2,582 research outputs found
Properties of iterative Monte Carlo single histogram reweighting
We present iterative Monte Carlo algorithm for which the temperature variable
is attracted by a critical point. The algorithm combines techniques of single
histogram reweighting and linear filtering. The 2d Ising model of ferromagnet
is studied numerically as an illustration. In that case, the iterations
uncovered stationary regime with invariant probability distribution function of
temperature which is peaked nearly the pseudocritical temperature of specific
heat. The sequence of generated temperatures is analyzed in terms of stochastic
autoregressive model. The error of histogram reweighting can be better
understood within the suggested model. The presented model yields a simple
relation, connecting variance of pseudocritical temperature and parameter of
linear filtering.Comment: 3 figure
The ALMA Early Science View of FUor/EXor objects. III. The Slow and Wide Outflow of V883 Ori
We present Atacama Large Millimeter/ sub-millimeter Array (ALMA) observations
of V883 Ori, an FU Ori object. We describe the molecular outflow and envelope
of the system based on the CO and CO emissions, which together
trace a bipolar molecular outflow. The CO emission traces the rotational
motion of the circumstellar disk. From the CO blue-shifted emission, we
estimate a wide opening angle of 150 for the outflow
cavities. Also, we find that the outflow is very slow (characteristic velocity
of only 0.65 km~s), which is unique for an FU Ori object. We calculate
the kinematic properties of the outflow in the standard manner using the
CO and CO emissions. In addition, we present a P Cygni profile
observed in the high-resolution optical spectrum, evidence of a wind driven by
the accretion and being the cause for the particular morphology of the
outflows. We discuss the implications of our findings and the rise of these
slow outflows during and/or after the formation of a rotationally supported
disk.Comment: 12 pages, 7 figures, 2 tables. Accepte
A pulsational distance to Omega Centauri based on Near-Infrared Period-Luminosity relations of RR Lyrae stars
We present new Near-Infrared (J,K) magnitudes for 114 RR Lyrae stars in the
globular cluster Omega Cen (NGC 5139) which we combine with data from the
literature to construct a sample of 180 RR Lyrae stars with J and K mean
magnitudes on a common photometric system. This is presently the largest such
sample in any stellar system. We also present updated predictions for J,K-band
Period-Luminosity relations for both fundamental and first-overtone RR Lyrae
stars, based on synthetic horizontal branch models with metal abundance ranging
from Z=0.0001 to Z=0.004. By adopting for the Omega Cen variables with measured
metal abundances an alpha-element enhancement of a factor of 3 (about 0.5 dex)
with respect to iron we find a true distance modulus of 13.70 (with a random
error of 0.06 and a systematic error of 0.06), corresponding to a distance
d=5.5 Kpc (with both random and systematic errors equal to 0.03 Kpc). Our
estimate is in excellent agreement with the distance inferred for the eclipsing
binary OGLEGC-17, but differ significantly from the recent distance estimates
based on cluster dynamics and on high amplitude Delta Scuti stars.Comment: 24 pages, 7 figures, accepted for publication on The Astrophysical
Journa
The ALMA Early Science View of FUor/EXor Objects - V. Continuum Disc Masses and Sizes
Low-mass stars build a significant fraction of their total mass during short outbursts of enhanced accretion known as FUor and EXor outbursts. FUor objects are characterized by a sudden brightening of âŒ5 mag at visible wavelengths within 1 yr and remain bright for decades. EXor objects have lower amplitude outbursts on shorter time-scales. Here we discuss a 1.3 mm Atacama Large Millimeter/submillimeter Array (ALMA) mini-survey of eight outbursting sources (three FUors, four EXors, and the borderline object V1647 Ori) in the Orion Molecular Cloud. While previous papers in this series discuss the remarkable molecular outflows observed in the three FUor objects and V1647 Ori, here we focus on the continuum data and the differences and similarities between the FUor and EXor populations. We find that FUor discs are significantly more massive (âŒ80â600 MJup) than the EXor objects (âŒ0.5â40 MJup). We also report that the EXor sources lack the prominent outflows seen in the FUor population. Even though our sample is small, the large differences in disc masses and outflow activity suggest that the two types of objects represent different evolutionary stages. The FUor sources seem to be rather compact (Rc \u3c 20â40 au) and to have a smaller characteristic radius for a given disc mass when compared to T Tauri stars. V1118 Ori, the only known close binary system in our sample, is shown to host a disc around each one of the stellar components. The disc around HBC 494 is asymmetric, hinting at a structure in the outer disc or the presence of a second disc
What children know about the source of their knowledge without reporting it as the source
We argue that, amongst 3- to 5- year-olds, failure to report the source of knowledge recently acquired in answer to âHow do you knowâŠ?â is due to a specific failure to make a causal inference, in line with source monitoring theory but not fuzzy trace theory. In three Experiments, children (N = 37; 30; 59) identified a hidden toy by seeing, feeling, or by being told, having had two modes of access on each trial, one informative (e.g. seeing a toy identified by colour) and the other uninformative (e.g. being told the toyâs colour by the Experimenter who had only felt it). Children who answered the know question wrongly nevertheless reported accurately who saw and who felt the toy, and what the well-informed player had said. They also realised when
the Experimenterâs uninformative access implied their own knowledge was unreliable, suggesting precocious working understanding of knowledge sources
the combination of a smoking cessation programme with rehabilitation increases stop smoking rate
Objective and study design: A parallel group study to investigate the effectiveness of a smoking cessation programme performed during routine rehabilitation practice for outpatients. Patients and methods: The study participants comprised an intervention group of 102 consecutive smokers who underwent a smoking cessation programme in a rehabilitation centre and a control group of 101 consecutive smokers who were referred to a smoking cessation centre in a pulmonary hospital. All participants underwent physical examination, pulmonary function tests and received identical behavioural and/or pharmacological treatment. In addition, the intervention group underwent rehabilitation practice 3 times a week for 3 months. Results: The continuous abstinence rate at 12 months, which was validated by an expired air carbon monoxide concentration of 10 parts per million or less and a household interview, was 68% in the intervention group and 32% in the control group. Multivariable analysis showed that rehabilitation was significantly associated with smoking cessation after ad justing for years of smoking, number of cigarettes smoked, gender and treatment (odds ratio = 4.34, p < 0.001). Conclusion: This study suggests that smoking cessation programmes during routine rehabilitation may be highly effective in helping smoking withdrawal and should be a strongly recommended component of rehabilitation practice
A Chemical Map of the Outbursting V883 Ori system: Vertical and Radial Structures
We present the first results of a pilot program to conduct an Atacama Large
Millimeter/submillimeter Array (ALMA) Band 6 (211-275 GHz) spectral line study
of young stellar objects (YSO) that are undergoing rapid accretion episodes,
i.e. FU Ori objects (FUors). Here, we report on molecular emission line
observations of the FUor system, V883 Ori. In order to image the FUor object
with full coverage from ~0.5 arcsec to the map size of ~30 arcsec, i.e. from
disc to outflow scales, we combine the ALMA main array (the 12-m array) with
the Atacama Compact Array (7-m array) and the total power (TP) array. We detect
HCN, HCO, CHOH, SO, DCN, and HCO emissions with most of these
lines displaying complex kinematics. From PV diagrams, the detected molecules
HCN, HCO, CHOH, DCN, SO, and HCO probe a Keplerian rotating
disc in a direction perpendicular to the large-scale outflow detected
previously with the CO and CO lines. Additionally, HCN and
HCO reveal kinematic signatures of infall motion. The north outflow is
seen in HCO, HCO, and SO emissions. Interestingly, HCO
emission reveals a pronounced inner depression or "hole" with a size comparable
to the radial extension estimated for the CHOH and 230 GHz continuum. The
inner depression in the integrated HCO intensity distribution of V883 Ori
is most likely the result of optical depth effects, wherein the optically thick
nature of the HCO and continuum emission towards the innermost parts of
V883 Ori can result in a continuum subtraction artifact in the final HCO
flux level
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