42,243 research outputs found
On the rotation periods of the components of the triple system TYC9300-0891-1AB/TYC9300-0529-1 in the Octans Association
Stellar rotation depends on different parameters. The range of values of
these parameters causes the dispersion in the rotation period distributions
observed in young stellar clusters/associations. We focus our investigation on
the effects of different circumstellar environments on stellar rotation. More
specifically, we are searching in stellar Associations for visual triple
systems where all stellar parameters are similar, with the only exceptions of
the unknown initial rotation period, and of the circum-stellar environment, in
the sense that one of the two about equal-mass components has a close-by third
'perturber' component. In the present study we analyse the 35-Myr old visual
triple system TYC 9300-0891-1AB + TYC 9300-0529-1 in the young Octans stellar
association consisting of three equal-mass K0V components. We collected from
the literature all information that allowed us to infer that the three
components are actually physically bound forming a triple system and are
members of the Octans Association. We collected broad-band photometric
timeseries in two observation seasons. We discovered that all the components
are variable, magnetically active, and from periodogram analysis we found the
unresolved components TYC 9300-0891-1AB to have a rotation period P = 1.383d
and TYC 9300-0529-1 a rotation period P = 1.634d. TYC 9300-0891-1A, TYC
9300-0891-1B, and TYC 9300-0529-1 have same masses, ages, and initial chemical
compositions. The relatively small 16% rotation period difference measured by
us indicates that all components had similar initial rotation periods and disc
lifetimes, and the separation of 157AU between the component A and the
'perturber' component B (or vice-versa) has been sufficiently large to prevent
any significant perturbation/shortening of the accretion-disc lifetime.Comment: Accepted by New Astronomy 201
Documentation of baseline and policy scenarios for Test Case 1
Environmental Economics and Policy,
Montana Kaimin, April 12, 1990
Student newspaper of the University of Montana, Missoula.https://scholarworks.umt.edu/studentnewspaper/9300/thumbnail.jp
Rep. Harvey Moss, Debbie Kemp, Lisha Hopper, Meghan Kemp, and Haley Kemp
Rep. Harvey Moss with Debbi Kemp, Lisha Hopper, Meghan Kemp, and Haley Kemphttps://scholarsjunction.msstate.edu/ua-photo-collection/9300/thumbnail.jp
The BG News October 13, 2010
The BGSU campus student newspaper October 13, 2010. Volume 101 - Issue 36https://scholarworks.bgsu.edu/bg-news/9300/thumbnail.jp
Re-enactment of the Education (Teachers' Qualification and Health Standards)(Education)Regulations 1999
A high resolution, multi-epoch spectral atlas of peculiar stars including RAVE, GAIA and HERMES wavelength ranges
We present an Echelle+CCD, high S/N, high resolution (R = 20\,000)
spectroscopic atlas of 108 well-known objects representative of the most common
types of peculiar and variable stars. The wavelength interval extends from 4600
to 9400 Ang, and includes the RAVE, Gaia and HERMES wavelength ranges.
Multi-epoch spectra are provided for the majority of observed stars. A total of
425 spectra of peculiar stars are presented, which have been collected during
56 observing nights between November 1998 and August 2002. The spectra are
given in FITS format and heliocentric wavelengths, with accurate subtraction of
both the sky background and the scattered light. Auxiliary material useful for
custom applications (telluric dividers, spectro-photometric stars, flat-field
tracings) is also provided. The atlas aims to provide a homogeneous database of
the spectral appearance of stellar peculiarities, a tool useful both for
classification purposes and inter-comparison studies. It could also serve the
planning for and training of automated classification algorithms designed for
RAVE, Gaia, HERMES and other large scale spectral surveys. The spectrum of XX
Oph is discussed in some detail as an example of the content of the present
atlas.Comment: AJ in press (issue 140:6 December 2010
Abundance and stratification analysis of the CP star HD 103498
Slow rotation and absence of strong mixing processes in atmospheres of
chemically peculiar stars develop ideal conditions for the appearance of
abundance anomalies through the mechanism of microscopic particle diffusion.
This makes these objects look spectroscopically and photometrically different
from their "normal" analogs. As a result, it is often difficult to accurately
determine atmospheric parameters of these stars and special methods are needed
for the consistent analysis of their atmospheres. The main aim of the present
paper is to analyse atmospheric abundance and stratification of chemical
elements in the atmosphere of the chemically peculiar star HD 103498. We find
that two model atmospheres computed with individual and stratified abundances
provide reasonable fit to observed spectroscopic and photometric indicators:
Teff=9300 K, logg=3.5 and Teff=9500K, logg=3.6. It is shown that Mg has a large
abundance gradient in the star's atmosphere with accumulation of Mg ions in the
uppermost atmospheric layers, whereas Si demonstrates opposite behaviour with
accumulation in deep layers. In addition, a detailed non-LTE analysis showed
that none of Mg transitions under consideration is a subject of noticeable
non-LTE effects. Comparing observed photometry transformed to physical units we
estimated the radius of HD 103498 to be between R=(4.56 +/- 0.77)Rsun for
Teff=9300K, logg=3.5 and R=(4.39 +/- 0.75)Rsun for Teff=9500K, logg=3.6 models
respectively. We note that the lack of suitable observations in absolute units
prevents us to uniquely determine the Teff of the star at the current stage of
analysis.Comment: 9 pages, 7 figures and 3 tables, accepted for publication in MNRA
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