398 research outputs found
II.5 Where to find the CoRoT data?
This book is dedicated to all the people interested in the CoRoT mission and the beautiful data that were delivered during its six year duration. Either amateurs, professional, young or senior researchers, they will find treasures not only at the time of this publication but also in the future twenty or thirty years. It presents the data in their final version, explains how they have been obtained, how to handle them, describes the tools necessary to understand them, and where to find them. It also highlights the most striking first results obtained up to now. CoRoT has opened several unexpected directions of research and certainly new ones still to be discovered
Estimating Be Star Disk Radii using H-alpha Emission Equivalent Widths
We present numerical models of the circumstellar disks of Be stars, and we
describe the resulting synthetic H-alpha emission lines and maps of the
wavelength-integrated emission flux projected onto the sky. We demonstrate that
there are monotonic relationships between the emission line equivalent width
and the ratio of the angular half-width at half maximum of the projected disk
major axis to the radius of the star. These relationships depend mainly upon
the temperatures of the disk and star, the inclination of the disk normal to
the line of sight, and the adopted outer boundary for the disk radius. We show
that the predicted H-alpha disk radii are consistent with those observed
directly through long baseline interferometry of nearby Be stars (especially
once allowance is made for disk truncation in binaries and for dilution of the
observed H-alpha equivalent width by continuum disk flux in the V-band).Comment: 12 pages, 2 figures, ApJL in pres
Near and mid-IR sub-arcsecond structure of the dusty symbiotic star R Aqr
The results of a high-resolution interferometric campaign targeting the
symbiotic long-period variable (LPV) R~Aqr are reported. With both
near-infrared measurements on baselines out to 10m and mid-infrared data
extending to 32m, we have been able to measure the characteristic sizes of
regions from the photosphere of the LPV and its extended molecular atmosphere,
out to the cooler circumstellar dust shell. The near-infrared data were taken
using aperture masking interferometry on the Keck-I telescope and show R~Aqr to
be partially resolved for wavelengths out to 2.2 microns but with a marked
enlargement, possibly due to molecular opacity, at 3.1 microns. Mid-infrared
interferometric measurements were obtained with the U.C. Berkeley Infrared
Spatial Interferometer (ISI) operating at 11.15 microns from 1992 to 1999.
Although this dataset is somewhat heterogeneous with incomplete coverage of the
Fourier plane and sampling of the pulsation cycle, clear changes in the
mid-infrared brightness distribution were observed, both as a function of
position angle on the sky and as a function of pulsation phase. Spherically
symmetric radiative transfer calculations of uniform-outflow dust shell models
produce brightness distributions and spectra which partially explain the data,
however limitations to this approximation are noted. Evidence for significant
deviation from circular symmetry was found in the mid-infrared and more
tentatively at 3.08 microns in the near-infrared, however no clear detection of
binarity or of non-LPV elements in the symbiotic system is reported.Comment: Accepted to Astrophysical Journal. To appear in volume 534. 14 pages;
3 postscript figure
Detection of Extended Red Emisson in the Diffuse Interstellar Medium
Extended Red Emission (ERE) has been detected in many dusty astrophysical
objects and this raises the question: Is ERE present only in discrete objects
or is it an observational feature of all dust, i.e. present in the diffuse
interstellar medium? In order to answer this question, we determined the blue
and red intensities of the radiation from the diffuse interstellar medium (ISM)
and examined the red intensity for the presence of an excess above that
expected for scattered light. The diffuse ISM blue and red intensities were
obtained by subtracting the integrated star and galaxy intensities from the
blue and red measurements made by the Imaging Photopolarimeter (IPP) aboard the
Pioneer 10 and 11 spacecraft. The color of the diffuse ISM was found to be
redder than the Pioneer intensities, contrary to that expected for scattered
light (Diffuse Galactic Light [DGL]). The red DGL was calculated using the blue
diffuse ISM intensities and the approximately invariant color of the DGL
calculated with the DGL model. Subtracting the calculated red DGL from the red
diffuse ISM intensities resulted in the detection of an excess red intensity.
This represents the likely detection of ERE in the diffuse ISM since H-alpha
emission cannot account for the strength of this excess and the only other
known emission process applicable to the diffuse ISM is ERE. Thus, ERE appears
to be a general characteristic of dust. From the correlation between N_HI and
ERE intensity the ERE photon conversion efficiency was estimated at 10 +/- 3%.Comment: 44 pages (41 figures included), to be published in the ApJ, new
version corrected for small error in fig. 2
MOST observations of the roAp stars HD 9289, HD 99563, and HD 134214
We report on the analysis of high-precision space-based photometry of the
roAp (rapidly oscillating Ap) stars HD 9289, HD 99563, and HD134214. All three
stars were observed by the MOST satellite for more than 25 days, allowing
unprecedented views of their pulsation. We find previously unknown candidate
frequencies in all three stars. We establish the rotation period of HD 9289
(8.5 d) for the first time and show that the star is pulsating in two modes
that show different mode geometries. We present a detailed analysis of HD
99563's mode multiplet and find a new candidate frequency which appears
independent of the previously known mode. Finally, we report on 11 detected
pulsation frequencies in HD 134214, 9 of which were never before detected in
photometry, and 3 of which are completely new detections. Thanks to the
unprecedentedly small frequency uncertainties, the p-mode spectrum of HD 134214
can be seen to have a well-defined large frequency spacing similar to the
well-studied roAp star HD 24712 (HR 1217).Comment: 11 pages, 12 figures, accepted for publication in A&
Luminous AGB stars in nearby galaxies. A study using Virtual Observatory tools
Aims. This study focuses on very luminous Mbol<-6.0 mag AGB stars with
J-Ks>1.5 mag and H-Ks>0.4 mag in the LMC, SMC, M31, and M33 from 2MASS data.
Methods.The data were taken from the 2MASS All-Sky Point Source catalogue
archive. We used Virtual Observatory tools and took advantage of its
capabilities at various stages in the analysis.
Results. It is well known that stars with the colors we selected correspond
mainly to carbon stars. Although the most luminous AGBs detected here contain a
large number of carbon stars,they are not included in existing catalogues
produced from data in the optical domain, where they are not visible since they
are dust-enshrouded. A comparison of the AGB stars detected with combined near
and mid-infrared data from MSX and 2MASS in the LMC shows that 10% of the
bright AGB stars are bright carbon stars never detected before and that the
other 50% are OH/IR oxygen rich stars, whereas the 40% that remain were not
cross-matched.
Conclusions. The catalogues of the most luminous AGB stars compiled here are
an important complement to existing data. In the LMC, these bright AGB stars
are centrally located, whereas they are concentrated in an active
star-formation ring in M31. In the SMC and M33, there are not enough of them to
draw definite conclusions, although they tend to be centrally located. Their
luminosity functions are similar for the four galaxies we studied.Comment: 16 pages, 12 figures, 4 tables (Appendix A), accepted in A&
Suture repair of umbilical hernia during caesarean section: a case-control study
Purpose: The objective of this study was to investigate the additional burdens in terms of pain, prolongation of surgery and morbidity which is added to elective caesarean section if umbilical hernia suture repair is performed simultaneously. Secondly, patient's satisfaction and hernia recurrence rate were assessed. Methods: Consecutive women with symptomatic umbilical hernia undergoing internal or external suture repair during elective caesarean were included in this retrospective cohort-control study. Data on post-operative pain, duration of surgery and morbidity of a combined procedure were collected. These patients were matched 1:10 to women undergoing caesarean section only. Additionally, two subgroups were assessed separately: external and internal suture hernia repair. These subgroups were compared for patient's satisfaction, cosmesis, body image and recurrence rate. Results: Fourteen patients with a mean age of 37years were analysed. Internal suture repair (n=7) prolonged caesarean section by 20min (p=0.001) and external suture repair (n=7) by 34min (p<0.0001). Suture repair did not increase morphine use (0.38±0.2 vs. 0.4±02mg/kg body weight), had no procedure-related morbidity and prolonged hospitalization by 0.5days (p=0.01). At a median follow-up of 37 (5-125) months, two recurrences in each surgical technique, internal and external suture repair, occurred (28%). Body image and cosmesis score showed a higher level of functioning in internal suture repair (p=0.02; p=0.04). Discussion: Despite a high recurrence rate, internal suture repair of a symptomatic umbilical hernia during elective caesarean section should be offered to women if requested. No additional morbidity or scar is added to caesarean section. Internal repair is faster, and cosmetic results are better, additional skin or fascia dissection is avoided, and it seems to be as effective as an external approach. Yet, women must be informed on the high recurrence rat
Building the cosmic distance scale: from Hipparcos to Gaia
Hipparcos, the first ever experiment of global astrometry, was launched by
ESA in 1989 and its results published in 1997 (Perryman et al., Astron.
Astrophys. 323, L49, 1997; Perryman & ESA (eds), The Hipparcos and Tycho
catalogues, ESA SP-1200, 1997). A new reduction was later performed using an
improved satellite attitude reconstruction leading to an improved accuracy for
stars brighter than 9th magnitude (van Leeuwen & Fantino, Astron. Astrophys.
439, 791, 2005; van Leeuwen, Astron. Astrophys. 474, 653, 2007).
The Hipparcos Catalogue provided an extended dataset of very accurate
astrometric data (positions, trigonometric parallaxes and proper motions),
enlarging by two orders of magnitude the quantity and quality of distance
determinations and luminosity calibrations. The availability of more than 20000
stars with a trigonometric parallax known to better than 10% opened the way to
a drastic revision of our 3-D knowledge of the solar neighbourhood and to a
renewal of the calibration of many distance indicators and age estimations. The
prospects opened by Gaia, the next ESA cornerstone, planned for launch in June
2013 (Perryman et al., Astron. Astrophys. 369, 339, 2001), are still much more
dramatic: a billion objects with systematic and quasi simultaneous astrometric,
spectrophotometric and spectroscopic observations, about 150 million stars with
expected distances to better than 10%, all over the Galaxy. All stellar
distance indicators, in very large numbers, will be directly measured,
providing a direct calibration of their luminosity and making possible detailed
studies of the impacts of various effects linked to chemical element
abundances, age or cluster membership. With the help of simulations of the data
expected from Gaia, obtained from the mission simulator developed by DPAC, we
will illustrate what Gaia can provide with some selected examples.Comment: 16 pages, 16 figures, Conference "The Fundamental Cosmic Distance
scale: State of the Art and the Gaia perspective, 3-6 May 2011, INAF,
Osservatorio Astronomico di Capodimonte, Naples. Accepted for publication in
Astrophysics & Space Scienc
Kinematic parameters and membership probabilities of open clusters in the Bordeaux PM2000 catalogue
We derive lists of proper-motions and kinematic membership probabilities for
49 open clusters and possible open clusters in the zone of the Bordeaux PM2000
proper motion catalogue (). We test
different parametrisations of the proper motion and position distribution
functions and select the most successful one. In the light of those results, we
analyse some objects individually. The segregation between cluster and field
member stars, and the assignment of membership probabilities, is accomplished
by applying a new and fully automated method based on both parametrisations of
the proper motion and position distribution functions, and genetic algorithm
optimization heuristics associated with a derivative-based hill climbing
algorithm for the likelihood optimization. We present a catalogue comprising
kinematic parameters and associated membership probability lists for 49 open
clusters and possible open clusters in the Bordeaux PM2000 catalogue region. We
note that this is the first determination of proper motions for five open
clusters. We confirm the non-existence of two kinematic populations in the
region of 15 previously suspected non-existent objects.Comment: 14 pages, 6 figures, 4 tables. Accepted for publication in Astronomy
& Astrophysic
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