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2010

On the use of structure functions to study blazar variability: caveats and problems

Emmanoulopoulos, D.; McHardy, I. M.; Uttley, P.

The extensive use of the structure function (SF) in the field of blazar variability across the electromagnetic spectrum suggests that characteristics time-scales are embedded in the light curves of these objects. We argue that for blazar variability ...
Improving PSF modelling for weak gravitational lensing using new methods in model selection

Rowe, Barnaby

A simple theoretical framework for the description and interpretation of spatially correlated modelling residuals is presented, and the resulting tools are found to provide a useful aid to model selection in the context of weak gravitational lensing ...
Astrometry.net: Blind Astrometric Calibration of Arbitrary Astronomical Images

Lang, Dustin; Hogg, David W.; Mierle, Keir; Blanton, Michael; Roweis, Sam

We have built a reliable and robust system that takes as input an astronomical image, and returns as output the pointing, scale, and orientation of that image (the astrometric calibration or World Coordinate System information). The system requires ...
Automated Classification of Variable Stars in the Asteroseismology Program of the Kepler Space Mission

Blomme, J.; Debosscher, J.; De Ridder, J.; Aerts, C.; Gilliland, R. L.; Christensen-Dalsgaard, J.; Kjeldsen, H.; Brown, T. M.; Borucki, W. J.; Koch, D.; Jenkins, J. M.; Kurtz, D. W.; Stello, D.; Stevens, I. R.; Suran, M. D.; Derekas, A.

We present the first results of the application of supervised classification methods to the Kepler Q1 long-cadence light curves of a subsample of 2288 stars measured in the asteroseismology program of the mission. The methods, originally developed i ...
Probing local non-Gaussianities within a Bayesian framework

Elsner, F.; Wandelt, B. D.; Schneider, M. D.

Aims: We outline the Bayesian approach to inferring fNL, the level of non-Gaussianities of local type. Phrasing fNL inference in a Bayesian framework takes advantage of existing techniques to account for instrumental effects and foreground contamina ...
Measuring galaxy segregation with the mark connection function

Martínez, V. J.; Arnalte-Mur, P.; Stoyan, D.

Context. The clustering properties of galaxies belonging to different luminosity ranges or having different morphological types are different. These characteristics or “marks” permit us to understand the galaxy catalogs that carry all this infor ...
The ILIUM forward modelling algorithm for multivariate parameter estimation and its application to derive stellar parameters from Gaia spectrophotometry

Bailer-Jones, C. A. L.

I introduce an algorithm for estimating parameters from multidimensional data based on forward modelling. It performs an iterative local search to effectively achieve a non-linear interpolation of a template grid. In contrast to many machine-learnin ...
Random Forests for Photometric Redshifts

Carliles, Samuel; Budavári, Tamás; Heinis, Sébastien; Priebe, Carey; Szalay, Alexander S.

The main challenge today in photometric redshift estimation is not in the accuracy but in understanding the uncertainties. We introduce an empirical method based on Random Forests to address these issues. The training algorithm builds a set of optim ...
Testing Tests on Active Galactic Nucleus Microvariability

de Diego, José A.

Literature on optical and infrared microvariability in active galactic nuclei (AGNs) reflects a diversity of statistical tests and strategies to detect tiny variations in the light curves of these sources. Comparison between the results obtained usi ...
A Bayesian test for periodic signals in red noise

Vaughan, S.

Many astrophysical sources, especially compact accreting sources, show strong, random brightness fluctuations with broad power spectra in addition to periodic or quasi-periodic oscillations (QPOs) that have narrower spectra. The random nature of the ...
Filaments in observed and mock galaxy catalogues

Stoica, R. S.; Martínez, V. J.; Saar, E.

Context. The main feature of the spatial large-scale galaxy distribution is an intricate network of galaxy filaments. Although many attempts have been made to quantify this network, there is no unique and satisfactory recipe for that yet. Aims: Th ...
Methods for Estimating Fluxes and Absorptions of Faint X-ray Sources

Getman, Konstantin V.; Feigelson, Eric D.; Broos, Patrick S.; Townsley, Leisa K.; Garmire, Gordon P.

X-ray sources with very few counts can be identified with low-noise X-ray detectors such as the Advanced CCD Imaging Spectrometer on board the Chandra X-ray Observatory. These sources are often too faint for parametric spectral modeling using well-e ...
A method for reconstructing the PDF of a 3D turbulent density field from 2D observations

Brunt, Christopher M.; Federrath, Christoph; Price, Daniel J.

We introduce a method for calculating the probability density function (PDF) of a turbulent density field in three dimensions using only information contained in the projected two-dimensional column density field. We test the method by applying it t ...
The scaling relation between richness and mass of galaxy clusters: a Bayesian approach

Andreon, S.; Hurn, M. A.

We use a sample of 53 galaxy clusters at 0.03 < z < 0.1 with available masses derived from the caustic technique and with velocity dispersions computed using 208 galaxies on average per cluster, in order to investigate the scaling between richness, ...
A Method for Measuring the Bias of High-redshift Galaxies from Cosmic Variance

Robertson, Brant E.

As deeper observations discover increasingly distant galaxies, characterizing the properties of high-redshift galaxy populations will become increasingly challenging and paramount. We present a method for measuring the clustering bias of high-redshi ...
The Light Curve Statistical Moments Analysis: The Identification of Eclipsing Binaries

Graczyk, D.; Eyer, L.

A semi-automatic method of identifying eclipsing binaries in large photometric surveys, based on the analysis of the light curve statistical moments, is presented. This method was tested on the OGLE-II database of variable stars in the Large Magella ...
Fitting isochrones to open cluster photometric data. A new global optimization tool

Monteiro, H.; Dias, W. S.; Caetano, T. C.

We present a new technique to fit color-magnitude diagrams of open clusters based on the cross-entropy global optimization algorithm. The method uses theoretical isochrones available in the literature and maximizes a weighted likelihood function bas ...
Searching for dark clouds in the outer galactic plane. I. A statistical approach for identifying extended red(dened) regions in 2MASS

Frieswijk, W. W. F.; Shipman, R. F.

Context. Most of what is known about clustered star formation to date comes from well studied star forming regions located relatively nearby, such as Rho-Ophiuchus, Serpens and Perseus. However, the recent discovery of infrared dark clouds may give ...
Bayesian analysis of caustic-crossing microlensing events

Cassan, A.; Horne, K.; Kains, N.; Tsapras, Y.; Browne, P.

Aims: Caustic-crossing binary-lens microlensing events are important anomalous events because they are capable of detecting an extrasolar planet companion orbiting the lens star. Fast and robust modelling methods are thus of prime interest in helpin ...
Adiabatic versus isocurvature non-Gaussianity

Hikage, Chiaki; Munshi, Dipak; Heavens, Alan; Coles, Peter

We study the extent to which one can distinguish primordial non-Gaussianity (NG) arising from adiabatic and isocurvature perturbations. We make a joint analysis of different NG models based on various inflationary scenarios: local-type and equilater ...