DOI QR코드

DOI QR Code

RADIO VARIABILITY AND RANDOM WALK NOISE PROPERTIES OF FOUR BLAZARS

  • PARK, JONG-HO (Department of Physics and Astronomy, Seoul National University) ;
  • TRIPPE, SASCHA (Department of Physics and Astronomy, Seoul National University)
  • 투고 : 2014.11.30
  • 심사 : 2015.06.30
  • 발행 : 2015.09.30

초록

We show the results of a time series analysis of the long-term light curves of four blazars. 3C 279, 3C 345, 3C 446, and BL Lacertae. We used densely sampled light curves spanning 32 years at three frequency bands (4.8, 8, 14.5 GHz), provided by the University of Michigan Radio Astronomy Observatory monitoring program. The spectral indices of our sources are mostly flat or inverted (-0.5 < ${\alpha}$ < 0), which is consistent with optically thick emission. Strong variability was seen in all light curves on various time scales. From the analyses of time lags between the light curves from different frequency bands and the evolution of the spectral indices with time, we find that we can distinguish high-peaking flares and low-peaking flares according to the Valtaoja et al. classification. The periodograms (temporal power spectra) of the light curves are in good agreement with random-walk power-law noise without any indication of (quasi-)periodic variability. We note that random-walk noise light curves can originate from multiple shocks in jets. The fact that all our sources are in agreement with being random-walk noise emitters at radio wavelengths suggests that such behavior is a general property of blazars. We are going to generalize our approach by applying our methodology to a much larger blazar sample in the near future.

키워드

참고문헌

  1. Abramowicz, M. A., et al., 1991, X-ray Variability Power Spectra of Active Galactic Nuclei, A&A, 245, 454
  2. Aller, M. F., Aller, H. D. & Hughes, P. A., 2003, Pearson-Readhead Survey Sources. II. The Long-Term Centimeter-Band Total Flux and Linear Polarization Properties of a Complete Radio Sample, ApJ, 586, 33 https://doi.org/10.1086/367538
  3. Beckmann, V. & Shrader, C., 2012, Active Galactic Nuclei, Weinheim: Wiley-VCH
  4. Benlloch, S., Wilms, J., & Edelson, R., et al., 2001, Quasiperiodic Oscillation in Seyfert Galaxies: Significance Levels. The Case of Markarian 766, ApJ, 562, L121 https://doi.org/10.1086/338252
  5. Fan, J. H., 1999, Infrared Variability Properties of the Blazar 3C 279, MNRAS, 308, 1032 https://doi.org/10.1046/j.1365-8711.1999.02767.x
  6. Fromm, C. M., Perucho, M., & Ros, E., et al., 2011, Catching the radio flare in CTA 102. I. Light curve analysis, A&A, 531, A95 https://doi.org/10.1051/0004-6361/201116857
  7. Marscher, A. P., & Gear, W. K., 1985, Models for Highfrequency Radio Outbursts in Extragalactic Sources, with Application to the Early 1983 Millimeter-to-infrared Flare of 3C 273, ApJ, 298, 114 https://doi.org/10.1086/163592
  8. Park, J. -H., & Trippe, S., 2012, Multiple Emission States in Active Galactic Nuclei, JKAS, 45, 147
  9. Park, J. -H., & Trippe, S. 2014, Radio Variability and Random Walk Noise Properties of Four Blazars, ApJ, 785, 76 https://doi.org/10.1088/0004-637X/785/1/76
  10. Press, W. H., 1978, Flicker Noises in Astronomy and Elsewhere, ComAp, 7, 103
  11. Priestley, M. B. 1981, Spectral Analysis and Time Series, London: Elsevier
  12. Rani, B., Gupta, A. C., & Joshi, U. C., et al., 2010, Quasiperiodic Oscillations of 15 Minutes in the Optical Light Curve of the BL Lac S5 0716+714, ApJ, 719, L153 https://doi.org/10.1088/2041-8205/719/2/L153
  13. Rani, B., Krichbaum, T. P., & Fuhrmann, L., et al., 2013, Radio to Gamma-ray Variability Study of Blazar S5 0716+714, A&A, 552, A11 https://doi.org/10.1051/0004-6361/201321058
  14. Scargle, J. D., 1982, Studies in Astronomical Time Series Analysis. II - Statistical Aspects of Spectral Analysis of Unevenly Spaced Data, ApJ, 263, 835 https://doi.org/10.1086/160554
  15. Spada, M., et al., 2001, Internal Shocks in the Jets of Radioloud Quasars, MNRAS, 325, 1559 https://doi.org/10.1046/j.1365-8711.2001.04557.x
  16. Timmer, J. & Konig, M., 1995, On Generating Power Law Noise, A&A, 300, 707
  17. Trippe, S., Krips, M., & Pietu, V., et al., 2011, The Longterm Millimeter Activity of Active Galactic Nuclei, A&A, 533, A97 https://doi.org/10.1051/0004-6361/201015558
  18. Uttley, P., McHardy, I. M., & Papadakis, I. E., 2002, Measuring the Broad-band Power Spectra of Active Galactic Nuclei with RXTE, MNRAS, 332, 231 https://doi.org/10.1046/j.1365-8711.2002.05298.x
  19. Valtaoja, E., Terasranta, H., & Urpo, S., et al., 1992, Five Years Monitoring of Extragalactic Radio Sources - Part Three - Generalized Shock Models and the Dependence of Variability on Frequency, A&A, 254, 71
  20. Webb, J. R., Smith, A. G., & Leacock, R. J., et al., 1988, Optical Observations of 22 Violently Variable Extragalactic Sources - 1968-1986, AJ, 95, 374 https://doi.org/10.1086/114641