National University of La Plata

About: National University of La Plata is a education organization based out in La Plata, Argentina. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 12993 authors who have published 30013 publications receiving 495118 citations. The organization is also known as: UNLP & Universidad Nacional de La Plata.

Stochastic sparse-spike deconvolution

Abstract: Sparse-spike deconvolution can be viewed as an inverse problem where the locations and amplitudes of a number of spikes reflectivity are estimated from noisy data seismic traces. The main objective is to find the least number of spikes that, when convolved with the available band-limited seismicwaveletestimate,fitthedatawithinagiventolerance errormisfit.Thedetectionofthespikes’timelagsisahighly nonlinearoptimizationproblemthatcanbesolvedusingvery fastsimulatedannealingSA.Amplitudesareeasilyestimated using linear least squares at each SA iteration. At this stage, quadratic regularization is used to stabilize the solution, to reduce its nonuniqueness, and to provide meaningful reflectivitysequences,thusavoidingtheneedtoconstrainthe spikes’time lags and/or amplitudes to force valid solutions. Impedanceconstraintsalsocanbeincludedatthisstage,providing the low frequencies required to recover the acoustic impedance.Oneadvantageoftheproposedmethodoverother sparse-spike deconvolution techniques is that the uncertaintyoftheobtainedsolutionscanbeestimatedstochastically.Further,errorsinthephaseofthewaveletestimatearetolerated,foranoptimumconstant-phaseshiftisobtainedtocalibratetheeffectivewaveletthatispresentinthedata.Results using synthetic data including simulated data for the Marmousi2 modelandfield 3D data show that physically meaningful high-resolution sparse-spike sections can be derived fromband-limitednoisydata,evenwhentheavailablewaveletestimateisinaccurate.

A Binary Progenitor for the Type IIb Supernova 2011dh in M51

Abstract: We perform binary stellar evolutionary calculations following the simultaneous evolution of both stars in the system to study a potential progenitor system for the Type IIb supernova 2011dh. Pre-explosion photometry as well as light-curve modeling has provided constraints on the physical properties of the progenitor system. Here, we present a close binary system (CBS) that is compatible with such constraints. The system is formed by stars of solar composition with 16 M {sub Sun} + 10 M {sub Sun} on a circular orbit with an initial period of 125 days. The primary star ends its evolution as a yellow supergiant with a mass of Almost-Equal-To 4 M {sub Sun }, a final hydrogen content of Almost-Equal-To (3-5) Multiplication-Sign 10{sup -3} M {sub Sun }, and with an effective temperature and luminosity in agreement with the Hubble Space Telescope (HST) pre-explosion observations of SN 2011dh. These results are nearly insensitive to the adopted accretion efficiency factor {beta}. At the time of explosion, the companion star has an effective temperature of 22,000-40,000 K, depending on the value of {beta}, and lies near the zero-age main sequence. Considering the uncertainties in the HST pre-SN photometry, the secondary star is only marginally detectable inmore » the bluest observed band. CBSs, as opposed to single stars, provide a natural frame to explain the properties of SN 2011dh.« less