300 research outputs found
II.1 The CoRoT observations
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
Regeneration of the tropical legume Aeschynomene sensitiva Sw. from root explants
Regeneration of #Aeschynomene sensitiva Sw. after callogenesis was obtained form small (2-5 mm long) root explants of 30-day-old seedlings aseptically cultivated on Murashige and Skoog medium supplemented with various concentrations of growth regulators. After 4 weeks, the best results were observed with 0.54 microM alpha-naphthaleneacetic acid and 2.22 microM benzyladenine. On this medium, the rate of regeneration depended on seedling age and agar concentration. The highest number of shoots per explant was obtained with small cuttings from 30-day-old seedlings grown on a medium containing 8 g/l of agar. Regeneration success was also dependent on explant size. When longer explants (7-20 mm) were cut from the main root, direct regeneration was obtained in two weeks. These cuttings also generated shoots through callogenesis in four weeks but always in lower quantities than with direct regeneration, whatever the seedling age. Here also, the best regeneration was obtained with cuttings from 30-day-old seedlings maintained on a medium with 8 g/l of agar. Regenerants were rooted on growth-regulator-free Murashige and Skoog medium and then acclimatized in a greenhouse. A better survival to transplantation was observed when plantlets were inoculated with the photosynthetic #Bradyrhizobium strain ORS 278. Stem and root nodules developed on the inoculated plantlets and were able to fix nitrogen. (Résumé d'auteur
gamma Doradus pulsation in two pre-main sequence stars discovered by CoRoT
Pulsations in pre-main sequence stars have been discovered several times
within the last years. But nearly all of these pulsators are of delta
Scuti-type. gamma Doradus-type pulsation in young stars has been predicted by
theory, but lack observational evidence. We present the investigation of
variability caused by rotation and (gammaDoradus-type) pulsation in two
pre-main sequence members of the young open cluster NGC2264 using
high-precision time series photometry from the CoRoT satellite and dedicated
high-resolution spectroscopy. Time series photometry of NGC2264VAS20 and NGC
2264VAS87 was obtained by the CoRoT satellite during the dedicated short run
SRa01 in March 2008. NGC2264VAS87 was re-observed by CoRoT during the short run
SRa05 in December 2011 and January 2012. Frequency analysis was conducted using
Period04 and SigSpec. The spectral analysis was performed using equivalent
widths and spectral synthesis. The frequency analysis yielded 10 and 14
intrinsic frequencies for NGC2264VAS20 and NGC2264VAS 87, respectively, in the
range from 0 to 1.5c/d which are attributed to be caused by a combination of
rotation and pulsation. The effective temperatures were derived to be
6380150K for NGC2264VAS20 and 6220150K for NGC2264VAS87. Membership
of the two stars to the cluster is confirmed independently using X-ray fluxes,
radial velocity measurements and proper motions available in the literature.
The derived Li abundances of log n(Li)=3.34 and 3.54 for NGC2264VAS20 and
NGC2264VAS87, respectively, are in agreement with the Li abundance for other
stars in NGC2264 of similar Teff reported in the literature. We conclude that
the two objects are members of NGC2264 and therefore are in their pre-main
sequence evolutionary stage. Assuming that part of their variability is caused
by pulsation, these two stars might be the first pre-main sequence gamma
Doradus candidates.Comment: 11 pages, 10 figures, A&A accepte
II.4 The “ready to use” 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
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
Regular frequency patterns in the young delta Scuti star HD 261711 observed by the CoRoT and MOST satellites
We concentrate on an asteroseismological study of HD 261711, a rather hot
delta Scuti type pulsating member of the young open cluster NGC 2264 located at
the blue border of the instability region. HD 261711 was discovered to be a
pre-main sequence delta Scuti star using the time series photometry obtained by
the MOST satellite in 2006. High-precision, time-series photometry of HD 261711
was obtained by the MOST and CoRoT satellites in 4 separate new observing runs
that are put into context with the star's fundamental atmospheric parameters
obtained from spectroscopy. With the new MOST data set from 2011/12 and the two
CoRoT light curves from 2008 and 2011/12, the delta Scuti variability was
confirmed and regular groups of frequencies were discovered. The two pulsation
frequencies identified in the data from the first MOST observing run in 2006
are confirmed and 23 new delta Scuti-type frequencies were discovered using the
CoRoT data. Weighted average frequencies for each group are related to l=0 and
l=1 p-modes. Evidence for amplitude modulation of the frequencies in two groups
is seen. The effective temperature was derived to be 8600200 K, log g is
4.10.2, and the projected rotational velocity is 531km/s. Using our
Teff value and the radius of 1.80.5 Rsun derived from SED fitting, we get
a log L/Lsun of 1.200.14 which agrees well to the seismologically
determined values of 1.65 Rsun and, hence, a log L/Lsun of 1.13. The radial
velocity of 142 km/s we derived for HD 261711, confirms the star's
membership to NGC 2264. Our asteroseismic models suggest that HD 261711 is a
delta Scuti-type star close to the zero-age main sequence (ZAMS) with a mass of
1.8 to 1.9Msun. HD 261711 is either a young ZAMS star or a late PMS star just
before the onset of hydrogen-core burning.Comment: 12 pages, 13 figures, A&A accepte
The LPS O-antigen in photosynthetic Bradyrhizobium strains is dispensable for the establishment of a successful symbiosis with Aeschynomene legumes
The photosynthetic bradyrhizobia are able to use a Nod-factor independent process to induce nitrogen-fixing nodules on some semi-aquatic Aeschynomene species. These bacteria display a unique LPS O-antigen composed of a new sugar, the bradyrhizose that is regarded as a key symbiotic factor due to its non-immunogenic character. In this study, to check this hypothesis, we isolated mutants affected in the O-antigen synthesis by screening a transposon mutant library of the ORS285 strain for clones altered in colony morphology. Over the 10,000 mutants screened, five were selected and found to be mutated in two genes, rfaL, encoding for a putative O-antigen ligase and gdh encoding for a putative dTDP-glucose 4,6-dehydratase. Biochemical analysis confirmed that the LPS of these mutants completely lack the O-antigen region. However, no effect of the mutations could be detected on the symbiotic properties of the mutants indicating that the O-antigen region of photosynthetic Bradyrhizobium strains is not required for the establishment of symbiosis with Aeschynomene
Revisiting the transits of CoRoT-7b at a lower activity level
CoRoT-7b, the first super-Earth with measured radius discovered, has opened
the new field of rocky exoplanets characterisation. To better understand this
interesting system, new observations were taken with the CoRoT satellite.
During this run 90 new transits were obtained in the imagette mode. These were
analysed together with the previous 151 transits obtained in the discovery run
and HARPS radial velocity observations to derive accurate system parameters. A
difference is found in the posterior probability distribution of the transit
parameters between the previous CoRoT run (LRa01) and the new run (LRa06). We
propose this is due to an extra noise component in the previous CoRoT run
suspected to be transit spot occultation events. These lead to the mean transit
shape becoming V-shaped. We show that the extra noise component is dominant at
low stellar flux levels and reject these transits in the final analysis. We
obtained a planetary radius, , in agreement
with previous estimates. Combining the planetary radius with the new mass
estimates results in a planetary density of
which is consistent with a rocky composition. The CoRoT-7 system remains an
excellent test bed for the effects of activity in the derivation of planetary
parameters in the shallow transit regime.Comment: 13 pages, 13 figures, accepted to A&
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