2,616 research outputs found
The first high-amplitude delta Scuti star in an eclipsing binary system
We report the discovery of the first high-amplitude delta Scuti star in an
eclipsing binary, which we have designated UNSW-V-500. The system is an
Algol-type semi-detached eclipsing binary of maximum brightness V = 12.52 mag.
A best-fitting solution to the binary light curve and two radial velocity
curves is derived using the Wilson-Devinney code. We identify a late A spectral
type primary component of mass 1.49+/-0.02 M_sun and a late K spectral type
secondary of mass 0.33+/-0.02 M_sun, with an inclination of 86.5+/-1.0 degrees,
and a period of 5.3504751+/-0.0000006 d. A Fourier analysis of the residuals
from this solution is performed using PERIOD04 to investigate the delta Scuti
pulsations. We detect a single pulsation frequency of f_1 = 13.621+/-0.015 c/d,
and it appears this is the first overtone radial mode frequency. This system
provides the first opportunity to measure the dynamical mass for a star of this
variable type; previously, masses have been derived from stellar evolution and
pulsation models.Comment: 7 pages, 6 figures, 2 tables, for submission to MNRAS, v2: paper size
change, small typographical changes to abstrac
The UNSW Extrasolar Planet Search: Methods and First Results from a Field Centred on NGC 6633
We report on the current status of the University of New South Wales
Extrasolar Planet Search project, giving details of the methods we use to
obtain millimagnitude precision photometry using the 0.5m Automated Patrol
Telescope. We use a novel observing technique to optimally broaden the PSF and
thus largely eliminate photometric noise due to intra-pixel sensitivity
variations on the CCD. We have observed 8 crowded Galactic fields using this
technique during 2003 and 2004. Our analysis of the first of these fields
(centred on the open cluster NGC 6633) has yielded 49 variable stars and 4
shallow transit candidates. Follow-up observations of these candidates have
identified them as eclipsing binary systems. We use a detailed simulation of
our observations to estimate our sensitivity to short-period planets, and to
select a new observing strategy to maximise the number of planets detected.Comment: 16 pages, 9 figures, version published in MNRAS Updated figures,
references, and additional discussion in section
Lateral and vertical heterogeneity in the lithospheric mantle at the northern margin of the Pannonian Basin reconstructed from peridotite xenolith microstructures
International audienceThis study analyzes the microstructures and deformational characteristics of spinel peridotite xenoliths from the Nógrád‐Gömör Volcanic Field (NGVF), located on the northern margin of a young extensional basin presently affected by compression. The xenoliths show a wide range of microstructures, bearing the imprints of heterogeneous deformation and variable degrees of subsequent annealing. Olivine crystal preferred orientations (CPOs) have dominantly [010]‐fiber and orthorhombic patterns. Orthopyroxene CPOs indicate coeval deformation with olivine. Olivine J indices correlate positively with equilibration temperatures, suggesting that the CPO strength increases with depth. In contrast, the intensity of intragranular deformation in olivine varies as a function of the sampling locality. We interpret the microstructures and CPO patterns as recording deformation by dislocation creep in a transpressional regime, which is consistent with recent tectonic evolution in the Carpathian‐Pannonian region due to the convergence between the Adria microplate and the European platform. Postkinematic annealing is probably linked to percolation of metasomatism by mafic melts through the upper mantle of the NGVF prior to the eruption of the host alkali basalt. Elevated equilibration temperatures in xenoliths from the central part of the volcanic field are interpreted to be associated with the last metasomatic event, which only shortly preceded the ascent of the host magma. Despite well‐developed olivine CPOs in the xenoliths, which imply a strong seismic anisotropy, the lithospheric mantle alone cannot account for the shear wave splitting delay times measured in the NGVF, indicating that deformation in both the lithosphere and the asthenosphere contributes to the observed shear wave splitting
A new detached K7 dwarf eclipsing binary system
We present an analysis of a new, detached, double-lined eclipsing binary
system with K7 Ve components, discovered as part of the University of New South
Wales Extrasolar Planet Search. The object is significant in that only 6 other
binary systems are known with comparable or lower mass. Such systems offer
important tests of mass-radius theoretical models. Follow-up photometry and
spectroscopy were obtained with the 40-inch and 2.3m telescopes at SSO
respectively. An estimate of the radial velocity amplitude from spectral
absorption features, combined with the orbital inclination (83.5 deg) estimated
from lightcurve fitting, yielded a total mass of M=(1.041 +/- 0.06)M_sun and
component masses of M_A=(0.529 +/- 0.035)M_sun and M_B=(0.512 +/- 0.035)M_sun.
The radial velocity amplitude estimated from absorption features (167 +/-
3)kmps was found to be less than the estimate from the H_alpha emission lines
(175 +/- 1.5)kmps. The lightcurve fit produced radii of R_A=(0.641 +/-
0.05)R_sun and R_B=(0.608 +/- 0.06)R_sun, and a temperature ratio of
T_B/T_A=0.980 +/- 0.015. The apparent magnitude of the binary was estimated to
be V=13.9 +/- 0.2. Combined with the spectral type, this gave the distance to
the binary as 169 +/- 14 pc. The timing of the secondary eclipse gave a lower
limit on the eccentricity of the binary system of 0.0025 +/- 0.0005. This is
the most statistically significant non-zero eccentricity found for such a
system, possibly suggesting the presence of a third companion.Comment: 6 pages, published in MNRAS (08/2006
High-P metamorphism of rodingites during serpentinite dehydration (Cerro del Almirez, Southern Spain): Implications for the redox state in subduction zones
The transition between antigorite-serpentinite and chlorite-harzburgite at Cerro del Almirez (Betic Cordillera, Southern Spain) exceptionally marks in the field the front of antigorite breakdown at high pressure (~16–19 kbar) and temperature (~650°C) in a paleosubducted serpentinite. These ultramafic lithologies enclose three types of metarodingite boudins of variable size surrounded by metasomatic reaction rims. Type 1 Grandite-metarodingite (garnet+chlorite+diopside+titanite±magnetite±ilmenite) mainly crops out in the antigorite-serpentinite domain and has three generations of garnet. Grossular-rich Grt-1 formed during rodingitization at the seafloor (10 kbar, ~350–650°C, ~FMQ buffer) to influx events of oxidizing fluids (fO ~HM buffer) released by brucite breakdown in the host antigorite-serpentinite. Type 2 Epidote-metarodingite (epidote+diopside+titanite±garnet) derives from Type 1 and is the most abundant metarodingite type enclosed in dehydrated chlorite-harzburgite. Type 2 formed by increasing μSiO (from −884 to −860 kJ/mol) and decreasing μCaO (from −708 to −725 kJ/mol) triggered by the flux of high amounts of oxidizing fluids during the high-P antigorite breakdown in serpentinite. The growth of Grt-4, with low-grandite and high-pyralspite components, in Type 2 metarodingite accounts for progressive reequilibration of garnet with changing intensive variables. Type 3 Pyralspite-metarodingite (garnet+epidote+amphibole+chlorite±diopside+rutile) crops out in the chlorite-harzburgite domain and formed at peak metamorphic conditions (16–19 kbar, 660–684°C) from Type 2 metarodingite. This transformation caused the growth of a last generation of pyralspite-rich garnet (Grt-5) and the recrystallization of diopside into tremolitic amphibole at decreasing fO and μCaO (from −726 to −735 kJ/mol) and increasing μMgO (from −630 to −626 kJ/mol) due to chemical mixing between the metarodingite and the reaction rims. The different bulk Fe/Fe ratios of antigorite-serpentinite and chlorite-harzburgite, and of the three metarodingite types, reflect the highly heterogeneous oxidation state of the subducting slab and likely point to the transfer of localized oxidized reservoirs, such as metarodingites, into the deep mantle.“Ministerio de Economía, Industria y Competitividad” (MINECO), Grant/Award Number: CGL2012-32067, CGL201675224-R; Junta de Andalucía, Grant/ Award Number: RNM-145, P12-RNM3141; Ramón y Cajal, Grant/Award Number: RYC-2012-11314; MINECO, Grant/Award Number: CGL2016-81085-R, PCIN-2015-05
Observational detection of eight mutual eclipses and occultations between the satellites of Uranus
We carried out observations, with five different instruments ranging in
aperture from 0.4m to 10m, of the satellites of Uranus during that planet's
2007 Equinox. Our observations covered specific intervals of time when mutual
eclipses and occultations were predicted.
The observations were carried out in the near-infrared part of the spectrum
to mitigate the glare from the planet. Frames were acquired at rates > 1/min.
Following modelling and subtraction of the planetary source from these frames,
differential aperture photometry was carried out on the satellite pairs
involved in the predicted events. In all cases but one, nearby bright
satellites were used as reference sources.
We have obtained fifteen individual lightcurves, eight of which show a clear
drop in the flux from the satellite pair, indicating that a mutual event took
place. Three of these involve the faint satellite Miranda. All eight
lightcurves were model-fitted to yield best estimates of the time of maximum
flux drop and the impact parameter. In three cases best-fit albedo ratios were
also derived. We used these estimates to generate intersatellite astrometric
positions with typical formal uncertainties of <0.01 arcsec, several times
better than conventional astrometry of these satellites. The statistics of our
estimated event midtimes show a systematic lag, with the observations later
than predictions. In addition, lightcurves of two partial eclipses of Miranda
show no statistically significant evidence of a light drop, at variance with
the predictions. These indicate that new information about the Uranian
satellite system is contained in observations of mutual events acquired here
and by other groups.Comment: 8 pages, 3 figures, accepted for publication in Astronomy and
Astrophysics Uses aa style packag
Journey decision making: the influence on drivers of dynamic information presented on variable message signs
In many highways environments electronic media such as variable message signs are increasingly being used to provide drivers with up-to-date dynamic information in order to influence driving decision making during journeys. These decisions may be associated with strategic choices, such as route selection, or tactical decisions, such as driving at a certain speed, or altering driving style. This paper presents a study that used two methods - a scenario approach and a medium-fidelity driving simulator. Data from both methods are presented here and include decision making and driving performance data. These data provide an insight into the role of information and other contextual influences in decision making in the driving context specifically, but also has useful implications for the way in which information should be designed in other decision making contexts, such as travel using public transport, or supporting real-time complex control operations. The use of multiple data collection approaches also enabled data comparisons to be made, thus improving overall confidence in conclusions. The paper highlights the role of familiarity with information wording and context, level of detail, interpreted meaning, previous experience and contextual cues on trust in information and consequently behaviour in response to the information presented
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