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We study a fully discrete finite element method for variable-order time-fractional diffusion equations with a time-dependent variable order. Optimal convergence estimates are proved with the first-order accuracy in time (and second order…

Numerical Analysis · Mathematics 2019-05-15 Xiangcheng Zheng , Fanhai Zeng , Hong Wang

We investigate a method to compute a finite set of preliminary orbits for solar system bodies using the first integrals of the Kepler problem. This method is thought for the applications to the modern sets of astrometric observations, where…

Mathematical Physics · Physics 2010-04-01 Giovanni Federico Gronchi , Linda Dimare , Andrea Milani

Cosmic rays have valuable information about universe surroundings us. Finding energy, mass and arrival direction of primary cosmic ray particle are the most important aspects of extensive air shower studies. In order to determine these…

Instrumentation and Methods for Astrophysics · Physics 2011-03-17 H. Hedayati Kh. , A. Anvari , M. Bahmanabadi , M. Khakian Ghomi , J. Samimi

Rapid variability before and near the maximum brightness of supernovae has the potential to provide a better understanding of nearly every aspect of supernovae, from the physics of the explosion up to their progenitors and the circumstellar…

Solar and Stellar Astrophysics · Physics 2020-10-28 E. Paraskeva , A. Z. Bonanos , A. Liakos , Z. T. Spetsieri , Justyn R. Maund

New time-domain surveys, such as the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST), will observe millions of transient alerts each night, making standard approaches of visually identifying new and interesting transients…

Instrumentation and Methods for Astrophysics · Physics 2022-10-07 Daniel Muthukrishna , Kaisey S. Mandel , Michelle Lochner , Sara Webb , Gautham Narayan

Abstract abridged. Eclipsing binary systems provide the opportunity to measure the fundamental parameters of their component stars in a stellar-model-independent way. This makes them ideal candidates for testing and calibrating theories of…

Instrumentation and Methods for Astrophysics · Physics 2024-02-12 Luc W. IJspeert , Andrew Tkachenko , Cole Johnston , Andrej Prša , Mark A. Wells , Conny Aerts

We present a method that allows to distinguish between nearly periodic and strictly periodic time series. To this purpose, we employ a conservative criterion for periodicity, namely that the time series can be interpolated by a periodic…

Data Analysis, Statistics and Probability · Physics 2015-11-11 Gerrit Ansmann

We present a detailed lightcurve analysis for a sample of bright semiregular variables based on long-term (70--90 years) visual magnitude estimates carried out by amateur astronomers. Fundamental changes of the physical state (amplitude…

Astrophysics · Physics 2009-10-31 L. L. Kiss , K. Szatmary , Gy. Szabo , J. A. Mattei

We study more general variational problems on time scales. Previous results are generalized by proving necessary optimality conditions for (i) variational problems involving delta derivatives of more than the first order, and (ii) problems…

Optimization and Control · Mathematics 2007-05-23 Rui A. C. Ferreira , Delfim F. M. Torres

We present a new approach to the analysis of time symmetry in light curves, such as those in the x-ray at the center of the Scorpius X-1 occultation debate. Our method uses a new parameterization for such events (the bilogistic event…

Instrumentation and Methods for Astrophysics · Physics 2011-02-11 Alexander W. Blocker , Pavlos Protopapas , Charles R. Alcock

CoRoT has allowed a quantitative leap for the solar-like-star seismology thanks to 5-month-long uninterrupted timeseries of high-precision photometric data. Kepler is also starting to deliver similar data. Now, several F and G main-sequence…

Solar and Stellar Astrophysics · Physics 2010-10-14 J. Ballot

Chandrasekaran, Parrilo and Willsky (2010) proposed a convex optimization problem to characterize graphical model selection in the presence of unobserved variables. This convex optimization problem aims to estimate an inverse covariance…

Optimization and Control · Mathematics 2012-09-27 Shiqian Ma , Lingzhou Xue , Hui Zou

Recently the identity method was proposed to calculate second moments of the multiplicity distributions from event-by-event measurements in the presence of the effects of incomplete particle identification. In this paper the method is…

Nuclear Theory · Physics 2012-10-30 A. Rustamov , M. I. Gorenstein

A class of methods for measuring time delays between astronomical time series is introduced in the context of quasar reverberation mapping, which is based on measures of randomness or complexity of the data. Several distinct statistical…

Instrumentation and Methods for Astrophysics · Physics 2017-08-16 Doron Chelouche , Francisco Pozo Nuñez , Shay Zucker

The field of time series anomaly detection is constantly advancing, with several methods available, making it a challenge to determine the most appropriate method for a specific domain. The evaluation of these methods is facilitated by the…

Machine Learning · Computer Science 2023-03-03 Sondre Sørbø , Massimiliano Ruocco

The evaluation of a matrix exponential function is a classic problem of computational linear algebra. Many different methods have been employed for its numerical evaluation [Moler C and van Loan C 1978 SIAM Review 20 4], none of which…

Mathematical Physics · Physics 2008-11-18 D H Gebremedhin , C A Weatherford , X Zhang , A Wynn , G Tanaka

Numerous studies have reported two types of doubling of invariant closed curves (ICCs) in dynamical systems: (a) the creation of two disjoint ICCs such that iterations flip between them; and (b) the creation of a single ICC of double the…

Dynamical Systems · Mathematics 2025-09-17 Sayanho Biswas , Soumitro Banerjee , Viktor Avrutin , Iryna Sushko

We apply Monte Carlo Markov Chain methods to the stellar parameter estimation problem. This technique is useful when dealing with non-linear models and allows to derive realistic error bars on the inferred parameters. We give the first…

Astrophysics · Physics 2008-03-19 M. Bazot , S. Bourguignon , J. Christensen-Dalsgaard

We describe the construction of a highly reliable sample of approximately 7,000 optically faint periodic variable stars with light curves obtained by the asteroid survey LINEAR across 10,000 sq.deg of northern sky. Majority of these…

If at cosmological distances, a small fraction of gamma-ray bursts should be multiply imaged by intervening galaxies or clusters, resulting in the appearance of two very similar bursts from the same location with a relative time delay of…

Astrophysics · Physics 2016-01-13 L. L. R. Williams , R. A. M. J. Wijers