The Discovery of a Strong Magnetic Field and Co-rotating Magnetosphere in the Helium-weak Star HD 176582

We report the detection of a strong, reversing magnetic field and variable H-alpha emission in the bright helium-weak star HD 176582 (HR 7185). Spectrum, magnetic and photometric variability of the star are all consistent with a precisely determined period of 1.5819840 +/- 0.0000030 days which we assume to be the rotation period of the star. From the magnetic field curve, and assuming a simple dipolar field geometry, we derive a polar field strength of approximately 7 kG and a lower limit of 52 degrees for the inclination of the rotation axis. However, based on the behaviour of the H-alpha emission we adopt a large inclination angle of 85 degrees and this leads to a large magnetic obliquity of 77 degrees. The H-alpha emission arises from two distinct regions located at the intersections of the magnetic and rotation equators and which corotate with the star at a distance of about 3.5 R* above its surface. We estimate that the emitting regions have radial and meridional sizes on the order of 2 R* and azimuthal extents (perpendicular to the magnetic equator) of less than approximately 0.6 R*. HD 176582 therefore appears to show many of the cool magnetospheric phenomena as that displayed by other magnetic helium-weak and helium-strong stars such as the prototypical helium-strong star sigma Ori E. The observations are consistent with current models of magnetically confined winds and rigidly-rotating magnetospheres for magnetic Bp stars.Comment: 16 pages, 6 figure

Chandra HETG Observations of the Colliding Stellar Wind System WR 147

We present an extended analysis of deep Chandra HETG observations of the WR+OB binary system WR 147 that was resolved into a double X-ray source (Zhekov & Park, 2010, ApJ, 709, L119). Our analysis of the profiles of strong emission lines shows that their centroids are blue-shifted in the spectrum of the northern X-ray source. We find no suppressed forbidden line in the He-like triplets which indicates that the X-ray emitting region is not located near enough to the stars in the binary system to be significantly affected by their UV radiation. The most likely physical picture that emerges from the entire set of HETG data suggests that the northern X-ray source can be associated with the colliding stellar wind region in the wide WR+OB binary system, while the X-rays of its southern counterpart, the WN8 star, are result from stellar wind shocking onto a close companion (a hypothesized third star in the system).Comment: 22 pages, 6 figures, 2 Tables; accepted for publication in The Astrophysical Journa

Chandra Detects the Rare Oxygen-type Wolf-Rayet Star WR 142 and OB Stars in Berkeley 87

We present first results of a Chandra X-ray observation of the rare oxygen-type Wolf-Rayet star WR 142 (= Sand 5 = St 3) harbored in the young, heavily-obscured cluster Berkeley 87. Oxygen type WO stars are thought to be the most evolved of the WRs and progenitors of supernovae or gamma ray bursts. As part of an X-ray survey of supposedly single Wolf-Rayet stars, we observed WR 142 and the surrounding Berkeley 87 region with Chandra ACIS-I. We detect WR 142 as a faint, yet extremely hard X-ray source. Due to weak emission, its nature as a thermal or nonthermal emitter is unclear and thus we discuss several emission mechanisms. Additionally, we report seven detections and eight non-detections by Chandra of massive OB stars in Berkeley 87, two of which are bright yet soft X-ray sources whose spectra provide a dramatic contrast to the hard emission from WR 142.Comment: To appear in the Astrophysical Journa

XMM-Newton X-ray study of early type stars in the Carina OB1 association

<p><b>Aims:</b> X-ray properties of the stellar population in the Carina OB1 association are examined with special emphasis on early-type stars. Their spectral characteristics provide some clues to understanding the nature of X-ray formation mechanisms in the winds of single and binary early-type stars.</p> <p><b>Methods:</b> A timing and spectral analysis of five observations with XMM-Newton is performed using various statistical tests and thermal spectral models.</p> <p><b>Results:</b> 235 point sources have been detected within the field of view. Several of these sources are probably pre-main sequence stars with characteristic short-term variability. Seven sources are possible background AGNs. Spectral analysis of twenty four sources of type OB and WR 25 was performed. We derived spectral parameters of the sources and their fluxes in three energy bands. Estimating the interstellar absorption for every source and the distance to the nebula, we derived X-ray luminosities of these stars and compared them to their bolometric luminosities. We discuss possible reasons for the fact that, on average, the observed X-ray properties of binary and single early type stars are not very different, and give several possible explanations.</p&gt

[Bis­(diphenyl­phosphino)methane-κ2 P,P′]dichloridopalladium(II)

The title complex, [PdCl2(C25H22P2)], is a slightly distorted square-planar bis­(diphenyl­phosphino)methane cis-complex of PdCl2. The structure of a polymorph of the title compound has been described earlier, but the arrangement of the mol­ecules observed in the current structure is distinctively different from that previously reported [Steffen & Palenik (1976 ▶). Inorg. Chem. 15, 2432–2439]. The earlier report describes a structure with individual well separated mol­ecules crystallizing in space group P21/n. The polymorph described here, which is isostructrural to its Pt analogue [Babai et al. (2006 ▶). Z. Anorg. Allg. Chem. 632, 639–644], crystallizes in C2/c with chains of C2-symmetric mol­ecules stretching parallel to the b axis. The Pd atoms and the bis­phosphino­methane units are located on two different positions created by a non-crystallographic mirror operation with an occupancy of 0.6677 (11) for the major (PCH2P)Pd moiety. The positions of the Cl atoms of the minor moiety do coincide perfectly with those of the next mol­ecule along the chain parallel to b, and they are thus not included in the disorder. The phenyl rings also do not take part in the disorder and are common to both the major and minor moieties of the (PCH2P)PdCl2 units. Assuming no defects, mol­ecules in each chain will thus have to be oriented the same way and the effect of the disorder of the (PCH2P)Pd unit is thus a reversal in direction of the chains parallel to b. The presence of light streaks of intensity between actual Bragg peaks indicates that a somehow ordered arrangement not resolved in the Bragg diffraction data may be present (i.e. an incommensurate superstructure) rather than a random or domain arrangement of the chains

Grids of stellar models with rotation II. WR populations and supernovae/GRB progenitors at Z = 0.014

We used a recent grid of stellar models computed with and without rotation to make predictions concerning the WR populations and the frequency of different types of core-collapse SNe. Current rotating models were checked to provide good fits to the following features: solar luminosity and radius at the solar age, main-sequence width, red-giant and red-supergiant (RSG) positions in the HRD, surface abundances, and rotational velocities. Rotating stellar models predict that about half of the observed WR stars and at least half of the type Ibc SNe may be produced through the single-star evolution channel. Rotation increases the duration of the WNL and WNC phases, while reducing those of the WNE and WC phases, as was already shown in previous works. Rotation increases the frequency of type Ic SNe. The upper mass limit for type II-P SNe is \sim 19.0 MSun for the non rotating models and \sim 16.8 MSun for the rotating ones. Both values agree with observations. Moreover, present rotating models provide a very good fit to the progenitor of SN 2008ax. We discuss future directions of research for further improving the agreement between the models and the observations. We conclude that the mass-loss rates in the WNL and RSG phases are probably underestimated at present. We show that up to an initial mass of 40 M\odot, a surface magnetic field inferior to about 200 G may be sufficient to produce some braking. Much lower values are needed at the red supergiant stage. We suggest that the presence/absence of any magnetic braking effect may play a key role in questions regarding rotation rates of young pulsars and the evolution leading to LGRBs.Comment: 19 pages, 12 figures, accepted for publication in A&

Mach's Principle and the Origin of Inertia

The current status of Mach's principle is discussed within the context of general relativity. The inertial properties of a particle are determined by its mass and spin, since these characterize the irreducible unitary representations of the inhomogeneous Lorentz group. The origin of the inertia of mass and intrinsic spin are discussed and the inertia of intrinsic spin is studied via the coupling of intrinsic spin with rotation. The implications of spin-rotation coupling and the possibility of history dependence and nonlocality in relativistic physics are briefly mentioned.Comment: 14 pages. Dedicated to Carl Brans in honor of his 80th birthday. To appear in the Brans Festschrift; v2: typo corrected, published in: At the Frontier of Spacetime, edited by T. Asselmeyer-Maluga (Springer, 2016), Chapter 10, pp. 177-18

1-Benzoyl-3-(2,4,5-trichloro­phen­yl)thio­urea

The benzene and phenyl rings in the title compound, C14H9Cl3N2OS, form a dihedral angle of 40.98 (6)°. The mol­ecule exists in the thione form with typical thio­urea C—S [1.666 (2) Å] and C—O [1.227 (3) Å] bond lengths as well as shortened C—N bonds [1.345 (3) and 1.386 (2) Å]. An intra­molecular N—H⋯O hydrogen bond stabilizes the mol­ecular conformation. In the crystal, pairs of N—H⋯S hydrogen bonds link the mol­ecules into centrosymmetric dimers

Evaluation and improvement of the regulatory inference for large co-expression networks with limited sample size

Abstract Background Co-expression has been widely used to identify novel regulatory relationships using high throughput measurements, such as microarray and RNA-seq data. Evaluation studies on co-expression network analysis methods mostly focus on networks of small or medium size of up to a few hundred nodes. For large networks, simulated expression data usually consist of hundreds or thousands of profiles with different perturbations or knock-outs, which is uncommon in real experiments due to their cost and the amount of work required. Thus, the performances of co-expression network analysis methods on large co-expression networks consisting of a few thousand nodes, with only a small number of profiles with a single perturbation, which more accurately reflect normal experimental conditions, are generally uncharacterized and unknown. Methods We proposed a novel network inference methods based on Relevance Low order Partial Correlation (RLowPC). RLowPC method uses a two-step approach to select on the high-confidence edges first by reducing the search space by only picking the top ranked genes from an intial partial correlation analysis and, then computes the partial correlations in the confined search space by only removing the linear dependencies from the shared neighbours, largely ignoring the genes showing lower association. Results We selected six co-expression-based methods with good performance in evaluation studies from the literature: Partial correlation, PCIT, ARACNE, MRNET, MRNETB and CLR. The evaluation of these methods was carried out on simulated time-series data with various network sizes ranging from 100 to 3000 nodes. Simulation results show low precision and recall for all of the above methods for large networks with a small number of expression profiles. We improved the inference significantly by refinement of the top weighted edges in the pre-inferred partial correlation networks using RLowPC. We found improved performance by partitioning large networks into smaller co-expressed modules when assessing the method performance within these modules. Conclusions The evaluation results show that current methods suffer from low precision and recall for large co-expression networks where only a small number of profiles are available. The proposed RLowPC method effectively reduces the indirect edges predicted as regulatory relationships and increases the precision of top ranked predictions. Partitioning large networks into smaller highly co-expressed modules also helps to improve the performance of network inference methods. The RLowPC R package for network construction, refinement and evaluation is available at GitHub: https://github.com/wyguo/RLowPC

3-Ammonio-4-hydroxy­benzoate monohydrate

The title compound, C7H7NO3·H2O, which crystallized as a hydrate, was obtained from an extraction of the plant species Saussurea atkinsonii of the asteraceae family collected from the hilly area (Ayubia) of Pakistan during the flowering season. The dihedral angle between the benzene ring and the carboxyl­ate group is 25.64 (5)°. In the crystal, the packing is consolidated by N—H⋯O and O—H⋯O hydrogen bonds, as well as weak aromatic π–π stacking [centroid–centroid separation = 3.9365 (9) Å] and C=O⋯π inter­actions