Application of the Trend Filtering Algorithm on the MACHO Database

Due to the strong effect of systematics/trends in variable star observations, we employ the Trend Filtering Algorithm (TFA) on a subset of the MACHO database and search for variable stars. TFA has been applied successfully in planetary transit searches, where weak, short-lasting periodic dimmings are sought in the presence of noise and various systematics (due to, e.g., imperfect flat fielding, crowding, etc). These latter effects introduce colored noise in the photometric time series that can lead to a complete miss of the signal. By using a large number of available photometric time series of a given field, TFA utilizes the fact that the same types of systematics appear in several/many time series of the same field. As a result, we fit each target time series by a (least-square-sense) optimum linear combination of templates and frequency-analyze the residuals. Once a signal is found, we reconstruct the signal by employing the full model, including the signal, systematics and noise. We apply TFA on the brightest ~5300 objects from subsets of each of the MACHO Large Magellanic Cloud fields #1 and #79. We find that the Fourier frequency analysis performed on the original data detect some 60% of the objects as trend-dominated. This figure decreases essentially to zero after using TFA. Altogether, We detect 387 variables in the two fields, 183 of which would have remained undetected without using TFA. Where possible, we give preliminary classification of the variables found.Comment: 12 pages, 15 figures, 3 tables with online material; to appear in Astronomy and Astrophysic

The rich frequency spectrum of the triple-mode variable AC And

Fourier analysis of the light curve of AC And from the HATNet database reveals the rich frequency structure of this object. Above 30 components are found down to the amplitude of 3 mmag. Several of these frequencies are not the linear combinations of the three basic components. We detect period increase in all three components that may lend support to the Pop I classification of this variable.Comment: Poster presented at IAU Symposium 301, "Precision Asteroseismology - Celebration of the Scientific Opus of Wojtek Dziembowski", 19-23 August 2013, Wroclaw, Polan

Zero temperature properties of mesons in a vector meson extended linear sigma model

A three flavor linear sigma model with vector and axial-vector mesons is discussed. Preliminary results concerning on the symmetry breaking pattern, the question of parameterization, as well as the resulting meson masses are presented.Comment: 4 pages, 0 figures, submitted to the Hot and Cold Baryonic Matter (HCBM 2010) conference proceeding

Scalar mesons in a linear sigma model with (axial-)vector mesons

The structure of the scalar mesons has been a subject of debate for many decades. In this work we look for $\bar{q}q$ states among the physical resonances using an extended Linear Sigma Model that contains scalar, pseudoscalar, vector, and axial-vector mesons both in the non-strange and strange sectors. We perform global fits of meson masses, decay widths and amplitudes in order to ascertain whether the scalar $\bar{q}q$ states are below or above 1 GeV. We find the scalar states above 1 GeV to be preferred as $\bar{q}q$ states.Comment: 6 pages, 1 figure, To appear in the proceedings of the XII. Hadron Physics Conference, Bento Goncalves, Brasil, April, 22 - 27, 201

The status of pentaquark spectroscopy on the lattice

The present work is a summary of the status of lattice pentaquark calculations. After a pedagogic introduction to the basics of lattice hadron spectroscopy we give a critical comparison of results presently available in the literature. Special emphasis is put on presenting some of the possible pitfalls of these calculations. In particular we discuss at length the choice of the hadronic operators and the separation of genuine five-quark states from meson-baryon scattering states.Comment: 13 pages LaTeX, 1 eps figur

Pentaquark hadrons from lattice QCD

We study spin 1/2 isoscalar and isovector candidates in both parity channels for the recently discovered \Theta^+(1540) pentaquark particle in quenched lattice QCD. Our analysis takes into account all possible uncertainties, such as statistical, finite size and quenching errors when performing the chiral and continuum extrapolations and we have indications that our signal is separated from scattering states. The lowest mass that we find in the I^P=0^- channel is in complete agreement with the experimental value of the \Theta^+ mass. On the other hand, the lowest mass state in the opposite parity I^P=0^+ channel is much higher. Our findings suggests that the parity of the \Theta^+ is negative.Comment: 13 pages, 5 figures. Final version, appeared in JHE

Effective resource management in digital forensics: an exploratory analysis of triage practices in four English constabularies

This is the author accepted manuscript. The final version is available from Emerald via the DOI in this recordPurpose: Building on the findings of a British Academy-funded project on the development of digital forensics in England and Wales, this article explores how triage, a process that helps prioritise digital devices for in-depth forensic analysis is experienced by digital forensic examiners and police officers in four English police forces. It is argued that while as a strategy triage can address the increasing demand in the examination of digital exhibits, careful consideration needs to be paid to the ways in which its set-up, undertaking and outcomes impact on the ability of law enforcement agencies to solve cases. Design/methodology/approach: The findings presented are the result of ethnographic observations and semi-structured interviews. They emphasise the challenges in the triage of digital exhibits as they are encountered in everyday practice. The discussion focuses on the tensions between the delivery of timely and accurate investigation results and current gaps in the infrastructural arrangements. It also emphasises the need to provide police officers with a baseline understanding of the role of digital forensics and the importance of clearly defined strategies in the examination of digital devices. Originality/value:This article aims to bridge policy and practice through an analysis of the ways in which digital forensic practitioners and police officers in four English constabularies reflect on the uses of triage in digital forensics to address backlogs and investigative demands. Highlighting the importance of digital awareness beyond the technical remit of digital forensic units, it offers new insights into the ways in which police forces seek to improve the evidential trail with limited resources.British AcademyEconomic and Social Research Council (ESRC