Comparison of chaos detection methods in the circular restricted three‐body problem

In this study, a sample of orbits is considered in the framework of the planar circular restricted three‐body problem. In order to separate ordered from chaotic orbits three numerical methods are compared: the Largest Lyapunov Characteristic Exponent (LLCE) and the Smaller Alignment Index (SALI) provide a fairly good characterization of the chaotic motions, while the computational time required is of the same order; the Correlation Dimension (CD) has the advantage of correctly classifying sticky orbits, but at the expense of a longer computational time. In order to classify a given orbit, any pair of the three methods can be considered, but LLCE and SALI are recommended due to their speed. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Symbiotic stars with spectral indication of bipolar ejection and stellar wind

Four out of a total of five symbiotic systems whose optical spectral lines contain satellite components indicating collimated ejection have an additional absorption of P Cyg type with different velocity. These systems are Z And, Hen 3‐1341, StHα 190, and BF Cyg. It is shown that the line profiles of every of these systems can be interpreted in the framework of a model of a collimated stellar wind from the hot compact component proposed initially to interpret the line profiles of Z And, observed during its last active phase after 2000. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

3XMM J185246.6+003317 as transient neutron star

We performed an X‐ray timing and spectral analysis of the variable source 3XMM J185246.6+003317 to investigate its physical nature. The data from all observations of 3XMMJ185246.6+003317 conducted by XMM‐Newton EPIC MOS1 and MOS2 with the same instrumental setup in 2004–2009 were reprocessed to form a homogenous data set of solar barycenter corrected photon arrival times and high S/N spectra of 3XMM J185246.6+003317. A Bayesian method for the search, detection, and estimation of the parameters of a periodic signal of unknown shape was employed, as developed by Gregory & Loredo (1992, 1993). The results show that 3XMM J185246.6+003317 is a transient neutron star with the genuine spin‐period of 23.11722 (23.11711–23.11727) s and its derivative of 5.3(0.3–5.5)×10^–11 s s^–1, implying a characteristic age of 7 (6–104) kyr, if the period derivative can be ascribed to the genuine spin‐down rate of the neutron star. The rotational‐phase averaged X‐ray spectra at the different brightness periods can be fitted with a highly absorbed blackbody model with different temperatures. The phase‐folded light curves in different energy bands with high S/N ratio show a double‐peaked profile; the variations depend on time and energy, indicating that radiation emerges from at least two emitting areas. The spectra at the phases corresponding to the maxima in the phase‐folded light curve show different spectral parameters of absorbed blackbody radiation, i.e. the hotter one has a smaller size. The source is detected only from September 2008 to April 2009 with persistently decreasing brightness, but not before, even though it was observed by XMM. Hence, it is a transient neutron star or a binary system hosting it. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Clusters and groups of galaxies in the 2dF galaxy redshift survey: A new catalogue

We create a new catalogue of groups and clusters, applying the friends‐of‐friends method to the 2dF GRS final release. We investigate various selection effects due to the use of a magnitude limited sample. For this purpose we follow the changes in group sizes and mean galaxy number densities within groups when shifting nearby observed groups to larger distances. We study the distribution of sizes of dark matter haloes in N ‐body simulations and compare properties of these haloes and the 2dF groups. We show that at large distances from the observer luminous and intrinsically greater groups dominate, but in these groups only very bright members are seen, which form compact cores of the groups. These two effects almost cancel each other, so that the mean sizes and densities of groups do not change considerably with distance. Our final sample contains 10750 groups in the Northern part, and 14465 groups in the Southern part of the 2dF survey with membership N _gal ≥ 2. We estimate the total luminosities of our groups, correcting for group members fainter than the observational limit of the survey. The cluster catalogue is available at our web‐site ( http://www.aai.ee/∼maret/2dfgr.html ). (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Suzaku observation of NGC 3516: complex absorption and the broad and narrow Fe K lines

We present preliminary results from a 150 ks Suzaku observation of the Seyfert 1 galaxy NGC 3516. Suzaku 's wide bandpass has enabled us to deconvolve the broadband emitting and absorbing components in this object, breaking model degeneracies inherent in previous, smaller‐bandpass spectra. The primary power‐law continuum is absorbed by an ionized absorber as well as a partial‐covering absorber; the column density of the ionized absorber has increased by a factor of ∼3 since XMM‐Newton observations in 2001. We detect a soft power‐law component which may be scattered emission. We confirm the presence of the broad Fe line, finding a eV equivalent width line that indicates emission extending down to a few Schwarzschild radii. Models which exclude either the broad line or the partial‐covering absorber are rejected. Suzaku 's high effective area and low background near 6 keV also allow us to resolve the narrow Fe K emission line; we find a FWHM velocity width near 4000 km s^–1, commensurate with Broad Line Region velocities. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Interaction between the controls on fluvial system development: tectonics,climate, base level and river capture – Rio Alias,Southeast Spain

Fluvial systems in uplifting terrain respond to tectonic, climatic, eustatic and local base‐level controls modified by specific local factors, such as river capture. The Rio Alias in southeast Spain is an ephemeral, transverse‐to‐structure fluvial system. The river drains two interconnected Neogene sedimentary basins, the Sorbas and Almeria basins, and crosses two major geological structures, the Sierras de Alhamilla/Cabrera and the Carboneras Fault Zone. Regional epeirogenic uplift resulted in sustained fluvial incision during the Quaternary, punctuated by major climatically driven periods of aggradation and dissection, which created a suite of five river terraces. The river terrace sequence was radically modified in the late Pleistocene by a major river capture (itself a response to regional tectonics), localized tectonic activity and eustatic base‐level change. The Rio Alias is defined by four reaches; within each the climatically‐generated, region‐wide, fluvial response was modified by tectonics, base‐level change or river capture to varying degrees. In the upper part of the basin (Lucainena reach), climate was the dominant control on river development, with limited modification of the sequence by uplift of the Sierra Alhamilla and local drainage reorganization by a local river capture. Downstream of the Sierra Alhamilla in the Polopus reach, the climatic signal is dominant, but its expression is radically modified by the response to a major river capture whereby the Alias system lost up to 70% of its pre‐capture drainage area. In the reach adjacent to the Carboneras Fault Zone (Argamason reach), modification of the terrace sequence by local tectonic activity and a resultant local base‐level fall led to a major local incisional event (propagating c. 3–4 km upstream from the area of tectonic disturbance). At the seaward end of the system (El Saltador reach) Quaternary sea‐level changes modified the patterns of erosion and incision and have resulted in steep incisional terrace profiles. The signals generated by regional tectonics and the Quaternary climate change can be identified throughout the basin but those generated by ongoing local tectonics, river capture and sea‐level change are spatially restricted and define the four reaches. The connectivity of the system from the headwaters to the coast decreased through time as incision progressed, resulting in changes in local coupling characteristics. Copyright © 2012 John Wiley & Sons, Ltd.     

Time‐series photometric spot modelling – VI. A new computer code and its application to 23 years of photometry of the active giant IM Pegasi

We present and apply a new computer program named SpotModeL to analyze single and multiple bandpass photometric data of spotted stars. It is based on the standard analytical formulae from Budding and Dorren. The program determines the position, size, and temperature of up to three spots by minimizing the fit residuals with the help of the Marquardt‐Levenberg non‐linear least‐squares algorithm. We also expand this procedure to full time‐series analysis of differential data, just as real observations would deliver. If multi‐bandpass data are available, all bandpasses can be treated simultaneously and thus the spot temperature is solved for implicitly. The program may be downloaded and used by anyone. In this paper, we apply our code to an ≈23 year long photometric dataset of the spotted RS CVn giant IM Peg. We extracted and modelled 33 individual light curves, additionally, we fitted the entire V dataset in one run. The resulting spot parameters reflect the long term light variability and reveal two active longitudes on the substellar point and on the antipode. The radius and longitude of the dominant spot show variations with 29.8 and 10.4 years period, respectively. Our multicolour data suggests that the spot temperature is increasing with the brightening of the star. The average spot temperature from V, I_C is 3550 ± 150 K or approximately 900 K below the effective temperature of the star.     

A search for luminous Be stars

As Be stars are restricted to luminosity classes III‐V, but early B‐type stars are believed to evolve into supergiants, it is to be expected that the Be phenomenon disappears at some point in the evolution of a moderately massive star, before it reaches the supergiant phase. As a first stage in an attempt to determine the physical reasons of this cessation, a search of the literature has provided a number of candidates to be Be stars with luminosity classes Ib or II. Spectroscopy has been obtained for candidates in a number of open clusters and associations, as well as several other bright stars in those clusters. Among the objects observed, HD 207329 is the best candidate to be a high‐luminosity Be star, as it appears like a fast‐rotating supergiant with double‐peaked emission lines. The lines of HD 229059, in Berkeley 87, also appear morphologically similar to those of Be stars, but there are reasons to suspect that this object is an interacting binary. At slightly lower luminosities, LS I +56°92 (B4 II) and HD 333452 (O9 II), also appear as intrinsically luminous Be stars. Two Be stars in NGC 6913, HD 229221 and HD 229239, appear to have rather higher intrinsic magnitudes than their spectral type (B0.2 III in both cases) would indicate, being as luminous as luminosity class II objects in the same cluster. HD 344863, in NGC 6823, is also a rather early Be star of moderately high luminosity. The search shows that, though high‐luminosity Be stars do exist, they are scarce and, perhaps surprisingly, tend to have early spectral types. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)