13,478 research outputs found
Absence of hot gas within the Wolft-Rayet Bubble around WR16
We present the analysis of XMM-Newton archival observations towards the
Wolf-Rayet (WR) bubble around WR16. Despite the closed bubble morphology of
this WR nebula, the XMM-Newton observations show no evidence of diffuse
emission in its interior as in the similar WR bubbles NGC6888 and S308. We use
the present observations to estimate a 3-\sigma upper limit to the X-ray
luminosity in the 0.3-1.5 keV energy band equal to 7.4x10^{32} erg s^{-1} for
the diffuse emission from the WR nebula, assuming a distance of 2.37 kpc. The
WR nebula around WR16 is the fourth observed by the current generation of X-ray
satellites and the second not detected. We also examine FUSE spectra to search
for nebular O VI absorption lines in the stellar continuum of WR16. The present
far-UV data and the lack of measurements of the dynamics of the optical WR
bubble do not allow us to confirm the existence of a conductive layer of gas at
T~3x10^5 K between the cold nebular gas and the hot gas in its interior. The
present observations result in an upper limit of n_e < 0.6 cm^-3 on the
electron density of the X-ray emitting material within the nebula.Comment: 6 pages, 3 figures, 1 table; To appear in Astronomy and Astrophysic
Hermite Coherent States for Quadratic Refractive Index Optical Media
Producción CientíficaLadder and shift operators are determined for the set of Hermite–Gaussian modes associated with an optical medium with quadratic refractive index profile. These operators allow to establish irreducible representations of the su(1, 1) and su(2) algebras. Glauber coherent states, as well as su(1, 1) and su(2) generalized coherent states, were constructed as solutions of differential equations admitting separation of variables. The dynamics of these coherent states along the optical axis is also evaluated.MINECO grant MTM2014-57129-C2-1-P and Junta de Castilla y Leon grant VA057U16
Revisiting the optical -symmetric dimer
Optics has proved a fertile ground for the experimental simulation of quantum
mechanics. Most recently, optical realizations of -symmetric
quantum mechanics have been shown, both theoretically and experimentally,
opening the door to international efforts aiming at the design of practical
optical devices exploiting this symmetry. Here, we focus on the optical
-symmetric dimer, a two-waveguide coupler were the materials show
symmetric effective gain and loss, and provide a review of the linear and
nonlinear optical realizations from a symmetry based point of view. We go
beyond a simple review of the literature and show that the dimer is just the
smallest of a class of planar -waveguide couplers that are the optical
realization of Lorentz group in 2+1 dimensions. Furthermore, we provide a
formulation to describe light propagation through waveguide couplers described
by non-Hermitian mode coupling matrices based on a non-Hermitian generalization
of Ehrenfest theorem.Comment: 25 pages, 12 figure
WISE morphological study of Wolf-Rayet nebulae
We present a morphological study of nebulae around Wolf-Rayet (WR) stars
using archival narrow-band optical and Wide-field Infrared Survey Explorer
(WISE) infrared images. The comparison among WISE images in different bands and
optical images proves to be a very efficient procedure to identify the nebular
emission from WR nebulae, and to disentangle it from that of the ISM material
along the line of sight. In particular, WR nebulae are clearly detected in the
WISE W4 band at 22 m. Analysis of available mid-IR Spitzer spectra shows
that the emission in this band is dominated by thermal emission from dust
spatially coincident with the thin nebular shell or most likely with the
leading edge of the nebula. The WR nebulae in our sample present different
morphologies that we classified into well defined WR bubbles (bubble -type nebulae), clumpy and/or disrupted shells (clumpy/disrupted -type nebulae), and material mixed with the diffuse medium (mixed -type nebulae). The variety of morphologies presented by WR nebulae shows a
loose correlation with the central star spectral type, implying that the
nebular and stellar evolutions are not simple and may proceed according to
different sequences and time-lapses. We report the discovery of an obscured
shell around WR35 only detected in the infrared.Comment: 11 pages, 6 figures, plus 23 appendix figures; to appear in Astronomy
and Astrophysic
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