22 research outputs found
The Effect of Teacher-Child Interaction Training (TCIT) on Children who are Exhibiting Disruptive Behaviors within the Classroom Setting
The current study examined the impact of Teacher- Child Interaction Training (TCIT) on child behavior, teacher-student relationships, and teacher satisfaction within a general preschool setting utilizing a three-tiered approach. Participants included three preschool children without clinical diagnoses. A single subject nonconcurrent multiple baseline design was utilized across participants. Results suggest that TCIT is effective in reducing disruptive behaviors within the classroom and successful in improving the teacher-student relationship. TCIT is also considered socially valid based on teacher responses, which indicate that the intervention is acceptable and feasible within the general preschool classroom setting
Astrometric orbits of SB9 stars
Hipparcos Intermediate Astrometric Data (IAD) have been used to derive
astrometric orbital elements for spectroscopic binaries from the newly released
Ninth Catalogue of Spectroscopic Binary Orbits (SB9). Among the 1374 binaries
from SB9 which have an HIP entry, 282 have detectable orbital astrometric
motion (at the 5% significance level). Among those, only 70 have astrometric
orbital elements that are reliably determined (according to specific
statistical tests discussed in the paper), and for the first time for 20
systems, representing a 10% increase relative to the 235 DMSA/O systems already
present in the Hipparcos Double and Multiple Systems Annex.
The detection of the astrometric orbital motion when the Hipparcos IAD are
supplemented by the spectroscopic orbital elements is close to 100% for
binaries with only one visible component, provided that the period is in the 50
- 1000 d range and the parallax is larger than 5 mas. This result is an
interesting testbed to guide the choice of algorithms and statistical tests to
be used in the search for astrometric binaries during the forthcoming ESA Gaia
mission.
Finally, orbital inclinations provided by the present analysis have been used
to derive several astrophysical quantities. For instance, 29 among the 70
systems with reliable astrometric orbital elements involve main sequence stars
for which the companion mass could be derived. Some interesting conclusions may
be drawn from this new set of stellar masses, like the enigmatic nature of the
companion to the Hyades F dwarf HIP 20935. This system has a mass ratio of 0.98
but the companion remains elusive.Comment: Astronomy & Astrophysics, in press (16 pages, 12 figures); also
available at http://www.astro.ulb.ac.be/Html/ps.html#Astrometr
Collisional Velocities and Rates in Resonant Planetesimal Belts
We consider a belt of small bodies around a star, captured in one of the
external or 1:1 mean-motion resonances with a massive perturber. The objects in
the belt collide with each other. Combining methods of celestial mechanics and
statistical physics, we calculate mean collisional velocities and collisional
rates, averaged over the belt. The results are compared to collisional
velocities and rates in a similar, but non-resonant belt, as predicted by the
particle-in-a-box method. It is found that the effect of the resonant lock on
the velocities is rather small, while on the rates more substantial. The
collisional rates between objects in an external resonance are by about a
factor of two higher than those in a similar belt of objects not locked in a
resonance. For Trojans under the same conditions, the collisional rates may be
enhanced by up to an order of magnitude. Our results imply, in particular,
shorter collisional lifetimes of resonant Kuiper belt objects in the solar
system and higher efficiency of dust production by resonant planetesimals in
debris disks around other stars.Comment: 31 pages, 11 figures (some of them heavily compressed to fit into
arxiv-maximum filesize), accepted for publication at "Celestial Mechanics and
Dynamical Astronomy
Spectroscopic binaries among Hipparcos M giants III. The eccentricity-period diagram and mass-transfer signatures
This paper is the third one in a series devoted to studying the properties of
binaries involving M giants. We use a new set of orbits to construct the first
(e-logP) diagram of an extensive sample of M giant binaries, to obtain their
mass-function distribution, and to derive evolutionary constraints for this
class of binaries and related systems. The orbital properties of binaries
involving M giants were analysed and compared with those of related families of
binaries (K giants, post-AGB stars, barium stars, Tc-poor S stars). The orbital
elements of post-AGB stars and M giants are not different, which may very
indicate that, for the considered sample of post-AGB binaries, the post-AGB
star left the AGB at quite an early stage (M4 or so). Neither are the orbital
elements of post-mass-transfer binaries like barium stars very different from
those of M giants, suggesting that the mass transfer did not alter the orbital
elements much, contrary to current belief. Finally, we show that binary systems
with e < 0.4 log P - 1 (with periods expressed in days) are predominantly
post-mass-transfer systems, because (i) the vast majority of barium and S
systems match this condition, and (ii) these systems have companion masses
peaking around 0.6 solar mass, as expected for white dwarfs. The latter
property has been shown to hold as well for open-cluster binaries involving K
giants, for which a lower bound on the companion mass may easily be set.Comment: 14 pages, 12 figures, accepted for publication in A&A, language
editing changes onl
Double-blind test program for astrometric planet detection with Gaia
We use detailed simulations of the Gaia observations of synthetic planetary
systems and develop and utilize independent software codes in double-blind mode
to analyze the data, including statistical tools for planet detection and
different algorithms for single and multiple Keplerian orbit fitting that use
no a priori knowledge of the true orbital parameters of the systems. 1) Planets
with astrometric signatures times the single-measurement error
and period yr can be detected reliably, with a very
small number of false positives. 2) At twice the detection limit, uncertainties
in orbital parameters and masses are typically . 3) Over 70% of
two-planet systems with well-separated periods in the range
yr, , and eccentricity are
correctly identified. 4) Favorable orbital configurations have orbital elements
measured to better than 10% accuracy of the time, and the value of the
mutual inclination angle determined with uncertainties \leq 10^{\degr}. 5)
Finally, uncertainties obtained from the fitting procedures are a good estimate
of the actual errors. Extrapolating from the present-day statistical properties
of the exoplanet sample, the results imply that a Gaia with = 8
as, in its unbiased and complete magnitude-limited census of planetary
systems, will measure several thousand giant planets out to 3-4 AUs from stars
within 200 pc, and will characterize hundreds of multiple-planet systems,
including meaningful coplanarity tests. Finally, we put Gaia into context,
identifying several areas of planetary-system science in which Gaia can be
expected to have a relevant impact, when combined with data coming from other
ongoing and future planet search programs.Comment: 32 pages, 24 figures, 6 tables. Accepted for pubolication in A&
CRIRES-POP: A library of high resolution spectra in the near-infrared
New instrumental capabilities and the wealth of astrophysical information
extractable from the near-infrared wavelength region have led to a growing
interest in the field of high resolution spectroscopy at 1-5 mu. We aim to
provide a library of observed high-resolution and high signal-to-noise-ratio
near-infrared spectra of stars of various types throughout the
Hertzsprung-Russell diagram. This is needed for the exploration of spectral
features in this wavelength range and for comparison of reference targets with
observations and models.
High quality spectra were obtained using the CRIRES near-infrared
spectrograph at ESO's VLT covering the range from 0.97 to 5.3 mu at high
spectral resolution. Accurate wavelength calibration and correction for of
telluric lines were performed by fitting synthetic transmission spectra for the
Earth's atmosphere to each spectrum individually. We describe the observational
strategy and the current status and content of the library which includes 13
objects. The first examples of finally reduced spectra are presented. This
publication will serve as a reference paper to introduce the library to the
community and explore the extensive amount of material.Comment: accepted for publication in A&A; see also the project webpage
http://www.univie.ac.at/crirespo
Angular diameter estimation of interferometric calibrators - Example of lambda Gruis, calibrator for VLTI-AMBER
Context. Accurate long-baseline interferometric measurements require careful
calibration with reference stars. Small calibrators with high angular diameter
accuracy ensure the true visibility uncertainty to be dominated by the
measurement errors. Aims. We review some indirect methods for estimating
angular diameter, using various types of input data. Each diameter estimate,
obtained for the test-case calibrator star lambda Gru, is compared with the
value 2.71 mas found in the Bord\'e calibrator catalogue published in 2002.
Methods. Angular size estimations from spectral type, spectral index, in-band
magnitude, broadband photometry, and spectrophotometry give close estimates of
the angular diameter, with slightly variable uncertainties. Fits on photometry
and spectrophotometry need physical atmosphere models with "plausible" stellar
parameters. Angular diameter uncertainties were estimated by means of residual
bootstrapping confidence intervals. All numerical results and graphical outputs
presented in this paper were obtained using the routines developed under
PV-WAVE, which compose the modular software suite SPIDAST, created to calibrate
and interprete spectroscopic and interferometric measurements, particularly
those obtained with VLTI-AMBER. Results. The final angular diameter estimate
2.70 mas of lambda Gru, with 68% confidence interval 2.65-2.81 mas, is obtained
by fit of the MARCS model on the ISO-SWS 2.38-27.5 mum spectrum, with the
stellar parameters T_eff = 4 250 K, log(g) = 2.0, z = 0.0 dex, M = 1.0 M_sun,
and xi_turb = 2.0 km/s.Comment: to be published in A&A, Main Journal (Astronomical Instrumentation
Tridimensional Dissipative Semi-Numerical Model
Our research combines mean motion resonances and dissipative forces in the averaged elliptic spatial restricted three-body problem. The models presented can be applied in many contexts mixing resonances and dissipations, e.g., asteroid belt, transneptunian region, exoplanets, systems of planetary rings, etc. We propose a semi-numerical model that simulates the behaviour of test particles under the effect of generic forces, functions of powers of the position and/or of the velocity. This model is valid for any orbital eccentricities or inclinations, even at high values. Captures around symmetric and asymmetric equilibria are reproduced and the apparitions of a plateau of inclination for long periods of time are dectected