An Exploration of Spotted White Dwarfs from K2

The 21st European Workshop on White Dwarfs was held in Austin, TX from July 23rd to 27th of 2018The Kepler K2 mission has discovered a significant population of white dwarf stars that exhibit photometric variability due to surface inhomogeneities likely related to magnetism. These “spotted” white dwarfs present not only in temperature regimes where we expect convection to dominate white dwarf photospheres, but also where radiation should dominate. We present an exploration of spotted white dwarfs as a function of various physical characteristics, including temperature, magnetic field strength, and rotational period, in order to better understand the origins of these photometric variations.Astronom

New insight on the Sivers transverse momentum dependent distribution function

Polarised Semi-Inclusive Deep Inelastic Scattering (SIDIS) processes allow to study Transverse Momentum Dependent partonic distributions (TMDs), which reveal a non trivial three dimensional internal structure of the hadrons in momentum space. One of the most representative of the TMDs is the so-called Sivers function that describes the distribution of unpolarized quarks inside a transversely polarized proton. We present a novel extraction of the Sivers distribution functions from the most recent experimental data of HERMES and COMPASS experiments. Using suitable parametrizations, within the TMD factorization scheme, and a simple fitting strategy, we also perform a preliminary exploration of the role of the proton sea quarks.Comment: Talk delivered by M. Boglione at SPIN2010, September 27-October 2, 2010, Juelich, Germany. Left panel of Fig. 5 replace

A New Gravitational Wave Verification Source

We report the discovery of a detached 20 min orbital period binary white dwarf. WD0931+444 (SDSS J093506.93+441106.9) was previously classified as a WD + M dwarf system based on its optical spectrum. Our time-resolved optical spectroscopy observations obtained at the 8m Gemini and 6.5m MMT reveal peak-to-peak radial velocity variations of 400 km/s every 20 min for the WD, but no velocity variations for the M dwarf. In addition, high-speed photometry from the McDonald 2.1m telescope shows no evidence of variability nor evidence of a reflection effect. An M dwarf companion is physically too large to fit into a 20 min orbit. Thus, the orbital motion of the WD is almost certainly due to an invisible WD companion. The M dwarf must be either an unrelated background object or the tertiary component of a hiearchical triple system. WD0931+444 contains a pair of WDs, a 0.32 Msol primary and a >0.14 Msol secondary, at a separation of >0.19 Rsol. After J0651+2844, WD0931+444 becomes the second-shortest period detached binary WD currently known. The two WDs will lose angular momentum through gravitational wave radiation and merge in <9 Myr. The log h ~ -22 gravitational wave strain from WD0931+444 is strong enough to make it a verification source for gravitational wave missions in the milli-Hertz frequency range, e.g. the evolved Laser Interferometer Space Antenna (eLISA), bringing the total number of known eLISA verification sources to nine.Comment: MNRAS Letters, in pres

Reply to Comment on "Reevaluation of the parton distribution of strange quarks in the nucleon"

A Comment on the recently published reevaluation of the polarization-averaged parton distribution of strange quarks in the nucleon using final data on the multiplicities of charged kaons in semi-inclusive deep-inelastic scattering is reviewed. Important features of the comparison of one-dimensional projections of the multidimensional HERMES data are pointed out. A test of the leading-order extraction of xS(x) using the difference between charged-kaon multiplicities is repeated. The results are consistent with leading-order predictions within the uncertainties in the input data, and do not invalidate the earlier extraction of xS(x).Comment: Reply Comment to arXiv:1407.372

Strategi Dinas Tenaga Kerja dalam Mengatasi Masalah Pengangguran di Kota Pekanbaru

This study will analyze how the Strategy Department of Labor in Addresing Unemployment Problem in Pekanbaru City. Given the number of unemployment both from within and from outside the area to find a job in Pekanbaru city government attempted to addressing the unemplotment problem by holding exhibitions labor market in order to facilitate job seekers find work.The steps of The Department of Labor in Addressing Unemployment Problem in Pekanbaru City be very important in providing counseling or disseminination to the public or unemployed to fill job vacancies that exist both within region and outside the region. Then, the Department of Labor Pekanbaru also perform or implement workforce training in accordance with labor market demand according to the expertise or skills possessed by job seekers. The purpose of this is to determine the strategy of the Department of Labor in Addressing Unemployment Problem in Pekanbaru City and to determine the factors that influence the strategy of the Department of Labor in Addressing Unemployment Problem in Pekanbaru City. To analyze this problem the authors use the theory Tripomo which strategy is the frame or plame that integrate goals, policy and action/program organization.This research was conducted in the Department of Labor Pekanbaru city, using qualitative research methods using snowball sampling methods in the analysis of research with key informants (key informants). In collecting the data, the researcher used interview techniques, observation and documentation studies. By using key informants and informant as a supplementary source of information in addressing unemployment problem in Pekanbaru city not run well in carrying out measures to addressing unemployment. The factors that influence among others factors of infrastructure, human resources and communications.Keywords: Strategy, unemploymen

Thermodynamic Optimization of Tube-Fin Evaporators Operating under Frosting Conditions

In this study, the method of entropy generation minimization (i.e., design aimed at facilitating both heat, mass and fluid flows) is used to improve the evaporator geometry (aspect ratio and fin density) considering the irreversibilities produced by the heat and mass transfer, and viscous flow processes. A fully algebraic semi-empirical model was put forward to simulate the thermal-hydraulic behavior of tube-fin evaporator coils running under frosting conditions. The model predictions were validated against experimental data from Silva (2012), showing a good agreement between calculated and measured counterparts, with errors within a ±5% band for the cooling capacity and the air flow rate. The optimization exercise pointed out that high aspect ratio heat exchanger designs lead to minimum entropy generation in cases of fixed heat duty and air flow rate constrained by the characteristic curve of the fan