1,700 research outputs found
Intrinsic Parameters of GRB990123 from Its Prompt Optical Flash and Afterglow
We have constrained the intrinsic parameters, such as the magnetic energy
density fraction (), the electron energy density fraction
(), the initial Lorentz factor () and the Lorentz factor
of the reverse external shock (), of GRB990123, in terms of the
afterglow information (forward shock model) and the optical flash information
(reverse shock model). Our result shows: 1) the inferred values of
and are consistent with the suggestion that they may be universal
parameters, comparing to those inferred for GRB970508; 2) the reverse external
shock may have become relativistic before it passed through the ejecta shell.
Other instrinsic parameters of GRB990123, such as energy contained in the
forward shock and the ambient density are also determined and discussed
in this paper.Comment: 5 pages, MN LaTeX style, a few changes made according to referee's
suggestions, references up dated, MNRAS accepte
Identification of the donor in GRS 1915+105
We report on the results of medium-resolution spectroscopy of GRS 1915+105 in
the H and K band using the 8m VLT at ESO. We clearly identify absorption
bandheads from CO12 and CO13. Together with other features this results in a
classification of the donor as a K-M III star.Comment: 4 pages, Kluwer style, to appear in Astrophys. Space Sci. Rev, Proc.
of 3rd Microquasar workshop, Granada, Sep. 2000, Eds. A.J. Castro-Tirado, J.
Greiner, J.M. Paredes; all proceedings contr. available at
http://www.aip.de/~jcg/granada.htm
Iron Line Diagnostics for the GRS 1915+105 Black Hole
The properties of the broad Fe line detected in two BeppoSAX observations of
the microquasar GRS 1915+105 are summarized.Comment: 4 pages, 2 figures. Proc. of the II BeppoSAX Meeting: "The Restless
High-Energy Universe" (Amsterdam, May 5-8, 2003), E.P.J. van den Heuvel,
J.J.M. in 't Zand, and R.A.M.J. Wijers Ed
Relaciones en conflicto. Nuevas perspectivas sobre relaciones internacionales desde la historia
Este libro recoge las aportaciones de los investigadores del IV Encuentro de Jóvenes Investigadores en Historia Contemporánea que tuvo lugar en el Valencia en septiembre de 2013
Optical afterglow of the not so dark GRB 021211
We determine Johnson and Cousins photometric CCD magnitudes for
the afterglow of GRB 021211 during the first night after the GRB trigger. The
afterglow was very faint and would have been probably missed if no prompt
observation had been conducted. A fraction of the so-called ``dark'' GRBs may
thus be just ``optically dim'' and require very deep imaging to be detected.
The early-time optical light curve reported by other observers shows prompt
emission with properties similar to that of GRB 990123. Following this, the
afterglow emission from min to days after the burst is
characterized by an overall power-law decay with a slope in the
passband. We derive the value of spectral index in the optical to near-IR
region to be 0.60.2 during 0.13 to 0.8 day after the burst. The flux decay
constant and the spectral slope indicate that optical observations within a day
after the burst lies between cooling frequency and synchrotron maximum
frequency.Comment: 4 pages, 2 figures, A&A Letters, 408, L2
Comportamiento electroquímico de aerogeles de carbón nanoporosos en fenómenos de desionización capacitiva
III Encuentro sobre Nanociencia y Nanotecnología de Investigadores y Tecnólogos Andaluce
INTEGRAL observation of 3EG J1736-2908
The possible identification by INTEGRAL of the EGRET source 3EG J1736-2908
with the active galactic nucleus GRS 1734-292 is discussed. The latter was
discovered in 1990 and later identified with a Seyfert 1 galaxy. At the time of
the compilation of the 3rd EGRET Catalog, it was not considered as a possible
counterpart of the source 3EG J1736-2908, which remained unidentified. A
detailed multiwavelength study of the EGRET error circle is presented, by
including archival radio, soft- and hard-X observations, suggesting that GRS
1734-292 could be a likely counterpart of 3EG J1736-2908, even though this
poses very interesting questions about the production mechanisms of gamma-rays
with energies greater than 100 MeV.Comment: 6 pages, 3 figures. Accepted for publication on A&A Main Journa
On the Optical Light Curves of Afterglows from Jetted Gamma-ray Burst Ejecta: Effects of Parameters
Due to some refinements in the dynamics, we can follow the overall evolution
of a realistic jet numerically till its bulk velocity being as small as . We find no obvious break in the optical light curve during
the relativistic phase itself. However, an obvious break does exist at the
transition from the relativistic phase to the non-relativistic phase, which
typically occurs at time --- s (i.e., 10 --- 30 d).
The break is affected by many parameters, such as the electron energy fraction
, the magnetic energy fraction , the initial half
opening angle , and the medium number density . Increase of any of
them to a large enough value will make the break disappear. Although the break
itself is parameter-dependent, afterglows from jetted GRB remnants are
uniformly characterized by a quick decay during the non-relativistic phase,
with power law timing index . This is quite different from
that of isotropic fireballs, and may be of fundamental importance for
determining the degree of beaming in -ray bursts observationally.Comment: 8 pages, 10 embedded eps figures, MNRAS in press, using epsfig.sty
and mn.st
Long time-scale variability in GRS1915+105
We present very high resolution hydrodynamical simulations of accretion discs
in black hole X-ray binaries accreting near the Eddington limit. The results
show that mass loss, irradiation and tidal interactions all have a profound
effect on the observed behaviour of long period X-ray transients. In
particular, the interplay of all of these effects in the outer regions of the
accretion disc is able to drive long time-scale (weeks to years) variability is
these objects, and is a possible origin for some of the extreme variability of
GRS1915+105.Comment: 7 pages, 9 figures (2 in colour), accepted for publication in MNRA
Kinetics of antibody-induced modulation of respiratory syncytial virus antigens in a human epithelial cell line
<p>Abstract</p> <p>Background</p> <p>The binding of viral-specific antibodies to cell-surface antigens usually results in down modulation of the antigen through redistribution of antigens into patches that subsequently may be internalized by endocytosis or may form caps that can be expelled to the extracellular space. Here, by use of confocal-laser-scanning microscopy we investigated the kinetics of the modulation of respiratory syncytial virus (RSV) antigen by RSV-specific IgG. RSV-infected human epithelial cells (HEp-2) were incubated with anti-RSV polyclonal IgG and, at various incubation times, the RSV-cell-surface-antigen-antibody complexes (RSV Ag-Abs) and intracellular viral proteins were detected by indirect immunoflourescence.</p> <p>Results</p> <p>Interaction of anti-RSV polyclonal IgG with RSV HEp-2 infected cells induced relocalization and aggregation of viral glycoproteins in the plasma membrane formed patches that subsequently produced caps or were internalized through clathrin-mediated endocytosis participation. Moreover, the concentration of cell surface RSV Ag-Abs and intracellular viral proteins showed a time dependent cyclic variation and that anti-RSV IgG protected HEp-2 cells from viral-induced death.</p> <p>Conclusion</p> <p>The results from this study indicate that interaction between RSV cell surface proteins and specific viral antibodies alter the expression of viral antigens expressed on the cells surface and intracellular viral proteins; furthermore, interfere with viral induced destruction of the cell.</p
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