57 research outputs found
Magnetic Fields in Evolved Stars: Imaging the Polarized Emission of High-Frequency SiO Masers
We present Submillimeter Array observations of high frequency SiO masers
around the supergiant VX Sgr and the semi-regular variable star W Hya. The
J=5-4, v=1 28SiO and v=0 29SiO masers of VX Sgr are shown to be highly linearly
polarized with a polarization from ~5-60%. Assuming the continuum emission
peaks at the stellar position, the masers are found within ~60 mas of the star,
corresponding to ~100 AU at a distance of 1.57 kpc. The linear polarization
vectors are consistent with a large scale magnetic field, with position and
inclination angles similar to that of the dipole magnetic field inferred in the
H2O and OH maser regions at much larger distances from the star. We thus show
for the first time that the magnetic field structure in a circumstellar
envelope can remain stable from a few stellar radii out to ~1400 AU. This
provides further evidence supporting the existence of large scale and
dynamically important magnetic fields around evolved stars. Due to a lack of
parallactic angle coverage, the linear polarization of masers around W Hya
could not be determined. For both stars we observed the 28SiO and 29SiO
isotopologues and find that they have a markedly different distribution and
that they appear to avoid each other. Additionally, emission from the SO
5_5-4_4 line was imaged for both sources. Around W Hya we find a clear offset
between the red- and blue-shifted SO emission. This indicates that W Hya is
likely host to a slow bipolar outflow or a rotating disk-like structure.Comment: 8 pages, 7 figures, accepted for publication in ApJ. Online table
will be available with published versio
Correlation between Infrared Colors and Intensity Ratios of SiO Maser Lines
We present the results of SiO millimeter-line observations of a sample of
known SiO maser sources covering a wide dust-temperature range. A cold part of
the sample was selected from the SiO maser sources found in our recent SiO
maser survey of cold dusty objects. The aim of the present research is to
investigate the causes of the correlation between infrared colors and SiO maser
intensity ratios among different transition lines. In particular, the
correlation between infrared colors and SiO maser intensity ratio among the
J=1-0 v=1, 2, and 3 lines are mainly concerned in this paper. We observed in
total 75 SiO maser sources with the Nobeyama 45m telescope quasi-simultaneously
in the SiO J=1-0 v=0, 1, 2, 3, 4 and J=2-1 v=1, 2 lines. We also observed the
sample in the 29SiO J=1-0 v=0 and J=2-1 v=0, and 30SiO J=1-0 v=0 lines, and the
H2O 6(1,6)-5(2,3) line. As reported in previous papers, we confirmed that the
intensity ratios of the SiO J=1-0 v=2 to v=1 lines clearly correlate with
infrared colors. In addition, we found possible correlation between infrared
colors and the intensity ratios of the SiO J=1-0 v=3 to v=1&2 lines. Two
overlap lines of H2O (i.e., 11(6,6) nu_2=1 -> 12(7,5) nu_2=0 and 5(0,5) nu_2=2
-> 6(3,4) nu_2=1) might explain these correlation if these overlap lines become
stronger with increase of infrared colors, although the phenomena also might be
explained by more fundamental ways if we take into account the variation of
opacity from object to object.Comment: 49 pages, 7 figures, 3 tables, accepted for publication in ApJ. Full
resolution version available at
http://www.asiaa.sinica.edu.tw/~junichi/paper
VLBI Observations of SiO Masers around AH Scorpii
We report the first Very Long Baseline Array (VLBA) observations of 43 GHz
v=1, J=1-0 SiO masers in the circumstellar envelope of the M-type semi-regular
supergiant variable star AH Sco at 2 epochs separated by 12 days in March 2004.
These high-resolution VLBA images reveal that the distribution of SiO masers is
roughly on a persistent elliptical ring with the lengths of the major and minor
axes of about 18.5 and 15.8 mas, respectively, along a position angle of
150^{\circ}. And the red-shifted masers are found to be slightly closer to the
central star than the blue-shifted masers. The line-of-sight velocity structure
of the SiO masers shows that with respect to the systemic velocity of -6.8 km/s
the higher velocity features are closer to the star, which can be well
explained by the simple outflow or infall without rotation kinematics of SiO
masers around AH Sco. Study of proper motions of 59 matched features between
two epochs clearly indicates that the SiO maser shell around AH Sco was
undergoing an overall contraction to the star at a velocity of ~13 km/s at a
distance of 2.26 kpc to AH Sco. Our 3-dimensional maser kinematics model
further suggests that such an inward motion is very likely due to the
gravitation of the central star. The distance to AH Sco of 2.260.19 kpc
obtained from the 3-dimensional kinematics model fitting is consistent with its
kinematic distance of 2.0 kpc.Comment: 23 pages, 4 figures, 4 tables, accepted for publication in Ap
The Very Slow Wind From the Pulsating Semiregular Red Giant L2 Pup
We have obtained 11.7 and 17.9 micron images at the Keck I telescope of the
circumstellar dust emission from L2 Pup, one of the nearest (D = 61 pc)
mass-losing, pulsating, red giants that has a substantial infrared excess. We
propose that the wind may be driven by the stellar pulsations with radiation
pressure on dust being relatively unimportant, as described in some recent
calculations. L2 Pup may serve as the prototype of this phase of stellar
evolution where it could lose about 15% of its initial main sequence mass.Comment: ApJ, in pres
Physical Activity Patterns of the Spanish Population Are Mostly Determined by Sex and Age: Findings in the ANIBES Study
Background
Representative data for the Spanish population regarding physical activity (PA) behaviors
are scarce and seldom comparable due to methodological inconsistencies.
Aim
Our objectives were to describe the PA behavior by means of the standardized self-reported
International Physical Activity Questionnaire (IPAQ) and to know the proportion of the Spanish
population meeting and not meeting international PA recommendations.
Material and Methods
PA was assessed using the IPAQ in a representative sample of 2285 individuals (males,
50.4%) aged 9â75 years and living in municipalities of at least 2,000 inhabitants. Data were
analyzed according to: age groups 9â12, 13â17, 18â64, and 65â75 years; sex; geographical
distribution; locality size and educational levels.
Results
Mean total PA was 868.8±660.9 min/wk, mean vigorous PA 146.4±254.1 min/wk, and mean
moderate PA 398.1±408.0 min/wk, showing significant differences between sexes
(p<0.05). Children performed higher moderate-vigorous PA than adolescents and seniors
(p<0.05), and adults than adolescents and seniors (p<0.05). Compared to recommendations,
36.2%of adults performed <150 min/week of moderate PA, 65.4% <75 min/week of vigorous PA and 27.0%did not perform any PA at all, presenting significant differences
between sexes (p<0.05). A total of 55.4%of children and adolescents performed less than
420 min/week of MVPA, being higher in the later (62.6%) than in the former (48.4%). Highest
non-compliance was observed in adolescent females (86.5%).
Conclusion
Sex and age are the main influencing factors on PA in the Spanish population. Males
engage in more vigorous and light PA overall, whereas females perform more moderate
PA. PA behavior differs between age groups and no clear lineal increase with age could be
observed. Twenty-seven percent of adults and 55.4% of children and adolescents do not
meet international PA recommendations. Identified target groups should be addressed to
increase PA in the Spanish populationCoca-Cola Iberia through Spanish Nutrition Foundation (FEN)Coca-Cola Iberi
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Hydrocarbon spills in continental waters: a new regulatory approach in light of MexicoÂŽs energy reform
By comparing the current regulatory requirements with the hypothetical scenario of the enactment of an environmental quality standard (EQS) for hydrocarbon contamination in continental waters, the research assesses, using expert interviews, which scenario most benefits Mexico. The research also assesses the criteria to be considered when designing such EQS, and the institutional challenges to face when trying to enforce such EQS. Furthermore, the research briefly explores different public policy approaches to regulation of water quality, and future research topics.The research assesses if Mexico will benefit from the enactment of an environmental quality standard (EQS) for water contaminated with hydrocarbons, in light of Mexicoâs energy reform. In addition, the research assesses the institutional challenges faced when trying to enforce such EQS, and the design elements for any such standard. The research compares the current regulatory framework for water contaminated with hydrocarbons in Mexico, which requires the preparation of an environmental risk assessment (ERA) for each case, with the enactment of two hypothetical EQS. The comparison is conducted using a multi-criteria analysis and information is gathered via expert interviews. Results indicate that Mexico will benefit from the enactment of an EQS, however several institutional challenges need to be solved to ensure effective enforcement.CONACYT-SECRETARĂA DE ENERGĂA-HIDROCARBUROS 2017 SĂPTIMO PERIOD
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