15537902
The Lick AGN Monitoring Project 2011: Reverberation Mapping of Markarian 50
The Lick AGN Monitoring Project 2011 observing campaign was carried out over the course of 11 weeks in spring 2011. Here we present the first results from this program, a measurement of the broad-line reverberation lag in the Seyfert 1 galaxy Mrk 50. Combining our data with supplemental observations obtained prior to the start of the main observing campaign, our data set covers a total duration of 4.5 months. During this time, Mrk 50 was highly variable, exhibiting a maximum variability amplitude of a factor of ~4 in the U-band continuum and a factor of ~2 in the Hβ line. Using standard cross-correlation techniques, we find that Hβ and Hγ lag the V-band continuum by τ_(cen) = 10.64^(+0.82)_(–0.93) and 8.43^(+1.30)_(–1.28) days, respectively, while the lag of He II λ4686 is unresolved. The Hβ line exhibits a symmetric velocity-resolved reverberation signature with shorter lags in the high-velocity wings than in the line core, consistent with an origin in a broad-line region (BLR) dominated by orbital motion rather than infall or outflow. Assuming a virial normalization factor of f = 5.25, the virial estimate of the black hole mass is (3.2 ± 0.5) × 10^7 M_☉. These observations demonstrate that Mrk 50 is among the most promising nearby active galaxies for detailed investigations of BLR structure and dynamics.
44837884
SLUG—STOCHASTICALLY LIGHTING UP GALAXIES. I. METHODS AND VALIDATING TESTS
The effects of stochasticity on the luminosities of stellar populations are an often neglected but crucial element for understanding populations in the low-mass or the low star formation rate regime. To address this issue, we present SLUG, a new code to "Stochastically Light Up Galaxies." SLUG synthesizes stellar populations using a Monte Carlo technique that properly treats stochastic sampling including the effects of clustering, the stellar initial mass function, star formation history, stellar evolution, and cluster disruption. This code produces many useful outputs, including (1) catalogs of star clusters and their properties such as their stellar initial mass distributions and their photometric properties in a variety of filters, (2) two dimensional histograms of color-magnitude diagrams of every star in the simulation, and (3) the photometric properties of field stars and the integrated photometry of the entire simulated galaxy. After presenting the SLUG algorithm in detail, we validate the code through comparisons with STARBURST99 in the well-sampled regime, and with observed photometry of Milky Way clusters. Finally, we demonstrate SLUG's capabilities by presenting outputs in the stochastic regime. SLUG is publicly distributed through the Web site http://sites.google.com/site/runslug/.
119512495
Mixed initial conditions to estimate the dynamic critical exponent in short-time Monte Carlo simulation
We explore the initial conditions in short-time critical dynamics to propose an alternative way to evaluate the dynamic exponent z. Estimates are obtained with high precision for the 2D Ising model and the 2D Potts model with three and four states by performing heat-bath Monte Carlo simulations.
118803404
Homogeneous photospheric parameters and C abundances in G and K nearby stars with and without planets
Aims. We present a determination of photospheric parameters and carbon abundances for a sample of 172 G and K dwarf, subgiant, and giant stars with and without detected planets in the solar ne ighbourhood. The analysis was based on high signal-to-noise ratio and high resolution spectra observed with the ELODIE spectrograph (Haute Provence Observatory, France) and for which the observational data was publicly available. We intend to contribute precise and homogeneous C abundances in studies that compare the behaviour of light elements in stars, hosting planets or not. This will br ing new arguments to the discussion of possible anomalies that have been suggested and will contribute to a better understanding of different planetary formation process. Methods. The photospheric parameters were computed through the excitation potential, equivalent widths, and ionisation equil ibrium of iron lines selected in the spectra. Carbon abundances were derived from spectral synthesis applied to prominent molecular head bands of C2 Swan (� 5128 and� 5165) and to a C atomic line (� 5380.3). Careful attention was drawn to carry out such a homogeneous procedure and to compute the internal uncertainties. Results. The distribution of [C/Fe] as a function of [Fe/H] shows no difference in the behaviour of planet-host stars in comparison with stars for which no planet was detected, for both dwarf and giant subsamples. This result is in agreement with the hypothesis of primordial origin for the chemical abundances presently observed instead of self-enrichment during the planetary system formation and evolution. Additionally, giant stars are clearly deple ted in [C/Fe] (by about 0.14 dex) when compared with dwarfs, which is probably related to evolution-induced mixing of H-burning products in the envelope of evolved stars. Subgiant stars, a lthough in small number, seems to follow the same C abundance distribution as dwarfs. We also analysed the kinematics of the sample stars that, in majority, are members of the Galaxy’s thin disc. Finally, comparisons with other analogue studies were performed and, within the uncertainties, showed good agreement.
121956644
A fast voltage preamplifier for use with MWPCs
Abstract We report the development of a voltage preamplifier for use with ionizing particles detection. It has been designed to match the requirements of a test station for muon Multiwire Proportional Chambers (MWPC) of the LHCb experiment at CERN. Simulation results and bench test measurements are presented, which exhibit the main circuit features: gain close to 500, rise time below 20 ns, bandwidth exceeding 30 MHz, input noise lower than 10 nV / Hz . Other results that demonstrate the applicability of the device in other contexts, specially with X-Ray imaging systems based on position sensitive detectors and proportional counters, are presented.
62806505
Two semi-automated computational approaches for spectroscopic analysis of stellar photospheres: detailed characterization at high resolution and abundance determination at medium resolution
We report on two distinct computational approaches to self-consistently measure photospheric properties of large samples of stars. Both procedures consist of a set of several semi-integrated tasks based on shell and Python scripts, which efficiently run either our own codes or open source software commonly adopted by the astronomical community. One approach aims to derive the main stellar photospheric parameters and abundances of a few elements by analysing high-resolution spectra from a given public library homogeneously constructed. The other one is applied to recover the abundance of a single element in stars with known photospheric parameters by using mid-resolution spectra from another open homogeneous database and calibrating derived abundances. Both semi-automated computational approaches provide homogeneity and objectivity to every step of the process and represent a fast way to reach partial and final results as well as to estimate measurement errors, making possible to systematically evaluate and improve the distinct steps.
119246221
Photospheric parameters and C abundances in solar-like stars with and without planets
We have been analyzing a large sample of solar-like stars with and without planets in order to homogeneously measure their photospheric parameters and Carbon abundances. Our sample contains around 200 stars in the solar neighborhood observed with the ELODIE spectrograph, for which the observational data are publicly available. We performed spectral synthesis of prominent bands of C 2 and CI lines, aiming to accurately obtain the C abundances. We intend to contribute homogeneous results to studies that compare elemental abundances in stars with and without known planets. New arguments will be brought forward to the discussion of possible chemical anomalies that have been suggested in the literature, leading us to a better understanding of the planetary formation process. In this work we focus on the C abundances in both stellar groups of our sample.