A New Method to Calibrate the Magnitudes of Type Ia Supernovae at Maximum Light

We present a new empirical method for fitting multicolor light curves of Type Ia supernovae. Our method combines elements from two widely used techniques in the literature: the delta_m15 template fitting method and the Multicolor Light-Curve Shape method. An advantage of our technique is the ease of adding new colors, templates, or parameters to the fitting procedure. We use a large sample of published light curves to calibrate the relations between the absolute magnitudes at maximum and delta_m15 in BVRI filters. We find that individual subsamples from a given survey or publication have significantly tighter relationships between light curve shape and luminosity than the relationship derived from the sum of all the samples, pointing to uncorrected systematic errors in the photometry, mainly in BV filters. Using our method, we calculate luminosity distances and host galaxy reddening to 89 SNe in the Hubble flow and construct a low-z Hubble diagram. The dispersion of the SNe in the Hubble diagram is 0.20 mag, or an error of ~9% in distance to a single SN. Our technique produces similar or smaller dispersion in the low-z Hubble diagram than other techniques in the literature.Comment: 43 pages, 16 figures, 6 tables, accepted by ApJ. For additional material go to http://www.astronomy.ohio-state.edu/~prieto/paper_dm15/dm15.htm

Convective line shifts for the Gaia RVS from the CIFIST 3D model atmosphere grid

To derive space velocities of stars along the line of sight from wavelength shifts in stellar spectra requires accounting for a number of second-order effects. For most stars, gravitational redshifts, convective blueshifts, and transverse stellar motion are the dominant contributors. We provide theoretical corrections for the net velocity shifts due to convection expected for the measurements from the Gaia Radial Velocity Spectrometer (RVS). We used a set of three-dimensional time-dependent simulations of stellar surface convection computed with CO5BOLD to calculate spectra of late-type stars in the Gaia RVS range and to infer the net velocity offset that convective motions will induce in radial velocities derived by cross-correlation. The net velocity shifts derived by cross-correlation depend both on the wavelength range and spectral resolution of the observations. Convective shifts for Gaia RVS observations are less than 0.1 km/s for late-K-type stars, and they increase with stellar mass, reaching about 0.3 km/s or more for early F-type dwarfs. This tendency is the result of an increase with effective temperature in both temperature and velocity fluctuations in the line-forming region. Our simulations also indicate that the net RVS convective shifts can be positive (i.e. redshifts) in some cases. Overall, the blueshifts weaken slightly with increasing surface gravity, and are enhanced at low metallicity. Gravitational redshifts amount up to 0.7 km/s and dominate convective blueshifts for dwarfs, but become much weaker for giants.Comment: 13 pages, to appear in A&A; model fluxes available from ftp://leda.as.utexas.edu/pub/callende/Gaia3D and soon from CD

TIGER Capacity Building Facility - Phase 1, lessons learnt

The TIGER Capacity Building Facility focused on closing the technological gap between the users and the earth observation community within the TIGER programme. Thirteen projects participated in different aspects of the capacity building facility: 1. - Basic education, provided via distance learning. 2. - Tailored short courses, selected according to the research interest and technical background of the participants. 3. - Research topic oriented supervision, provided by specialists of the research fields of the participants. 4. - Advanced short courses focusing on selected earth observation techniques. Distance education turned to be efficient and cost effective in the programme - but only for those, who followed the courses completely. There was a relatively large percentage that could not complete the studies. The second and the third type of education were carried out in ITC, in the Netherlands. The participants evaluated the courses and the supervision very effective and adequate. Nevertheless, the follow-up was not always possible. Two advanced short courses were held in Africa (Cape Town and Nairobi). One of them addressed the 'scientific elite' of the EO community, whilst the second focused on the users of this technology

A Wire Position Monitor System for the 1.3 GHZ Tesla-Style Cryomodule at the Fermilab New-Muon-Lab Accelerator

The first cryomodule for the beam test facility at the Fermilab New-Muon-Lab building is currently under RF commissioning. Among other diagnostics systems, the transverse position of the helium gas return pipe with the connected 1.3 GHz SRF accelerating cavities is measured along the ~15 m long module using a stretched-wire position monitoring system. An overview of the wire position monitor system technology is given, along with preliminary results taken at the initial module cool down, and during further testing. As the measurement system offers a high resolution, we also discuss options for use as a vibration detector.Comment: 4 pp. 15th International Conference on RF Superconductivity (SRF2011). 25-29 Jul 2011. Chicago, Illinois, US

Ground state and constrained domain walls in Gd/Fe multilayers

The magnetic ground state of antiferromagnetically coupled Gd/Fe multilayers and the evolution of in-plane domain walls is modelled with micromagnetics. The twisted state is characterised by a rapid decrease of the interface angle with increasing magnetic field. We found that for certain ratios M(Fe):M(Gd), the twisted state is already present at low fields. However, the magnetic ground state is not only determined by the ratio M(Fe):M(Gd) but also by the thicknesses of the layers, that is the total moments of the layer. The dependence of the magnetic ground state is explained by the amount of overlap of the domain walls at the interface. Thicker layers suppress the Fe aligned and the Gd aligned state in favour of the twisted state. Whereas ultrathin layers exclude the twisted state, since wider domain walls can not form in these ultrathin layers

Velocities from Cross-Correlation: A Guide for Self-Improvement

The measurement of Doppler velocity shifts in spectra is a ubiquitous theme in astronomy, usually handled by computing the cross-correlation of the signals, and finding the location of its maximum. This paper addresses the problem of the determination of wavelength or velocity shifts among multiple spectra of the same, or very similar, objects. We implement the classical cross-correlation method and experiment with several simple models to determine the location of the maximum of the cross-correlation function. We propose a new technique, 'self-improvement', to refine the derived solutions by requiring that the relative velocity for any given pair of spectra is consistent with all others. By exploiting all available information, spectroscopic surveys involving large numbers of similar objects may improve their precision significantly. As an example, we simulate the analysis of a survey of G-type stars with the SDSS instrumentation. Applying 'self-improvement' refines relative radial velocities by more than 50% at low signal-to-noise ratio. The concept is equally applicable to the problem of combining a series of spectroscopic observations of the same object, each with a different Doppler velocity or instrument-related offset, into a single spectrum with an enhanced signal-to-noise ratio.Comment: 7 pages, 3 figures, uses emulateapj.cls; to appear in the Astronomical Journal; see http://hebe.as.utexas.edu/stools/ to obtain the companion softwar

Medida de la eficacia de dos hidrofugantes aplicados a rocas graníticas

We evaluated the efficacy of two water-repellents applied to three types of granitic rock widely used in building construction and restoration in Galicia (NW Spain). The depth of penetration of the water-repellents was determined by measuring capillary absorption by the treated rock. The efficacies of the water-repellent were evaluated in terms of two parameters characteristic of surface wet: water-rock contact angle and the time taken for absorption of microgroplets. The effects of the treatments on the rocks' surface color and permeability to water vapor were also determined. The results indicate that neither water-repellent effectively penetrates the rock surface, and both induce undesirably high reductions in vapor permeability. Notwithstanding, both agents effectively improved the rocks' resistance to surface wetting, without altering its surface color. Overall, determination of water-rock contact angle and the time taken for absorption of microdroplets, together with colorimetric characterization of the treated rock, constitutes an useful approach to evaluation of the effects of water-repellents on granitic rocks. Nonetheless, it should be borne in mind that the marked heterogeneity of this type of rock, and the associated mineralogy and dominant type of fissuration are sources of considerable variation in the measurement parameters.Se presentan los resultados de la aplicación de dos tratamientos hidrofugantes a tres rocas graníticas ampliamente utilizadas en la construcción y restauración en Galicia. Se ha determinado la profundidad de penetración de los hidrofugantes a través de la absorción capilar, la eficacia de los tratamientos comparando dos parámetros relacionados con el mojado superficial (ángulo de contacto roca-agua y tiempo de absorción de microgotas), y las variaciones en el color y en la permeabilidad al vapor. Se comprueba que si bien ambos tratamientos penetran deforma muy escasa en las rocas graníticas y reducen significativamente la permeabilidad al vapor, mejoran sensiblemente su comportamiento frente al mojado superficial sin modificar el color original. El ángulo de contacto, el tiempo de absorción de microgotas y la determinación colorimétrica utilizada, constituyen una buena metodología en la evaluación de los efectos de tratamientos hidrofugantes en rocas graníticas; sin embargo, el fuerte carácter heterogéneo este tipo de rocas, la mineralogía y el tipo de fisuración predominante, suponen un factor de variación significativo en la determinación de estos parámetros