Superorbital variability of the X-ray flux in the Be-donor binaries SXP 138, GX-304, and γ Cas

© 2015, Pleiades Publishing, Ltd. RXTE observations of the X-ray binary systems SXP 138, GX-304, and γ Cas in 1997–2011 have shown for the first time that these objects (X-ray binaries with Be donors) display X-ray flux variations on timescales of ∼1000 days. This timescale is about 10 times longer than their orbital periods, and is comparable to the total time of the observations. The observed variations are apparently not strictly periodic and represent stochastic variability, as is characteristic of such systems in the optical. γ Cas is considered as an example. The series of optical observations of this system available in the AAVSO database covers 78 years, and is much longer than the timescale of the variability studied. Our analysis of this series has shown that γ Cas variability on a timescale of tens of years is predominantly stochastic with a power-law spectrum

Super-Eddington accretion discs with advection and outflows around magnetized neutron stars

We present a model for a super-Eddington accretion disc around a magnetized neutron star taking into account advection of heat and the mass loss by the wind. The model is semi-analytical and predicts radial profiles of all the basic physical characteristics of the accretion disc. The magnetospheric radius is found as an eigenvalue of the problem. When the inner disc is in radiation-pressure-dominated regime but does not reach its local Eddington limit, advection is mild, and the radius of the magnetosphere depends weakly on the accretion rate. Once it approaches the local Eddington limit the disc becomes advection-dominated, and the scaling for the magnetospheric radius with the mass accretion rate is similar to the classical Alfven relation. Allowing for the mass loss in a wind leads to an increase in the magnetospheric radius. Our model can be applied to a wide variety of magnetized neutron stars accreting close to or above their Eddington limits: ultra-luminous X-ray pulsars, Be/X-ray binaries in outbursts, and other systems. In the context of our model we discuss the observational properties of NGC5907 X-1, the brightest ultra-luminous pulsar currently known, and NGC300 ULX1, which is apparently a Be/X-ray binary experiencing a very bright super-Eddington outburst

Superorbital variability of the X-ray flux in the Be-donor binaries SXP 138, GX-304, and γ Cas

© 2015, Pleiades Publishing, Ltd. RXTE observations of the X-ray binary systems SXP 138, GX-304, and γ Cas in 1997–2011 have shown for the first time that these objects (X-ray binaries with Be donors) display X-ray flux variations on timescales of ∼1000 days. This timescale is about 10 times longer than their orbital periods, and is comparable to the total time of the observations. The observed variations are apparently not strictly periodic and represent stochastic variability, as is characteristic of such systems in the optical. γ Cas is considered as an example. The series of optical observations of this system available in the AAVSO database covers 78 years, and is much longer than the timescale of the variability studied. Our analysis of this series has shown that γ Cas variability on a timescale of tens of years is predominantly stochastic with a power-law spectrum

Superorbital variability of the X-ray flux in the Be-donor binaries SXP 138, GX-304, and γ Cas

© 2015, Pleiades Publishing, Ltd. RXTE observations of the X-ray binary systems SXP 138, GX-304, and γ Cas in 1997–2011 have shown for the first time that these objects (X-ray binaries with Be donors) display X-ray flux variations on timescales of ∼1000 days. This timescale is about 10 times longer than their orbital periods, and is comparable to the total time of the observations. The observed variations are apparently not strictly periodic and represent stochastic variability, as is characteristic of such systems in the optical. γ Cas is considered as an example. The series of optical observations of this system available in the AAVSO database covers 78 years, and is much longer than the timescale of the variability studied. Our analysis of this series has shown that γ Cas variability on a timescale of tens of years is predominantly stochastic with a power-law spectrum

Dynamics of Kidney Function in Patients with Chronic Kidney Disease and Atrial Fibrillation Who Receive Dabigatran

Atrial fibrillation (AF) is the most frequent type of supraventricular arrhythmias. The anticoagulant therapy should be prescribed to prevent thromboembolic events. According to randomized clinical trials, anticoagulants do not always prove their high efficiency in the real clinical practice. It is a complicated issue for any doctor to prescribe the anticoagulant therapy for patients with AF and CKD. 30 % of patients with atrial fibrillation are known to have chronic kidney disease, while 10-15% of patients with chronic kidney disease are diagnosed with atrial fibrillation. Currently, there are scarce studies into the use of direct oral anticoagulants in patients with atrial fibrillation and chronic kidney disease (in case of Glomerular Filtration Rate (GFR) below 45 ml/min/1.73 m2).Aim. To determine the dynamics of GFR in patients with AF and CKD (in case of GFR below 45 ml/min/1.73 m2).Material and Methods. The sub-analysis was carried out to examine a single-centre prospective study into the optimization of the anticoagulant therapy in the outpatient practice. Initially, 133 dabigatran taking patients were enrolled in the study, and 79 patients were included in the final analysis. Endpoints were changes in Glomerular Filtration Rate (CKD-EPI) formulae as of the inclusion date, in 6, 12, 24 and 60 months after the inclusion. Changes in the renal function shall mean a decrease or increase in GFR by ≥5 ml/min.Results. The average follow-up period for patients was 1785 ± 218 days. A GFR>45 ml/min/1.73 m2 occurred in 116 (87.2%) patients, and a GFR <45 ml/min/1.73 m2 was found in 17 (12.8%) patients. The average HAS-BLED score was 1.8, and CHA2DS2VASc score - 3.8. During the observation period, there were 3 cases of major bleeding and 133 cases of minor bleeding. Both major (р=0.025) and minor (р=0.012) bleeding were statistically significant more frequent in patients with GFR below 45 ml/min. During 5 years of follow-up, 66 (49.6%) patients had an average decrease in GFR of 3.32 ml/min/1.73 m2 per year. Patients with the initially declined GFR (below 45 ml/min) did not demonstrate a significant dynamic of the renal function during the dabigatran therapy. The mortality rate in this group during the observation period was 61.5%.Conclusion. In 49.6% of patients during 5 years of follow-up, GFR decreased by an average of 3.32 ml/min/1.73 m2 per year, which does not exceed the indicators typical for patients with cardiovascular events and CKD