90 research outputs found
Diseño y adopción de políticas operativas y procedimientos para identificar los bienes en forma individualizada y dar de baja en cuentas, en el municipio de Chiquinquirá
1 recurso en línea (1 archivo de texto, 1 archivo con anexo) : ilustraciones color, tablas.Las políticas que se presentan en este informe, al municipio de Chiquinquirá para el manejo de activos surgen de la indagación e investigación realizada, fortaleciendo el proceso contable, suministro de información y mejora en la calidad de control interno contable. Se pretende dar cumplimiento a las resoluciones“192; 193 del 2016” y proporcionar políticas operativas que describan los detalles de ingreso y salida de los bienes administrados por el municipio de Chiquinquirá.Bibliografía y webgrafía: páginas 80-82.PregradoContador Públic
A Neutron Star Binary Merger Model for GW170817/GRB170817a/SSS17a
The merging neutron star gravitational wave event GW170817 has been observed
throughout the entire electromagnetic spectrum from radio waves to
-rays. The resulting energetics, variability, and light curves are
shown to be consistent with GW170817 originating from the merger of two neutron
stars, in all likelihood followed by the prompt gravitational collapse of the
massive remnant. The available -ray, X-ray and radio data provide a
clear probe for the nature of the relativistic ejecta and the non-thermal
processes occurring within, while the ultraviolet, optical and infrared
emission are shown to probe material torn during the merger and subsequently
heated by the decay of freshly synthesized -process material. The simplest
hypothesis that the non-thermal emission is due to a low-luminosity short
-ray burst (sGRB) seems to agree with the present data. While low
luminosity sGRBs might be common, we show here that the collective prompt and
multi-wavelength observations are also consistent with a typical, powerful sGRB
seen off-axis. Detailed follow-up observations are thus essential before we can
place stringent constraints on the nature of the relativistic ejecta in
GW170817.Comment: 9 pages, 5 figures, accepted to ApJ Letter
Electromagnetic Evidence that SSS17a is the Result of a Binary Neutron Star Merger
11 hours after the detection of gravitational wave source GW170817 by the
Laser Interferometer Gravitational-Wave Observatory and Virgo Interferometers,
an associated optical transient SSS17a was discovered in the galaxy NGC 4993.
While the gravitational wave data indicate GW170817 is consistent with the
merger of two compact objects, the electromagnetic observations provide
independent constraints of the nature of that system. Here we synthesize all
optical and near-infrared photometry and spectroscopy of SSS17a collected by
the One-Meter Two-Hemisphere collaboration. We find that SSS17a is unlike other
known transients. The source is best described by theoretical models of a
kilonova consisting of radioactive elements produced by rapid neutron capture
(the r-process). We find that SSS17a was the result of a binary neutron star
merger, reinforcing the gravitational wave result.Comment: 21 pages, 4 figures, accepted to Scienc
Nativos digitales, ciudadanos europeos
Se describen los objetivos y funcionamiento del programa eTwinning de hermanamientos escolares a través de Internet. Se hace balance del programa a nivel nacional aportándose datos de participación y desta-cando los factores que lo han convertido en una de la acciones de mayor aceptación entre el profesorado para establecer proyectos de aprendizaje colaborativo con otros países. 
Double-Peaked Balmer Emission Indicating Prompt Accretion Disk Formation in an X-Ray Faint Tidal Disruption Event
We present the multi-wavelength analysis of the tidal disruption event (TDE)
AT~2018hyz (ASASSN-18zj). From follow-up optical spectroscopy, we detect the
first unambiguous case of resolved double-peaked Balmer emission in a TDE. The
distinct line profile can be well-modelled by a low eccentricity
() accretion disk extending out to 100 and a
Gaussian component originating from non-disk clouds, though a bipolar outflow
origin cannot be completely ruled out. Our analysis indicates that in
AT~2018hyz, disk formation took place promptly after the most-bound debris
returned to pericenter, which we estimate to be roughly tens of days before the
first detection. Redistribution of angular momentum and mass transport,
possibly through shocks, must occur on the observed timescale of about a month
to create the large \Ha-emitting disk that comprises 5\% of the
initial stellar mass. With these new insights from AT~2018hyz, we infer that
circularization is efficient in at least some, if not all optically-bright,
X-ray faint TDEs. In these efficiently circularized TDEs, the detection of
double-peaked emission depends on the disk inclination angle and the relative
strength of the disk contribution to the non-disk component, possibly
explaining the diversity seen in the current sample.Comment: 24 pages, 8 figures, 6 tables. Accepted for publication in Ap
Discovery of a Fast Iron Low-ionization Outflow in the Early Evolution of the Nearby Tidal Disruption Event AT2019qiz
We report the results of UV and optical photometric and spectroscopic
analysis on the tidal disruption event (TDE) AT2019qiz. Our follow-up
observations started shortly after (10 days) its optical light begin
to rise and lasted for a period of six months. Our late-time host-dominated
spectrum indicates that the host galaxy likely harbours a weak AGN. The initial
HST spectrum of AT2019qiz exhibits a iron and low-ionization broad absorption
line (FeLoBAL) system that is seen for the first time in a TDE. This spectrum
also bears a striking resemblance to that of Gaia16apd, a superluminous
supernova. Our observations provide insights into the outflow properties in
TDEs and show evidence for a connection between TDEs and engine-powered
supernovae at early phase, as originally suggested in Metzger & Stone (2016).
In a time frame of 50 days, the UV spectra of AT2019qiz started to resemble
previous TDEs with only high-ionization BALs. The change in UV spectral
signatures is accompanied by a decrease in the outflow velocity, which began at
km s and decelerated to km s. A similar
evolution in the H emission line width further supports the speculation
that the broad Balmer emission lines are formed in TDE outflows. In addition,
we detect narrow absorption features on top of the FeLoBAL signatures in the
early HST UV spectrum of AT2019qiz. The measured HI column density corresponds
to a Lyman-limit system whereas the metal absorption lines, such as NV, CIV,
FeII, and MgII, are likely probing the circumnuclear gas and interstellar
medium in the host galaxy.Comment: 24 pages, 13 figures, 3 tables. Submitted to ApJ on Nov 03 202
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