89 research outputs found
A theoretical approach for the interpretation of pulsating PMS intermediate-mass stars
The investigation of the pulsation properties of pre-main-sequence
intermediate-mass stars is a promising tool to evaluate the intrinsic
properties of these stars and to constrain current evolutionary models. Many
new candidates of this class have been discovered during the last decade and
very accurate data are expected from space observations obtained for example
with the CoRoT satellite. In this context we aim at developing a theoretical
approach for the interpretation of observed frequencies, both from the already
available ground-based observations and from the future more accurate and
extensive CoRoT results. To this purpose we have started a project devoted to
the computations of fine and extensive grids of asteroseismic models of
intermediate mass pre-main-sequence stars. The obtained frequencies are used to
derive an analytical relation between the large frequency separation and the
stellar luminosity and effective temperature and to develop a tool to compare
theory and observations in the echelle diagram. The predictive capabilities of
the proposed method are verified through the application to two test stars. As
a second step, we apply the procedure to two true observations from multisite
campaigns and we are able to constrain their stellar parameters, in particular
the mass, in spite of the small number of frequencies. We expect that with a
significantly higher number of frequencies both the stellar mass and age could
be constrained and, at the same time, the physics of the models could be
tested.Comment: Accepted for publication on A&
Microscopic Diffusion in Stellar Evolution Codes: First Comparison results of ESTA-Task~3
We present recent work undertaken by the Evolution and Seismic Tools Activity
(ESTA) team of the CoRoT Seismology Working Group. The new ESTA-Task 3 aims at
testing, comparing and optimising stellar evolution codes which include
microscopic diffusion of the chemical elements resulting from pressure,
temperature and concentration gradients. The results already obtained are
globally satisfactory, but some differences between the different numerical
tools appear that require further investigations.Comment: to appear in "Stellar Evolution and Seismic Tools for
Asteroseismology", (Eds) C. W. Straka, Y. Lebreton and M. J. P. F. G.
Monteiro, EAS Publications Series, 200
Multisite photometry of the pulsating Herbig Ae star V346 Ori
CONTEXT: The study of pulsation in Pre--Main--Sequence intermediate-mass
stars represents an important tool for deriving information on fundamental
stellar parameters and internal structure, as well as for testing current
theoretical models. Interest in this class of variable stars has significantly
increased during the last decade and about 30 members are presently known in
the literature. AIMS: We have constructed the frequency spectrum of the
oscillations in V346 Ori. We apply asteroseismic tools to these data to
estimate the intrinsic parameters (mass, luminosity, effective temperature) of
V346 Ori and to obtain information on its internal structure. METHODS: CCD time
series photometry in the Johnson V filter has been obtained for a total of
145.7 h of observations distributed over 36 nights. The resulting light curves
have been subjected to a detailed frequency analysis using updated numerical
techniques. Photometric and spectroscopic data have also been acquired to
determine reliable estimates of the stellar properties. RESULTS: We have
identified 13 oscillation frequencies, 6 of which with higher significance.
These have been compared with the predictions of non-radial adiabatic models.
The resulting best fit model has a mass of 2.10.2 , luminosity
, and effective temperature
7300200 K. These values are marginally consistent with the association of
V346 Ori to Orion OB1a. Alternatively, V346 Ori could be placed at a slightly
larger distance than previously estimated.Comment: Accepted for publication on A&A. 14 Pages, 11 Figure
Design and validation of the Health Professionals' Attitudes Toward the Homeless Inventory (HPATHI)
BACKGROUND: Recent literature has called for humanistic care of patients and for medical schools to begin incorporating humanism into medical education. To assess the attitudes of health-care professionals toward homeless patients and to demonstrate how those attitudes might impact optimal care, we developed and validated a new survey instrument, the Health Professional Attitudes Toward the Homeless Inventory (HPATHI). An instrument that measures providers' attitudes toward the homeless could offer meaningful information for the design and implementation of educational activities that foster more compassionate homeless health care. Our intention was to describe the process of designing and validating the new instrument and to discuss the usefulness of the instrument for assessing the impact of educational experiences that involve working directly with the homeless on the attitudes, interest, and confidence of medical students and other health-care professionals. METHODS: The study consisted of three phases: identifying items for the instrument; pilot testing the initial instrument with a group of 72 third-year medical students; and modifying and administering the instrument in its revised form to 160 health-care professionals and third-year medical students. The instrument was analyzed for reliability and validity throughout the process. RESULTS: A 19-item version of the HPATHI had good internal consistency with a Cronbach's alpha of 0.88 and a test-retest reliability coefficient of 0.69. The HPATHI showed good concurrent validity, and respondents with more than one year of experience with homeless patients scored significantly higher than did those with less experience. Factor analysis yielded three subscales: Personal Advocacy, Social Advocacy, and Cynicism. CONCLUSIONS: The HPATHI demonstrated strong reliability for the total scale and satisfactory test-retest reliability. Extreme group comparisons suggested that experience with the homeless rather than medical training itself could affect health-care professionals' attitudes toward the homeless. This could have implications for the evaluation of medical school curricula
Report on the CoRoT Evolution and Seismic Tools Activity
We present the work undertaken by the Evolution and Seismic Tools Activity
(ESTA) team of the CoRoT Seismology Working Group. We have focused on two main
tasks: Task 1 - now finished - has aimed at testing, comparing and optimising
seven stellar evolution codes which will be used to model the internal
structure and evolution of the CoRoT target stars. Task 2, still underway, aims
at testing, comparing and optimising different seismic codes used to calculate
the oscillations of models for different types of stars. The results already
obtained are quite satisfactory, showing minor differences between the
different numerical tools provided the same assumptions on the physical
parameters are made. This work gives us confidence on the numerical tools that
will be available to interpret the future CoRoT seismic data.Comment: To appear in: "The CoRoT Book", (Eds) F. Favata, A. Baglin & J.
Lochard, ESA Publications Division, ESA S
Atmospheric parameters and pulsational properties for a sample of \,Sct, \,Dor, and hybrid {\it Kepler} targets
We report spectroscopic observations for 19 \,Sct candidates observed
by the {\it Kepler} satellite both in long and short cadence mode. For all
these stars, by using spectral synthesis, we derive the effective temperature,
the surface gravity and the projected rotational velocity. An equivalent
spectral type classification has been also performed for all stars in the
sample. These determinations are fundamental for modelling the frequency
spectra that will be extracted from the {\it Kepler} data for asteroseismic
inference. For all the 19 stars, we present also periodograms obtained from
{\it Kepler} data. We find that all stars show peaks in both low-
(\,Dor; g mode) and high-frequency (\,Sct; p mode) regions.
Using the amplitudes and considering 5\,c/d as a boundary frequency, we
classified 3 stars as pure \,Dor, 4 as \,Dor\,-\,\
hybrid, Sct, 5 as \,Sct\,-\,\,Dor hybrid, and 6 as pure
\,Sct. The only exception is the star KIC\,05296877 which we suggest
could be a binary.Comment: 11 pages, 6 figures, MNRAS main journa
ELT high resolution spectrograph: phase-A software architecture study
High resolution spectroscopy has been considered of a primary importance to exploit the main scientific cases foreseen for ESO ELT, the Extremely Large Telescope, the future largest optical-infrared telescope in the world. In this context ESO commissioned a Phase-A feasibility study for the construction of a high resolution spectrograph for the ELT, tentatively named HIRES. The study, which lasted 1.5 years, started on March 2016 and was completed with a review phase held at Garching ESO headquarters with the aim to assess the scientific and technical feasibility of the proposed instrument. One of the main tasks of the study is the architectural design of the software covering all the aspects relevant to control an astronomical instrument: from observation preparation through instrument hardware and detectors control till data reduction and analysis. In this paper we present the outcome of the Phase-A study for the proposed HIRES software design highlighting its peculiarities, critical areas and performance aspects for the whole data flow. The End-toEnd simulator, a tool already capable of simulating HIRES end products and currently being used to drive some design decision, is also shortly described
The Gaia-ESO Public Spectroscopic Survey: Motivation, implementation, GIRAFFE data processing, analysis, and final data products
The Gaia-ESO Public Spectroscopic Survey is an ambitious project designed to
obtain astrophysical parameters and elemental abundances for 100,000 stars,
including large representative samples of the stellar populations in the
Galaxy, and a well-defined sample of 60 (plus 20 archive) open clusters. We
provide internally consistent results calibrated on benchmark stars and star
clusters, extending across a very wide range of abundances and ages. This
provides a legacy data set of intrinsic value, and equally a large wide-ranging
dataset that is of value for homogenisation of other and future stellar surveys
and Gaia's astrophysical parameters. This article provides an overview of the
survey methodology, the scientific aims, and the implementation, including a
description of the data processing for the GIRAFFE spectra. A companion paper
(arXiv:2206.02901) introduces the survey results. Gaia-ESO aspires to quantify
both random and systematic contributions to measurement uncertainties. Thus all
available spectroscopic analysis techniques are utilised, each spectrum being
analysed by up to several different analysis pipelines, with considerable
effort being made to homogenise and calibrate the resulting parameters. We
describe here the sequence of activities up to delivery of processed data
products to the ESO Science Archive Facility for open use. The Gaia-ESO Survey
obtained 202,000 spectra of 115,000 stars using 340 allocated VLT nights
between December 2011 and January 2018 from GIRAFFE and UVES. The full
consistently reduced final data set of spectra was released through the ESO
Science Archive Facility in late 2020, with the full astrophysical parameters
sets following in 2022
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