bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fundamental constants and high‐resolution spectroscopy
Authors: Bonifacio P. , Rahmani H. , Whitmore J.B. , Wendt M. , Centurion M. , Molaro P. , Srianand R. , Murphy M.T. , Petitjean P. , Agafonova I.I. , D'Odorico S. , Evans T.M. , Levshakov S.A. , Lopez S. , Martins C.J.A.P. , Reimers D. , Vladilo G. 
Published: October 2014

AbstractAbsorption‐line systems detected in high resolution quasar spectra can be used to compare the value of dimensionless fundamental constants such as the fine‐structure constant, α, and the proton‐to‐electron mass ratio, μ = mp/me, as measured in remote regions of the Universe to their value today on Earth. In recent years, some evidence has emerged of small temporal and also spatial variations in α on cosmological scales which may reach a fractional level of ≈ 10 ppm (parts per million). We are conducting a Large Programme of observations with the Very Large Telescope's Ultraviolet and Visual Echelle Spectrograph (UVES), and are obtaining high‐resolution (R ≈ 60000) and high signal‐to‐noise ratio (S/N ≈ 100) spectra calibrated specifically to study the variations of the fundamental constants. We here provide a general overview of the Large Programme and report on the first results for these two constants, discussed in detail in Molaro et al. (2013) and Rahmani et al. (2013). A stringent bound for Δα /α is obtained for the absorber at zabs = 1.6919 towards HE 2217‐2818. The absorption profile is complex with several very narrow features, and is modeled with 32 velocity components. The relative variation in α in this system is +1.3 ± 2.4stat ± 1.0sys ppm if Al II λ 1670 Å and three FeII transitions are used, and +1.1 ± 2.6stat ppm in a slightly different analysis with only FeII transitions used. This is one of the tightest bounds on α ‐variation from an individual absorber and reveals no evidence for variation in α at the 3‐ppm precision level (1σ confidence). The expectation at this sky position of the recently‐reported dipolar variation of α is (3.2–5.4) ± 1.7 ppm depending on dipole model used and this constraint of Δα /α at face value is not supporting this expectation but not inconsistent with it at the 3σ level. For the proton‐to‐electron mass ratio the analysis of the H2 absorption lines of the zabs ≈ 2.4018 damped Lyα system towards HE 0027–1836 provides Δμ /μ = (–7.6 ± 8.1stat ± 6.3sys) ppm which is also consistent with a null variation. The cross‐correlation analysis between individual exposures taken over three years and comparison with almost simultaneous asteroid observations revealed the presence of a possible wavelength dependent velocity drift as well as of inter‐order distortions which probably dominate the systematic error and are a significant obstacle to achieve more accurate measurements. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Constraints on variations of mp/me based on UVES observations of H2
Authors: Wendt M. 
Published: October 2014

AbstractThis article summarizes the latest results on the proton‐to‐electron mass ratio μ derived from H2 observations at high redshift in the light of possible variations of fundamental physical constants. The focus lies on UVES observations of the past years as enormous progress was achieved since the first positive results on Δμ /μ were published. With the better understanding of systematics, dedicated observation runs, and numerous approaches to improve wavelength calibration accuracy, all current findings are in reasonable good agreement with no variation and provide an upper limit of Δμ /μ < 1 × 10–5 for the redshift range of 2 < z < 3. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Inverse Compton origin of pulsar γ ‐ray emission and the reconnection model of Crab Nebula flares
Authors: Lyutikov M. 
Published: October 2014

AbstractThere is growing evidence that the pulsar high‐energy emission is generated by the inverse Compton effect. The particles producing the Crab nebula flares, and possibly most of the Crab Nebula's high‐energy emission, are accelerated by reconnection events, and not by a shock according to the Fermi mechanism. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Review of the theory of pulsar‐wind nebulae
Authors: Bucciantini N. 
Published: October 2014

AbstractPulsar‐wind nebulae (PWNe) are ideal astro‐physical laboratories where high energy relativistic phenomena can be inves‐tigated. They are close, well resolved in our observations, and the knowledge derived in their study has a strong impact in many other fields, from AGNs to GRBs. Yet there are still unresolved issues, that prevent us from a full clear under‐standing of these objects. The lucky combination of high resolution X‐ray imaging and numerical codes to handle the outflow and dynamical properties of relativistic MHD, has opened a new avenue of investigation that has lead to inter‐esting progressed in the last years. Despite all of these, we do not understand yet how particles are accelerated, and the functioning of the pulsar wind and pulsar magnetosphere, that power PWNe. I will review what is now commonly known as the MHD paradigm, and in particular I will focus on various approaches that have been and are currently used to model these systems. For each I will highlight its advantages and limitations, and degree of applicability. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High‐energy pulsar models: Developments and new questions
Authors: Venter C. , Harding A.K. 
Published: October 2014

AbstractThe past few years have seen a major advance in observational knowledge of high‐energy (HE) pulsars. The Fermi Large Area Telescope (LAT) and AGILE have increased the number of known γ‐ray pulsars by an order of magnitude, its members being divided roughly equally among millisecond pulsars (MSPs), young radio‐loud pulsars, and young radio‐quiet pulsars. Many new and diverse emission characteristics are being measured, while radio and X‐ray follow‐up observations increase the pulsar detection rate and enrich our multiwavelength picture of these extreme sources. The wealth of new data has provided impetus for further development and improvement of existing theoretical pulsar models. Geometric light curve (LC) modelling has uncovered three broad classes into which HE pulsars fall: those where the radio profile leads, is aligned with, or lags the γ‐ray profile. For example, the original MSP and original black widow system are members of the second class, requiring co‐located emission regions and thereby breaking with traditional notions of radio emission origin. These models imply narrow accelerator gaps in the outer magnetosphere, indicating copious pair production even in MSP magnetospheres that were previously thought to be pair‐starved. The increased quality and variety of the LCs necessitate construction of ever more sophisticated models. We will review progress in global magnetosphere solutions which specify a finite conductivity on field lines above the stellar surface, filling the gap between the standard vacuum and force‐free (FF; plasma‐filled) models. The possibility of deriving phase‐resolved spectra for the brightest pulsars, coupled with the fact that the HE pulsar population is sizable enough to allow sampling of various pulsar geometries, will enable much more stringent testing of future radiation models. Reproduction of the observed phase‐resolved behavior of this disparate group will be one of the next frontiers in pulsar science, impacting on our understanding of particle acceleration, emission, and magnetosphere geometry. One may now also study evolutionary trends of the measured or inferred quantities, and probe pulsar visibility and population properties such as radiation beam sizes of different pulsar classes, as well as the distribution of spin‐down power, γ‐ray luminosity, conversion efficiency, spectral index, and cutoff energy across the population. Lastly, the recent detection of very‐high‐energy (VHE) pulsations from the Crab pulsar generated quite a few ideas to explain this emission, leading to an extension of standard models and possibly even a bridge between the physics of pulsars and pulsar wind nebulae (PWNe). (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A phase‐variable absorption feature in the X‐ray spectrum of the magnetar SGR 0418+5729
Authors: Tiengo A. , Esposito P. , Mereghetti S. , Turolla R. , Nobii L. , Gastaldello F. , Götz D. , Israel G.L. , Rea N. , Stella L. , Zane S. , Bignami G.F. 
Published: October 2014

AbstractAn absorption feature, the properties of which strongly depend on the pulse phase, has been recently discovered in the X‐ray spectrum of the soft gamma repeater SGR0418+5729. If interpreted as a proton cyclotron line, its energy implies a magnetic field ranging from 2× 1014 G to more than 1015 G, which confirms the magnetar interpretation for this source and provides us with the most direct measurement of the magnetic field intensity of an isolated neutron star. The lower value of the dipole field inferred from the timing parameters for SGR 0418+5729 (B = 6× 1012 G) requires that the high magnetic field responsible for the observed feature resides in a strong multi‐polar component located close to the neutron star surface, in agreement with the predictions of the magnetar model. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic field instabiities in neutron stars
Authors: Ciolfi R. 
Published: October 2014

AbstractMagnetic fields represent a crucial aspect of the physics and astro‐physics of neutron stars. Despite its great relevance, the internal magnetic field configuration of neutron stars is very poorly constrained by the observations, and understanding its properties is a long‐standing theoretical challenge. The investigation on the subject is focused on the search for those magnetic field geometries which are stable on several Alfvèn timescales, thus constituting a viable description of neutron star interiors. Assessing the stability of a given magnetic field geometry is therefore an important part of this research. So far only simple configurations, such as the purely poloidal or purely toroidal ones, have been studied in detail in perturbation theory and, most recently, by means of nonlinear magnetohydrodynamic simulations. Here we review the basic results of the state‐of‐the‐art general relativistic nonlinear studies, discussing the present status of the field and its future directions. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
X‐ray observations and the search for Fermi ‐LAT γ‐ray pulsars
Authors: Saz Parkinson P. M. , Belfiore A. , Caraveo P. , De Luca A. , Marelli M. 
Published: October 2014

AbstractThe Large Area Telescope (LAT) on Fermi has detected ∼150 γ‐ray pulsars, about a third of which were discovered in blind searches of the γ‐ray data. Because the angular resolution of the LAT is relatively poor and blind searches for pulsars (especially millisecond pulsars, MSPs) are very sensitive to an error in the position, one must typically scan large numbers of locations. Identifying plausible X‐ray counterparts of a putative pulsar drastically reduces the number of trials, thus improving the sensitivity of pulsar blind searches with the LAT. I discuss our ongoing program of Swift, XMM‐Newton, and Chandra observations of LAT unassociated sources in the context of our blind searches for γ‐ray pulsars. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Chandra imaging of gamma‐ray binaries
Authors: Kargaltsev O. , Rangelov B. , Hare J. , Pavlov G.G. 
Published: October 2014

AbstractWe review the multiwavelength properties of the few known γ ‐ray binaries, focusing on extended emission recently resolved with Chandra. We discuss the implications of these findings for the nature of compact objects and for physical processes operating in these systems. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling statistical properties of the X‐ray emission from aged pulsar wind nebulae
Authors: Bandiera R. 
Published: October 2014

AbstractThe number of known pulsar wind nebulae (PWNe) has recently increased considerably, and the majority of them are now middle‐age objects. Recent studies have shown a clear correlation of both X‐ray luminosity and size with the PWN age, but fail in providing a thorough explanation of the observed trends. Here I propose a different approach to these effects, based on the hypothesis that the observed trends do not simply reproduce the evolution of a “typical” PWN, but are a combined effect of PWNe evolving under different ambient conditions, the leading parameter being the ambient medium density. Using a simple analytic approach, I show that most middle‐aged PWNe are more likely observable during the reverberation phase, and I succeed in reproducing trends consistent with those observed, provided that the evolution of the X‐ray emitting electrons remains adiabatic over the whole reverberation phase. As a direct consequence, I show that the X‐ray spectra of older PWNe should be harder, also consistent with observations. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Long‐term X‐ray timing of the double pulsar PSR J0737–3039
Authors: Iacolina M. N. , Pellizzoni A. , Egron E. 
Published: October 2014

AbstractThe relativistic double neutron star binary PSR J0737–3039 is a truly unique system offering the diagnostics of two interacting radio pulsars in a short orbital period system. Clear evidences of orbital phase‐dependent interactions between the two neutron stars are seen both in radio and X‐rays observations. We present the timing analysis results of the PSRJ0737– 3039 observations performed in the context of the 2006 and 2011 XMM‐Newton Large programs providing ∼ 20000 X‐ray counts overall from the system. Despite only marginal orbital flux variability is detected, both pulsars of the system are clearly seen in X‐ray providing physical insights on the physics of the mutual interactions in their close environment. In particular, we discuss possible processes behind the peculiar X‐ray brightening of the “lazy pulsar” PSR B via energy transfer from the “power plant” PSR A. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetars: The strongest magnets in the Universe
Authors: Rea N. 
Published: October 2014

AbstractNeutron stars provide a unique environment where we can test (at the same time) our understanding of matter with extreme density, temperature, and magnetic field. In particular, the properties of matter under the influence of magnetic fields and the role of electromagnetism in physical processes are key areas of research in physics. However, despite decades of research, our limited knowledge on the physics of strong magnetic fields is clear: we only need to note that the strongest steady magnetic field achieved in terrestrial laboratories is some millions Gauss, only thousands of times stronger than a common refrigerator magnet. In this general context, I will review here the state of the art of our research on the most magnetic objects in the Universe, a small sample of neutron stars called magnetars. The study of the strong high energy emission, and the flares from these strongly magnetised (∼1015 G) neutron stars is providing crucial information about the physics involved at these extremes conditions, resulting in many unexpected discoveries. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Beyond the 2nd Fermi Pulsar Catalog
Authors: Hou X. , Smith D.A. , Reposeur T. , Rousseau R. 
Published: October 2014

AbstractOver thirteen times more γ‐ray pulsars have now been studied with the Large Area Telescope on NASA's Fermi satellite than the ten seen with the Compton Gamma‐Ray Observatory in the nineteen‐nineties. The large sample is diverse, allowing better understanding both of the pulsars themselves and of their roles in various cosmic processes. Here we explore the prospects for even more γ‐ray pulsars as Fermi enters the 2nd half of its nominal ten‐year mission. New pulsars will naturally tend to be fainter than the first ones discovered. Some of them will have unusual characteristics compared to the current population, which may help discriminate between models. We illustrate a vision of the future with a sample of six pulsars discovered after the 2nd Fermi Pulsar Catalog was written. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The CMC15, the last issue of the series “Carlsberg Meridian Catalogue, La Palma”
Authors: Muiños J.L. , Evans D. W. 
Published: October 2014

AbstractCMC15 is the last of the series “Carlsberg Meridian Catalogue, La Palma” and comprises all the observations made between March 1999 and March 2011 with the Carlsberg Automatic Meridian Circle in El Roque de los Muchachos Observatory on the island of La Palma (Spain). The catalogues CMC12, CMC13, and CMC14 are superseded by this one. It contains more than 122 million observations of right ascension, declination, and magnitude of stars in the magnitude range of 9m < r′ < 17m and declination range of –40° < δ < +50°. The catalogue internal errors in astrometry are below 30 mas in both coordinates for stars brighter than r′ = 13, reaching 60 mas for r′ = 16. The internal magnitude error is below 0.020 mag for stars brighter than r′ = 13, and about 0.090 mag for r′ = 16. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spectra of faint sources in crowded fields with FRODOSpec on the Liverpool Robotic Telescope
Authors: Shalyapin V. N. , Goicoechea L. J. 
Published: October 2014

AbstractWe check the performance of the FRODOSpec integral‐field spectrograph for observations of faint sources in crowded fields. Although the standard processing pipeline L2 yields too noisy fibre spectra, we present a new processing software (L2LENS) that gives rise to accurate spectra for the two images of the gravitationally lensed quasar Q0957+561. Among other things, this L2LENS reduction tool accounts for the presence of cosmic‐ray events, scattered‐light backgrounds, blended sources, and chromatic source displacements due to differential atmospheric refraction. Our non‐standard reduction of Q0957+561 data shows the ability of FRODOSpec to provide useful information on a wide variety of targets, and thus, the big potential of integral‐field spectrographs on current and future robotic telescopes. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Discussing the physical meaning of the absorption feature at 2.1 keV in 4U 1538–52
Authors: Rodes‐Roca J. J. , Torrejón J. M. , Martínez‐Nuñez S. , Giménez‐García A. , Bernabéu G. 
Published: October 2014

AbstractHigh resolution X‐ray spectroscopy is a powerful tool for studying the nature of the matter surrounding the neutron star in X‐ray binaries and its interaction between the stellar wind and the compact object. In particular, absorption features in their spectra could reveal the presence of atmospheres of the neutron star or their magnetic field strength. Here we present an investigation of the absorption feature at 2.1 keV in the X‐ray spectrum of the high mass X‐ray binary 4U 1538–52 based on our previous analysis of the XMM‐Newton data. We study various possible origins and discuss the different physical scenarios in order to explain this feature. A likely interpretation is that the feature is associated with atomic transitions in an O/Ne neutron star atmosphere or of hydrogen and helium like Fe or Si ions formed in the stellar wind of the donor. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of a transiting planet candidate in Trumpler 37: An astro‐physical false positive eclipsing spectroscopic binary star *
Authors: Errmann R. , Torres G. , Schmidt T.O.B. , Seeliger M. , Howard A.W. , Maciejewski G. , Neuhäuser R. , Meibom S. , Kellerer A. , Dimitrov D.P. , Dincel B. , Marka C. , Mugrauer M. , Ginski Ch. , Adam Ch. , Raetz St. , Schmidt J.G. , Hohle M.M. , Berndt A. , Kitze M. , Trepl L. , Moualla M. , Eisenbeiß T. , Fiedler S. , Dathe A. , Graefe Ch. , Pawellek N. , Schreyer K. , Kjurkchieva D.P. , Radeva V.S. , Yotov V. , Chen W.P. , Hu S.C.‐L. , Wu Z.‐Y. , Zhou X. , Pribulla T. , Budaj J. , Vaňko M. , Kundra E. , Hambälek Ľ. , Krushevska V. , Bukowiecki Ł. , Nowak G. , Marschall L. , Terada H. , Tomono D. , Fernandez M. , Sota A. , Takahashi H. , Oasa Y. , Briceño C. , Chini R. , Broeg C.H. 
Published: October 2014

AbstractWe report our investigation of the first transiting planet candidate from the YETI project in the young (∼4 Myr old) open cluster Trumpler 37. The transit‐like signal detected in the lightcurve of F8V star 2M21385603+5711345 repeats every 1.364894 + 0.000015 days, and has a depth of 54.5 + 0.8 mmag in R. Membership in the cluster is supported by its mean radial velocity and location in the color‐magnitude diagram, while the Li diagnostic and proper motion are inconclusive in this regard. Follow‐up photometric monitoring and adaptive optics imaging allow us to rule out many possible blend scenarios, but our radial‐velocity measurements show it to be an eclipsing single‐lined spectroscopic binary with a late‐type (mid‐M) stellar companion, rather than one of planetary nature. The estimated mass of the companion is 0.15–0.44 M⊙. The search for planets around very young stars such as those targeted by the YETI survey remains of critical importance to understand the early stages of planet formation and evolution. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)