63 research outputs found
Visual orbit for the low-mass binary Gliese 22 AC from speckle interferometry
Based on 14 data points obtained with near-infrared speckle interferometry
and covering an almost entire revolution, we present a first visual orbit for
the low-mass binary system Gliese 22 AC. The quality of the orbit is largely
improved with respect to previous astrometric solutions. The dynamical system
mass is 0.592 +- 0.065 solar masses, where the largest part of the error is due
to the Hipparcos parallax. A comparison of this dynamical mass with
mass-luminosity relations on the lower main sequence and theoretical
evolutionary models for low-mass objects shows that both probably underestimate
the masses of M dwarfs. A mass estimate for the companion Gliese 22 C indicates
that this object is a very low-mass star with a mass close to the hydrogen
burning mass limit.Comment: Accepted by Astronomy and Astrophysics, 6 pages, 2 figure
Tracing the young massive high-eccentricity binary system Theta 1 Orionis C through periastron passage
The nearby high-mass star binary system Theta 1 Orionis C is the brightest
and most massive of the Trapezium OB stars at the core of the Orion Nebula
Cluster, and it represents a perfect laboratory to determine the fundamental
parameters of young hot stars and to constrain the distance of the Orion
Trapezium Cluster. Between January 2007 and March 2008, we observed T1OriC with
VLTI/AMBER near-infrared (H- and K-band) long-baseline interferometry, as well
as with bispectrum speckle interferometry with the ESO 3.6m and the BTA 6m
telescopes (B'- and V'-band). Combining AMBER data taken with three different
3-telescope array configurations, we reconstructed the first VLTI/AMBER
closure-phase aperture synthesis image, showing the T1OriC system with a
resolution of approx. 2 mas. To extract the astrometric data from our
spectrally dispersed AMBER data, we employed a new algorithm, which fits the
wavelength-differential visibility and closure phase modulations along the H-
and K-band and is insensitive to calibration errors induced, for instance, by
changing atmospheric conditions. Our new astrometric measurements show that the
companion has nearly completed one orbital revolution since its discovery in
1997. The derived orbital elements imply a short-period (P=11.3 yrs) and
high-eccentricity orbit (e=0.6) with periastron passage around 2002.6. The new
orbit is consistent with recently published radial velocity measurements, from
which we can also derive the first direct constraints on the mass ratio of the
binary components. We employ various methods to derive the system mass
(M_system=44+/-7 M_sun) and the dynamical distance (d=410+/-20 pc), which is in
remarkably good agreement with recently published trigonometric parallax
measurements obtained with radio interferometry.Comment: 15 pages, 15 figures, accepted by A&
Analytical “Bake-Off” of Whole Genome Sequencing Quality for the Genome Russia Project Using a Small Cohort for Autoimmune Hepatitis
A comparative analysis of whole genome sequencing (WGS) and genotype calling was initiated for ten human genome samples sequenced by St. Petersburg State University Peterhof Sequencing Center and by three commercial sequencing centers outside of Russia. The sequence quality, efficiency of DNA variant and genotype calling were compared with each other and with DNA microarrays for each of ten study subjects. We assessed calling of SNPs, indels, copy number variation, and the speed of WGS throughput promised. Twenty separate QC analyses showed high similarities among the sequence quality and called genotypes. The ten genomes tested by the centers included eight American patients afflicted with autoimmune hepatitis (AIH), plus one case’s unaffected parents, in a prelude to discovering genetic influences in this rare disease of unknown etiology. The detailed internal replication and parallel analyses allowed the observation of two of eight AIH cases carrying a rare allele genotype for a previously described AIH-associated gene (FTCD), plus multiple occurrences of known HLA-DRB1 alleles associated with AIH (HLA-DRB1-03:01:01, 13:01:01 and 7:01:01). We also list putative SNVs in other genes as suggestive in AIH influence
Draft de novo Genome Assembly of the Elusive Jaguarundi, Puma yagouaroundi
The Puma lineage within the family Felidae consists of 3 species that last shared a common ancestor around 4.9 million years ago. Whole-genome sequences of 2 species from the lineage were previously reported: the cheetah (Acinonyx jubatus) and the mountain lion (Puma concolor). The present report describes a whole-genome assembly of the remaining species, the jaguarundi (Puma yagouaroundi). We sequenced the genome of a male jaguarundi with 10X Genomics linked reads and assembled the whole-genome sequence. The assembled genome contains a series of scaffolds that reach the length of chromosome arms and is similar in scaffold contiguity to the genome assemblies of cheetah and puma, with a contig N50 = 100.2 kbp and a scaffold N50 = 49.27 Mbp. We assessed the assembled sequence of the jaguarundi genome using BUSCO, aligned reads of the sequenced individual and another published female jaguarundi to the assembled genome, annotated protein-coding genes, repeats, genomic variants and their effects with respect to the protein-coding genes, and analyzed differences of the 2 jaguarundis from the reference mitochondrial genome. The jaguarundi genome assembly and its annotation were compared in quality, variants, and features to the previously reported genome assemblies of puma and cheetah. Computational analyzes used in the study were implemented in transparent and reproducible way to allow their further reuse and modification. </p
Chromosomal-level assembly of the Asian Seabass genome using long sequence reads and multi-layered scaffolding
We report here the ~670 Mb genome assembly of the Asian seabass (Lates calcarifer), a tropical marine teleost. We used long-read sequencing augmented by transcriptomics, optical and genetic mapping along with shared synteny from closely related fish species to derive a chromosome-level assembly with a contig N50 size over 1 Mb and scaffold N50 size over 25 Mb that span ~90% of the genome. The population structure of L. calcarifer species complex was analyzed by re-sequencing 61 individuals representing various regions across the species' native range. SNP analyses identified high levels of genetic diversity and confirmed earlier indications of a population stratification comprising three clades with signs of admixture apparent in the South-East Asian population. The quality of the Asian seabass genome assembly far exceeds that of any other fish species, and will serve as a new standard for fish genomics
Genome-wide sequence analyses of ethnic populations across Russia
The Russian Federation is the largest and one of the most ethnically diverse countries in the world, however no centralized reference database of genetic variation exists to date. Such data are crucial for medical genetics and essential for studying population history. The Genome Russia Project aims at filling this gap by performing whole genome sequencing and analysis of peoples of the Russian Federation. Here we report the characterization of genome-wide variation of 264 healthy adults, including 60 newly sequenced samples. People of Russia carry known and novel genetic variants of adaptive, clinical and functional consequence that in many cases show allele frequency divergence from neighboring populations. Population genetics analyses revealed six phylogeographic partitions among indigenous ethnicities corresponding to their geographic locales. This study presents a characterization of population-specific genomic variation in Russia with results important for medical genetics and for understanding the dynamic population history of the world's largest country
Hydrogen content in Kazarian galaxies
Several H I related astrophysical parameters such as neutral
hydrogen total mass and hydrogen mean projected density, indicative total mass
as well as usual ratios , and
for 23 galaxies from Kazarian lists are derived. Their variation ranges are rather
wide almost coinciding with those for normal galaxies belonging to the same
morphological types. Kazarian galaxies do not constitute a homogeneous sample
by any of the commonly used H I related parameters. Comparison with Markarian and
blue Haro galaxies demonstrate that Kazarian galaxies have quite
similar H I properties and contain rather high relative numbers ()
of peculiar objects. Brief comments on the peculiar galaxies Kaz 63, Kaz 65, Kaz 69
and Kaz 211 are given
21-cm line observations of galaxies from Kazarian's lists
The 21-cm neutral hydrogen line has been measured for the first
time in 39 non-Seyfert type galaxies from Kazarian list, with the
Nançay radiotelescope. The line profiles, widths at 20% and 50%
of the peak intensity, radial velocities as well as total fluxes are
presented. The values of radial velocity are in fairly good agreement
with those obtained from optical spectra. The width values at 20% of the
peak vary in wide range from 113 km s-1 (KAZ 579) to 608 km s-1
for KAZ 566.
Nine of our objects remained undetected, whether their HI-flux
was too faint, the integration time too short, or the frequency sighted wrong.
However, for part of them, there were positive hint of detection.
Comments on individual objects are given
Simulating multiple stars in preparation for Gaia
International audienceThe scientific preparation of the Gaia mission encompasses both the data reduction algorithms and the generation of simulated data which have to be as realistic as possible. In this respect, binaries and multiple stars are a mandatory component in the simulation of the Milky Way as they impact on the performance tests of the on-ground data processing. The ingredients for the simulation of multiple stars are described and the predictions are compared to observed data or outcomes from stellar multiplicity studies
Dynamical masses of a selected sample of orbital binaries
Orbital binary stars are essential objects for determining dynamical and physical
properties of stars through a combined analysis of photometric and astrometric data. We
compiled a set of orbital binaries with known trigonometric parallaxes and orbits of high
quality, using data from current versions of the Catalogue of Orbits and Ephemerides of
Visual Double Stars and the Sixth Catalog of Orbits of Visual Binary Stars as well as
including updated information from WDS and SIMBAD. We constructed distributions of orbital
binaries among dynamical mass, period, semi-major axis, and eccentricity of systems, which
characterize the set. Some problems related to the parameterization of orbital binaries
are also discussed in the paper
- …