WEBT multiwavelength monitoring and XMM-Newton observations of BL Lacertae in 2007-2008. Unveiling different emission components

In 2007-2008 we carried out a new multiwavelength campaign of the Whole Earth Blazar Telescope (WEBT) on BL Lacertae, involving three pointings by the XMM-Newton satellite, to study its emission properties. The source was monitored in the optical-to-radio bands by 37 telescopes. The brightness level was relatively low. Some episodes of very fast variability were detected in the optical bands. The X-ray spectra are well fitted by a power law with photon index of about 2 and photoelectric absorption exceeding the Galactic value. However, when taking into account the presence of a molecular cloud on the line of sight, the data are best fitted by a double power law, implying a concave X-ray spectrum. The spectral energy distributions (SEDs) built with simultaneous radio-to-X-ray data at the epochs of the XMM-Newton observations suggest that the peak of the synchrotron emission lies in the near-IR band, and show a prominent UV excess, besides a slight soft-X-ray excess. A comparison with the SEDs corresponding to previous observations with X-ray satellites shows that the X-ray spectrum is extremely variable. We ascribe the UV excess to thermal emission from the accretion disc, and the other broad-band spectral features to the presence of two synchrotron components, with their related SSC emission. We fit the thermal emission with a black body law and the non-thermal components by means of a helical jet model. The fit indicates a disc temperature greater than 20000 K and a luminosity greater than 6 x 10^44 erg/s.Comment: 11 pages, 7 figures, accepted for publication in A&

Hearing musical streams

cote interne IRCAM: McAdams79aNone / NoneNational audienceNon

Toward An Improved Model Of Auditory Saliency

Presented at the 19th International Conference on Auditory Display (ICAD2013) on July 6-9, 2013 in Lodz, Poland.While visual saliency models are approaching maturity, their auditory counterparts remain in their infancy. This is mainly due to the difficulties of gathering basic data, and oversimplifications such as an assumption of monaural signals. Moreover, conventional testing approaches for evaluating auditory saliency models tend to be overly simplistic. To address these shortcomings, we developed an experimental procedure for testing auditory saliency along with more formalized stimulus-selection criteria to support more versatile and ecologically relevant saliency models. This work is described, along with an analysis of some relevant acoustical correlates that emerge from the experiments. The results motivate the formulation of a measure of sound complexity and appear to favor time-domain, rather than frequency-domain analysis to describe saliency. Finally, some conclusions are drawn regarding the definition of an expanded feature set to be used for auditory saliency modeling and prediction in the context of natural, everyday sounds

Rhythmic masking release: effects of asynchrony, temporal overlap, harmonic relations, and source separation on cross-spectral grouping.

The rhythm created by spacing a series of brief tones in a regular pattern can be disguised by interleaving identical distractors at irregular intervals. The disguised rhythm can be unmasked if the distractors are allocated to a separate stream from the rhythm by integration with temporally overlapping captors. Listeners identified which of 2 rhythms was presented, and the accuracy and rated clarity of their judgment was used to estimate the fusion of the distractors and captors. The extent of fusion depended primarily on onset asynchrony and degree of temporal overlap. Harmonic relations had some influence, but only an extreme difference in spatial location was effective (dichotic presentation). Both preattentive and attentionally driven processes governed performance. (PsycINFO Database Record (c) 2007 APA, all rights reserved