We present the X-ray broadband power spectral density function (PSD) of the X-ray-luminous Seyfert IC 4329a, constructed from light curves obtained via Rossi X-ray Timing Explorer monitoring and an XMM-Newton observation. Modeling the 3–10 keV PSD using a broken power-law PSD shape, a break in power-law slope is significantly detected at a temporal frequency of 2.5 −1.7×10 −6 Hz, which correspo...

Sharp breaks have been observed in the afterglow light curves of several GRBs; this is generally explained by the jet model. However, there are still some uncertainties concerning this interpretation due to the unclear hydrodynamics of jet sideways expansion. Here we propose an alternative explanation to these observed breaks. If we assume that the multiwavelength spectra of GRB afterglows are ...

We present a power spectrum analysis of the long ASCA observation of Ark 564 in June/July 2001. The observed power spectrum covers a frequency range of ∼ 3.5 decades. We detect a high frequency break at ∼ 2 × 10 −3 Hz. The power spectrum has an rms of ∼ 30% and a slope of ∼ −1 and ∼ −2 below and above the break frequency. When combined with the results from a long RXTE observation (Pounds et al...

We analyzed the rapid aperiodic X-ray variability of the recently discovered millisecond X-ray pulsar SAX J1808.4–3658. The power density spectrum is dominated by a strong band-limited noise component, which follows a power-law with index 1.0– 1.3 at high frequencies with a break that varies between 0.25 and 1.6 Hz, below which the spectrum is relatively flat. Superimposed on this, a broad bump...

We investigate van Rijsbergen’s -measure, break-even point, and 11-point averaged precision, all of which can be translated into 1-dimensional scalar quantity from the precision and the recall. These investigations can be done by comparing to tetrachoric (four-fold) correlation coefficient and phi (four-fold point) coefficient, which are often used as the index of statistical association in a 2...

An understanding of the limit on potential predictability is crucial for developing appropriate tools for extended-range prediction of active/break spells of the Indian summer monsoon (ISM). The global low-frequency changes in climate modulate the annual cycle of the ISM and can influence the intrinsic predictability limit of the ISM intraseasonal oscillations (ISOs). Using 104-year (1901–2004)...