Extreme intra-hour variability of the radio source J1402+5347 discovered with Apertif
T. A. Oosterloo, H. K. Vedantham, A. M. Kutkin, E. A. K. Adams, B. Adebahr, A. H. W. M. Coolen, S. Damstra, W. J. G. de Blok, H. De'nes, K. M. Hess, B. Hut, G. … 展开作者
T. A. Oosterloo, H. K. Vedantham, A. M. Kutkin, E. A. K. Adams, B. Adebahr, A. H. W. M. Coolen, S. Damstra, W. J. G. de Blok, H. De'nes, K. M. Hess, B. Hut, G. M. Loose, D. M. Lucero, Y. Maan, R. Morganti, V. A. Moss, H. Mulder, M. J. Norden, A. R. Offringa, L. C. Oostrum, E. Orru`, M. Ruiter, R. Schulz, R. H. van den Brink, J. M. van der Hulst, J. van Leeuwen, N. J. Vermaas, D. Vohl, S. J. Wijnholds, J. Ziemke
The propagation of radio waves from distant compact radio sources through turbulent interstellar plasma in our Galaxy causes these sources to twinkle, a phenomenon called interstellar scintillation. Such scintillations are a unique probe of the micro-arcsecond structure of radio sources as well as of the sub-AU-scale structure of the Galactic interstellar medium. Weak scintillations (i.e. an intensity modulation of a few percent) on timescales of a few days or longer are commonly seen at centimetre wavelengths and are thought to result from the line-of-sight integrated turbulence in the interstellar plasma of the Milky Way. So far, only three sources were known that show more extreme variations, with modulations at the level of some dozen percent on timescales shorter than an hour. This requires propagation through nearby (d <~10 pc) anomalously dense (n_e ~10^2 cm^-3) plasma clouds. Here we report the discovery with Apertif of a source (J1402+5347) showing extreme (~50%) and rapid variations on a timescale of just 6.5 minutes in the decimetre band (1.4 GHz). The spatial scintillation pattern is highly anisotropic, with a semi-minor axis of about 20,000 km. The canonical theory of refractive scintillation constrains the scattering plasma to be within the Oort cloud. The sightline to J1402+5347, however, passes unusually close to the B3 star Alkaid (eta UMa) at a distance of 32 pc. If the scintillations are associated with Alkaid, then the angular size of J1402+5347 along the minor axis of the scintels must be smaller than ~10 micro arcsec yielding an apparent brightness temperature for an isotropic source of >~ 10^ 14K. }
Search for intra-day optical variability in Mrk 501
我们提出了我们的观测$γ$射线BL Lac对象Mrk 501的光学日内变化（IDV）。2005年4月至2012年5月，在云南天文台使用1.02 m和2.4 m光学望远镜进行了观测。2010年5月15日$R$条带的光变曲线通过了两项变异性检验（$F$检验和ANOVA检验）。在2010年5月15日的光变曲线中，耀斑的星等变化为$Δm = 0.03 \pm 0.005_{\rm{stat}} \pm 0.007_{\rm{sys}}$等，\textbf{a darkening timescale of $τ_{\rm{d}}=$ 26.7 minutes}，振幅为IDV $Amp=2.9\% \pm0.7\%$。耀斑内的下降\textbf{described by 11 consecutive flux measurements}可以在$> 99.99\%$的置信水平下与Pearson相关系数$r = 0.945$线性拟合。在假设IDV与黑洞的质量紧密相连的情况下，\textbf{and that the flare duration, being two times $τ_{\rm{d}}$, is representative of the minimum characteristic timescale, we can derive upper bounds to the mass…
The optical microvariability and spectral changes of the BL Lacertae object S5 0716+714
2008年10月、2008年12月和2009年2月，我们在光学波段监测了BL Lac天体S5 0716+714，在BVRI波段的最佳时间分辨率约为5分钟。四个快速耀斑的振幅范围从0.3至0.75马格南。源保持活跃，在整个监测活动，显示在所有天的微变，除了一个。总体变化幅度为Δ B ~ 0.89等，Δ V ~ 0.80等，Δ R ~ 0.73等和Δ I ~0.51等。微变的典型时间尺度范围为2至8小时。总体V-R颜色指数范围为0.37至0.59。强烈的蓝时，明亮的色差被发现在夜间的时间尺度。然而，不同的光谱行为被发现intrinight时间尺度。发现一个晚上B和I带之间可能存在约11分钟的时间滞后。喷流中的激波模型和几何效应可以用来解释源的夜内行为。
