1,729 research outputs found
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
Colorado Ultraviolet Transit Experiment Data Simulator
The Colorado Ultraviolet Transit Experiment (CUTE) is a 6U NASA CubeSat
carrying on-board a low-resolution (R~2000--3000), near-ultraviolet (2500--3300
{\AA}) spectrograph. It has a rectangular primary Cassegrain telescope to
maximize the collecting area. CUTE, which is planned for launch in Spring 2020,
is designed to monitor transiting extra-solar planets orbiting bright, nearby
stars aiming at improving our understanding of planet atmospheric escape and
star-planet interaction processes. We present here the CUTE data simulator,
which we complemented with a basic data reduction pipeline. This pipeline will
be then updated once the final CUTE data reduction pipeline is developed. We
show here the application of the simulator to the HD209458 system and a first
estimate of the precision on the measurement of the transit depth as a function
of temperature and magnitude of the host star. We also present estimates of the
effect of spacecraft jitter on the final spectral resolution. The simulator has
been developed considering also scalability and adaptability to other missions
carrying on-board a long-slit spectrograph. The data simulator will be used to
inform the CUTE target selection, choose the spacecraft and instrument settings
for each observation, and construct synthetic CUTE wavelength-dependent transit
light curves on which to develop the CUTE data reduction pipeline.Comment: Accepted for publication in the Journal of Astronomical Telescopes,
Instruments and System
Association mapping of Stagonospora nodorum blotch resistance in modern European winter wheat varieties
Association mapping in populations relevant for wheat breeding has a large potential for validating and fine-mapping QTLs identified in F2- or DH (double haploid)-derived populations. In this study, associations between markers in the region of QSng.sfr-3BS, a major QTL for resistance to Stagonospora nodorum glume blotch (SNG), and SNG resistance were investigated by linkage and association analyses. After increasing marker density in 240 F5:7 recombinant inbred lines (RILs), QSng.sfr-3BS explained 43% of the genetic variance and peaked 0.6cM proximal from the marker SUN2-3B. Association between SNG resistance and markers mapped in the region of QSng.sfr-3BS was investigated in a population of 44 modern European winter wheat varieties. Two genetically distinct subpopulations were identified within these lines. In agreement with linkage analyses, association mapping by a least squares general linear model (GLM) at marker loci in the region of QSng.sfr-3BS revealed the highest association with SNG resistance for SUN2-3B (p<0.05). Association mapping can provide an effective mean of relating genotypes to complex quantitative phenotypes in hexaploid wheat. Linkage disequilibrium (r 2) in chromosome 3B extended less than 0.5cM in 44 varieties, while it extended about 30cM in 240 RILs, based on 91 SSR and STS marker-pair comparisons. This indicated that the association mapping population had a marker resolution potential at least 390-fold higher compared to the RIL populatio
A kinetic BGK edge-based scheme including vibrational and electronic energy modes for high-Mach flows
A first principles formulation for the calorically imperfect behavior of gases is here proposed within a Boltzmann-type discretisation of the Navier–Stokes equations. The formulation is intended to enhance the consistency of gas kinetic schemes (GKS) with the physics of supersonic and hypersonic regimes where vibrational and electronic energy modes are activated before any thermal nonequilibrium or chemical activity takes place. The so-called node-pair BGK scheme, an edge-based implementation of the GKS, is considered in the present work for the implementation of a thermodynamic model where the calorically imperfect behavior is obtained from a modification of the way the different moments of the particle distribution function are computed and eventually used to determine the fluxes of conserved quantities across the boundary of each control volume. The method is validated on a series of canonical test cases for supersonic and hypersonic flows
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