2,917 research outputs found
Further constraints on neutron star crustal properties in the low-mass X-ray binary 1RXS J180408.9342058
We report on two new quiescent {\it XMM-Newton} observations (in addition to
the earlier {\it Swift}/XRT and {\it XMM-Newton} coverage) of the cooling
neutron star crust in the low-mass X-ray binary 1RXS J180408.9342058. Its
crust was heated during the 4.5 month accretion outburst of the source.
From our quiescent observations, fitting the spectra with a neutron star
atmosphere model, we found that the crust had cooled from 100 eV to
73 eV from 8 days to 479 days after the end of its outburst.
However, during the most recent observation, taken 860 days after the end
of the outburst, we found that the crust appeared not to have cooled further.
This suggested that the crust had returned to thermal equilibrium with the
neutron star core. We model the quiescent thermal evolution with the
theoretical crustal cooling code NSCool and find that the source requires a
shallow heat source, in addition to the standard deep crustal heating
processes, contributing 0.9 MeV per accreted nucleon during outburst to
explain its observed temperature decay. Our high quality {\it XMM-Newton} data
required an additional hard component to adequately fit the spectra. This
slightly complicates our interpretation of the quiescent data of 1RXS
J180408.9342058. The origin of this component is not fully understood.Comment: Accepted for publication by MNRA
Editorial: hepatocellular carcinoma ā a rare complication of hepatic venous outflow tract obstruction
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111131/1/apt13198.pd
Influence of sodium pyruvate on Neurospora fructose diphosphatase
Influence of sodium pyruvate on fructose diphosphatas
Priprava i vrednovanje matriksnog agensa na bazi ispagule za kontrolirano oslobaÄanje
The objective of the present investigation was to prepare and evaluate an ispaghula husk based directly compressible (DC) adjuvant that can be used as matrixing agent using an agglomeration technique. Addition of hydroxylpropyl methylcellulose was found necessary to improve cohesion. Lactose (X1), calcium hydrogen phosphate diydrate (X2) and Avicel PH101 (X3), used along with ispaghula in preparation of agglomerates, were selected as three independent variables in a simplex lattice design affecting compressional and dissolution characteristics of the drug from the DC adjuvant. The agglomerates were evaluated for their flow properties. Tablets were prepared using 70% agglomerates and 30% acetaminophen, a poorly compressible drug, and were subjected to the in vitro drug release study. Amounts of the drug released at the end of 60 min (Y60), 300 min (Y300) and 480 min (Y480) were selected as dependent variables in a simplex lattice design. Batch IH05 that contained lactose and calcium hydrogen phosphate dihydrate in a 1:2 ratio could control the release for 12 hours and thus form the basis for twice-a-day dosing.Cilj rada bio je priprava i vrednovanje pomoÄne tvari za izravnu kompresiju dobivene iz ljuski ispagule, primjenjive u izradi pripravaka metodom aglomeracije. Dodatak hidroksipropil metilceluloze bio je neophodan za poveÄanje kohezije. U pripravi aglomerata s ispagulom upotrebljeni su laktoza (X1), kalcijev hidrogenfosfat dihidrat (X2) i Avicel PH101 (X3). U eksperimentalnom dizajnu (simplex lattice design) te tri tvari izabrane su kao nezavisne varijable. ProuÄavan je njihov utjecaj na kompresibilnost i oslobaÄanje ljekovite tvari iz pripravka dobivenih izravnom kompresijom te svojstva teÄnosti aglomerata. Tako dobiveni aglomerati upotrebljeni su za pripravu tableta teÅ”ko kompresibilne tvari acetaminofena (omjer aglomerata i ljekovite tvari 7:3). KoliÄine osloboÄene tvari in vitro pri kraju 60 min (Y60), 300 min (Y300) i 480 min (Y480) bils su zavisne varijable. Iz pripravka IH05 koji sadrži laktozu i kalcijev hidrogenfosfat dihidrat u omjeru 1:2 kontrolirano se oslobaÄa ljekovita tvar tijekom 12 sati, Å”to je dobar temelj za doziranje dva puta dnevno
Very hard states in neutron star low-mass X-ray binaries
We report on unusually very hard spectral states in three confirmed
neutron-star low-mass X-ray binaries (1RXS J180408.9-342058, EXO 1745-248, and
IGR J18245-2452) at a luminosity between ~ 10^{36-37} erg s^{-1}. When fitting
the Swift X-ray spectra (0.5 - 10 keV) in those states with an absorbed
power-law model, we found photon indices of \Gamma ~ 1, significantly lower
than the \Gamma = 1.5 - 2.0 typically seen when such systems are in their so
called hard state. For individual sources very hard spectra were already
previously identified but here we show for the first time that likely our
sources were in a distinct spectral state (i.e., different from the hard state)
when they exhibited such very hard spectra. It is unclear how such very hard
spectra can be formed; if the emission mechanism is similar to that operating
in their hard states (i.e., up-scattering of soft photons due to hot electrons)
then the electrons should have higher temperatures or a higher optical depth in
the very hard state compared to those observed in the hard state. By using our
obtained \Gamma as a tracer for the spectral evolution with luminosity, we have
compared our results with those obtained by Wijnands et al. (2015). We confirm
their general results in that also our sample of sources follow the same track
as the other neutron star systems, although we do not find that the accreting
millisecond pulsars are systematically harder than the non-pulsating systems.Comment: Accepted for publication in MNRA
Black hole candidate GRS 1739-278 is exhibiting an unusual, long-duration quasi-steady hard state
Black hole candidate GRS 1739-278 is exhibiting an unusual, long-duration quasi-steady hard state
GaN evaporation and enhanced diffusion of Ar during high-temperature ion implantation
GaN films were implanted with 150 keV Ar+ at temperatures up to 1100 Ā°C to a dose of 3Ć1015 cm-2. Concentration profiles of Ar were measured by secondary ion mass spectroscopy and depth distributions of ion-induced damage were estimated from Rutherford backscattering/channeling spectra. No redistribution of Ar atoms was detected up to 700 Ā°C. At 1000 Ā°C a deep penetrating diffusion tail and a shift of the Ar peak to the surface were observed. At temperatures higher than 800 Ā°C shift of the damage peak to the surface was also observed. We attributed the shift of the Ar peak and the damage peaks to evaporation of thin layer of GaN during high-temperature implantation and estimated its temperature dependence
A strongly changing accretion morphology during the outburst decay of the neutron star X-ray binary 4U 1608ā52
It is commonly assumed that the properties and geometry of the accretion flow in transient low-mass X-ray binaries (LMXBs) significantly change when the X-ray luminosity decays below ā¼10ā»Ā² of the Eddington limit (L_(Edd)). However, there are few observational cases where the evolution of the accretion flow is tracked in a single X-ray binary over a wide dynamic range. In this work, we use NuSTAR and NICER observations obtained during the 2018 accretion outburst of the neutron star LMXB 4U 1608ā52, to study changes in the reflection spectrum. We find that the broad FeāKĪ± line and Compton hump, clearly seen during the peak of the outburst when the X-ray luminosity is ā¼10Ā³ā· erg sā»Ā¹ (ā¼0.05 L_(Edd)), disappear during the decay of the outburst when the source luminosity drops to ā¼4.5 Ć 10Ā³āµ erg sā»Ā¹ (ā¼0.002 L_(Edd)). We show that this non-detection of the reflection features cannot be explained by the lower signal-to-noise ratio at lower flux, but is instead caused by physical changes in the accretion flow. Simulating synthetic NuSTAR observations on a grid of inner disc radius, disc ionization, and reflection fraction, we find that the disappearance of the reflection features can be explained by either increased disc ionization (logāĪ¾ ā³ 4.1) or a much decreased reflection fraction. A changing disc truncation alone, however, cannot account for the lack of reprocessed FeāKĪ± emission. The required increase in ionization parameter could occur if the inner accretion flow evaporates from a thin disc into a geometrically thicker flow, such as the commonly assumed formation of a radiatively inefficient accretion flow at lower mass accretion rates
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