326 research outputs found
Measuring Microlensing using Spectra of Multiply Lensed Quasars
We report on a program of spectroscopic observations of
gravitationally-lensed QSOs with multiple images. We seek to establish whether
microlensing is occurring in each QSO image using only single-epoch
observations. We calculate flux ratios for the cores of emission lines in image
pairs to set a baseline for no microlensing. The offset of the continuum flux
ratios relative to this baseline yields the microlensing magnification free
from extinction, as extinction affects the continuum and the lines equally.
When we find chromatic microlensing, we attempt to constrain the size of the
QSO accretion disk. SDSSJ1004+4112 and HE1104-1805 show chromatic microlensing
with amplitudes and mag,
respectively. Modeling the accretion disk with a Gaussian source () of size and using magnification maps
to simulate microlensing we find ) and for SDSS1004+4112, and
) and
for HE1104-1805. For SDSSJ1029+2623 we find strong chromaticity
of mag in the continuum flux ratio, which probably arises from
microlensing although not all the available data fit within this explanation.
For Q0957+561 we measure B-A magnitude differences of 0.4 mag, much greater
than the 0.05 mag amplitude usually inferred from lightcurve variability.
It may substantially modify the current interpretations of microlensing in this
system, likely favoring the hypothesis of smaller sources and/or larger
microdeflectors. For HS0818+1227, our data yield posible evidence of
microlensing.Comment: 45pp, 17figs, ApJ accepted (june 4th 2012
RXJ 0921+4529: a binary quasar or gravitational lens?
We report the new spectroscopic observations of the gravitational lens RXJ
021+4529 with the multi-mode focal reducer SCORPIO of the SAO RAS 6-m
telescope. The new spectral observations were compared with the previously
observed spectra of components A and B of RXJ 0921+4529, i.e. the same
components observed in different epochs. We found a significant difference in
the spectrum between the components that cannot be explained with microlensing
and/or spectral variation. We conclude that RXJ 0921+4529 is a binary quasar
system, where redshifts of quasars A and B are 1.6535 +/- 0.0005 and 1.6625 +/-
0.0015, respectively.Comment: 6 pages, 5 figures, accepted for publication in The Astrophysical
Journal Letter
Spectroscopy of the Lens Galaxy of Q0957+561A,B. Implications of a possible central massive dark object
We present new long-slit William Herschel Telescope spectroscopic
observations of the lens galaxy G1 associated with the double-imaged QSO
0957+561A,B. The obtained central stellar velocity dispersion, sigma_l = 310
+/- 20 km/s, is in reasonable agreement with other measurements of this
dynamical parameter. Using all updated measurements of the stellar velocity
dispersion in the internal region of the galaxy (at angular separations < 1".5)
and a simple isotropic model, we discuss the mass of a possible central massive
dark object. It is found that the data of Falco et al. (1997) suggest the
existence of an extremely massive object of (0.5-2.1) x 10E10/h M_\odot (80%
confidence level), whereas the inclusion of very recent data (Tonry & Franx
1998, and this paper) substantially changes the results: the compact central
mass must be 6 x10E9/h M_\odot at the 90% confidence level. We note that,
taking into account all the available dynamical data, a compact nucleus with a
mass of 10E9/h M_\odot (best fit) cannot be ruled out.Comment: 20 pages, 10 figures ApJ, in pres
Luxación esternoclavicular posterior: a propósito de un caso y revisión de la literatura
La luxación esternoclavicular posterior es una patología poco frecuente. Se presenta sobre todo en
varones jóvenes asociada a traumatismos de alta energía. Puede presentar complicaciones potencialmente letales por
compresión de estructuras mediastínicas, por lo que es necesario su reducción urgente. El diagnóstico radiográfico
puede ser difícil debido a la superposición de estructuras, siendo de gran utilidad la TC para determinar el tipo y grado
de desplazamiento, así como la relación anatómica con las estructuras mediastínicas. Se presenta el caso de un
paciente varón, de 23 años de edad, que presentó una luxación esternoclavicular posterior traumática aguda tras accidente
de tráfico en el que se consiguió la reducción cerrada mediante manipulación bajo anestesia general y posterior
inmovilización antiálgica durante 3 semanas, sin objetivarse inestabilidad esternoclavicular posterior que obligase
a más procedimientos. Se realiza una revisión de la literatura médica al respecto de esta patología.Posterior sternoclavicular dislocation is a rare disease. It occurs mainly in young men associated with
high-energy trauma. It can be life-threatening due to compression of mediastinal structures, so its reduction is
urgently needed. The radiographic diagnosis can be difficult because of overlapping structures, CT is very helpful to
determine the type and degree of displacement and the anatomic relationship with the mediastinal structures. We present
the case of a male patient, aged 23, with an acute traumatic posterior sternoclavicular dislocation after accident,
in which closed reduction was achieved by manipulation under general anesthesia, followed by analgesic immobilization
for 3 weeks resulting in sternoclavicular healing without instability, so no more procedures were needed. A literature
review is presented regarding to this case
Effect of indirect composite treatment microtensile bond strength of self-adhesive resin cements
Background: No specific indications about the pre-treatment of indirect composite restorations is provided by the
manufacturers of most self-adhesive resin cements. The potential effect of silane treatment to the bond strength of
the complete tooth/indirect restoration complex is not available.The aim of this study was to determine the contribution of different surface treatments on microtensile bond strength of composite overlays to dentin using several
self-adhesive resin cements and a total-etch one.
Material and Methods: Composite overlays were fabricated and bonding surfaces were airborne-particle abraded
and randomly assigned to two different surface treatments: no treatment or silane application (RelyX Ceramic
Primer) followed by an adhesive (Adper Scotchbond 1 XT). Composite overlays were luted to flat dentin surfaces
using the following self-adhesive resin cements: RelyX Unicem, G-Cem, Speedcem, Maxcem Elite or Smartcem2,
and the total-etch resin cement RelyX ARC. After 24 h, bonded specimens were cut into sticks 1 mm thick and
stressed in tension until failure. Two-way ANOVA and SNK tests were applied at α=0.05.
Results: Bond strength values were significantly influenced by the resin cement used (
p
<0.001). However, composite surface treatment and the interaction between the resin cement applied and surface treatment did not significantly
affect dentin bond strength (
p
>0.05). All self-adhesive resin cements showed lower bond strength values than the
total-etch RelyX ARC. Among self-adhesive resin cements, RelyX Unicem and G-Cem attained statistically higher
bond strength values. Smartcem2 and Maxcem Elite exhibited 80-90% of pre-test failures.
Conclusions: The silane and adhesive application after indirect resin composite sandblasting did not improve the
bond strength of dentin-composite overlay complex. Selection of the resin cement seems to be a more relevant
factor when bonding indirect composites to dentin than its surface treatmen
Complex emission line region of Mrk 817
In this work we study the physical and kinematical properties of the emission
line region of Seyfert 1.5 galaxy Mrk 817 using three sets of observations,
among which are high-resolution spectra obtained with the Isaac Newton
Telescope on Canary Islands. We find that in Mrk 817 the Narrow (NEL) and Broad
Emission Lines (BEL) are very complex, indicating that structure of both the
Narrow (NLR) and Broad Line Region (BLR) is complex and consists of at least
two sub-regions with different kinematical properties. We find that the BEL can
be fitted with the two-component model, where the core of the line is coming
from a spherical region with isotropic velocity distribution, and wings might
be affected by a low inclined accretion disc (or disc-like emitting region).
Also, we discuss the physical properties of the BLR. Moreover, we find that an
outflow is present in the NLR, that may be driven by an approaching jet.Comment: 7 pages, 9 figures, accepted for publication in MNRA
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