Period-luminosity relations in evolved red giants explained by solar-like oscillations

Solar-like oscillations in red giants have been investigated with CoRoT and Kepler, while pulsations in more evolved M giants have been studied with ground-based microlensing surveys. After 3.1 years of observation with Kepler, it is now possible to make a link between these different observations of semi-regular variables. We aim to identify period-luminosity sequences in evolved red giants identified as semi-regular variables. Then, we investigate the consequences of the comparison of ground-based and space-borne observations. We have first measured global oscillation parameters of evolved red giants observed with Kepler with the envelope autocorrelation function method. We then used an extended form of the universal red giant oscillation pattern, extrapolated to very low frequency, to fully identify their oscillations. From the link between red giant oscillations observed by Kepler and period-luminosity sequences, we have identified these relations in evolved red giants as radial and non-radial solar-like oscillations. We were able to expand scaling relations at very low frequency. This helped us to identify the different sequences of period-luminosity relations, and allowed us to propose a calibration of the K magnitude with the observed frequency large separation. Interpreting period-luminosity relations in red giants in terms of solar-like oscillations allows us to investigate, with a firm physical basis, the time series obtained from ground-based microlensing surveys. This can be done with an analytical expression that describes the low-frequency oscillation spectra. The different behavior of oscillations at low frequency, with frequency separations scaling only approximately with the square root of the mean stellar density, can be used to address precisely the physics of the semi-regular variables.Comment: Accepted in A&

Parametric high resolution techniques for radio astronomical imaging

The increased sensitivity of future radio telescopes will result in requirements for higher dynamic range within the image as well as better resolution and immunity to interference. In this paper we propose a new matrix formulation of the imaging equation in the cases of non co-planar arrays and polarimetric measurements. Then we improve our parametric imaging techniques in terms of resolution and estimation accuracy. This is done by enhancing both the MVDR parametric imaging, introducing alternative dirty images and by introducing better power estimates based on least squares, with positive semi-definite constraints. We also discuss the use of robust Capon beamforming and semi-definite programming for solving the self-calibration problem. Additionally we provide statistical analysis of the bias of the MVDR beamformer for the case of moving array, which serves as a first step in analyzing iterative approaches such as CLEAN and the techniques proposed in this paper. Finally we demonstrate a full deconvolution process based on the parametric imaging techniques and show its improved resolution and sensitivity compared to the CLEAN method.Comment: To appear in IEEE Journal of Selected Topics in Signal Processing, Special issue on Signal Processing for Astronomy and space research. 30 page

Free radially expanding liquid sheet in air: time- and space-resolved measurement of the thickness field

The collision of a liquid drop against a small target results in the formation of a thin liquid sheet that extends radially until it reaches a maximum diameter. The subsequent retraction is due to the air-liquid surface tension. We have used a time- and space-resolved technique to measure the thickness field of this class of liquid sheet, based on the grey level measurement of the image of a dyed liquid sheet recorded using a fast camera. This method enables a precise measurement of the thickness in the range $(10-450) \, \mathrm{\mu m}$, with a temporal resolution equal to that of the camera. We have measured the evolution with time since impact, $t$, and radial position, $r$, of the thickness, $h(r,t)$, for various drop volumes and impact velocities. Two asymptotic regimes for the expansion of the sheet are evidenced. The scalings of the thickness with $t$ and $r$ measured in the two regimes are those that were predicted in \citet{Rozhkov2004} fort the short-time regime and \citet{Villermaux2011} for the long time regime, but never experimentally measured before. Interestingly, our experimental data also evidence the existence of a maximum of the film thickness $h_{\rm{max}}(r)$ at a radial position $r_{\rm{h_{max}}}(t)$ corresponding to the crossover of these two asymptotic regimes. The maximum moves with a constant velocity of the order of the drop impact velocity, as expected theoretically. Thanks to our visualization technique, we also evidence an azimuthal thickness modulation of the liquid sheets.Comment: accepted for publication in Journal of Fluid Mechanic

Measurement of the Electric and Magnetic Polarizabilities of the Proton

The Compton scattering cross section on the proton has been measured at laboratory angles of 90$^\circ$ and 135$^\circ$ using tagged photons in the energy range 70--100 MeV and simultaneously using untagged photons in the range 100--148~MeV. With the aid of dispersion relations, these cross sections were used to extract the electric and magnetic polarizabilities, $\bar{\alpha}$ and $\bar{\beta}$ respectively, of the proton. We find $$\bar{\alpha}+\bar{\beta} = ( 15.0 \pm 2.9 \pm 1.1 \pm 0.4 ) \times 10^{-4} \: {\rm fm}^3,$$ in agreement with a model-independent dispersion sum rule, and $$\bar{\alpha}-\bar{\beta} = ( 10.8 \pm 1.1 \pm 1.4 \pm 1.0 ) \times 10^{-4} \: {\rm fm}^3,$$ where the errors shown are statistical, systematic, and model-dependent, respectively. A comparison with previous experiments is given and global values for the polarizabilities are extracted.Comment: 35 pages, 11 PostScript figures, uses RevTex 3.

Extended Modified Observable Technique for a Multi-Parametric Trilinear Gauge Coupling Estimation at LEP II

This paper describes the extension of the Modified Observables technique in estimating simultaneously more than one Trilinear Gauge Couplings. The optimal properties, unbiasedness and consistent error estimation of this method are demonstrated by Monte Carlo experimentation using $\ell \nu jj$ four-fermion final state topologies. Emphasis is given in the determination of the expected sensitivities in estimating the $\lambda_{\gamma} - \Delta g_{1}^{z}$ and $\Delta k_{\gamma} - \Delta g_{1}^{z}$ pair of couplings with data from the 183 GeV LEPII run.Comment: (17 pages, 8 figures

Analysis of the TOF resolution: a "tomography" study of the time of flight detector of the ALICE experiment at the LHC

Questa tesi presenta uno studio dettagliato della risoluzione del rilevatore a tempo di volo TOF dell’esperimento ALICE, utilizzando dati di collisioni Pb-Pb del RUN 2 dell’acceleratore LHC del CERN. È stata effettuata un’analisi dei profili della risoluzione temporale lungo i principali assi di simmetria del rivelatore (l’asse del fascio e quelli che definiscono il piano trasverso), così da evidenziare discontinuità date dalla struttura del rivelatore. Le strutture osservate corrispondono in larga parte a effetti previsti. Le dipendenze previste sono quelle date dalla presenza di materiale, modulate dalla distanza media di traccia, che sono state confermate da una correlazione statisticamente significativa con la risoluzione. Sono anche state osservate alcune strutture impreviste, probabilmente derivanti da malfunzionamenti nell’operatività e nell’elettronica del rivelatore, che saranno oggetto di studi futuri

A model independent safeguard for unbinned Likelihood

We present a universal method to include residual un-modeled background shape uncertainties in likelihood based statistical tests for high energy physics and astroparticle physics. This approach provides a simple and natural protection against mismodeling, thus lowering the chances of a false discovery or of an over constrained confidence interval, and allows a natural transition to unbinned space. Unbinned likelihood allows optimal usage of information for the data and the models, and enhances the sensitivity. We show that the asymptotic behavior of the test statistic can be regained in cases where the model fails to describe the true background behavior, and present 1D and 2D case studies for model-driven and data-driven background models. The resulting penalty on sensitivities follows the actual discrepancy between the data and the models, and is asymptotically reduced to zero with increasing knowledge

Radial distribution of stars, gas and dust in SINGS galaxies. I. Surface photometry and morphology

We present ultraviolet through far-infrared surface brightness profiles for the 75 galaxies in the Spitzer Infrared Nearby Galaxies Survey (SINGS). The imagery used to measure the profiles includes GALEX UV data, optical images from KPNO, CTIO and SDSS, near-IR data from 2MASS, and mid- and far-infrared images from Spitzer. Along with the radial profiles, we also provide multi-wavelength asymptotic magnitudes and several non-parametric indicators of galaxy morphology: the concentration index (C_42), the asymmetry (A), the Gini coefficient (G) and the normalized second-order moment of the brightest 20% of the galaxy's flux (M_20). Our radial profiles show a wide range of morphologies and multiple components (bulges, exponential disks, inner and outer disk truncations, etc.) that vary not only from galaxy to galaxy but also with wavelength for a given object. In the optical and near-IR, the SINGS galaxies occupy the same regions in the C_42-A-G-M_20 parameter space as other normal galaxies in previous studies. However, they appear much less centrally concentrated, more asymmetric and with larger values of G when viewed in the UV (due to star-forming clumps scattered across the disk) and in the mid-IR (due to the emission of Polycyclic Aromatic Hydrocarbons at 8.0 microns and very hot dust at 24 microns).Comment: 66 pages in preprint format, 14 figures, published in ApJ. The definitive publisher authenticated version is available online at http://dx.doi.org/10.1088/0004-637X/703/2/156