164 research outputs found
The heritability of fruit ripening date in Vitis vinifera L.
An analysis of the inheritance of fruit ripening date in V. vinifera grapes, based on data collected on 2200 genotypes from 55 families generated by crosses among 35 parents, reveals that this trait is controlled by genes highly additive in their effects. The heritability of this trait was estimated to be 0.50 ± 0.04. The expected average gain of the progeny of randomly mated parents ranked in the upper 10 percent of the parental generation was calculated. The results indicate that relatively rapid genetic gain can be expected in this population by selecting parents on the basis of their own performance and subsequent mating inter se.Die Erblichkeit des Reifungszeitpunktes der Trauben von Vitis vinifera L.An 2200 Genotypen von Vitis vinifera aus 55 Familien, die aus der Kreuzung von 35 Elternpflanzen hervorgegangen waren, wurde die Vererbung des Reifungstermins der Trauben analysiert. Es zeigte sich, daß dieses Merkmal durch Gene bestimmt wird, die in hohem Maße additiv wirken. Der Heritabilitätskoeffizient des Merkmals wurde auf 0,50 ± 0,04 geschätzt. Der durchschnittlich zu erwartende Leistungszuwachs bei der Nachkommenschaft zufällig gepaarter Eltern, die zu den oberen 10 Prozent ihrer Generation zählten, wurde errechnet. Die Befunde weisen darauf hin, daß bei einer solchen Population ein relativ rascher Kreuzungserfolg erwartet werden kann, wenn man die Eltern aufgrund ihrer Leistungseigenschaften auswählt und sie anschließend untereinander kreuzt
A 3D extinction map of the northern Galactic plane based on IPHAS photometry
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. ©: 2014 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.We present a 3D map of extinction in the northern Galactic plane derived using photometry from the INT/WFC Photometric Hα Survey of the northern Galactic plane. The map has fine angular (~10 arcmin) and distance (100 pc) sampling allied to a significant depth (≳5 kpc). We construct the map using a method based on a hierarchical Bayesian model described in a previous article by Sale. In addition to mean extinction, we also measure differential extinction, which arises from the fractal nature of the interstellar medium, and show that it will be the dominant source of uncertainty in estimates of extinction to some arbitrary position. The method applied also furnishes us with photometric estimates of the distance, extinction, effective temperature, surface gravity, and mass for ~38 million stars. Both the extinction map and the catalogue of stellar parameters are made publicly available via http://www.iphas.org/extinction.Peer reviewe
Variable emission from a gaseous disc around a metal-polluted white dwarf
We present the discovery of strongly variable emission lines from a gaseous disc around the DA white dwarf SDSS J1617+1620, a star previously found to have an infrared excess indicative of a dusty debris disc formed by the tidal disruption of a rocky planetary body. Time series spectroscopy obtained during the period 2006–2014 has shown the appearance of strong double-peaked Ca II emission lines in 2008. The lines were weak, at best, during earlier observations, and monotonically faded through the remainder of our monitoring. Our observations represent unambiguous evidence for short-term variability in the debris environment of evolved planetary systems. Possible explanations for this extraordinary variability include the impact on to the dusty disc of either a single small rocky planetesimal, or of material from a highly eccentric debris tail. The increase in flux from the emission lines is sufficient that similar events could be detected in the broad-band photometry of ongoing and future large-area time domain surveys
A hidden population of white dwarfs with atmospheric carbon traces in the Gaia bifurcation
The ESA Gaia space mission has revealed a bifurcation of the white dwarf (WD)
sequence on the color magnitude diagram in two branches: A and B. While the A
branch consists mostly of WDs with H-rich atmospheres, the B branch is not
completely understood. Although invoked to be populated mainly by He-rich WDs,
the B branch overlaps a evolutionary track with a pure He
envelope, fact that would imply an unexpected peak in the WD mass distribution.
In cold He-rich WDs, it is expected that the outer convective zone penetrates
into deep C-rich layers, thus leading to a slight C contamination in their
surfaces at K. Here we aim at studying the Gaia bifurcation as the
natural consequence of C dredge-up by convection in cold He-dominated WDs.
Relying on accurate atmosphere models, we provide a new set of evolutionary
models for He-rich WDs employing different prescriptions for the C enrichment.
On the basis of these models, we made a population synthesis study of the Gaia
100pc WD sample to constrain the models that best fit the bifurcation. Our
study shows that He-rich WD models with a slight C contamination below the
optical detection limit can accurately reproduce the Gaia bifurcation. We refer
to these stars as stealth DQ WDs because they do not exhibit detectable C
signatures in their optical spectra, but the presence of C in their atmosphere
produces a continuum absorption favouring the emission in bluer wavelengths,
thereby creating the B branch of the bifurcation. Also, we show that the mass
distribution for He-rich WDs obtained when a stealth C contamination is
considered is consistent with the mass distribution for H-rich WDs and with the
standard evolutionary channels for their formation. We conclude that stealth DQ
WDs can account for the lower branch in the Gaia bifurcation. The C signatures
of these stars could be detectable in Ultra-Violet spectra.Comment: 9 pages, 8 figures, accepted for publication in Astronomy &
Astrophysic
The search for ZZ Ceti stars in the original Kepler mission
We report the discovery of 42 white dwarfs in the original Kepler mission
field, including nine new confirmed pulsating hydrogen-atmosphere white dwarfs
(ZZ Ceti stars). Guided by the Kepler-INT Survey (KIS), we selected white dwarf
candidates on the basis of their U-g, g-r, and r-H_alpha photometric colours.
We followed up these candidates with high-signal-to-noise optical spectroscopy
from the 4.2-m William Herschel Telescope. Using ground-based, time-series
photometry, we put our sample of new spectroscopically characterized white
dwarfs in the context of the empirical ZZ Ceti instability strip. Prior to our
search, only two pulsating white dwarfs had been observed by Kepler.
Ultimately, four of our new ZZ Cetis were observed from space. These rich
datasets are helping initiate a rapid advancement in the asteroseismic
investigation of pulsating white dwarfs, which continues with the extended
Kepler mission, K2.Comment: 9 pages, 6 figures, accepted for publication in MNRA
Carbon-oxygen ultra-massive white dwarfs in general relativity
We employ the La Plata stellar evolution code, LPCODE, to compute the first
set of constant rest-mass carbon-oxygen ultra-massive white dwarf evolutionary
sequences for masses higher than 1.29 Msun that fully take into account the
effects of general relativity on their structural and evolutionary properties.
In addition, we employ the LP-PUL pulsation code to compute adiabatic g-mode
Newtonian pulsations on our fully relativistic equilibrium white dwarf models.
We find that carbon-oxygen white dwarfs more massive than 1.382 Msun become
gravitationally unstable with respect to general relativity effects, being this
limit higher than the 1.369 Msun we found for oxygen-neon white dwarfs. As the
stellar mass approaches the limiting mass value, the stellar radius becomes
substantially smaller compared with the Newtonian models. Also, the
thermo-mechanical and evolutionary properties of the most massive white dwarfs
are strongly affected by general relativity effects. We also provide magnitudes
for our cooling sequences in different passbands. Finally, we explore for the
first time the pulsational properties of relativistic ultra-massive white
dwarfs and find that the period spacings and oscillation kinetic energies are
strongly affected in the case of most massive white dwarfs. We conclude that
the general relativity effects should be taken into account for an accurate
assessment of the structural, evolutionary, and pulsational properties of white
dwarfs with masses above 1.30 Msun.Comment: 12 pages, 12 figures, accepted for publication in MNRAS. arXiv admin
note: text overlap with arXiv:2208.1414
Stellar archaeology with Gaia: the Galactic white dwarf population
Gaia will identify several 1e5 white dwarfs, most of which will be in the
solar neighborhood at distances of a few hundred parsecs. Ground-based optical
follow-up spectroscopy of this sample of stellar remnants is essential to
unlock the enormous scientific potential it holds for our understanding of
stellar evolution, and the Galactic formation history of both stars and
planets.Comment: Summary of a talk at the 'Multi-Object Spectroscopy in the Next
Decade' conference in La Palma, March 2015, to be published in ASP Conference
Series (editors Ian Skillen & Scott Trager
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