29,220 research outputs found
Viscous timescale in high mass X-ray binaries
Context: Low mass X-ray binaries were found to have very low frequency breaks
in their power density spectra below which the power density spectra are nearly
in white noise structure and at higher frequencies they approximately follow
the law.
Aims: In 2005, Gilfanov and Arefiev studied X-ray variability of persistent
LMXBs in the Hz frequency range and
To determine whether high mass X-ray binary power density spectra have
similar properties and the findings for low mass X-ray binaries are also valid
for high mass binaries, we analyzed the time series of high mass X-ray binary
sources produced by All Sky Monitor of Rossi X-ray Timing Explorer.
Method: We obtained the power density spectra of the high mass X-ray binaries
using the cosine transform of autocorrelation function.
Results: We identified break frequencies for seven sources, namely OAO
1657-415, SS 433, Vela X-1, SMC X-1, 4U 1700-377, GX 301-2, and LMC X-1. The
normalized break frequencies with respect to the orbital frequency
() for sources OAO 1657-415, SS 433, SMC X-1 and LMC X-1
are consistent with those of Roche lobe overflow systems. The other high mass
X-ray binary systems, Vela X-1, GX 301-2, and 4U 1700-377, however, have larger
break frequency ratios, , which are indicative of short
viscous times. These are all wind-accreting sources and the stellar winds in
the systems allow the formation of only short radius discs.
Consequently, we qualitatively distinguished the Roche lobe overflow binaries
from the wind accreting system by comparing their normalized break frequencies.Comment: 9 pages, 5 figures, accepted by A&
A blowout jet associated with one obvious extreme-ultraviolet wave and one complicated coronal mass ejection event
In this paper, we present a detailed analysis of a coronal blowout jet
eruption which was associated with an obvious extreme-ultraviolet (EUV) wave
and one complicated coronal mass ejection (CME) event based on the
multi-wavelength and multi-view-angle observations from {\sl Solar Dynamics
Observatory} and {\sl Solar Terrestrial Relations Observatory}. It is found
that the triggering of the blowout jet was due to the emergence and
cancellation of magnetic fluxes on the photosphere. During the rising stage of
the jet, the EUV wave appeared just ahead of the jet top, lasting about 4
minutes and at a speed of 458 - \speed{762}. In addition, obvious dark material
is observed along the EUV jet body, which confirms the observation of a
mini-filament eruption at the jet base in the chromosphere. Interestingly, two
distinct but overlapped CME structures can be observed in corona together with
the eruption of the blowout jet. One is in narrow jet-shape, while the other
one is in bubble-shape. The jet-shaped component was unambiguously related with
the outwardly running jet itself, while the bubble-like one might either be
produced due to the reconstruction of the high coronal fields or by the
internal reconnection during the mini-filament ejection according to the
double-CME blowout jet model firstly proposed by Shen et al. (2012b),
suggesting more observational evidence should be supplied to clear the current
ambiguity based on large samples of blowout jets in future studies.Comment: APJ, Accepted October 19, 201
Covariant calculation of mesonic baryon decays
We present covariant predictions for pi and eta decay modes of N and Delta
resonances from relativistic constituent-quark models based on
one-gluon-exchange and Goldstone-boson-exchange dynamics. The results are
calculated within the point-form approach to Poincare-invariant relativistic
quantum mechanics applying a spectator-model decay operator. The direct
predictions of the constituent-quark models for covariant pi and eta decay
widths show a behaviour completely different from previous ones calculated in
nonrelativistic or so-called semirelativistic approaches. It is found that the
present theoretical results agree with experiment only in a few cases but
otherwise always remain smaller than the experimental data (as compiled by the
Particle Data Group). Possible reasons for this behaviour are discussed with
regard to the quality of both the quark-model wave functions and the mesonic
decay operator.Comment: 10 pages, 2 figures, accepted for publication in Phys. Rev.
Polarization of Broad Absorption Line QSOs I. A Spectropolarimetric Atlas
We present a spectropolarimetric survey of 36 broad absorption line
quasi-stellar objects (BAL QSOs). The continuum, absorption trough, and
emission line polarization of BAL QSOs yield clues about their structure. We
confirm that BAL QSOs are in general more highly polarized than non-BAL QSOs,
consistent with a more equatorial viewing direction for the former than the
latter. We have identified two new highly-polarized QSOs in our sample
(1232+1325 and 1333+2840). The polarization rises weakly to the blue in most
objects, perhaps due to scattering and absorption by dust particles. We find
that a polarization increase in the BAL troughs is a general property of
polarized BAL QSOs, indicating an excess of scattered light relative to direct
light, and consistent with the unification of BAL QSOs and non-BAL QSOs. We
have also discovered evidence of resonantly scattered photons in the red wing
of the C IV broad emission lines of a few objects. In most cases, the broad
emission lines have lower polarization and a different position angle than the
continuum. The polarization characteristics of low-ionization BAL QSOs are
similar to those of high-ionization BAL QSOs, suggesting a similar BAL wind
geometry.Comment: 39 pages, 6 figures (20 .gif files), accepted for publication in The
Astrophysical Journal Supplement
Vector meson-vector meson interaction in a hidden gauge unitary approach
The formalism developed recently to study vector meson--vector meson
interaction, and applied to the case of , is extended to study the
interaction of the nonet of vector mesons among themselves. The interaction
leads to poles of the scattering matrix corresponding to bound states or
resonances. We show that 11 states (either bound or resonant) get dynamically
generated in nine strangeness-isospin-spin channels. Five of them can be
identified with those reported in the PDG, i.e., the , ,
, , and . The masses of the latter three
tensor states have been used to fine-tune the free parameters of the unitary
approach, i.e., the subtraction constants in evaluating the vector meson
-vector meson loop functions in the dimensional regularization scheme. The
branching ratios of these five dynamically generated states are found to be
consistent with data. The existence of the other six states should be taken as
predictions to be tested by future experiments.Comment: typos corrected; more discussions; one of the appendix rearrange
The Volatility Trend of Protosolar and Terrestrial Elemental Abundances
We present new estimates of protosolar elemental abundances based on an
improved combination of solar photospheric abundances and CI chondritic
abundances. These new estimates indicate CI chondrites and solar abundances are
consistent for 60 elements. We compare our new protosolar abundances with our
recent estimates of bulk Earth composition (normalized to aluminium), thereby
quantifying the devolatilization in going from the solar nebula to the
formation of the Earth. The quantification yields a linear trend , where is the Earth-to-Sun abundance ratio and
is the 50 condensation temperature of elements. The best fit
coefficients are: and . The
quantification of these parameters constrains models of devolatilization
processes. For example, the coefficients and determine a
critical devolatilization temperature for the Earth K. The terrestrial abundances of elements with are depleted compared with solar abundances,
whereas the terrestrial abundances of elements with are indistinguishable from solar abundances. The
terrestrial abundance of Hg ( = 252 K) appears anomalously high under the
assumption that solar and CI chondrite Hg abundances are identical. To resolve
this anomaly, we propose that CI chondrites have been depleted in Hg relative
to the Sun by a factor of . We use the best-fit volatility trend to
derive the fractional distribution of carbon and oxygen between volatile and
refractory components (, ). We find (, ) for carbon and (, ) for
oxygen.Comment: Accepted for publication in Icarus. 28 pages, 12 figures, 5 tables.
Compared to v1, the results and conclusion are the same, while discussion of
results and implications is expanded considerabl
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