Roberto Vio

Time series analysis in astronomy : an application to quasar variability studies

Many astrophysical objects can be associated with continuous non-linear stochastic systems. Up to now, however, the signals coming from these systems have been analyzed mainly through linear approaches, such as the power spectrum (PS) and the structure function (SF) techniques, frequently with controversial results. Here, it is shown that in the study of astronomical time series the PS (even in the maximum entropy or CLEAN version) and the SF techniques are often of little use or even misleading, since they do not take into account all the information contained in the data

The nature of the broad-line region in the radio-loud active galactic nucleus 3C 390.3

We present an analysis of the ultraviolet and X-Ray variability of the Broad- Line-Radio Galaxy 3C390.3 over 15 years. The UV continuum showed large variations with amplitudes of up to a factor of 10. We find: (1) The variations of CIV and Ly_alpha are highly correlated with the UV continuum, and are delayed with respect to the continuum variations by 50-110 days with the red wing of both CIV and Ly_alpha , leading the blue wing; (2) The CIV/Ly_alpha ratio is positively correlated with both the continuum flux and UV line strength, a behavior different from other AGNs studied so far; (3) The blue sides of the Ly_alpha and CIV profiles are similar to the blue side of the Balmer lines, while the red sides are different, suggesting a different origin for the red peak in the Balmer lines. Our results suggest: (1) The broad CIV and Ly_alpha emitting gas is infalling towards the central object; (2) The overall behaviour of the CIV/Ly_alpha ratio and the absence of a big blue bump, strongly indicate the coexistence of optically thick as well as optically thin BLR clouds; (3) Assuming circular symmetry and predominantly circular motion, the BLR gas is situated at 83

On the Reconstruction of Irregularly Sampled Time Series

\pm

A simple but efficient algorithm for multiple-image deblurring

25 lightdays from the central source; (4) Under these assumptions and with the derived circular velocity of

Numerical Simulation of Non‐Gaussian Random Fields with Prescribed Correlation Structure

v_{rot} \simeq

Spectroscopic observations of the sodium atmosphere of the Moon

2850 km s

3C 345 - Is the variability of quasars nonlinear?

^{-1}

Some good reasons to use matched filters for the detection of point sources in CMB maps

, the central mass inside this radius is confined to

On optimal detection of point sources in CMB maps

1.3~10^8 M\odot < M_{CM}< 4.0~10^8 M\odot

Echo mapping of active galactic nuclei broad-line regions: Fundamental algorithms

; (6) Comparing our results with those obtained from VLBI and observations of the Fe