days--weeks tended to exhibit a spectral hysteresis; their rising phases were bluer than their decay phases around the flare maxima. In contrast to the strong flux--color correlation, the correlation of the flux and polarization degree was relatively weak; only 10 objects showed significant positive correlations. Rotations of polarization were detected only in three objects: PKS 1510-089, 3C 454.3, and PKS 1749+096, and possibly in S5 0716+714. We also investigated the dependence of the degree of variability on the luminosity and the synchrotron peak frequency, \nu_peak. As a result, we found that lower luminosity and higher \nu_peak objects had smaller variations in their amplitudes both in the flux, color, and polarization degree. Our observation suggests the presence of several distinct emitting sources, which have different variation time-scales, colors, and polarizations. We propose that the energy injection by, for example, internal shocks in relativistic shells is a major factor for blazar variations on time scales of both days and months.

[1]  Yu. V. Golubinsky,et al.  BVRI CCD-Photometry of Comparison Stars in the Neighborhoods of Galaxies with Active Nuclei. II , 2005 .

[2]  Y. Wadadekar,et al.  Submitted to ApJS Preprint typeset using L ATEX style emulateapj v. 10/09/06 THE SIXTH DATA RELEASE OF THE SLOAN DIGITAL SKY SURVEY , 2022 .

[3]  R. Antonucci,et al.  A survey for high optical polarization in quasars with core-dominant radio structure : is there a beamed optical continuum ? , 1992 .

[4]  Paolo Giommi,et al.  CGRaBS: An All-Sky Survey of Gamma-Ray Blazar Candidates , 2007, 0709.1735.

[5]  Spectral energy distributions of a large sample of BL Lacertae objects , 2005, astro-ph/0509045.

[6]  Naoko Iyomoto,et al.  Characteristic X-Ray Variability of TeV Blazars: Probing the Link between the Jet and the Central Engine , 2001 .

[7]  R Edelson,et al.  The Discrete Correlation Function: a New Method for Analyzing Unevenly Sampled Variability Data , 1988 .

[8]  Paul S. Smith,et al.  PROBING THE INNER JET OF THE QUASAR PKS 1510−089 WITH MULTI-WAVEBAND MONITORING DURING STRONG GAMMA-RAY ACTIVITY , 2010, 1001.2574.

[9]  P. Giommi,et al.  A change in the optical polarization associated with a γ-ray flare in the blazar 3C 279 , 2010 .

[10]  Paul S. Smith,et al.  Optical and Hubble Space Telescope ultraviolet spectropolarimetry of 3C 273 and PG 1114+445 , 1993 .

[11]  H. R. Miller,et al.  The timescales of the optical variability of blazars. III - OJ 287 and BL Lacertae , 1992 .

[12]  P. Giommi,et al.  Extreme Synchrotron BL Lac Objects Stretching the Blazar sequence , 2001 .

[13]  P. Hertz,et al.  H1722 + 119 - A highly polarized X-ray-selected BL Lacertae object , 1990 .

[14]  N. Efimova,et al.  The Outburst of the Blazar AO 0235+164 in 2006 December: Shock-in-Jet Interpretation , 2007, 0709.3550.

[15]  F. D'Alessio,et al.  Optical and Radio Monitoring of S5 1803+784 , 2002, astro-ph/0204365.

[16]  Junhui Fan,et al.  Optical Monitoring of S5 0716+714 from 1994 to 2000 , 2002 .

[17]  J. Angel,et al.  The noise of BL Lacertae , 1982 .

[18]  E. Liang,et al.  Photometric monitoring of 12 BL Lacertae objects , 2002 .

[19]  J. R. Mattox,et al.  Redshifts of Candidate Gamma-Ray Blazars , 2003 .

[20]  B. Ramsey,et al.  Optical Variability of Blazars , 2000 .

[21]  Martin J. Rees,et al.  Comptonization of Diffuse Ambient Radiation by a Relativistic Jet: The Source of Gamma Rays from Blazars? , 1994 .

[22]  H. Krawczynski,et al.  Complex Spectral Variability from Intensive Multiwavelength Monitoring of Markarian 421 in 1998 , 2000, astro-ph/0008505.

[23]  The recognition of blazars and the blazar spectral sequence , 2004, astro-ph/0409643.

[24]  J. Bregman,et al.  Optical and radio variability in blazars , 1992 .

[25]  D. Schlegel,et al.  Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds , 1997, astro-ph/9710327.

[26]  et al,et al.  Radio-to-UV monitoring of AO 0235+164 by the WEBT and Swift during the 2006-2007 outburst , 2008, 0801.1236.

[27]  C. Barache,et al.  The construction of the large quasar astrometric catalogue (LQAC) , 2009 .

[28]  W. P. Chen,et al.  A new activity phase of the blazar 3C 454.3. Multifrequency observations by the WEBT and XMM-Newton in 2007-2008 , 2008, 0810.2424.

[29]  The CLASS blazar survey: testing the blazar sequence , 2003, astro-ph/0311384.

[30]  S. Ciprini,et al.  The continuum spectral features of blazars in the optical region , 2004 .

[31]  Paul S. Smith,et al.  Optical and near-infrared observations of BL Lacertae objects and active quasars , 1987 .

[32]  C. Raiteri,et al.  The nature of optical and near-infrared variability of BL Lacertae , 2009, 0912.1867.

[33]  E. I. Robson,et al.  The multiwavelength variability of 3C 273 , 2008, 0805.3411.

[34]  D. Schlegel,et al.  Maps of Dust Infrared Emission for Use in Estimation of Reddening and Cosmic Microwave Background Radiation Foregrounds , 1998 .

[35]  M. Kidger,et al.  Optical and Near-Infrared Calibration of AGN Field Stars: An All-Sky Network of Faint Stars Calibrated on the Landolt System , 2001 .

[36]  P. Giommi,et al.  What Types of Jets Does Nature Make? A New Population of Radio Quasars , 2003, astro-ph/0301227.

[37]  A. Comastri,et al.  A theoretical unifying scheme for gamma-ray bright blazars , 1998, astro-ph/9807317.

[38]  A. Treves,et al.  PG 1553+11 : A BRIGHT OPTICALLY SELECTED BL LACERTAE OBJECT. , 1990 .

[39]  Davide Lazzati,et al.  Internal shocks in the jets of radio-loud quasars , 2001 .

[40]  Optical variability of the BL Lacertae object GC 0109+224. Multiband behaviour and time scales from , 2003, astro-ph/0301325.

[41]  D. Trèvese,et al.  Spectral Slope Variability of BL Lacertae Objects in the Optical Band , 2002, astro-ph/0212524.

[42]  R. J. Leacock,et al.  Long-term optical behavior of 144 compact extragalactic objects - 1969-1988 , 1988 .

[43]  Paul S. Smith,et al.  Optical spectroscopy and polarization of a new sample of optically bright flat radio spectrum sources , 1996 .

[44]  J. Angel,et al.  Optical and Infrared Polarization of Active Extragalactic Objects , 1980 .

[45]  P. Giommi,et al.  Roma-BZCAT: A multifrequency catalogue of Blazars , 2008, 0810.2206.

[46]  C. Raiteri,et al.  BVR photometry of comparison stars in selected blazar fields - I. Photometric sequences for 10 BL Lacertae objects , 1998 .

[47]  E. McGrath,et al.  Optical and radio variability of the BL Lacertae object AO 0235+16: A possible 5-6 year periodicity , 2001, astro-ph/0108165.

[48]  J. E. Pesce,et al.  Ultraviolet and Multiwavelength Variability of the Blazar 3c 279: Evidence for Thermal Emission , 1999 .

[49]  D. York,et al.  The Extent of Nebular Emission Associated with the Z = 0.525 Absorber near AO 0235+164 , 1989 .

[50]  T. Ohsugi,et al.  Detection of Polarimetric Variations Associated with the Shortest Time-Scale Variability in S5 0716+714 , 2008, 0812.1416.

[51]  A. Sandage.  The Redshift-Distance Relation. 111. Photometry and the Hubble Diagram for Radio Sources and the Possible Turn-On Time for QSOS , 1972 .

[52]  F. Ringwald,et al.  BLUE-LIGHT MONITORING OF 3C 273, 3C 351, 3C 454.3, 3C 66A, PKS 2141+17, OJ 287, AND ZW 0039.5+004 , 1988 .

[53]  P. Véron,et al.  A catalogue of quasars and active nuclei: 13th edition , 2010 .

[54]  Paul S. Smith,et al.  FLARING BEHAVIOR OF THE QUASAR 3C 454.3 ACROSS THE ELECTROMAGNETIC SPECTRUM , 2010, 1003.4293.

[55]  J. Condon,et al.  Optical identifications of Parkes sources with flat spectra. , 1977 .

[56]  J. Prieto,et al.  Variability and stability in blazar jets on time-scales of years: optical polarization monitoring of OJ 287 in 2005–2009 , 2009, 0912.0005.

[57]  A. Treves,et al.  ESO Very Large Telescope Optical Spectroscopy of BL Lacertae Objects. II. New Redshifts, Featureless Objects, and Classification Assessments , 2006, astro-ph/0601506.

[58]  N. Kawai,et al.  Multiwavelength Observations of the Powerful Gamma-Ray Quasar PKS 1510–089: Clues on the Jet Composition , 2007, 0709.1528.

[59]  E. Pian,et al.  Four Years of Monitoring Blazar PKS 2155–304 with BeppoSAX: Probing the Dynamics of the Jet , 2002, astro-ph/0202378.

[60]  H. R. Miller,et al.  Correlated Multi-Wave Band Variability in the Blazar 3C 279 from 1996 to 2007 , 2008, 0808.2194.

[61]  J. Chiang,et al.  Synchrotron and Synchrotron Self-Compton Spectral Signatures and Blazar Emission Models , 2001, astro-ph/0109165.

[62]  C. Raiteri,et al.  Monitoring of AO 0235+164 during a faint state , 1998 .

[63]  M. C. Cosgrove.  Writing for “the audience” , 1984, IEEE Transactions on Professional Communication.

[64]  H. Sol,et al.  The multifrequency emission of Mrk 501 From radio to TeV gamma-rays , 2001 .

[65]  J. Fan,et al.  Optical Variability and Periodicity Analysis for Blazars. I. Light Curves for Radio-selected BL Lacertae Objects , 2000 .

[66]  S. Pak,et al.  Multi-colour optical monitoring of eight red blazars , 2006, astro-ph/0602180.

[67]  The unprecedented optical outburst of the quasar 3C 454.3 - The WEBT campaign of 2004–2005 , 2006, astro-ph/0603386.

[68]  P. Giommi,et al.  The Sedentary Survey of Extreme High Energy Peaked BL Lacs. II. The Catalog and Spectral Properties , 2004 .

[69]  E. Pecontal,et al.  Historic Light Curve and Long-Term Optical Variation of BL Lacertae 2200+420 , 1998, astro-ph/9809050.

[70]  A high redshift BL Lacertae object - PKS 0215+015 , 1982 .

[71]  Yasushi Fukazawa,et al.  Multiband Photopolarimetric Monitoring of an Outburst of the Blazar 3C 454.3 in 2007 , 2010 .

[72]  M. Carini,et al.  Multiband Microvariability Observations of BL Lacertae during the Outburst of 1997 , 2001 .

[73]  B. Rani,et al.  Short-term flux and colour variations in low-energy peaked blazars , 2010, 1001.5206.

[74]  T. Weekes,et al.  Gamma-Ray Variability of the BL Lacertae Object Markarian 421 , 1996 .

[75]  I. Papadakis,et al.  The long-term optical spectral variability of BL Lacertae , 2007, 0705.2094.

[76]  M. Skrutskie,et al.  The Two Micron All Sky Survey (2MASS) , 2006 .

[77]  H. R. Miller,et al.  The Timescales of the Optical Variability of Blazars. V. 3C 371 , 1990 .

[78]  T. Jones,et al.  Magnetic field structures in active compact radio sources , 1985 .

[79]  Paul S. Smith,et al.  The inner jet of an active galactic nucleus as revealed by a radio-to-γ-ray outburst , 2008, Nature.

[80]  The WEBT BL Lacertae Campaign 2000 , 2002, astro-ph/0205479.

[81]  C. Megan Urry,et al.  The Hubble Space Telescope Survey of BL Lacertae Objects. I. Surface Brightness Profiles, Magnitudes, and Radii of Host Galaxies , 1999, astro-ph/9911147.

[82]  C. Raiteri,et al.  Optical observations of five X-ray selected BL Lacertae objects , 2000 .

[83]  T. Takahashi,et al.  Variability Pattern and the Spectral Evolution of the BL Lacertae Object PKS 2155–304 , 1999 .

[84]  Paul S. Smith,et al.  The optical and near-infrared polarization properties of the OVV quasar 3C 345 , 1986 .

[85]  M. Malkan,et al.  The miniblazar in 3C 273 , 1989 .

[86]  J. Pforr,et al.  Host galaxy subtraction of TeV candidate BL Lacertae objects , 2007, 0709.2533.

[87]  Francis Allard,et al.  Night ventilation for building cooling in summer , 1997 .

[88]  P. Giommi,et al.  THE SPECTRAL ENERGY DISTRIBUTION OF FERMI BRIGHT BLAZARS , 2009, The Astrophysical Journal.

[89]  Christopher D Impey,et al.  New Blazars Discovered by Polarimetry , 1988 .

[90]  D. Dale,et al.  An Optical Survey of the Position Error Contours of Unidentified High-Energy Gamma-Ray Sources at Galactic Latitude |b| > 20° , 2004, astro-ph/0404059.

[91]  F. D'Alessio,et al.  Spectral Variability of BL Lac Objects , 2002, Publications of the Astronomical Society of Australia.

[92]  E. Feigelson,et al.  H 0323 + 022 - A new BL Lacertae object with extremely rapid variability , 1986 .

[93]  R. Griffiths,et al.  4U1722 + 11 - The discovery of an X-ray selected BL Lac object , 1989 .

[94]  T. Ohsugi,et al.  Bayesian Approach to Find a Long-Term Trend in Erratic Polarization Variations Observed in Blazars , 2009, 0911.2950.

[95]  J. E. Pesce,et al.  The Hubble Space Telescope Survey of BL Lacertae Objects. II. Host Galaxies , 1999, astro-ph/9911109.

[96]  B. Kapanadze.  Optical R-band variability of seven X-ray-selected BL Lacertae objects , 2009 .

[97]  W. Voges,et al.  Optical identification of ROSAT-FSC sources , 2006 .

[98]  BATC 13 Band Photometry of the Open Cluster NGC 7789 , 2007, astro-ph/0701282.

[99]  C. Megan Urry,et al.  VARIABILITY OF ACTIVE GALACTIC NUCLEI , 1997 .

[100]  H. Zhang,et al.  CCD Photometry and Optical Variability of the BL Lacertae Object H0323+022 , 2008 .

[101]  P. Padovani.  The blazar sequence: validity and predictions , 2006, astro-ph/0610545.

[102]  R. Scalzo,et al.  Observations of the BL Lacertae Object 3C 66A with STACEE , 2005, astro-ph/0504515.

[103]  R. J. Leacock,et al.  The 1987-1990 Outburst of the OVV Quasar 3C 279 , 1990 .

[104]  Atsushi Yamazaki,et al.  TRISPEC: A Simultaneous Optical and Near‐Infrared Imager, Spectrograph, and Polarimeter , 2005 .

[105]  G. Fossati,et al.  A unifying view of the spectral energy distributions of blazars , 1998 .

[106]  S. Komossa,et al.  A Narrow-Line Seyfert 1-Blazar Composite Nucleus in 2MASX J0324+3410 , 2007, astro-ph/0702329.

[107]  Paul S. Smith,et al.  Multiwavelength Monitoring of the BL Lacertae Object PKS 2155–304 in 1994 May. III. Probing the Inner Jet through Multiwavelength Correlations , 1997, astro-ph/9704194.

[108]  E. Lindfors,et al.  Detection of the host galaxy of S5 0716+714 , 2008, 0807.0203.

[109]  Robert P. Johnson,et al.  THE FIRST CATALOG OF ACTIVE GALACTIC NUCLEI DETECTED BY THE FERMI LARGE AREA TELESCOPE , 2010, 1002.0150.

[110]  Noriko Y. Yamasaki,et al.  ASCA Observation of an X-Ray/TeV Flare from the BL Lacertae Object Markarian 421 , 1996 .

[111]  V. Hagen-Thorn,et al.  3C 345 in 1981–86: the spectral energy distribution of the variable component in the infrared and optical regions , 1994 .

[112]  E. Burbidge,et al.  Redshifts of fourteen quasi-stellar radio sources. , 1966 .

[113]  P. Hodge,et al.  Radio polarization rotators - BL Lacertae and 0727-115 , 1981 .