AUTOREGRESSIVE MODELING OF THE VARIABILITY OF AN ACTIVE GALAXY

作者：Morariu V^*; Vamos C; Pop A; Soltuz S; Buimaga Iarinca L

来源：Romanian Journal of Physics, 2010, 55(7-8): 676-686.

• Autoregressive model
• short-range correlation
• galaxies

Many natural phenomena can be described by power-laws of the temporal or spatial correlations. The equivalent in frequency domain is the 1/f spectrum. A closer look at various natural data reveals more or less significant deviations from a l/f characteristic. Such deviations are especially evident at low frequencies and less evident at high frequencies where spectra are very noisy. We exemplify such cases with a phenomenon offered by astrophysics. The X ray variability of the NGC 5506 galaxy can be better approximated by AR(1) - a first order autoregressive model, than by a 1/f model (long-range memory). The same spectra can be more or less easily confused and/or approximated by power-laws. A key step to detect non-power laws in the spectra, already suggested by Mandelbrot, is to average out the spectra.

• 出版日期2010