85,468 research outputs found
Planetary companions orbiting M giants HD 208527 and HD 220074
Aims. The purpose of the present study is to research the origin of planetary
companions by using a precise radial velocity (RV) survey.
Methods. The high-resolution spectroscopy of the fiber-fed Bohyunsan
Observatory Echelle Spectrograph (BOES) at Bohyunsan Optical Astronomy
Observatory (BOAO) is used from September 2008 to June 2012.
Results. We report the detection of two exoplanets in orbit around HD 208527
and HD 220074 exhibiting periodic variations in RV of 875.5 +/- 5.8 and 672.1
+/- 3.7 days. The RV variations are not apparently related to the surface
inhomogeneities and a Keplerian motion of the planetary companion is the most
likely explanation. Assuming possible stellar masses of 1.6 +/- 0.4 and 1.2 +/-
0.3 M_Sun, we obtain the minimum masses for the exoplanets of 9.9 +/- 1.7 and
11.1 +/- 1.8 M_Jup around HD 208527 and HD 220074 with an orbital semi-major
axis of 2.1 +/- 0.2 and 1.6 +/- 0.1 AU and an eccentricity of 0.08 and 0.14,
respectively. We also find that the previously known spectral classification of
HD 208527 and HD 220074 was in error: Our new estimation of stellar parameters
suggest that both HD 208527 and HD 220074 are M giants. Therefore, HD 208527
and HD 220074 are so far the first candidate M giants to harbor a planetary
companion.Comment: 7 pages, 9 figures, 4 tables, accepted for publisation in Astronomy &
Astrophysic
Dynamic instability transitions in 1D driven diffusive flow with nonlocal hopping
One-dimensional directed driven stochastic flow with competing nonlocal and
local hopping events has an instability threshold from a populated phase into
an empty-road (ER) phase. We implement this in the context of the asymmetric
exclusion process. The nonlocal skids promote strong clustering in the
stationary populated phase. Such clusters drive the dynamic phase transition
and determine its scaling properties. We numerically establish that the
instability transition into the ER phase is second order in the regime where
the entry point reservoir controls the current and first order in the regime
where the bulk is in control. The first order transition originates from a
turn-about of the cluster drift velocity. At the critical line, the current
remains analytic, the road density vanishes linearly, and fluctuations scale as
uncorrelated noise. A self-consistent cluster dynamics analysis explains why
these scaling properties remain that simple.Comment: 11 pages, 14 figures (25 eps files); revised as the publised versio
Electroexcitation of the Roper resonance in the relativistic quark models
The amplitudes of the transition gamma* N -> P11(1440) are calculated within
light-front relativistic quark model assuming that the P11(1440) is the first
radial excitation of the 3q ground state. The results are presented along with
the predictions obtained in other relativistic quark models. In comparison with
the previous calculations, we have extended the range of Q^2 up to 4.5 GeV^2 to
cover the kinematic interval of the forthcoming experimental data. Using
approach based on PCAC, we have checked the relative sign between quark model
predictions for the N and P11(1440) contributions to the pion electroproduction
found in previous investigations.Comment: 5 pages, 1 figure, accepted by PR
Origin of the high piezoelectric response in PbZr(1-x)TixO3
High resolution x-ray powder diffraction measurements on poled PbZr(1-x)TixO3
(PZT) ceramic samples close to the rhombohedral-tetragonal phase boundary (the
so-called morphotropic phase boundary, MPB) have shown that for both
rhombohedral and tetragonal compositions, the piezoelectric elongation of the
unit cell does not occur along the polar directions but along those directions
associated with the monoclinic distortion. This work provides the first direct
evidence for the origin of the very high piezoelectricity in PZT.Comment: 4 pages, 4 EPS figures embedded. More specific title and abstract. To
appear in Phys. Rev. Let
Analytic study of the urn model for separation of sand
We present an analytic study of the urn model for separation of sand recently
introduced by Lipowski and Droz (Phys. Rev. E 65, 031307 (2002)). We solve
analytically the master equation and the first-passage problem. The analytic
results confirm the numerical results obtained by Lipowski and Droz. We find
that the stationary probability distribution and the shortest one among the
characteristic times are governed by the same free energy. We also analytically
derive the form of the critical probability distribution on the critical line,
which supports their results obtained by numerically calculating Binder
cumulants (cond-mat/0201472).Comment: 6 pages including 3 figures, RevTe
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