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Photometric Observations of Blazars: Insights from the 8th Sino-German Meeting

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The 8th Sino-German Meeting, held from February 23-27 in Kunming, China, focused on photometric observations of blazars, which are extragalactic objects known for their rapid variability and high luminosity. Led by J.H. Fan and co-workers from the Center for Astrophysics at Guangzhou University, the study highlighted the variability characteristics of blazars over different time scales. Observational results were drawn from significant studies covering both optical and radio bands, offering insights into their emission mechanisms and underlying structures. The meeting emphasized collaborative efforts in understanding these fascinating cosmic phenomena.

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Photometric Observations of Blazars: Insights from the 8th Sino-German Meeting
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  1. 8th Sino-German Meeting, Feb. 23-27, Kunming, China Photometric Observations of Blazars J.H. Fan Center for Astrophysics, Guangzhou University Co-Workers: Tao, J., Qian, B.C., Shen, Z.Q., Zhang, Y.W., Peng, Q.S., Liu, Y.

  2. Outline • Introduction • Variability Light Curves • Long-term Photometric Observations • Summary

  3. INTRODUCTION INTRODUCTION BLAZARS BLAZARS (BL Lacs and FSRQs) extragalactic objects with rapid variability, high luminosity, high and variable polarization, or superluminal motions. The term “blazar” was coined, half in jest, by Ed Speigel at the first conference on BL lac objects in Pittsburg.

  4. INTRODUCTION Observations show that some sources with particular observational properties RBLs LBLs 1) BL Lacertae objects--BLs, XBLs HBLs 2) Flat Spectrum Radio Quasars—FSRQs

  5. 2 Variation of Blazars Variation is one of the main observation characteristics of blazars. Variability over different time scales: Short-term variability with variability time scale of introday, Middle-term variability with time scale of days to months, and long-term variability with time scale of years.

  6. 2. Variation of Blazars The variability may shed some light on the emission mechanism, the emission size, and even the structure at the center of blazars.

  7. Recent Working Groups on Optical Variation Observations --- Argentina: Romero et al. --- China: Fan et al., Tao, et al., Wei,J.Y. et al. Xie et al. --- Finland: Takalo, Sillanpaa, Valtaojia et al. --- Georgia: Kurtanidze et al. --- Germany: Wagner et al. --- India: Gupta et al. --- Italy: Tosti, Villata, Raiteri et al. --- USA: Nobel, Miller, Clement et al. --- etc

  8. 2.1 Light curves in Optical Bands

  9. 0.5 mag introday variability in both R and V bands were measured 1.2 mag. Variation from night to night. Romero et al. 2000 Individual Sources-0235+164

  10. Individual Sources-0736 Clements, Jenks, and Torres, 2003, AJ, 126 1.3 mag. over 2.0 hrs

  11. Individual Source-3C 66A It is in a bright state in the observational period of 1994 to 1997 Lainela, 1999, ApJ, 521

  12. Folded Light Curve of 3C 66A Lainela, et al., 1999, ApJ, 521

  13. Individual Sources-BL Lacertae Villata, et al. 2002, A&A, 390, 407

  14. Individual Sources-3C 446 Kinman 1975, IAUS, 67

  15. Individual Sources-BL Lac Fan, et al. 1998, ApJ, 507

  16. Individual Source-ON231 Fan & Lin, 2000, ApJ, 537

  17. The observed V light curve (filled points) and the simulated V light curve (solid curve) with the periods of 4.16 and 7.0 considered. Individual Sources-PKS2155-304 Fan & Lin, 2000, A&A, 355

  18. Individual Source-3C 273 Fan, Romero & Lin, 2001, ChA&A, 25

  19. Infrared:Individual Sources-3C279 Fan, 1999, MNRAS, 308

  20. Period Analysis Results 5.87+/-1,3

  21. Analysis Results

  22. In optical/Infrared bands: Time-Scale: Minutes—Hours-Days-Months-Years

  23. 2.2 X-ray and Gamma-Ray

  24. 0323+022 Feigelson et al. 1986, ApJ, 302 It shows a time scale of 33 seconds in the X-ray band. The rapidly variable X-rays and polarized optical emission may be produced in the intense environment of non-thermal particles and photons that is thought to surround an accreting magnetized rotating lack hole, or in a thin shock in a relativistic jet

  25. Individual Sources-0420-014 Wanger, et al. 1995, A&A, 298

  26. During 1993 January the source was unusually bright in optical and gamma-ray regions. During this period Wagner observed a rapid, symmetrical flare in the optical wavelength range which lasted for about 4 days. EGRET detected a similar rapid flare peaking about 22 hr after the optical outburst.Because such rapid flares are rare events, it is likely that the outbursts in the two frequency regimes are correlated. This delay can not be well explained by the existing model. Individual Sources-1406-076 Wanger, et al. 1995, ApJ, 454 L97

  27. TeV Variability-Mkn 421 Catanese & Weekes 1999, PASP, 111, 1193

  28. TeV Variability-Mkn 501 Catanese & Weekes 1999, PASP, 111, 1193

  29. Individual Source-Mkn501 Lightcurve above 1.5 TeV energy; . 2-10KeV from RXTE-ASM Kranich et al., 1999, astro- ph/ 9907205

  30. 3C273- 13.5-year period in the X-ray light curve by Manchanda, K. R., 2002, JApA, 23, 243. The period is similar to that, 13.65+/-0.2 year found in the optical band (Fan) Time Scale: minutes—Days—Months--Years

  31. 2.3 In the Radio Bands

  32. 0235+164 Kraus et al. A&A, 344, 807–816 (1999)

  33. Radio Variability Valtaojia et al. 1999, ApJS

  34. Periodicity Analysis Results for MURAO Data Base There are light curves for the 168 sources, we found 203 astrophysics meaningful periods ( FAP < 0:50 and Tms < 2/3 ObT) are obtained for 66 sources. P= 2.2 to 20.8 years for 34 FSRQs P=2.5 to 18.0 years for 17 BLs Fan et al. 2007, A&A

  35. Variability in Radio Bands

  36. Probability for the two distribution to come from the same parent distribution is p=67%

  37. 3. Long-Term Photometric Observations

  38. We made observations of blazars since 1994 in Shanghai Astronomical Observatory(ShAO) with the 1.56m telescope. 1 pixel = 0.024mm The seeing at the She-shan Station of ShAO varied from 1".3 to 2".0

  39. 3.1 4C29.45(1156+295) Fan, J.H., 2006, PASJ Observing period 1998-2002

  40. T = 3.55±0.02 yearsT =1.58±0.01 years,

  41. 3.2 Optical monitoring of 3C 390.3 Tao, Fan, Qian, 2008, AJ Mar.95-Aug. 04

  42. 8.30 ±1.17, 5.37± 0.49, 3.51±0.21, 2.13 ±0.08 years

  43. 3.3 OJ 287 Fan et al. 2009, ApJS (accepted) OJ 287 is one of the best studied blazars. It is also a prime target in our long term blazar monitoring program carried out with the 1.56-m telescope at Sheshan Station of Shanghai Astronomical Observatory (ShAO), China. Here we present optical photometry results of V, R, and I passbands of the BL Lac object OJ 287 (0851+202) carried out during January 2002 to February 2007. Largest variations: △ V = 1.96 mag (14.01 to 15.97 mag), △ R = 2.36 mag(13.39 to 15.75 mag), and △ I = 1.95 mag (12.79 to 14.74 mag) Intra-day variation time scales of ～ 10 minutes to 2 hours were detected in optical passbands.

  44. △T=10min

  45. Implication of 10 minutes

  46. Historic Light Curve of OJ 287 1897-2007

  47. Periodicity Analysis New √ √

  48. Binary Black Hole We have

  49. Masses of the Binary BHs From the host galaxy, we have R=-23.69, which suggests a (McLure & Dunlop 2001, log M = -0.5*R-2.69) Then 12.38 year period suggests