arXiv subjects

R. Baranowski

Publications and source records attributed to R. Baranowski.

3 recordsLinked to original sources

arXiv2009

V440 Per: the longest period overtone Cepheid

V440 Per is a Population I Cepheid with the period of 7.57 day and low amplitude, almost sinusoidal light and radial velocity curves. With no reliable data on the 1st harmonic, its pulsation mode identification remained controversial. We obtained a radial velocity curve of V440 Per with our new high precision and high throughput Poznan Spectroscopic Telescope. Our data reach the accuracy of 130 m/s per individual measurement and yield a secure detection of the 1st harmonic with the amplitude of A_2= 140+/- 15 m/s. The velocity Fourier phase ϕ_21 of V440 Per is inconsistent at the 7.25 σlevel with those of the fundamental mode Cepheids, implying that the star must be an overtone Cepheid, as originally proposed by Kienzle et al.(1999). Thus, V440 Per becomes the longest period Cepheid with the securely established overtone pulsations. We show, that the convective nonlinear pulsation hydrocode can reproduce the Fourier parameters of V440 Per very well. Requirement to match the observed properties of V440 Per constrains free parameters of the dynamical convection model used in the pulsation calculations, in particular the radiative losses parameter.

astro-ph.SR↗

arXiv2007

How random is your heart beat?

We measure the content of random uncorrelated noise in heart rate variability using a general method of noise level estimation using a coarse grained entropy. We show that usually - except for atrial fibrillation - the level of such noise is within 5 - 15% of the variance of the data and that the variability due to the linearly correlated processes is dominant in all cases analysed but atrial fibrillation. The nonlinear deterministic content of heart rate variability remains significant and may not be ignored.

physics.med-ph↗

arXiv2004

Type I intermittency in a dynamical system with dichotomous parameter change

In type I intermittency, simple models known for at least twenty years show that a characteristic u-shaped probability distribution is obtained for the laminar phase length. We have shown elsewhere that, for some cases of pathology, the laminar phase length distribution characteristic for type I intermittency may be obtained in human heart rate variability data. The heart and its regulatory systems are presumed to be both noisy and nonstationary. Although the effect of additive noise on the laminar phase distribution in type I intermittency is well known, neither the effect of multiplicative noise nor of nonstationarity (i.e. changes of the control parameter with the time) have been studied. In this paper, we first discuss the properties of two classes of models of type I intermittency: a) the control parameter of the logistic map is changed dichotomously from a value within the intermittency range to just below the bifurcation point and back; b) the control parameter is changed randomly within the same parameter range as in the model class a). We show that the properties of both models are importantly different from those obtained for type I intermittency in the presence additive noise as obtained by Hirsch twenty years ago. The two models help explain some of the features seen in the intermittency in human heart rate variability.

nlin.CD↗