A SEARCH FOR AGN INTRA-DAY VARIABILITY WITH KVN

DOI QR코드

DOI QR Code

LEE, TAESEOK;TRIPPE, SASCHA;OH, JUNGHWAN;BYUN, DO-YOUNG;SOHN, BONG-WON;LEE, SANG-SUNG

  • 투고 : 2015.07.27
  • 심사 : 2015.10.26
  • 발행 : 2015.10.31

초록

Active galactic nuclei (AGN) are known for irregular variability on all time scales, down to intra-day variability with relative variations of a few percent within minutes to hours. On such short timescales, unexplored territory, such as the possible existence of a shortest characteristic time scale of activity and the shape of the high frequency end of AGN power spectra, still exists. We present the results of AGN single-dish fast photometry performed with the Korean VLBI Network (KVN). Observations were done in a “anti-correlated” mode using two antennas, with always at least one antenna pointing at the target. This results in an effective time resolution of less than three minutes. We used all four KVN frequencies, 22, 43, 86, and 129 GHz, in order to trace spectral variability, if any. We were able to derive high-quality light curves for 3C 111, 3C 454.3, and BL Lacertae at 22 and 43 GHz, and for 3C 279 at 86 GHz, between May 2012 and April 2013. We performed a detailed statistical analysis in order to assess the levels of variability and the corresponding upper limits. We found upper limits on flux variability ranging from ~1.6% to ~7.6%. The upper limits on the derived brightness temperatures exceed the inverse Compton limit by three to six orders of magnitude. From our results, plus comparison with data obtained by the University of Michigan Radio Astronomy Observatory, we conclude that we have not detected source-intrinsic variability which would have to occur at sub-per cent levels.

키워드

galaxies: active —galaxies: individual: 3C 111;3C 279;3C 454.3;BL Lac —radiation mechanisms: non-thermal —methods: statistical

참고문헌

  1. Park, J.-H., & Trippe, S. 2012, Multiple Emission States in Active Galactic Nuclei, JKAS, 45, 147
  2. Wajima, K., Fujisawa, K., Hayashida, M., et al. 2014, Short-Term Radio Variability and Parsec-scale Structure in a Gamma-ray Narrow-line Seyfert 1 Galaxy 1H 0323+342, ApJ, 781, 75 https://doi.org/10.1088/0004-637X/781/2/75
  3. Witzel, A., Heeschen, D. S., Schalinski, C., & Krichbaum, T. P. 1986, Kurzzeit-Variabilit¨at extragalaktischer Radioquellen, Mitt. Astron. Ges., 65, 239
  4. Kraus, A., Krichbaum, T. P., Witzel, A., et al. 2003, Intraday Variability in Compact Extragalactic Radio Sources, A&A, 401, 161 https://doi.org/10.1051/0004-6361:20030118
  5. Lee, S.-S., Byun, D.-Y., Oh, C. S., et al. 2011, Single-Dish Performance of KVN 21 m Radio Telescopes: Simultaneous Observations at 22 and 43 GHz, PASP, 123, 1398 https://doi.org/10.1086/663326
  6. Lovell, J. E. J., Rickett, B. J., Macquart, J.-P., et al. 2008, The Micro-Arcsecond Scintillation-Induced Variability (MASIV) Survey. II. The First Four Epochs, ApJ, 689, 108 https://doi.org/10.1086/592485
  7. Marscher, A. P., & Gear, W. K. 1985, Models for High-Frequency 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. 2014, Radio Variability and Random Walk Noise Properties of Four Blazars, ApJ, 785, 76 https://doi.org/10.1088/0004-637X/785/1/76
  9. Readhead, A. C. S. 1994, Equipartition Brightness Temperature and the Inverse Compton Catastrophe, ApJ, 426, 51 https://doi.org/10.1086/174038
  10. Rickett, B. J. 1990, Radio Propagation Through the Turbulent Interstellar Plasma, ARAA, 28, 561 https://doi.org/10.1146/annurev.aa.28.090190.003021
  11. 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
  12. Trippe, S., Krips, M., Piétu, V., et al. 2011, The Long Term Millimeter Activity of Active Galactic Nuclei, A&A, 533, A97 https://doi.org/10.1051/0004-6361/201015558
  13. Wagner, S. J., & Witzel, A. 1995, Intraday Variability in Quasars and BL Lac Objects, ARAA, 33, 163 https://doi.org/10.1146/annurev.aa.33.090195.001115
  14. Abramowicz, M. A., Bao, G., Lanza, A., & Zhang, X.-H. 1991, X-Ray Variability Power Spectra of Active Galactic Nuclei, A&A, 245, 454
  15. Armandroff, T. E., & Da Costa, G. S. 1986, The Radial Velocity, Velocity Dispersion, and Mass-to-Light Ratio of the Sculptor Dwarf Galaxy, AJ, 92, 777 https://doi.org/10.1086/114211
  16. Beckmann, V., & Shrader, C. 2012, Active Galactic Nuclei (Weinheim: Wiley VCH)
  17. Gupta, A. C., Krichbaum, T. P., Wiita, P. J., et al. 2012, Multiwavelength Intraday Variability of the BL Lac S5 0716+714, MNRAS, 425, 1357 https://doi.org/10.1111/j.1365-2966.2012.21550.x
  18. Benlloch, S., Wilms, J., Edelson, R., Yaqoob, T., & Staubert, R. 2001, Quasi-Periodic Oscillation in Seyfert Galaxies: Significance Levels. The Case of Markarian 766, ApJ, 562, L121 https://doi.org/10.1086/338252
  19. Blandford, R. D., & Königl, A. 1979, Relativistic Jets as Compact Radio Sources, ApJ, 232, 34 https://doi.org/10.1086/157262
  20. Fuhrmann, L., Krichbaum, T. P., Witzel, A., et al. 2008, Testing the Inverse-Compton Catastrophe Scenario in the Intra-Day Variable Blazar S5 0716+71. III. Rapid and Correlated Flux Density Variability from Radio to submm Bands, A&A, 490, 1019 https://doi.org/10.1051/0004-6361:20078893
  21. Hargreaves, J. C., Gilmore, G., Irwin, M. J., & Carter, D. 1994, A Dynamical Study of the Sextans Dwarf Spheroidal Galaxy, MNRAS, 269, 957 https://doi.org/10.1093/mnras/269.4.957
  22. Kellermann, K. I., & Pauliny-Toth, I. I. K. 1969, The Spectra of Opaque Radio Sources, ApJ, 155, L71 https://doi.org/10.1086/180305
  23. Kim, K.-T., Byun, D.-Y., Je, D. H., et al. 2011, 100-GHz Band Test Observations of the KVN 21-m Radio Telescopes, JKAS, 44, 81
  24. Kim, J.-Y., & Trippe, S. 2013, How to Monitor AGN Intra-Day Variability at 230 GHz, JKAS, 46, 65

과제정보

연구 과제번호 : 우주탄생과 진화연구