203 research outputs found
Robotic Telescopes and Networks: New Tools for Education and Science
Nowadays many telescopes around the world are automated and some networks of
robotic telescopes are active or planned as shown by the lists we draw up. Such
equipment could be used for the training of students and for science in the
Universities of Developing Countries and of New Astronomical Countries, by
sending them observational data via Internet or through remotely controlled
telescopes. It seems that it is time to open up for discussion with UN and ESA
organizations and also with IAU, how to implement links between robotic
telescopes and such Universities applying for collaborations. Many scientific
fields could thus be accessible to them, for example on stellar variability,
near-earth object follow-up, gamma-ray burst counterpart tracking, and so on.Comment: 18 pages, review presented at Eight UN/ESA Workshop on Basic Space
Science: Scientific Exploration from Space, held in Mafraq (Jordan), 13-17
March 1999, to be published in Astrophys. and Space Sc. (Kluwer
Carbon Stars in the Hamburg/ESO Survey: Abundances
We have carried out a detailed abundance analysis for a sample of 16 carbon
stars found among candidate extremely metal-poor (EMP) stars from the
Hamburg/ESO Survey. We find that the Fe-metallicities for the cooler C-stars
(Teff ~ 5100K) have been underestimated by a factor of ~10 by the standard HES
survey tools. The results presented here provided crucial supporting data used
by Cohen et al (2006) to derive the frequency of C-stars among EMP stars.
C-enhancement in these EMP C-stars appears to be independent of
Fe-metallicity and approximately constant at ~1/5 the solar C/H. The mostly low
C12/C13 ratios (~4) and the high N abundances in many of these stars suggest
that material which has been through proton burning via the CN cycle comprises
most of the stellar envelope. C-enhancement is associated with strong
enrichment of heavy nuclei beyond the Fe-peak for 12 of the 16 stars. The
remaining C-stars from the HES, which tend to be the most Fe-metal poor, show
no evidence for enhancement of the heavy elements. Very high enhancements of
lead are detected in some of the C-stars with highly enhanced Ba. (We show
that) the s-process is responsible for the enhancement of the heavy elements
for the majority of the C-stars in our sample.
We suggest that both the s-process rich and Ba-normal C-stars result from
phenomena associated with mass transfer in binary systems. This leads directly
to the progression from C-stars to CH stars and then to Ba stars as the
Fe-metallicity increases. (abridged and slightly edited to shorten)Comment: AJ, in press, submitted 13 Dec, 2005, accepted 21 March 200
A photometricity and extinction monitor at the Apache Point Observatory
An unsupervised software ``robot'' that automatically and robustly reduces
and analyzes CCD observations of photometric standard stars is described. The
robot measures extinction coefficients and other photometric parameters in real
time and, more carefully, on the next day. It also reduces and analyzes data
from an all-sky camera to detect clouds; photometric data taken
during cloudy periods are automatically rejected. The robot reports its
findings back to observers and data analysts via the World-Wide Web. It can be
used to assess photometricity, and to build data on site conditions. The
robot's automated and uniform site monitoring represents a minimum standard for
any observing site with queue scheduling, a public data archive, or likely
participation in any future National Virtual Observatory.Comment: accepted for publication in A
Occurrence of hashimoto thyroiditis among the first- and second-degree relatives of systemic lupus erythematosus patients with Hashimoto thyroiditis
Occurrence of Hashimoto thyroiditis among the first- and second-degree relatives of systemic lupus erythematosus patients with Hashimoto thyroiditis
EPICA Dome C electronic control system
AbstractA new deep drill has been developed within the framework of the European Programme for Ice Coring in Antarctica (EPICA). Several versions of the EPICA drill exist. The version used at Dome Concordia (75Ë06'1" S, 123Ë23'71" E) was operated with a new electronic control system developed by the Ente per le Nuove tecnologie, l'Energia e l'Ambiente (ENEA) Research Center in Brasimone, Italy. This electronic control system was used for the first time during the 1997/98 Antarctic summer season
Spectroscopic Study of IRAS 19285+0517(PDS 100): A Rapidly Rotating Li-Rich K Giant
We report on photometry and high-resolution spectroscopy for IRAS 19285+0517.
The spectral energy distribution based on visible and near-IR photometry and
far-IR fluxes shows that the star is surrounded by dust at a temperature of
250 K. Spectral line analysis shows that the star is a K
giant with a projected rotational velocity = 9 2 km s.
We determined the atmospheric parameters: = 4500 K, log =
2.5, = 1.5 km s, and [Fe/H] = 0.14 dex. The LTE abundance
analysis shows that the star is Li-rich (log (Li) = 2.50.15),
but with essentially normal C, N, and O, and metal abundances. Spectral
synthesis of molecular CN lines yields the carbon isotopic ratio
C/C = 9 3, a signature of post-main sequence evolution and
dredge-up on the RGB. Analysis of the Li resonance line at 6707 \AA for
different ratios Li/Li shows that the Li profile can be fitted best
with a predicted profile for pure Li. Far-IR excess, large Li abundance,
and rapid rotation suggest that a planet has been swallowed or, perhaps, that
an instability in the RGB outer layers triggered a sudden enrichment of Li and
caused mass-loss.Comment: To appear in AJ; 40 pages, 9 figure
Spectropolarimetry of R Coronae Borealis in 1998--2003: Discovery of Transient Polarization at Maximum Brightness
We present an extended optical spectropolarimetry of R CrB from 1998 January
to 2003 September. The polarization was almost constant in the phase of maximum
brightness, being consistent with past observations. We detected, however,
temporal changes of polarization ( %) in 2001 March and August, which
were the first detection of large polarization variability in R CrB near
maximum brightness. The amplitude and the position angle of the `transient
polarization' were almost constant with wavelength in both two events. There
was a difference by about 20 degrees in the position angle between the two
events. Each event could be explained by light scattering due to short-lived
dust puff occasionally ejected off the line of sight. The flatness of the
polarization against the wavelength suggests that the scatterer is a mixture of
dust grains having various sizes. The rapid growth and fading of the transient
polarization favors the phenomenological model of dust formation near the
stellar photosphere (e.g., within two stellar radii) proposed for the time
evolution of brightness and chromospheric emission lines during deeply
declining periods, although the fading timescale can hardly be explained by a
simple dispersal of expanding dust puff with a velocity of km s
. Higher expansion velocity or some mechanism to destroy the dust grains
should be needed.Comment: 22 pages, 10 figures, accepted for publication in A
Winds in R Coronae Borealis Stars
We present new spectroscopic observations of the He I 10830 line in
R Coronae Borealis (RCB) stars which provide the first strong evidence that
most, if not all, RCB stars have winds. It has long been suggested that when
dust forms around an RCB star, radiation pressure accelerates the dust away
from the star, dragging the gas along with it. The new spectra show that nine
of the ten stars observed have P-Cygni or asymmetric blue-shifted profiles in
the He I 10830 line. In all cases, the He I line indicates a mass
outflow - with a range of intensity and velocity. Around the RCB stars, it is
likely that this state is populated by collisional excitation rather than
photoionization/recombination. The line profiles have been modeled with an SEI
code to derive the optical depth and the velocity field of the helium gas. The
results show that the typical RCB wind has a steep acceleration with a terminal
velocity of \Vinf = 200-350 \kms and a column density of N
cm in the He I 10830 line. There is a possible relationship
between the lightcurve of an RCB star and its He I 10830 profile.
Stars which have gone hundreds of days with no dust-formation episodes tend to
have weaker He I features. The unusual RCB star, V854 Cen, does not follow this
trend, showing little or no He I absorption despite high mass-loss activity.
The He I 10830 line in R CrB itself, which has been observed at four
epochs between 1978 and 2001, seems to show a P-Cygni or asymmetric
blue-shifted profile at all times whether it is in decline or at maximum light.Comment: 14 pages, 4 figures, ApJ in pres
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