63,205 research outputs found
PEPSI deep spectra. II. Gaia benchmark stars and other M-K standards
We provide a homogeneous library of high-resolution, high-S/N spectra for 48
bright AFGKM stars, some of them approaching the quality of solar-flux spectra.
Our sample includes the northern Gaia benchmark stars, some solar analogs, and
some other bright Morgan-Keenan (M-K) spectral standards. Well-exposed deep
spectra were created by average-combining individual exposures. The
data-reduction process relies on adaptive selection of parameters by using
statistical inference and robust estimators.We employed spectrum synthesis
techniques and statistics tools in order to characterize the spectra and give a
first quick look at some of the science cases possible. With an average
spectral resolution of R=220,000 (1.36 km/s), a continuous wavelength coverage
from 383 nm to 912 nm, and S/N of between 70:1 for the faintest star in the
extreme blue and 6,000:1 for the brightest star in the red, these spectra are
now made public for further data mining and analysis. Preliminary results
include new stellar parameters for 70 Vir and alpha Tau, the detection of the
rare-earth element dysprosium and the heavy elements uranium, thorium and
neodymium in several RGB stars, and the use of the 12C to 13C isotope ratio for
age-related determinations. We also found Arcturus to exhibit few-percent CaII
H&K and H-alpha residual profile changes with respect to the KPNO atlas taken
in 1999.Comment: in press, 15 pages, 7 figures, data available from pepsi.aip.d
Robotic observations of the most eccentric spectroscopic binary in the sky
The visual A component of the Gliese 586AB system is a double-lined
spectroscopic binary consisting of two cool stars with the exceptional orbital
eccentricity of 0.976. Such an extremely eccentric system may be important for
our understanding of low-mass binary formation. We present a total of 598
high-resolution echelle spectra from our robotic facility STELLA from 2006-2012
which we used to compute orbital elements of unprecedented accuracy. The orbit
constrains the eccentricity to 0.97608+/-0.00004 and the orbital period to
889.8195+/-0.0003d. The masses of the two components are 0.87+/-0.05 Msun and
0.58+/-0.03 Msun if the inclination is 5+/-1.5degr as determined from
adaptive-optics images, that is good to only 6% due to the error of the
inclination although the minimum masses reached a precision of 0.3%. The flux
ratio Aa:Ab in the optical is betwee n 30:1 in Johnson-B and 11:1 in I. Radial
velocities of the visual B-component (K0-1V) appear constant to within 130 m/s
over six years. Sinusoidal modulations of Teff of Aa with an amplitude of apprx
55 K are seen with the orbital period. Component Aa appears warmest at
periastron and coolest at apastron, indicating atmospheric changes induced by
the high orbital eccentricity. No light variations larger than approximately 4
mmag are detected for A, while a photometric period of 8.5+/-0.2 d with an
amplitude of 7 mmag is discovered for the active star B, which we interpret to
be its rotation period. We estimate an orbital period of approx 50,000 yr for
the AB system. The most likely age of the AB system is >=2 Gyr, while the
activity of the B component, if it were a single star, would imply 0.5 Gyr.
Both Aa and B are matched with single-star evolutionary tracks of their
respective mass
Weber and Simmelâs philosophical and political stances : a dialogue in three acts
This article is an imagined dialogue between Weber and Simmel which makes a modest use of some of the resources of theatrical play in order to provide an overall portrait of both thinkers and to bring their thought to bear on our present. The dialogue consists of three acts focused on three central problematics in as many critical moments in Weber and Simmelâs lives: Act I takes place during the preparations for the first conference of the German Sociological Association and thus deals with the constitution of sociology as a socio-cultural science. Act II takes place amidst the First World War and its theme is evidently politics. Finally, Act III, where our two characters correspond instead of maintaining a face-to-face dialogue, is situated towards the end of the war and focuses on the attitude to life and indeed to death, as Simmelâs tragic yet admirable death takes place then. A brief introduction explains how we tried to use the possibilities of the dialogical form to expound Weberâs and Simmelâs thought, to compel them to confront their own blind spots and âunthoughtsâ, as well as to explore new ways of teaching the classics and transmitting their thought
Quark deconfinement in high-mass neutron stars
In this paper, we explore whether or not quark deconfinement may occur in
high-mass neutron stars such as J1614-2230 (1.97 \pm 0.04 M_Sun) and J0348+0432
(2.01 \pm 0.04 M_Sun). Our study is based on a non-local extension of the SU(3)
Nambu Jona-Lasinio (n3NJL) model with repulsive vector interactions among the
quarks. This model goes beyond the frequently used local version of the Nambu
Jona-Lasinio (NJL) model by accounting for several key features of QCD which
are not part of the local model. Confined hadronic matter is treated in the
framework of non-linear relativistic mean field theory. We find that both the
local as well as the non-local NJL model predict the existence of extended
regions of mixed quark-hadron (quark-hybrid) matter in high-mass neutron stars
with masses of 2.1 to 2.4 M_Sun. Pure quark matter in the cores of neutron
stars is obtained for certain parametrizations of the hadronic lagrangian and
choices of the vector repulsion among quarks. The radii of high-mass neutron
stars with quark-hybrid matter and/or pure quark matter cores in their centers
are found to lie in the canonical range of 12 to 13 km.Comment: 31 pages, 17 figures, PRC accepted versio
Z Pole Observables in the MSSM
We present the currently most accurate prediction of Z pole observables such
as sin^2 theta_eff, Gamma_Z, R_b, R_l, and sigma^0_had in the Minimal
Supersymmetric Standard Model (MSSM). We take into account the complete
one-loop results including the full complex phase dependence, all available
MSSM two-loop corrections as well as the full SM results. We furthermore
include higher-order corrections in the MSSM Higgs boson sector, entering via
virtual Higgs boson contributions. For Gamma(Z -> neutralino{1} neutralino{1})
we present a full one-loop calculation. We analyse the impact of the different
sectors of the MSSM with particular emphasis on the effects of the complex
phases. The predictions for the Z boson observables and M_W are compared with
the current experimental values. Furthermore we provide an estimate of the
remaining higher-order uncertainties in the prediction of sin^2 theta_eff.Comment: 53 pages, 20 figures, journal versio
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