Influence of heart rate in non-linear HRV indices as a sampling rate effect evaluated on supine and standing

The purpose of this study is to characterize and attenuate the influence of mean heart rate (HR) on nonlinear heart rate variability (HRV) indices (correlation dimension, sample, and approximate entropy) as a consequence of being the HR the intrinsic sampling rate of HRV signal. This influence can notably alter nonlinear HRV indices and lead to biased information regarding autonomic nervous system (ANS) modulation. First, a simulation study was carried out to characterize the dependence of nonlinear HRV indices on HR assuming similar ANS modulation. Second, two HR-correction approaches were proposed: one based on regression formulas and another one based on interpolating RR time series. Finally, standard and HR-corrected HRV indices were studied in a body position change database. The simulation study showed the HR-dependence of non-linear indices as a sampling rate effect, as well as the ability of the proposed HR-corrections to attenuate mean HR influence. Analysis in a body position changes database shows that correlation dimension was reduced around 21% in median values in standing with respect to supine position (p < 0.05), concomitant with a 28% increase in mean HR (p < 0.05). After HR-correction, correlation dimension decreased around 18% in standing with respect to supine position, being the decrease still significant. Sample and approximate entropy showed similar trends. HR-corrected nonlinear HRV indices could represent an improvement in their applicability as markers of ANS modulation when mean HR changes

The properties of the clumpy torus and BLR in the polar-scattered Seyfert 1 galaxy ESO 323-G77 through X-ray absorption variability

We report results from multi-epoch X-ray observations of the polar-scattered Seyfert 1 galaxy ESO 323-G77. The source exhibits remarkable spectral variability from months to years timescales. The observed spectral variability is entirely due to variations of the column density of a neutral absorber towards the intrinsic nuclear continuum. The column density is generally Compton-thin ranging from a few times 10$^{22}$ cm$^{-2}$ to a few times 10$^{23}$ cm$^{-2}$. However, one observation reveals a Compton-thick state with column density of the order of 1.5 $\times$ 10$^{24}$ cm$^{-2}$. The observed variability offers a rare opportunity to study the properties of the X-ray absorber(s) in an active galaxy. We identify variable X-ray absorption from two different components, namely (i) a clumpy torus whose individual clumps have a density of $\leq$ 1.7 $\times$ 10$^8$ cm$^{-3}$ and an average column density of $\sim$ 4 $\times$ 10$^{22}$ cm$^{-2}$, and (ii) the broad line region (BLR), comprising individual clouds with density of 0.1-8 $\times$ 10$^9$ cm$^{-3}$ and column density of 10$^{23}$-10$^{24}$ cm$^{-2}$. The derived properties of the clumpy torus can also be used to estimate the torus half-opening angle, which is of the order of 47 $^\circ$. We also confirm the previously reported detection of two highly ionized warm absorbers with outflow velocities of 1000-4000 km s$^{-1}$. The observed outflow velocities are consistent with the Keplerian/escape velocity at the BLR. Hence, the warm absorbers may be tentatively identified with the warm/hot inter-cloud medium which ensures that the BLR clouds are in pressure equilibrium with their surroundings. The BLR line-emitting clouds may well be the cold, dense clumps of this outflow, whose warm/hot phase is likely more homogeneous, as suggested by the lack of strong variability of the warm absorber(s) properties during our monitoring.Comment: 15 pages, 4 tables, and 9 figures. Accepted for publication in MNRA

Accurate classification of 75 counterparts of objects detected in the 54 month Palermo Swift/BAT hard X-ray catalogue

Through an optical campaign performed at 4 telescopes located in the northern and the southern hemispheres, we have obtained optical spectroscopy for 75 counterparts of unclassified or poorly studied hard X-ray emitting objects detected with Swift/BAT and listed in the 54 month Palermo BAT catalogue. All these objects have also observations taken with Swift/XRT, ROSAT or Chandra satellites which allowed us to reduce the high energy error box and pinpoint the most likely optical counterpart/s. We find that 69 sources in our sample are Active Galactic Nuclei (AGNs); of them, 35 are classified as type 1 (with broad and narrow emission lines), 33 are classified as type 2 (with only narrow emission lines) and one is an high redshift QSO; the remaining 6 objects are galactic cataclysmic variables (CVs). Among type 1 AGNs, 32 are objects of intermediate Seyfert type (1.2-1.9) and one is Narrow Line Seyfert 1 galaxy; for 29 out of 35 type 1 AGNs, we have been able to estimate the central black hole mass and the Eddington ratio. Among type 2 AGNs, two display optical features typical of the LINER class, 3 are classified as transition objects, 1 is a starburst galaxy and 2 are instead X-ray bright, optically normal galaxies. All galaxies classified in this work are relatively nearby objects (0.006 - 0.213) except for one at redshift 1.137.Comment: 19 pages, 5 figures, 6 tables, accepted for publications on Astronomy and Astrophysics, main journal. arXiv admin note: text overlap with arXiv:1206.509

Fossil group origins - VI. Global X-ray scaling relations of fossil galaxy clusters

We present the first pointed X-ray observations of 10 candidate fossil galaxy groups and clusters. With these Suzaku observations, we determine global temperatures and bolometric X-ray luminosities of the intracluster medium (ICM) out to $r_{500}$ for six systems in our sample. The remaining four systems show signs of significant contamination from non-ICM sources. For the six objects with successfully determined $r_{500}$ properties, we measure global temperatures in the range $2.8 \leq T_{\mathrm{X}} \leq 5.3 \ \mathrm{keV}$, bolometric X-ray luminosities of $0.8 \times 10^{44} \ \leq L_{\mathrm{X,bol}} \leq 7.7\times 10^{44} \ \mathrm{erg} \ \mathrm{s}^{-1}$, and estimate masses, as derived from $T_{\mathrm{X}}$, of $M_{500} > 10^{14} \ \mathrm{M}_{\odot}$. Fossil cluster scaling relations are constructed for a sample that combines our Suzaku observed fossils with fossils in the literature. Using measurements of global X-ray luminosity, temperature, optical luminosity, and velocity dispersion, scaling relations for the fossil sample are then compared with a control sample of non-fossil systems. We find the fits of our fossil cluster scaling relations are consistent with the relations for normal groups and clusters, indicating fossil clusters have global ICM X-ray properties similar to those of comparable mass non-fossil systems.Comment: 17 pages, 7 figures, 8 tables. Accepted for publication in MNRA

XMM-Newton view of galaxy pairs: activation of quiescent black holes?

We report on XMM-Newton observations of three nearby galaxy pairs, AM0707-273, AM1211-465, and AM2040-674. All six galaxies were previously classified as HII galaxies based on optical and IR spectroscopic analysis. All galaxies were detected with XMM-Newton and each member was isolated and analyzed independently. The X-ray spectra reveal strong evidence of AGN activity in the NE member of AM1211-465 pair. We measured a luminosity of 1.94(+0.11/-0.15)x10^42 erg/s in the 2-10 keV band and the presence of a neutral FeK_alpha line with a confidence level of 98.8%. The high nH value, 2.2+/-0.2x10^22 cm^-2, would explain the misclassification of the source. Marginal evidence of AGN nature was found in the X-ray spectra of AM1211-465SW and AM0707-273E. The X-ray emission of the three remaining galaxies can be explained by starburst activity.Comment: Accepted for publication in A&

Cardiovascular Changes Induced by Acute Emotional Stress Estimated from the Pulse Transit Time Difference

In the present work, the difference between arrival times of photoplethysmographic (PPG) pulses from two different sites of the arterial tree (PTTD) is calculated. As the PTTD is considered to be related with arterial pulse wave velocity, an evaluation of it''s usefulness to identify states of acute mental stress is performed. A subset of fourteen healthy volunteers undergoing a stress protocol was analysed and a statistical test was carried out to evaluate the validity of the proposed method. The results showed that the standard deviation of the PTTD had sufficient statistical capacity to discern between states of stress and relaxation. Furthermore, a generalised descending trend of the mean PTTD can be seen from relaxation to stress

Detection of blueshifted emission and absorption and a relativistic Iron line in the X-ray spectrum of ESO 323-G077

We report on the X-ray observation of the Seyfert 1 ESO323-G077 performed with XMM-Newton. The spectra show a complex spectrum with conspicuous absorption and emission features. The continuum emission can be modelled with a power law with an index of 1.99+/-0.02 in the whole XMM-Newton energy band, marginally consistent with typical values of Type-I objects. An absorption component with an uncommonly high equivalent Hydrogen column, n_H=5.82(+0.12/-0.11)x10^22 cm-2, is affecting the soft part of the spectrum. Additionally, two warm absorption components are also present. The lower ionised one has an ionisation parameter of Log(U)=2.14(+0.06/-0.07) and an outflowing velocity of v=3200(+600/-200) km/s. Two absorption lines located at ~6.7 and ~7.0 keV can be modelled with the highly ionised absorber. The ionisation parameter and outflowing velocity of the gas measured are Log(U)=3.26(+0.19/-0.15) and v=1700(+600/-400) km/s, respectively. Four emission lines were also detected in the soft energy band. The most likely explanation for these emission lines is that they are associated with an outflowing gas with a velocity of ~2000 km/s. The data suggest that the same gas which is causing the absorption could also being responsible of these emission features. Finally, the spectrum shows the presence of a relativistic iron emission line likely originated in the accretion disc of a Kerr BH with an inclination of ~25 deg. We propose a model to explain the observed X-ray properties which invokes the presence of a two-phase outflow with cone-like structure and a velocity of the order of 2,000-4,000 km/s. The inner layer of the cone would be less ionised, or even neutral, than the outer layer. The inclination angle would be lower than the opening angle of the outflowing cone.Comment: 11 pages, accepted in MNRA