202 research outputs found
Ripeness attributes of Arkansas-grown peaches and nectarines at harvest and during postharvest storage
Since peaches and nectarines are a valued fresh-market crop worldwide, evaluating postharvest potential helps determine feasibility for commercial markets. The ripeness attributes of 10 peach and nectarine genotypes were evaluated at harvest (day 0) and after 7 and 14 d storage at 4° C. The fruit was hand harvested at tree ripeness (ripened on the tree) and commercial ripeness (ripened during storage). The attributes of the tree-ripened fruit and commercially-ripened fruit varied at harvest and included chlorophyll (0.04-0.86 abs), peach weight (132-264 g), soluble solids (7.23-12.57%), pH (3.18-4.66), titratable acidity (0.16-1.21%), and flesh firmness (6.92-35.72 N). In general, tree-ripened fruit had higher fruit weight, soluble solids, and pH and lower chlorophyll, titratable acidity, and firmness than commercially-ripened fruit at harvest. For the tree-ripened fruit, A-811 CN was the largest (247.67 g), A-794 CN had the highest soluble solids (12.57%) and titratable acidity (0.88%), âSouvenirsâ (6.92 N) had the lowest firmness, and âAmoore Sweetâ (18.28 N) was the firmest. During storage of commercially-ripened fruit, chlorophyll and fruit weight decreased, while soluble solids increased, but there were no changes in pH or titratable acidity. During storage, A-885 (0.35 abs) had the lowest chlorophyll and âEffieâ had the largest fruit (203.11 g) and highest soluble solids (12.02%). Some ripeness attributes of the commercially-ripened fruit, such as chlorophyll and weight, were not achieved as compared to the tree-ripened fruit. The results of this study provide insight on the potential for releasing new peach and nectarine genotypes from the University of Arkansas Fruit Breeding Program
The Anomalous Infrared Emission of Abell 58
We present a new model to explain the excess in mid and near infrared
emission of the central, hydrogen poor dust knot in the planetary nebula (PN)
Abell 58. Current models disagree with ISO measurement because they apply an
average grain size and equilibrium conditions only. We investigate grain size
distributions and temperature fluctuations affecting infrared emission using a
new radiative transfer code and discuss in detail the conditions requiring an
extension of the classical description. The peculiar infrared emission of V605
Aql, the central dust knot in Abell 58, has been modeled with our code. V605
Aql is of special interest as it is one of only three stars ever observed to
move from the evolutionary track of a central PN star back to the post-AGB
state.Comment: 17 pages, 4 figures; accepted and to be published in Ap
Thermal infrared observations of near-Earth asteroid 2002 NY40
We obtained N-band observations of the Apollo asteroid 2002 NY40 during its
close Earth fly-by in August 2002 with TIMMI2 at the ESO 3.6 m telescope. The
photometric measurement allowed us to derive a radiometric diameter of
0.28+/-0.03 km and an albedo of 0.34+/-0.06 through the near-Earth asteroid
thermal model (NEATM) and a thermophysical model (TPM). The values are in
agreement with results from radar data, visual and near-IR observations. In
this first comparison between these two model approaches we found that the
empirical NEATM beaming parameter =1.0 corresponds to a thermal inertia
values of about 100 for a typical range of
surface roughness, assuming an equator-on viewing angle. Our TPM analysis
indicated that the surface of 2002 NY40 consists of rocky material with a thin
or no dust regolith. The asteroid very likely has a prograde sense of rotation
with a cold terminator at the time of our observations. Although both model
approaches can fit the thermal spectra taken at phase angles of 22
and 59, we did not find a consistent model solution that describes
all pieces of photometric and spectroscopic data. In addition to the 2002 NY40
analysis, we discuss the possibilities to distinguish between different models
with only very few photometric and/or spectroscopic measurements spread over a
range of phase angles.Comment: 6 pages, 4 figures, A&A accepte
The fluorine abundance in a Galactic Bulge AGB star measured from CRIRES spectra
We present measurements of the fluorine abundance in a Galactic Bulge
Asymptotic Giant Branch (AGB) star. The measurements were performed using high
resolution K-band spectra obtained with the CRIRES spectrograph, which has been
recently installed at ESO's VLT, together with state-of-the-art model
atmospheres and synthetic spectra. This represents the first fluorine abundance
measurement in a Galactic Bulge star, and one of few measurements of this kind
in a third dredge-up oxygen-rich AGB star. The F abundance is found to be close
to the solar value scaled down to the metallicity of the star, and in agreement
with Disk giants that are comparable to the Bulge giant studied here. The
measurement is of astrophysical interest also because the star's mass can be
estimated rather accurately (1.4 \lesssim M/\mathrm{M}_{\sun} \lesssim 2.0).
AGB nucleosynthesis models predict only a very mild enrichment of F in such low
mass AGB stars. Thus, we suggest that the fluorine abundance found in the
studied star is representative for the star's natal cloud, and that fluorine
must have been produced at a similar level in the Bulge and in the Disk.Comment: 11 pages, 1 figure, accepted for publication by Ap
Large Interstellar Polarisation Survey. LIPS I: FORS2 spectropolarimetry in the Southern Hemisphere
Polarimetric studies of light transmitted through interstellar clouds may
give constraints on the properties of the interstellar dust grains.
Traditionally, broadband linear polarisation (BBLP) measurements have been
considered an important diagnostic tool for the study of the interstellar dust,
while comparatively less attention has been paid to spectropolarimetric
measurements. However, spectropolarimetry may offer stronger constraints than
BBLP, for example by revealing narrowband features, and by allowing us to
distinguish the contribution of dust from the contribution of interstellar gas.
Therefore, we have decided to carry out a Large Interstellar Polarisation
Survey (LIPS) using spectropolarimetric facilities in both hemispheres. Here we
present the results obtained in the Southern Hemisphere with the FORS2
instrument of the ESO Very Large Telescope. Our spectra cover the wavelength
range 380--950\,nm at a spectral resolving power of about 880. We have produced
a publicly available catalogue of 127 linear polarisation spectra of 101
targets. We also provide the Serkowski-curve parameters, as well as the
wavelength gradient of the polarisation position angle for the interstellar
polarisation along 76 different lines of sight. In agreement with previous
literature, we found that the best-fit parameters of the Serkowski-curve are
not independent of each other. However, the relationships that we obtained are
not always consistent with what was found in previous studies.Comment: Accepted by A&A (replaced on 12 October 2017 simply to correct a
Metadata error
A comparison between Pa alpha and H alpha emission: The relation between HII region mean reddening, local gas density and metallicity
We measure reddenings to HII regions in NGC 2903, NGC 1512, M51, NGC 4449 and
NGC 6946 from Hubble Space Telescope Pa alpha and H alpha images. Extinctions
range from A_V ~ 5 - 0 depending upon the galaxy. For the galaxies with HST
images in both lines, NGC 2903, NGC 1512 and M51, the Pa alpha and H alpha
emission are almost identical in morphology which implies that little emission
from bright HII regions is hidden from view by regions of comparatively high
extinction. The scatter in the measured extinctions is only +- 0.5 mag.
We compare the reddenings we measure in five galaxies using the Pa alpha to H
alpha ratios to those measured previously from the Balmer decrement in the LMC
and as a function of radius in M101 and M51. We find that luminosity weighted
mean extinctions of these ensembles of HI regions are correlated with gas
surface density and metallicity. The correlation is consistent with the mean
extinction depending on dust density where the dust to gas mass ratio scales
with the metallicity. This trend is expected if HII regions tend to be located
near the mid-plane of a gas disk and emerge from their parent molecular clouds
soon after birth. In environments with gas densities below a few hundred
Msol/pc^2 star formation rates estimated from integrated line fluxes and mean
extinctions are likely to be fairly accurate.Comment: accepted for publication in A
Improved orbital solution and masses for the very low-mass multiple system LHS 1070
We present a refined orbital solution for the components A, B, and C of the
nearby late-M type multiple system LHS 1070. By combining astrometric
datapoints from NACO/VLT, CIAO/SUBARU, and PUEO/CFHT, as well as a radial
velocity measurement from the newly commissioned near infrared high-resolution
spectrograph CRIRES/VLT, we achieve a very precise orbital solution for the B
and C components and a first realistic constraint on the much longer orbit of
the A-BC system. Both orbits appear to be co-planar. Masses for the B and C
components calculated from the new orbital solution (M_(B+C) = 0.157 +/- 0.009
M_sun) are in excellent agreement with theoretical models, but do not match
empirical mass-luminosity tracks. The preliminary orbit of the A-BC system
reveals no mass excess for the A component, giving no indication for a
previously proposed fourth (D) component in LHS 1070.Comment: published in A&A, 2008, 484, 429; added CFHT acknowledgemen
AN ISOCAM MID-IR SURVEY OF TMC-2 Searching for sub stellar objects
Abstract We are conducting a mid-infrared survey of the Taurus Molecular Cloud 2 complex (TMC-2) in order to identify new low mass members and build a more complete IMF down to the sub stellar regime. Here we present a preliminary analysis of one of the surveyed fields. This field contains two previously known members of TMC-2. Based on the observed mid-IR excess we identify 6 new member candidates. Assuming a distance of 140 pc we find luminosities of âŒ1.5â3.5 10 â3 L for these objects, placing them squarely in the brown dwarf domain. In addition to the two known stars and the 6 new brown dwarf candidates, we do not detect more luminous stars or brown dwarfs with IR excesses
IRAS04496-6958: A luminous carbon star with silicate dust in the Large Magellanic Cloud
We describe ISO observations of the obscured Asymptotic Giant Branch (AGB)
star IRAS04496-6958 in the Large Magellanic Cloud (LMC). This star has been
classified as a carbon star. Our new ISOCAM CVF spectra show that it is the
first carbon star with silicate dust known outside of the Milky Way. The
existence of this object, and the fact that it is one of the highest luminosity
AGB stars in the LMC, provide important information for theoretical models of
AGB evolution and understanding the origin of silicate carbon stars.Comment: 4 pages, 3 figures, accepted for publication in A&A Letter
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