386 research outputs found
Submillimeter vibrationally excited water emission from the peculiar red supergiant VY CMa
Vibrationally excited emission from the SiO and H2O molecules probes the
innermost circumstellar envelopes of oxygen-rich red giant and supergiant
stars. VY CMa is the most prolific known stellar emission source in these
molecules. Observations were made to search for rotational lines in the lowest
vibrationally excited state of H2O. The APEX telescope was used for
observations of H2O lines at frequencies around 300 GHz. Two vibrationally
excited H2O lines were detected, a third one could not be found. In one of the
lines we find evidence for weak maser action, similar to known (sub)millimeter
H2O lines. We find that the other line's intensity is consistent with thermal
excitation by the circumstellar infrared radiation field. Several SiO lines
were detected together with the H2O lines.Comment: APEX A&A special issue, accepte
Epidemiology of sports injuries in european union countries
La práctica deportiva es una actividad que se recomienda para mantener y promocionar la salud y los buenos hábitos. Sin embargo puede acarrear un riesgo importante de lesiones. Este estudio presenta, mediante técnicas de análisis multivariante, la relación que existe entre la tipo de lesiones, lugares del cuerpo donde se producen, los deportes más populares; fútbol, baloncesto, voleibol, y gimnasia, edad y paÃses donde se practica, tomando datos de cinco paÃses de la Unión Europea. Si relacionamos estas caracterÃsticas entre sÃ, podemos elaborar estrategias especÃficas al tipo de deporte y paÃs donde se practica, con el objeto de mejorar la prevención y poder disminuir la cantidad de lesiones que se producen.Participation in sports is a health promotion activity and maintains good habits that entail an important injury risk. The present article is a study using Multivariatye Analysis, the relationship between type of injury, location of injury, the most popular sports; soccer, basketball, volleyball, gymnastics, county where it has been practiced and age, in five European Union countries. With these relationships, we can develop specific strategies to improve prevention and to reduce the injuries that occur
Ground-State SiO Maser Emission Toward Evolved Stars
We have made the first unambiguous detection of vibrational ground-state
maser emission from SiO toward six evolved stars. Using the Very Large Array,
we simultaneously observed the v=0, J=1-0, 43.4-GHz, ground-state and the v=1,
J=1-0, 43.1-GHz, first excited-state transitions of SiO toward the oxygen-rich
evolved stars IRC+10011, o Ceti, W Hya, RX Boo, NML Cyg, and R Cas and the
S-type star chi Cyg. We detected at least one v=0 SiO maser feature from six of
the seven stars observed, with peak maser brightness temperatures ranging from
10,000 K to 108,800 K. In fact, four of the seven v=0 spectra show multiple
maser peaks, a phenomenon which has not been previously observed. Ground-state
thermal emission was detected for one of the stars, RX Boo, with a peak
brightness temperature of 200 K. Comparing the v=0 and the v=1 transitions, we
find that the ground-state masers are much weaker with spectral characteristics
different from those of the first excited-state masers. For four of the seven
stars the velocity dispersion is smaller for the v=0 emission than for the v=1
emission, for one star the dispersions are roughly equivalent, and for two
stars (one of which is RX Boo) the velocity spread of the v=0 emission is
larger. In most cases, the peak flux density in the v=0 emission spectrum does
not coincide with the v=1 maser peak. Although the angular resolution of these
VLA observations were insufficient to completely resolve the spatial structure
of the SiO emission, the SiO spot maps produced from the interferometric image
cubes suggest that the v=0 masers are more extended than their v=1
counterparts
New observations and models of circumstellar CO line emission of AGB stars in the Herschel SUCCESS programme
CONTEXT: Asymptotic giant branch (AGB) stars are in one of the latest
evolutionary stages of low to intermediate-mass stars. Their vigorous mass loss
has a significant effect on the stellar evolution, and is a significant source
of heavy elements and dust grains for the interstellar medium. The mass-loss
rate can be well traced by carbon monoxide (CO) line emission.
AIMS: We present new Herschel HIFI and IRAM 30m telescope CO line data for a
sample of 53 galactic AGB stars. The lines cover a fairly large range of
excitation energy from the line to the line, and even the
line in a few cases. We perform radiative transfer modelling for 38
of these sources to estimate their mass-loss rates.
METHODS: We used a radiative transfer code based on the Monte Carlo method to
model the CO line emission. We assume spherically symmetric circumstellar
envelopes that are formed by a constant mass-loss rate through a smoothly
accelerating wind.
RESULTS: We find models that are consistent across a broad range of CO lines
for most of the stars in our sample, i.e., a large number of the circumstellar
envelopes can be described with a constant mass-loss rate. We also find that an
accelerating wind is required to fit, in particular, the higher-J lines and
that a velocity law will have a significant effect on the model line
intensities. The results cover a wide range of mass-loss rates (
to ) and gas expansion
velocities (2 to km s), and include M-, S-, and C-type AGB stars.
Our results generally agree with those of earlier studies, although we tend to
find slightly lower mass-loss rates by about 40%, on average. We also present
"bonus" lines detected during our CO observations.Comment: 36 page
Herschel/HIFI observations of molecular emission in protoplanetary nebulae and young planetary nebulae
We performed Herschel/HIFI observations of intermediate-excitation molecular
lines in the far-infrared/submillimeter range in a sample of ten protoplanetary
nebulae and young planetary nebulae. The high spectral resolution provided by
HIFI yields accurate measurements of the line profiles. The observation of
these high-energy transitions allows an accurate study of the excitation
conditions, particularly in the warm gas, which cannot be properly studied from
the low-energy lines.
We have detected FIR/sub-mm lines of several molecules, in particular of
12CO, 13CO, and H2O. Emission from other species, like NH3, OH, H2^{18}O, HCN,
SiO, etc, has been also detected. Wide profiles showing sometimes spectacular
line wings have been found. We have mainly studied the excitation properties of
the high-velocity emission, which is known to come from fast bipolar outflows.
From comparison with general theoretical predictions, we find that CRL 618
shows a particularly warm fast wind, with characteristic kinetic temperature Tk
>~ 200 K. In contrast, the fast winds in OH 231.8+4.2 and NGC 6302 are cold, Tk
~ 30 K. Other nebulae, like CRL 2688, show intermediate temperatures, with
characteristic values around 100 K. We also discuss how the complex structure
of the nebulae can affect our estimates, considering two-component models. We
argue that the differences in temperature in the different nebulae can be due
to cooling after the gas acceleration (that is probably due to shocks); for
instance, CRL 618 is a case of very recent acceleration, less than ~ 100 yr
ago, while the fast gas in OH 231.8+4.2 was accelerated ~ 1000 yr ago. We also
find indications that the densest gas tends to be cooler, which may be
explained by the expected increase of the radiative cooling efficiency with the
density.Comment: 24 pages, 31 figure
The wind of W Hya as seen by Herschel. II. The molecular envelope of W Hya
The evolution of low- and intermediate-mass stars on the asymptotic giant
branch (AGB) is mainly controlled by the rate at which these stars lose mass in
a stellar wind. Understanding the driving mechanism and strength of the stellar
winds of AGB stars and the processes enriching their surfaces with products of
nucleosynthesis are paramount to constraining AGB evolution and predicting the
chemical evolution of galaxies. In a previous paper we have constrained the
structure of the outflowing envelope of W Hya using spectral lines of the
CO molecule. Here we broaden this study by modelling an extensive set of
HO and SiO lines observed by the three instruments on board
Herschel using a state-of-the-art molecular excitation and radiative transfer
code. The oxygen isotopic ratios and the SiO abundance profile can be
connected to the initial stellar mass and to crucial aspects of dust formation
at the base of the stellar wind, respectively. The modelling of HO and
SiO confirms the properties of the envelope model of W Hya derived from
CO lines. We find an HO ortho-to-para ratio of
2.5\,, consistent with what is expected for an AGB wind. The
O/O ratio indicates that W Hya has an initial mass of about 1.5
M. Although the ortho- and para-HO lines observed by HIFI appear
to trace gas of slightly different physical properties, a turbulence velocity
of km s fits the HIFI lines of both spin isomers and those
of SiO well. The ortho- and para-HO and SiO abundances
relative to H are , , and , respectively. Assuming a solar
silicon-to-carbon ratio, the SiO line emission model is consistent with
about one-third of the silicon atoms being locked up in dust particles
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