72 research outputs found
The impact of real estate, inequality and current account imbalances on excessive credit: A cross country analysis
The numerous financial crises in the 20th and 21st century demonstrate the role of excessive credit
as the main instigator of financial crises. Could this excessive credit be natural byproducts of
lingering economic ailments such as, income inequality, property bubbles and persistent current
account imbalances? This study attempts to answer this question by applying the Least Squares
Dummy Variable (LSDVC) and dynamic GMM estimations based on the data of ten countries
from the year 2004 to 2012. Whilst past literature have investigated the effect of income
inequality, dominant real estate sector and current account imbalances on excessive credit
separately, this study extends the literature by examining the impact of all three variables on
excessive credit aggregately. Our findings tend to indicate that there do exist a positive
relationship between all three variables and excessive credit. However, we found that only income
inequality and the real estate sector contribute significantly to excessive credit but current
account imbalances only marginally do so. We also discovered that the contribution to excessive
credit by the banking sector is just about twice the amount of all three variables combined. Our
results serve as evidence for policymakers interested in reducing excessive credit by controlling
all three variables as well as the banking sector
The impact of real estate, inequality and current account imbalances on excessive credit: A cross country analysis
The numerous financial crises in the 20th and 21st century demonstrate the role of excessive credit
as the main instigator of financial crises. Could this excessive credit be natural byproducts of
lingering economic ailments such as, income inequality, property bubbles and persistent current
account imbalances? This study attempts to answer this question by applying the Least Squares
Dummy Variable (LSDVC) and dynamic GMM estimations based on the data of ten countries
from the year 2004 to 2012. Whilst past literature have investigated the effect of income
inequality, dominant real estate sector and current account imbalances on excessive credit
separately, this study extends the literature by examining the impact of all three variables on
excessive credit aggregately. Our findings tend to indicate that there do exist a positive
relationship between all three variables and excessive credit. However, we found that only income
inequality and the real estate sector contribute significantly to excessive credit but current
account imbalances only marginally do so. We also discovered that the contribution to excessive
credit by the banking sector is just about twice the amount of all three variables combined. Our
results serve as evidence for policymakers interested in reducing excessive credit by controlling
all three variables as well as the banking sector
Risk Taking Behavior and Capital Adequacy in a Mixed Banking System: New Evidence from Malaysia using Dynamic OLS and Two-step Dynamic System GMM Estimators
The financial and banking crises around the world have prompted the regulators to revise, among others, the capital level of the banks to deal with the excessive risks taken by the banks, both conventional and Islamic. This study is the first attempt to investigate the relationship between risky assets and capital level in a mixed banking system applying the panel VECM and dynamic GMM estimators. The Malaysian mixed banking system is used as a case study taking panel data covering the period from December 2006 to October 2013. Our statistical results based on dynamic OLS (DOLS) tend to indicate that there is a positive relationship between the capital ratio (CAR) and risk weighted asset ratio (RWA) in the long run and also, the causality analysis based on panel VECM and two-step dynamic System GMM tends to indicate unidirectional causality in that the RWA is positively driven by CAR. Our results appear to suggest that higher capital buffer (excess capital above regulatory capital requirement) might have opened up more space for bank managers to taking risky positions while assisted by increasing domestic demand for credit facilities under favorable economic condition of Malaysia. In other words, high capital growth and capital buffer provides an extra cushion for Malaysian banks to pursue relatively riskier financing activities. For the full-fledge Islamic banks (IB) and Islamic bank subsidiaries (IBS), the existence of a cointegrating relationship between RWA and CAR suggests that the way the managers of Islamic banks behave towards risky assets follows the conventional practice
Barium & related stars and their white-dwarf companions II. Main-sequence and subgiant stars
Barium (Ba) dwarfs and CH subgiants are the less-evolved analogues of Ba and
CH giants. They are F- to G-type main-sequence stars polluted with heavy
elements by a binary companion when the latter was on the Asymptotic Giant
Branch (AGB). This companion is now a white dwarf that in most cases cannot be
directly detected. We present a large systematic study of 60 objects classified
as Ba dwarfs or CH subgiants. Combining radial-velocity measurements from
HERMES and SALT high-resolution spectra with radial-velocity data from CORAVEL
and CORALIE, we determine the orbital parameters of 27 systems. We also derive
their masses by comparing their location in the Hertzsprung-Russell diagram
with evolutionary models. We confirm that Ba dwarfs and CH subgiants are not at
different evolutionary stages and have similar metallicities, despite their
different names. Additionally, Ba giants appear significantly more massive than
their main-sequence analogues. This is likely due to observational biases
against the detection of hotter main-sequence post-mass-transfer objects.
Combining our spectroscopic orbits with the Hipparcos astrometric data, we
derive the orbital inclinations and the mass of the WD companion for four
systems. Since this cannot be done for all systems in our sample yet (but
should be with upcoming Gaia data releases), we also analyse the mass-function
distribution of our binaries. We can model this distribution with very narrow
mass distributions for the two components and random orbital orientation on the
sky. Finally, based on BINSTAR evolutionary models, we suggest that the orbital
evolution of low-mass Ba systems can be affected by a second phase of
interaction along the Red Giant Branch of the Ba star, impacting on the
eccentricities and periods of the giants.Comment: Accepted for publication in A&A on the 5th of April, 201
Risk Taking Behavior and Capital Adequacy in a Mixed Banking System: New Evidence from Malaysia using Dynamic OLS and Two-step Dynamic System GMM Estimators
The financial and banking crises around the world have prompted the regulators to revise, among others, the capital level of the banks to deal with the excessive risks taken by the banks, both conventional and Islamic. This study is the first attempt to investigate the relationship between risky assets and capital level in a mixed banking system applying the panel VECM and dynamic GMM estimators. The Malaysian mixed banking system is used as a case study taking panel data covering the period from December 2006 to October 2013. Our statistical results based on dynamic OLS (DOLS) tend to indicate that there is a positive relationship between the capital ratio (CAR) and risk weighted asset ratio (RWA) in the long run and also, the causality analysis based on panel VECM and two-step dynamic System GMM tends to indicate unidirectional causality in that the RWA is positively driven by CAR. Our results appear to suggest that higher capital buffer (excess capital above regulatory capital requirement) might have opened up more space for bank managers to taking risky positions while assisted by increasing domestic demand for credit facilities under favorable economic condition of Malaysia. In other words, high capital growth and capital buffer provides an extra cushion for Malaysian banks to pursue relatively riskier financing activities. For the full-fledge Islamic banks (IB) and Islamic bank subsidiaries (IBS), the existence of a cointegrating relationship between RWA and CAR suggests that the way the managers of Islamic banks behave towards risky assets follows the conventional practice
Binary-object spectral-synthesis in 3D (BOSS-3D) -- Modelling H-alpha emission in the enigmatic multiple system LB-1
Context: To quantitatively decode the information stored within an observed
spectrum, detailed modelling of the physical state and accurate radiative
transfer solution schemes are required. In the analysis of stellar spectra, the
numerical model often needs to account for binary companions and 3D structures
in the stellar envelopes. The enigmatic binary (or multiple) system LB-1
constitutes a perfect example of such a complex multi-D problem. Aims: To
improve our understanding of the LB-1 system, we directly modelled the
phase-dependent H-alpha line profiles of this system. To this end, we developed
a multi-purpose binary-object spectral-synthesis code in 3D (BOSS-3D). Methods:
BOSS-3D calculates synthetic line profiles for a given state of the
circumstellar material. The standard pz-geometry commonly used for single stars
is extended by defining individual coordinate systems for each involved object
and by accounting for the appropriate coordinate transformations. The code is
then applied to the LB-1 system, considering two main hypotheses, a binary
containing a stripped star and Be star, or a B star and a black hole with a
disc. Results: Comparing these two scenarios, neither model can reproduce the
detailed phase-dependent shape of the H-alpha line profiles. A satisfactory
match with the observations, however, is obtained by invoking a disc around the
primary object in addition to the Be-star disc or the black-hole accretion
disc. Conclusions: The developed code can be used to model synthetic line
profiles for a wide variety of binary systems, ranging from transit spectra of
planetary atmospheres, to post-asymptotic giant branch binaries including
circumstellar and circumbinary discs and massive-star binaries with stellar
winds and disc systems. For the LB-1 system, our modelling provides strong
evidence that each object in the system contains a disc-like structure
Is HR 6819 a triple system containing a black hole? -- An alternative explanation
HR 6819 was recently proposed to be a triple system consisting of an inner
B-type giant + black hole binary with an orbital period of 40d and an outer Be
tertiary. This interpretation is mainly based on two inferences: that the
emission attributed to the outer Be star is stationary, and that the inner
star, which is used as mass calibrator for the black hole, is a B-type giant.
We re-investigate the properties of HR 6819 by spectral disentangling and an
atmosphere analysis of the disentangled spectra to search for a possibly
simpler alternative explanation for HR 6819. Disentangling implies that the Be
component is not a static tertiary, but rather a component of the binary in the
40-d orbit. The inferred radial velocity amplitudes imply an extreme mass ratio
of M_2/M_1 = 15 +/- 3. We infer spectroscopic masses of 0.4
Msun and 6 Msun for the primary and secondary, which agree well
with the dynamical masses for an inclination of i = 32 deg. This indicates that
the primary might be a stripped star rather than a B-type giant. Evolutionary
modelling suggests that a possible progenitor system would be a tight (P_i ~
2d) B+B binary system that experienced conservative mass transfer. While the
observed nitrogen enrichment of the primary conforms with the predictions of
the evolutionary models, we find no indications for the predicted He
enrichment. We suggest that HR 6819 is a binary system consisting of a stripped
B-type primary and a rapidly-rotating Be star that formed from a previous
mass-transfer event. In the framework of this interpretation, HR 6819 does not
contain a black hole. Interferometry can distinguish between these two
scenarios by providing an independent measurement of the separation between the
visible components.Comment: Submitted to A&A, 13 pages (16 figures and 2 tables); 4 pages
supplementary material (4 figures and 4 tables). Comments are welcom
Empirical mass-loss rates and clumping properties of Galactic early-type O supergiants
International audienceAims. We investigate the impact of optically thick clumping on spectroscopic stellar wind diagnostics in O supergiants and constrain wind parameters associated with porosity in velocity space. This is the first time the effects of optically thick clumping have been investigated for a sample of massive hot stars, using models which include a full optically thick clumping description. Methods. We re-analyse existing spectroscopic observations of a sample of eight O supergiants previously analysed with the non-local-thermodynamic-equilibrium (NLTE) atmosphere code CMFGEN. Using a genetic algorithm wrapper around the NLTE atmosphere code FASTWIND we obtain simultaneous fits to optical and ultraviolet spectra and determine photospheric properties, chemical surface abundances and wind properties. Results. We provide empirical constraints on a number of wind parameters including the clumping factors, mass-loss rates and terminal wind velocities. Additionally, we establish the first systematic empirical constraints on velocity filling factors and interclump densities. These are parameters that describe clump distribution in velocity-space and density of the interclump medium in physical-space, respectively. We observe a mass-loss rate reduction of a factor of 3.6 compared to theoretical predictions from Vink et al. (2000), and mass-loss rates within a factor 1.4 of theoretical predictions from Björklund et al. (2021). Conclusions. We confirm that including optically thick clumping allows simultaneous fitting of optical recombination lines and ultraviolet resonance lines, including the unsaturated ultraviolet phosphorus lines (P v λλ1118-1128), without reducing the phosphorus abundance. We find that, on average, half of the wind velocity field is covered by dense clumps. We also find that these clumps are 25 times denser than the average wind, and that the interclump medium is 3-10 times less dense than the mean wind. The former result agrees well with theoretical predictions, the latter suggests that lateral filling-in of radially compressed gas might be critical for setting the scale of the rarefied interclump matter
Tango of celestial dancers: A sample of detached eclipsing binary systems containing g-mode pulsating components. A case study of KIC9850387
Context. Eclipsing binary systems with components that pulsate in gravity modes (g modes) allow for simultaneous and independent constraints of the chemical mixing profiles of stars. The high precision of the dynamical masses and radii as well as the imposition of identical initial chemical compositions and equivalent ages provide strong constraints during the modelling of g-mode period-spacing patterns.
Aims. We aim to assemble a sample of g-mode pulsators in detached eclipsing binaries with the purpose of finding good candidates for future evolutionary and asteroseismic modelling. In addition, we present a case study of the eclipsing binary KIC9850387, identified as our most promising candidate, and detail the results of the observational spectroscopic, photometric, and asteroseismic analysis of the system.
Methods. We selected all of the detached eclipsing binaries in the Kepler eclipsing binary catalogue with Kepler Input Catalogue (KIC) temperatures between 6000 K and 10 000 K, and performed a visual inspection to determine the presence and density of g modes, and the presence of g-mode period-spacing patterns in their frequency spectra. We then characterised our sample based on their g-mode pulsational parameters and binary and atmospheric parameters. A spectroscopic follow-up of our most promising candidate was then performed, and the orbital elements of the system were extracted. We then performed spectral disentangling followed by atmospheric modelling and abundance analysis for the primary star. We utilised an iterative approach to simultaneously optimise the pulsational and eclipse models, and subsequently performed an analysis of the pressure- (p-) and g-mode pulsational frequencies.
Results. We compiled a sample of 93 Kepler eclipsing binary stars with g-mode pulsating components and identified clear g-mode period-spacing patterns in the frequency spectra of seven of these systems. We also identified 11 systems that contained hybrid p- and g-mode pulsators. We found that the g-mode pulsational parameters and the binary and atmospheric parameters of our sample are weakly correlated at best, as expected for detached main-sequence binaries. We find that the eclipsing binary KIC9850387 is a double-lined spectroscopic binary in a near-circular orbit with a hybrid p- and g-mode pulsating primary with M_p = 1.66_(−0.01)^(+0.01) M⊙ and R_p = 2.154_(−0.004)^(+0.002) R⊙, and a solar-like secondary with M_s = 1.062_(−0.005)^(+0.003) M⊙ and R_s = 1.081_(−0.002)^(+0.003) R⊙. We find ℓ = 1 and ℓ = 2 period-spacing patterns in the frequency spectrum of KIC9850387 spanning more than ten radial orders each, which will allow for stringent constraints of stellar structure during future asteroseismic modelling
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