339 research outputs found
Modelling the energy dependencies of high-frequency QPO in black hole X-ray binaries
We model energy dependencies of the quasi periodic oscillations (QPO) in the
model of disc epicyclic motions, with X-ray modulation caused by varying
relativistic effects. The model was proposed to explain the high frequency QPO
observed in X-ray binaries. We consider two specific scenarios for the geometry
of accretion flow and spectral formation. Firstly, a standard cold accretion
disc with an active X-ray emitting corona is assumed to oscillate. Secondly,
only a hot X-ray emitting accretion flow oscillates, while the cold disc is
absent at the QPO radius. We find that the QPO spectra are generally similar to
the spectrum of radiation emitted at the QPO radius, and they are broadened by
the relativistic effects. In particular, the QPO spectrum contains the disc
component in the oscillating disc with a corona scenario. We also review the
available data on energy dependencies of high frequency QPO, and we point out
that they appear to lack the disc component in their energy spectra. This would
suggest the hot flow geometry in the spectral states when high frequency QPO
are observed.Comment: 8 pages, accepted for publication in MNRA
Energy spectra of X-ray quasi-periodic oscillations in accreting black hole binaries
We investigate the energy dependencies of X-ray quasi-periodic oscillations
in black hole X-ray binaries. We analyze RXTE data on both the low- and
high-frequency QPO. We construct the low-f QPO energy spectra, and demonstrate
that they do not contain the thermal disk component, even though the latter is
present in the time averaged spectra. The disk thus does not seem to
participate in the oscillations. Moreover the QPO spectra are harder than the
time averaged spectra when the latter are soft, which can be modeled as a
result of modulations occurring in the hot plasma. The QPO spectra are softer
than the time averaged spectra when the latter are hard. The absence of the
disk component in the QPO spectra is true also for the high-frequency
(hecto-Hz) QPO observed in black hole binaries. We compute the QPO spectra
expected from the model of disk resonances.Comment: 4 pages, Proc. of IAU Symposium 238, "Black Holes from Stars to
Galaxies - across the range of masses", Prague, Aug 200
X-ray observations of the hot phase in Sgr~A*
We analyze 134 ks Chandra ACIS-I observations of the Galactic Centre (GC)
performed in July 2011. The X-ray image with the field of view
contains the hot plasma surrounding the Sgr~A*. The obtained surface brightness
map allow us to fit Bondi hot accretion flow to the innermost hot plasma around
the GC. We have fitted spectra from region up to from Sgr~A* using a
thermal bremsstrahlung model and four Gaussian profiles responsible for
K emission lines of Fe, S, Ar, and Ca. The X-ray surface brightness
profile up to from Sgr~A* found in our data image, was successfully fitted
with the dynamical model of Bondi spherical accretion. By modelling the surface
brightness profile, we derived the temperature and number density profiles in
the vicinity of the black hole. The best fitted model of spherical Bondi
accretion shows that this type of flow works only up to and implies outer
plasma density and temperature to be:
cm and keV respectively. We show
that the Bondi flow can reproduce observed surface brightness profile up to
from Sgr~A* in the Galactic Center. This result strongly suggests the
position of stagnation radius in the complicated dynamics around GC. The
Faraday rotation computed from our model towards the pulsar PSR J1745-2900 near
the GC agrees with the observed one, recently reported.Comment: 10 pages, 7 figures, accepted for publication in A&
What can we learn about quasars from alpha_OX measurements in galactic black hole binaries?
We draw a comparison between AGN and Galactic black hole binaries using a
uniform description of spectral energy distribution of these two classes of
accreting X-ray sources. We parametrize spectra of GBHs with an alpha_GBH
parameter which we define as a slope of a nominal power law function between 3
and 20 keV. We show that this parameter can be treated as an equivalent of the
X-ray loudness, alpha_OX, used to describe AGN spectra. We do not find linear
correlation between the alpha_GBH and disc flux (similar to that between
alpha_OX and optical/UV luminosity found in AGN). Instead, we show that
alpha_GBH follows a well defined pattern during a GBH outburst. We find that
alpha_GBH tend to cluster around 1, 1.5 and 2, which correspond to a hard, very
high/intermediate and soft spectral state, respectively. We conclude that
majority of the observed Type 1 radio quiet AGN are in a spectral state
corresponding to a very high/intermediate state of GBHs. The same conclusion is
valid for radio loud AGN. We also study variations of the spectral slopes
(alpha_GBH and the X-ray photon index, Gamma) as a function of disc and
Comptonization fluxes. We discuss these dependencies in the context of
correlations of alpha_OX and Gamma with the optical/UV and X-ray 2 keV fluxes
considered for AGN and quasars.Comment: 10 pages, 7 figures, accepted for publication in MNRA
Synthetic catalog of black holes in the Milky Way
We present an open-access database which includes a synthetic catalog of
black holes in the Milky Way. To calculate evolution of single and binary stars
we used updated population synthesis code StarTrack. We applied a new model of
star formation history and chemical evolution of Galactic disk, bulge and halo
synthesized from observational and theoretical data. We find that at the
current moment Milky Way (disk+bulge+halo) contains about 1.2 x 10^8 single
black holes with average mass of about 14 Msun and 9.3 x 10^6 BHs in binary
systems with average mass of 19 Msun. We present basic statistical properties
of BH populations such as distributions of single and binary BH masses,
velocities, orbital parameters or numbers of BH binary systems in different
evolutionary configurations. We find that the most massive BHs are formed in
mergers of binary systems, such as BH-MS, BH+He, BH-BH. The metallicity of
stellar population has a significant impact on the final BH mass due to the
stellar winds. Therefore the most massive single BH in our simulation, 113
Msun, originates from a merger of a helium star and a black hole in a low
metallicity stellar environment in Galactic halo. The most massive BH in binary
system is 60 Msun and was also formed in Galactic halo. We constrain that only
0.006% of total Galactic halo mass (including dark matter) could be hidden in
the form of stellar origin BHs which are not detectable by current
observational surveys. Galactic binary BHs are minority (10% of all Galactic
BHs) and most of them are in BH-BH systems. The current Galactic merger rates
for two considered common envelope models which are: 3-81 Myr^-1 for BH-BH, 1-9
Myr^-1, for BH-NS and 14-59 Myr^-1 for NS-NS systems. Data files are available
at https://bhc.syntheticuniverse.org/.Comment: 21 pages, A&A accepted, data from catalog available onlin
effects of in ovo injection of prebiotics and synbiotics on the productive performance and microstructural features of the superficial pectoral muscle in broiler chickens
ABSTRACT The aim of the study was to compare the effects of 2 prebiotics and 2 synbiotics injected in ovo on productivity parameters, quality, and microstructure of the superficial pectoral muscle in 35-day-old broiler chickens. On day 12 of incubation, 9,000 eggs Ross 308 were randomly divided into 5 experimental groups treated with different bioactives in ovo injected: C, control with physiological saline; PI, with 1.760 mg inulin; PB, with 0.528 mg of commercial prebiotic Bi2 tos; SI, with 1.760 mg inulin and 1,000 CFU Lactococcus lactis spp. lactis IBB SL1; SB, with 0.528 mg Bi2 tos and 1,000 CFU Lactococcus lactis spp. cremoris IBB SC1. The synbiotic solution contained 20 μl bacterial suspension and 180 μl prebiotic solution. For productive parameters and further tests ten male birds for each experimental group were used. The birds were slaughtered on day 35 of age. At slaughter, samples of the left pectoral muscles were taken and preserved by freezing in liquid nitrogen. The pH and color of the meat were evaluated at 45 min and 24 h post-mortem. Water holding capacity (WHC) was measured and expressed as the percentage of free water in meat. Microscopic specimens were analysed using MultiScan software for the measurement of the percentage of oxidative and glycolytic fibres and mean diameter of the muscle fibres. In ovo injection of prebiotics Bi2 tos had a positive effect on body weight. In prebiotic group (PI) a negative impact on hatchability was observed. Prebiotics and synbiotics had no influence on the yield of the carcass and pectoral muscle. Bioactive compounds had a significant effect on the quality of meat parameters such as: pH 24 h (PI and PB group), L* 45' (SI and SB group), and WHC (groups PB, SI, and SB). The analysis of the enzymatic profile showed a significant increase in the percentage of glycolytic fibres in the pectoral muscle from chicken treated with a synbiotic with the addition of inulin (group SI)
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