660 research outputs found
The outburst radial velocity curve of X-Ray Nova Scorpii 1994 (=GRO J1655--40)
We present a reanalysis of the outburst radial velocity data for X-Ray Nova
Scorpii 1994. Using a model based on X-ray heating of the secondary star we
suggest a more realistic treatment of the radial velocity data. Solutions are
obtained in the (K_2,q) plane which, when combined with the published value for
the binary mass ratio and inclination, constrain the mass of the black hole to
within the region 4.1<M_1<6.6 Msun (90 per cent confidence), which is
significantly lower than the value obtained by Orosz & Bailyn (1997). This
reduced lower bound for the black hole mass together with the high space
velocity of the system is consistent with the idea that it was formed by the
post-supernova collapse of a neutron star.Comment: Accepted for MNRAS, 4 pages Latex, 4 figure
Inflation and financial sector correlation: the case of Bangladesh
This paper examines the impact of inflation on financial development in case of Bangladesh for the period of 1985-2005. In doing so, ARDL bounds testing approach and Error Correction Method (ECM) have been employed. Empirical findings reveal that high trends of inflation impede the performance of financial markets. GDP per capita promotes development of financial sector through its causal channels.Financial Sector, Inflation, Pakistan, ARDL Approach
Aquila X--1: a low inclination soft X-ray transient
We have obtained I-band photometry of the neutron star X-ray transient Aql
X--1 during quiescence. We find a periodicity at 2.487 cd-1, which we interpret
as twice the orbital frequency (19.30+/-0.05 h). Folding the data on the
orbital period, we model the light curve variations as the ellipsoidal
modulation of the secondary star. We determine the binary inclination to be
20--31 degrees (90 per cent confidence) and also 95 per cent upper limits to
the radial velocity semi-amplitude and rotational broadening of the secondary
star to be 117 kms-1 and 50 kms-1 respectively.Comment: 4 pages text, 3 figures, to appear in MNRA
A TiO study of the black-hole binary GRO J0422+32 in a very low state
We present 53 simultaneous photometric (I band) and spectroscopic (6900-9500
Angstroms) observations of J0422+32, taken during December 1997. From these we
determine that J0422+32 was in its lowest state yet observed, at
I=20.44+/-0.08. Using relative spectrophotometry, we show that it is possible
to correct very accurately for telluric absorption. Following this, we use the
TiO bands at 7055 Angstroms and 7589 Angstroms for a radial velocity study and
thereby obtain a semi-amplitude of 378+/-16kms-1, which yields
f(M)=1.191+/-0.021M_solar and q=9.0+2.2-2.7, consistent with previous
observations. We further demonstrate that this little explored method is very
powerful for such systems. We also determine a new orbital ephemeris of
HJD=2450274.4156+/-0.0009 + 0.2121600+/-0.0000002E.
We see some evidence for an ellipsoidal modulation, from which we determine
the orbital inclination of J0422+32 to be less than 45 degrees. We therefore
calculate a minimum mass for the primary of 2.22M_solar, consistent with a
black hole, but not necessarily the super-massive one proposed by Beekman et al
(1997). We obtain an M4-5 spectral type for the secondary star and determine
that the secondary contributes 38+/-2% of the flux that we observe from
J0422+32 over the range 6950-8400 Angstroms. From this we calculate the
distance to the system to be 1.39+/-0.15kpc.Comment: (1) Department of Physics, Keele University, Keele, Staffordshire,
ST5 5BG (2) Department of Astrophysics, Nuclear Physics Laboratory, Keble
Road, Oxfo rd, OX1 3RH Accepted, to appear in MNRAS 8 pages, 5 figure
Recommended from our members
Lamina Cribrosa and Choroid Features and Their Relationship to Stage of Pseudoexfoliation Glaucoma.
PurposeTo better understand the relationship of lamina cribrosa (LC) and choroid features to the severity of pseudoexfoliation glaucoma (PXG).MethodsIn this cross-sectional study, 137 eyes of 122 subjects (47 eyes with moderate/advanced PXG [mean deviation (MD), -15.0 ± 7.7 dB], 34 eyes with mild PXG [MD, -2.7 ± 1.5 dB], 32 aged-matched pseudoexfoliation syndrome [PXS] eyes, and 24 aged-matched control eyes) were investigated. Optic discs, LC thickness, and anterior LC depth (ALD; midsuperior, center, and midinferior) as well as peripapillary choroidal thickness were determined. Linear mixed modeling was used to adjust for age, sex, and axial length.ResultsA progressive decrease in LC thickness was found when comparing controls (271.9 ± 61.3 μm), PXS (212.6 ± 51.5 μm), mild PXG (180.8 ± 24.6 μm), and moderate/advance PXG (138.9 ± 37.5 μm) (P < 0.001). ALD was greater (P < 0.001) in moderate/advance glaucoma (306.7 ± 105.3 μm) and mild PXG (209.5 ± 79.7 μm) compared with PXS (155 ± 86.7 μm) and healthy controls (149.2 ± 103 μm). Although eyes with moderate/advance PXG had the thinnest choroid (117.2 ± 36.6 μm), choroidal thickness was comparable in mild PXG, PXS, and controls (150.0 ± 46.1, 159.7 ± 65.5, and 157.5 ± 51.1 μm, respectively; P = 0.002). Worse MD was the only factor associated with thinner LC (β = 2.344, P < 0.001) and choroid (β = 1.717, P = 0.009 μm) in PXG eyes. Higher IOP (β = 4.305, P = 0.013) and worse MD (β = -6.390, P < 0.001) were associated with deeper ALD in PXG.ConclusionsIn pseudoexfoliation, LC thinning is an early sign, and there is progressive thinning with advancing glaucoma. Choroidal thinning is observable only with moderate/advanced glaucoma. In PXG eyes, LC thickness, depth, and peripapillary choroidal thickness are associated with glaucoma severity
Optimising Agronomic Options At The Farm Scale
Strategic planning and policy development for environmentally sustainable and economically viable management options for the rice based farming systems require the assessment of management options using mathematical models which integrate our understanding of water and salt movement with economic considerations at both the farm and regional scales. This project also had strong links with LWRRDC/MIL/CSIRO project on optimising irrigation intensities in the Murray Valley. During this project a standalone farm scale hydrological economic model SWAGMAN Farm (Salt Water and Groundwater MANagement) was developed and customised for situations in the Coleambally and Murray Irrigation Areas. The model processes were developed and refined by using feed back from irrigation managers, regulators and community groups. The following major achievements have been made: · Collection of crop, soil, irrigation, climatic and economic data sets for fourteen farms in the Murray Irrigation Districts · Rigorous validation of model processes by applying the model to fourteen farms with a range of enterprise, soil and groundwater conditions. · Development of simulation and optimisation modes in SWAGMAN Farm to assess environmental and economic impacts of existing and optimal cropping patterns · Various improvements of water and salt balance processes to suit conditions in the Murray Districts and the Coleambally Irrigation Area · Incorporation of soil water content accounting which provides flexibility in the representation of various starting soil profile water content conditions, water availability to crops and rational computation of recharge and watertable rise during the cropping and fallow periods · Development of a Windows based GAMS independent version of SWAGMAN Farm. GAMS (General Algebraic Modelling System) was an expensive software platform for the previous version with inflexible licence requirements. The new version written in C++ language uses Microsoft Access databases and will be linked with a GIS interface in near future. These sensitivity runs and model developments gained the confidence of members of the steering committee who provided vital inputs throughout this project. While considerable progress was made, they see the need for the work to continue to the stage where it can be applied to assist strategic planning and policy development, taking into account local regional conditions. Parallel to the modelling project an intensive paddock water monitoring project titled “Rigorously determined water balance benchmarks for irrigated crops and pasture’ was also initiated by the steering committee with the assistance of CSIRO, MIL, NSW Agriculture and LWRRDC. The purpose of the monitoring project was to further customise SWAGMAN Farm to local conditions and to validate the model results with the field data. Since monitoring projects take significant time in setting up and calibrating equipment, data analysis has only recently started, however initial comparisons of model results with the field results suggest that the improved SWAGMAN Farm can reasonably simulate field situations. However this work needs to continue to maximise the benefits of the paddock water balance monitoring. However, due to the wide range of groundwater, enterprise and soil conditions in the irrigation areas, SWAGMAN Farm needs to be applied to every farm to develop soundly based policy options. The need for application to individual farms is further driven by the complex regional groundwater interactions causing reversal (downward to upward and local discharge zones) of leakage rates in parts of the irrigation areas e.g. Murray Valley. This project has demonstrated that it is possible to develop methodology which helps assess optimal irrigation intensity within a multitude of biophysical and socio-economic constraints. The methods developed have scientific validity in capturing and representing key processes, and have community acceptance as a way of examining options that are important to them
Chemical Abundances in the Secondary Star in the Black Hole Binary A0620-00
Using a high resolution spectrum of the secondary star in the black hole
binary A0620-00, we have derived the stellar parameters and veiling caused by
the accretion disk in a consistent way. We have used a chi^2 minimization
procedure to explore a grid of 800 000 LTE synthetic spectra computed for a
plausible range of both stellar and veiling parameters. Adopting the best model
parameters found, we have determined atmospheric abundances of Fe, Ca, Ti, Ni
and Al. The Fe abundance of the star is [Fe/H]=0.14 +- 0.20. Except for Ca, we
found the other elements moderately over-abundant as compared with stars in the
solar neighborhood of similar iron content. Taking into account the small
orbital separation, the mass transfer rate and the mass of the convection zone
of the secondary star, a comparison with element yields in supernova explosion
models suggests a possible explosive event with a mass cut comparable to the
current mass of the compact object. We have also analyzed the Li abundance,
which is unusually high for a star of this spectral type and relatively low
mass.Comment: 32 pages, 5 tables and 11 figures, uses rotate.st
Towards Open World Object Detection
Humans have a natural instinct to identify unknown object instances in their
environments. The intrinsic curiosity about these unknown instances aids in
learning about them, when the corresponding knowledge is eventually available.
This motivates us to propose a novel computer vision problem called: `Open
World Object Detection', where a model is tasked to: 1) identify objects that
have not been introduced to it as `unknown', without explicit supervision to do
so, and 2) incrementally learn these identified unknown categories without
forgetting previously learned classes, when the corresponding labels are
progressively received. We formulate the problem, introduce a strong evaluation
protocol and provide a novel solution, which we call ORE: Open World Object
Detector, based on contrastive clustering and energy based unknown
identification. Our experimental evaluation and ablation studies analyze the
efficacy of ORE in achieving Open World objectives. As an interesting
by-product, we find that identifying and characterizing unknown instances helps
to reduce confusion in an incremental object detection setting, where we
achieve state-of-the-art performance, with no extra methodological effort. We
hope that our work will attract further research into this newly identified,
yet crucial research direction.Comment: To appear in CVPR 2021 as an ORAL paper. Code is available in
https://github.com/JosephKJ/OWO
Correlated Timing and Spectral Variations of the Soft X-ray Transient Aquila X-1: Evidence for an Atoll classification
Based on Rossi X-ray Timing Explorer data, we discuss the classification of
the soft X-ray transient Aquila X-1 in the Z/atoll scheme, and the relation of
its kilohertz quasi-periodic oscillations (kHz QPO) properties to the X-ray
colors. The color-color diagram shows one elongated ("banana") structure and
several "islands" of data points. The power spectra of the island are best
represented by a broken power-law, whereas those of the banana by a power-law
below ~ 1 Hz plus an exponentially cut-off component at intermediate
frequencies (30-60 Hz). The parameters of these two components change in
correlation with the position of the source in the color-color diagram. Based
on the pattern that the source shows in the color-color diagram and its
aperiodic variability we conclude that Aquila X-1 is an atoll source. We have
also investigated the possible correlation between the frequency of the kHz QPO
and the position of the source in the color-color diagram. The complexity seen
in the frequency versus count rate diagram is reduced to a single track when
the frequency is plotted against hard or soft color.Comment: 9 pages, 5 figures. Accepted for publication in Ap
Loss of function mutations in RP1 are responsible for retinitis pigmentosa in consanguineous familial cases.
PurposeThis study was undertaken to identify causal mutations responsible for autosomal recessive retinitis pigmentosa (arRP) in consanguineous families.MethodsLarge consanguineous families were ascertained from the Punjab province of Pakistan. An ophthalmic examination consisting of a fundus evaluation and electroretinography (ERG) was completed, and small aliquots of blood were collected from all participating individuals. Genomic DNA was extracted from white blood cells, and a genome-wide linkage or a locus-specific exclusion analysis was completed with polymorphic short tandem repeats (STRs). Two-point logarithm of odds (LOD) scores were calculated, and all coding exons and exon-intron boundaries of RP1 were sequenced to identify the causal mutation.ResultsThe ophthalmic examination showed that affected individuals in all families manifest cardinal symptoms of RP. Genome-wide scans localized the disease phenotype to chromosome 8q, a region harboring RP1, a gene previously implicated in the pathogenesis of RP. Sanger sequencing identified a homozygous single base deletion in exon 4: c.3697delT (p.S1233Pfs22*), a single base substitution in intron 3: c.787+1G>A (p.I263Nfs8*), a 2 bp duplication in exon 2: c.551_552dupTA (p.Q185Yfs4*) and an 11,117 bp deletion that removes all three coding exons of RP1. These variations segregated with the disease phenotype within the respective families and were not present in ethnically matched control samples.ConclusionsThese results strongly suggest that these mutations in RP1 are responsible for the retinal phenotype in affected individuals of all four consanguineous families
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