4,329 research outputs found
Swift J053041.9-665426, a new Be/X-ray binary pulsar in the Large Magellanic Cloud
We observed the newly discovered X-ray source Swift J053041.9-665426 in the
X-ray and optical regime to confirm its proposed nature as a high mass X-ray
binary. We obtained XMM-Newton and Swift X-ray data, along with optical
observations with the ESO Faint Object Spectrograph, to investigate the
spectral and temporal characteristics of Swift J053041.9-665426. The XMM-Newton
data show coherent X-ray pulsations with a period of 28.77521(10) s (1 sigma).
The X-ray spectrum can be modelled by an absorbed power law with photon index
within the range 0.76 to 0.87. The addition of a black body component increases
the quality of the fit but also leads to strong dependences of the photon
index, black-body temperature and absorption column density. We identified the
only optical counterpart within the error circle of XMM-Newton at an angular
distance of ~0.8 arcsec, which is 2MASS J05304215-6654303. We performed optical
spectroscopy from which we classify the companion as a B0-1.5Ve star. The X-ray
pulsations and long-term variability, as well as the properties of the optical
counterpart, confirm that Swift J053041.9-665426 is a new Be/X-ray binary
pulsar in the Large Magellanic Cloud.Comment: 10 pages, 8 figures, accepted for publication in A&
Discovery of SXP265, a Be/X-ray binary pulsar in the Wing of the Small Magellanic Cloud
We identify a new candidate for a Be/X-ray binary in the XMM-Newton slew
survey and archival Swift observations that is located in the transition region
of the Wing of the Small Magellanic Cloud and the Magellanic Bridge. We
investigated and classified this source with follow-up XMM-Newton and optical
observations. We model the X-ray spectra and search for periodicities and
variability in the X-ray observations and the OGLE I-band light curve. The
optical counterpart has been classified spectroscopically, with data obtained
at the SAAO 1.9 m telescope, and photometrically, with data obtained using
GROND at the MPG 2.2 m telescope. The X-ray spectrum is typical of a high-mass
X-ray binary with an accreting neutron star. We detect X-ray pulsations, which
reveal a neutron-star spin period of P = (264.516+-0.014) s. The source likely
shows a persistent X-ray luminosity of a few 10^35 erg/s and in addition type-I
outbursts that indicate an orbital period of ~146 d. A periodicity of 0.867 d,
found in the optical light curve, can be explained by non-radial pulsations of
the Be star. We identify the optical counterpart and classify it as a
B1-2II-IVe star. This confirms SXP 265 as a new Be/X-ray binary pulsar
originating in the tidal structure between the Magellanic Clouds.Comment: 11 pages, 12 figures, accepted for publication in MNRA
Extraction of the electron mass from factor measurements on light hydrogenlike ions
The determination of the electron mass from Penning-trap measurements with
C ions and from theoretical results for the bound-electron
factor is described in detail. Some recently calculated contributions slightly
shift the extracted mass value. Prospects of a further improvement of the
electron mass are discussed both from the experimental and from the theoretical
point of view. Measurements with He ions will enable a consistency
check of the electron mass value, and in future an improvement of the He
nuclear mass and a determination of the fine-structure constant
Semidefinite Representation of the -Ellipse
The -ellipse is the plane algebraic curve consisting of all points whose
sum of distances from given points is a fixed number. The polynomial
equation defining the -ellipse has degree if is odd and degree
if is even. We express this polynomial equation as
the determinant of a symmetric matrix of linear polynomials. Our representation
extends to weighted -ellipses and -ellipsoids in arbitrary dimensions,
and it leads to new geometric applications of semidefinite programming.Comment: 16 pages, 5 figure
Simple test for quantum channel capacity
Basing on states and channels isomorphism we point out that semidefinite
programming can be used as a quick test for nonzero one-way quantum channel
capacity. This can be achieved by search of symmetric extensions of states
isomorphic to a given quantum channel. With this method we provide examples of
quantum channels that can lead to high entanglement transmission but still have
zero one-way capacity, in particular, regions of symmetric extendibility for
isotropic states in arbitrary dimensions are presented. Further we derive {\it
a new entanglement parameter} based on (normalised) relative entropy distance
to the set of states that have symmetric extensions and show explicitly the
symmetric extension of isotropic states being the nearest to singlets in the
set of symmetrically extendible states. The suitable regularisation of the
parameter provides a new upper bound on one-way distillable entanglement.Comment: 6 pages, no figures, RevTeX4. Signifficantly corrected version. Claim
on continuity of channel capacities removed due to flaw in the corresponding
proof. Changes and corrections performed in the part proposing a new upper
bound on one-way distillable etanglement which happens to be not one-way
entanglement monoton
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