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收集了Fermi/LAT, Catalina, OVRO发布的CGRaBS J2345-1555长期射电(15 GHz)、伽马、光学V波段的流量和星等数据, 用离散相关函数方法评估了多波段间的相关性, 结果显示伽马波段和射电波段的相关系数为0.53, 时间延迟约为90天, 伽马波段比射电波段超前约90天; 射电和光学V波段的相关系数为0.84, 时间延迟约为–300天, 光学V波段比射电波段超前约300天; 伽马和光学V波段没得出具体相关性. 说明光学波段由同步辐射主导, 射电波段与光学波段的时间延迟可以解释为光学波段的辐射区域在上游, 射电波段在下游. 而伽马波段与射电波段是同源的. 用亮温度方法计算了该天体射电波段的多普勒因子, 多普勒因子平均值为12.25, 并随光变曲线振荡. 分析得出喷流具有明显聚束效应. 射电波段辐射流量变化来自于喷流.In this paper, CGRaBS J2345-1555’s long-term radio band, gamma ray flux and optical V-band magnitude data are collected from Fermi/LAT, Catalina, and OVRO dataset. The correlation between multi-bands is evaluated by the discrete correlation function method. The results show that the correlation coefficient between gamma band and radio band is 0.53, and the time delay is about 90 days, a variation of the gamma band is about 90 days ahead of radio band; the correlation coefficient between radio band and optical V-band is 0.84, and the time delay is about –300 days, a variation of the optical V-band is about 300 days ahead of radio band; there is no significant correlation between gamma and optical V-band. These results show that the optical band is dominated by synchrotron radiation, and the time delay between the radio band and the optical band can be explained as the fact that the radiation region of the optical band is upstream, and the radio band is downstream. The gamma band and the radio band are both homologous. The distribution of brightness temperature is used to calculate the Doppler factor of the celestial body’s radio band. The averaged Doppler factor is 12.64, and it oscillates with the light curve. So the jet has obvious bunching effect, and the variation of radiation flux in radio band comes from the jet.
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Keywords:
- discrete correlation function method /
- correlations /
- time delay /
- Doppler factor
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图 1 从2008年1月5日至2020年7月1日射电波段15 GHz流量数据, 红色矩形内为大爆发, 绿色矩形内为小爆发
Fig. 1. 15 GHz radio frequency data from January 5, 2008 to July 1, 2020. Strong bursts are inside the red rectangles, weak bursts are inside the green rectangles.
图 2 从2008年8月19日至2019年4月24日伽马波段流量数据, 红色矩形内为爆发
Fig. 2. Gamma band data from August 19, 2008 to April 24, 2019. Bursts are inside the red rectangles.
图 3 从2005年11月30日至2010年8月13日光学V波段流量数据
Fig. 3. Optical V-band data from November 30, 2005 to August 13, 2010. Bursts are inside the red rectangles.
图 4 红色曲线为99.7%置信曲线, 黑色点为伽马和射电15 GHz波段离散相关函数的计算结果
Fig. 4. Red curve is the 99.7% confidence curve, and the black points are the calculation results of the discrete correlation function of the gamma band and the radio 15 GHz band.
图 5 红色曲线为99.9%置信曲线, 黑色点为射电波段和光学V波段离散相关函数计算结果
Fig. 5. Red curve is the 99.9% confidence curve, and the black points are the calculation results of the discrete correlation function of the radio band and the optical V band.
图 6 伽马波段和光学V波段离散相关函数计算结果
Fig. 6. Calculation results of the discrete correlation function of the gamma band and the optical V band.
表 1 射电波段11个爆发的多普勒因子
Table 1. Doppler factor of 11 bursts in radio band.
流量范围(JD = 2400000+) $\Delta F/{\rm Jy}$ ${t_{ {\text{ob} } } }/{\rm days}$ $ \delta $ 1 54655.5—54947.0 0.2760 138.30 6.31 2 55025.5—55340.7 0.2736 64.57 10.46 3 55637.8—55918.1 0.5232 52.96 14.82 4 55994.9—56441.6 0.5645 195.38 6.36 5 56455.6—56588.2 0.5886 76.50 12.06 6 56588.2—56832.6 0.2192 50.21 11.49 7 56832.6—57041.0 0.6899 54.54 15.93 8 57041.0—57228.4 0.5185 60.65 13.97 9 57258.4—57638.3 0.8702 214.22 6.9 10 57951.5—58488.1 0.8944 61.37 16.06 11 58509.9—58645.6 0.3126 25.25 20.44 
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[1] Blandford R D, Königl A 1979 Astrophys. J. 232 34
Google Scholar
[2] Jones T W, O’dell S L, Stein W A 1974 Astrophys. J. 188 353
Google Scholar
[3] Böettcher M, Reimer A, Sweeney K, Prakash A 2013 Astrophys. J. 768 54
Google Scholar
[4] Dermer C D, Schlickeiser R 2002 Astrophys. J. 575 667
Google Scholar
[5] Sikora M, Stawarz L, Moderski R, Nalewajko K, Madejski G M 2009 Astrophys. J. 704 38
Google Scholar
[6] Böttcher M, Reimer A, Zhang H C 2013 EPJ Web of Conferences 61 05003
Google Scholar
[7] Fuhrmann L, Larsson S, Chiang J, Angelakis E, Zensus J A, Nestoras I, Krichbaum T P, Ungerechts H, Sievers A, Pavlidou V, Readhead A C S, Max M W, Pearson T J 2014 Mon. Not. R. Astron. Soc. 441 1899
Google Scholar
[8] Cohen D P, Romani R W, Filippenko A V, Cenko S B, Lott B, Zheng W K, Li W 2014 Astrophys. J. 797 137
Google Scholar
[9] Zhang B K, Zhao X Y, Zhang L, Dai B Z 2017 Astrophys. J. 231 14
Google Scholar
[10] Ghisellini G, Maraschi L, Tavecchio F 2009 Mon. Not. R. Astron. Soc. 396 L105
Google Scholar
[11] Abdo A A, Ackermann M, Ajello M, et al. 2010 Astrophys. J. 715 429
Google Scholar
[12] Jiang Y G, Hu S M, Chen X, Shao X, Huo Q H 2020 Mon. Not. R. Astron. Soc. 493 3757
Google Scholar
[13] Ghisellini G, Tavecchio F, Foschini F, Bonnoli G, Tagliaferri G 2013 Mon. Not. R. Astron. Soc. 432 L66
Google Scholar
[14] Richards J L, Moerbeck W M, Pavlidou V, et al. 2011 Astrophys. J. 194 29
Google Scholar
[15] Edelson R A, Krolik J H 1988 Astrophys. J. 333 646
Google Scholar
[16] White R J, Peterson B M 1994 Pub. Astron. Soc. Pac. 106 879
[17] Kellermann K I, Pauliny T I I K 1969 Astrophys. J. 155L 71K
[18] Lähteenmäki A, Valtaoja E, Wiik K 1999 Astrophys. J. 511 112
Google Scholar
[19] Readhead A C S 1994 Astrophys. J. 426 51
Google Scholar
[20] Wagner S J, Witzel A 1995 Ann. Rev. Astron. Astrophys. J. 33 163
Google Scholar
[21] Shaw M S, Romani R W, Cotter G, Healey S E, Michelson P F, Readhead A C S, Richards J L, Max M W, King O G, Potter W J 2012 Astrophys. J. 748 49
Google Scholar
[22] Max M W, Hovatta T, Richards J L, King O G, Pearson T J, Readhead A C S, Reeves R, Shepherd M C, Stevenson M A, Angelakis E, Fuhrmann L, Grainge K J B, Pavlidou V, Romani R W, Zensus J A 2014 Mon. Not. R. Astron. Soc. 445 428
Google Scholar
[23] Liodakis I, Pavlidou V 2015 Mon. Not. R. Astron. Soc. 454 1767
Google Scholar
[24] Caproni A, Abraham Z, Monteiro H 2012 Mon. Not. R. Astron. Soc. 428 280
Google Scholar
[25] Stirling A M, Cawthorne T V, Stevens J A, Jorstad S G, Marscher A P, Lister M L, Gomez J L, Smith P S, Agudo I, Gabuzda D C, Robson E I, Gear W K 2010 Mon. Not. R. Astron. Soc. 341 405
[26] Caproni A, Abraham Z, Motter J C, Monteiro H 2017 Astrophys. J. 851 L39
Google Scholar
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