bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inverse Mapping of Pulsar Magnetospheres: Optical Emission Comes From 300 km Above the Surface
Authors: de Búrca Diarmaid , O'Connor Padraig , McDonald John , Shearer Andy 
Published: April 2012

AbstractIn order to determine the emission height of the optical photons from pulsars we present an inverse mapping approach, which is directly constrained by empirical data. The model discussed is for the case of the Crab pulsar. Our method, which uses the optical Stokes parameters, determines the most likely geometry for emission including the magnetic-field inclination angle (α), the observer's line-of-sight angle (χ) and emission height. We discuss the computational implementation of the approach, and the physical assumptions made. We find that the most likely emission altitude is at 20% of the light-cylinder radius above the stellar surface in the open field region.
The Catalina Real-time Transient Survey
Authors: Drake A. J. , Djorgovski S. G. , Mahabal A. , Prieto J. L. , Beshore E. , Graham M. J. , Catalan M. , Larson S. , Christensen E. , Donalek C. , Williams R. 
Published: April 2012

AbstractThe Catalina Real-time Transient Survey (CRTS) currently covers 33,000 deg2 of the sky in search of transient astrophysical events, with time base-lines ranging from 10 minutes to ~7 years. Data provided by the Catalina Sky Survey provide an unequalled base-line against which > 4,000 unique optical transient events have been discovered and openly published in real-time. Here we highlight some of the discoveries of CRTS.
Searching for Periodic Variables in the EROS-2 Database
Authors: Dubath P. , Lecoeur I. , Rimoldini L. , Süveges M. , Blomme J. , López M. , Sarro L. M. , De Ridder J. , Cuypers J. , Guy L. , Nienartowicz K. , Jan A. , Beck M. , Mowlavi N. , Ordóñez-Blanco D. , Marquette J. B. , Beaulieu J. P. , Tisserand P. , Lesquoy É. , Eyer L. 
Published: April 2012

AbstractWe started a systematic search for periodic variable-star candidates in the EROS-2 database in the context of preparatory work for the Gaia satellite mission. The goal is to evaluate different classification tools and strategies, and to identify a large sample of variable candidates. In this paper we present the results of an assessment study of a three-step identification and classification process. In the study we took a sample of about 80,000 stars from one of the LMC EROS fields.
Testing the Standard Model of Active Galactic Nuclei through Quasar Variability
Authors: Ederoclite Alessandro , Polednikova Jana , Cepa Jordi , de Diego Onsurbe José Antonio , González-Serrano Ignacio 
Published: April 2012

AbstractThe standard model of Active Galactic Nuclei (AGNs) predicts that Type 2 AGNs and Type 1 AGNs only differ in the orientation of a dust torus, which does or does not allow one to observe the central region. If the model is correct, the time-scales and the amplitudes of observed temporal variations should be different between obscured and unobscured objects. In order to test this hypothesis, we started a multi-wavelength (BRIJKs) monitoring campaign of a sample of quasars of both types. Here we present the data and preliminary results of that project.
Time-Domain Studies of Gravitationally Lensed Quasars
Authors: Goicoechea Luis J. , Shalyapin Vyacheslav N. 
Published: April 2012

AbstractWe present an overview and current results of an ongoing optical/NIR monitoring of seven gravitationally-lensed quasars (GLQs) with the 2-m Liverpool Robotic Telescope. The photometric data from the first seven years (2005–2011) of this programme are leading to high-quality light curves, which in turn are being used as key tools for different standard and novel studies. While brightness records of non-lensed distant quasars may contain unrecognized extrinsic variations, one can disentangle intrinsic from extrinsic signals in certain GLQs. Thus, some GLQs in our sample allow us to assess their extrinsic and intrinsic variations; we then discuss the origin of both kinds of fluctuations. We also demonstrate the usefulness of GLQ time-domain data for obtaining successful reverberation maps of the inner regions of accretion disks around distant supermassive black holes, and for estimating the redshifts of distant lensing galaxies.
Hottest Superfluid and Superconductor in the Universe: Lessons from the Cooling of the Cassiopeia A Neutron Star
Authors: Ho Wynn C. G. , Heinke Craig O. , Patnaude Daniel J. , Shternin Peter S. , Yakovlev Dmitry G. 
Published: April 2012

AbstractThe cooling rate of young neutron stars gives direct insight into their internal makeup. Using Chandra observations of the 330-year-old Cassiopeia A supernova remnant, we find that the temperature of the youngest-known neutron star in the Galaxy has declined by 4% over the last 10 years. The decline is explained naturally by superconductivity and superfluidity of the protons and neutrons in the stellar core. The protons became superconducting early in the life of the star and suppressed the early cooling rate; the neutron star thus remained hot before the (recent) onset of neutron superfluidity. Once the neutrons became superfluid, the Cooper pair-formation process produced a splash of neutrino emission which accelerated the cooling and resulted in the observed rapid temperature decline. This is the first time a young neutron star has been seen to cool in real time, and is the first direct evidence, from cooling observations, of superfluidity and superconductivity in the core of neutron stars.
What To Do with Sparkers?
Authors: Keane E. F. , Stappers B. W. , Kramer M. , Lyne A. G. 
Published: April 2012

AbstractIn 2007, the discovery of the so-called “Lorimer Burst” was announced—a single radio pulse that was so dispersed that it could only have originated outside our Galaxy. The apparently unique event, together with the large inferred distance (a redshift z ~0.2 is required to explain its high dispersion) implies a very high luminosity. Suggested progenitors include a supernova, a binary neutron-star merger, and a black-hole annihilation event. Crude estimates of the rates of such events predict that many such bursts should already be detectable in archived pulsar-survey data, and has led to detailed searches which have had some success.
Towards Improving the Prospects for Coordinated Gravitational-Wave and Electromagnetic Observations
Authors: Mandel Ilya , Kelley Luke Z. , Ramirez-Ruiz Enrico 
Published: April 2012

AbstractWe discuss two approaches to searches for gravitational-wave (GW) and electromagnetic (EM) counterparts of binary neutron-star mergers. The first approach relies on triggering archival searches of GW detector data based on detections of EM transients. Quantitative estimates of the improvement to GW detector reach due to the increased confidence in the presence and parameters of a signal from a binary merger gained from the EM transient suggest utilizing other transients in addition to short gamma-ray bursts. The second approach involves following up GW candidates with targeted EM observations. We argue for the use of slower but optimal parameter-estimation techniques and for a more sophisticated use of astrophysical prior information, including galaxy catalogues to find preferred follow-up locations.
Statistics of Stellar Variability in Kepler Data with ARC Systematics Removal
Authors: McQuillan Amy , Aigrain Suzanne , Roberts Stephen 
Published: April 2012

AbstractWe investigate the variability properties of main-sequence stars in the first month of Kepler data, using a new astrophysically robust systematics correction. We find that 36% appear more variable than the Sun, and confirm the trend of increasing variability with decreasing effective temperature. We define low- and high-variability samples, with a cut at twice the level of the active Sun, and compare properties of the stars belonging to each sample. We find tentative evidence that the more active stars have lower proper motions. The frequency content of the variability shows clear evidence for periodic or quasi-periodic behaviour in 16% of stars, and highlights significant differences in the nature of variability between spectral types. Most A and F stars have short periods (< 2 days) and highly sinusoidal variability, suggestive of pulsations, whilst G, K and M stars tend to have longer periods (> 5 days, with a trend towards longer periods at later spectral types) and show a mixture of periodic and stochastic variability, indicative of activity. Finally, we use autoregressive models to characterise the stochastic component of the variability, and show that its typical amplitude and time-scale increase towards later spectral types, which we interpret as an increase in the characteristic size and life-time of active regions. Full details will be published shortly.
Variability Analysis based on POSS1/POSS2 Photometry
Authors: Mickaelian Areg M. , Sarkissian Alain , Sinamyan Parandzem K. 
Published: April 2012

AbstractWe introduce accurate magnitudes as combined calculations from catalogues based on accurate measurements of POSS1- and POSS2-epoch plates. The photometric accuracy of various catalogues was established, and statistical weights for each of them have been calculated. To achieve the best possible magnitudes, we used weighted averaging of data from APM, MAPS, USNO-A2.0, USNO-B1.0 (for POSS1-epoch), and USNO-B1.0 and GSC 2.3.2 (for POSS2-epoch) catalogues. The r.m.s. accuracy of magnitudes achieved for POSS1 is 0.184 in B and 0.173 mag in R, or 0.138 in B and 0.128 in R for POSS2. By adopting those new magnitudes we examined the First Byurakan Survey (FBS) of blue stellar objects for variability, and uncovered 336 probable and possible variables among 1103 objects with POSS2–POSS1 ≥ 3σ of the errors, including 161 highly probable variables. We have developed methods to control and exclude accidental errors for any survey. We compared and combined our results with those given in Northern Sky Variability Survey (NSVS) database, and obtained firm candidates for variability. By such an approach it will be possible to conduct investigations of variability for large numbers of objects.
Search for Turbulent Gas through Interstellar Scintillation
Authors: Moniez M. , Ansari R. , Habibi F. , Rahvar S. 
Published: April 2012

AbstractStars twinkle because their light propagates through the atmosphere. The same phenomenon is expected when the light of remote stars crosses a Galactic—disk or halo—refractive medium such as a molecular cloud. We present the promising results of a test performed with the ESO–NTT, and consider its potential.
Optical Polarimetry of the Crab Nebula
Authors: Moran Paul , Shearer Andy , Mignani Roberto 
Published: April 2012

AbstractTime-resolved polarisation measurements of pulsars provide an unique insight into the geometry of the emission regions. Hubble Space Telescope (HST) polarisation data of the Crab Nebula were obtained from the Multimission Archive at STScI (MAST). The data are composed of a series of observations of the Crab Nebula with the HST and ACS camera system taken in three different polarisation filters (0°, 60° and 120°) between 2003 August and 2005 December. Polarisation vector maps of the Nebula were produced with the polarimetry software IMPOL. The degree of polarisation (P.D.) and the position angle (P.A.) of the pulsar's integrated pulse beam were measured, and also that of the nearby Synchrotron Knot, yielding P.D. = 4.90 ± 0.33 %, P.A. = 106°.46 ± 1°.9 for the pulsar, and P.D. = 61.70 ± 0.72 %, P.A. = 126°.86 ± 0°.23 for the Synchrotron Knot. These results are consistent with those of obtained by others using INTEGRAL.
Time-Domain Astrophysics with SuperWASP
Authors: Norton A. J. ,   the SuperWASP Consortium
Published: April 2012

AbstractSuperWASP is the world's leading ground-based survey for transiting exoplanets. Its database now contains over 300 billion data points covering 30 million unique objects from 10 million images obtained over 1700 nights since 2004. In addition to having discovered 70 transiting exoplanets, SuperWASP enables long-baseline, high-cadence studies of variable stars to be performed. We summarise some of the studies already carried out, and look ahead to the prospects for studying periodic variables with varying periods. The science which is thus supported will include studies of the Blazhko effect in RR Lyræ stars, migrating starspots in rotational variables, third bodies in eclipsing binaries, and coalescing binary stars.
ARCONS: a Highly Multiplexed Superconducting UV-to-Near-IR Camera
Authors: O'Brien Kieran , Mazin Ben , McHugh Sean , Meeker Seth , Bumble Bruce 
Published: April 2012

AbstractARCONS, the Array Camera for Optical to Near-infrared Spectrophotometry, was recently commissioned at the coudé focus of the 200-inch Hale Telescope at the Palomar Observatory. At the heart of this unique instrument is a 1024-pixel Microwave Kinetic Inductance Detector (MKID), exploiting the Kinetic Inductance effect to measure the energy of the incoming photon to better than several percent. The ground-breaking instrument is lens-coupled with a pixel scale of 0″.23/pixel, each pixel recording the arrival time (< 2 μ sec) and energy of a photon (~10%) in the optical to near-IR (0.4–1.1 microns) range. The scientific objectives of the instrument include the rapid follow-up and classification of transient phenomena.
Using the Gregory-Loredo Algorithm for the Detection of Variability in the Chandra Source Catalog
Authors: Rots Arnold H. 
Published: April 2012

AbstractIn searching for a reliable variability indicator for Chandra X-ray event data, we implemented the Gregory-Loredo (G–L) algorithm to assess variability and to generate light curves for the Chandra Source Catalog. A test was performed on 118 sources detected in a single observation, spanning the intensity range 5–24,000 photons over a total observing time of 102,000 sec. We conclude that the G–L algorithm is extremely robust, yielding both a reliable variability indicator and light curves with optimal resolution, while requiring a very modest amount of CPU time. The algorithm can also work on binned data, and is capable of handling data gaps as well as variations in effective area.
On Our Multi-Wavelength Campaign of the 2011 Outburst of T Pyx
Authors: Schmidtobreick L. , Bayo A. , Momany Y. , Ivanov V. , Barria D. , Beletsky Y. , Boffin H. M. J. , Brammer G. , Carraro G. , de Wit W.-J. , Girard J. , Hau G. , Moerchen M. , Nuernberger D. , Pretorius M. , Rivinius T. , Sanchez-Janssen R. , Selman F. , Stefl S. , Yegorova I. 
Published: April 2012

AbstractThe well-known recurrent nova T Pyx has brightened by 7 magnitudes, starting on 2011 April 14, its first eruption since 1966. T Pyx is unique amongst recurrent novæ in being surrounded by a nebula formed of material ejected during previous eruptions. The latest eruption therefore offers the rare opportunity to observe a light echo sweeping through the existing shell, and a new one forming. The sudden exposure of the existing shell to high-energy light is expected to result in a change of the dust morphology as well as in the part destruction of molecules. We observe this process in the near- and mid-IR during several epochs using ESO's VLT instruments Sinfoni, Visir and Isaac. Unfortunately, in the data analysed so far we only have a tentative detection in Brα from the shell, so might in the end have to be content with upper limits for the emission from the various molecular bands and ionised lines.
Multi-wave Monitoring of the Gravitational Lensed Quasar Q0957+561
Authors: Shalyapin Vyacheslav N. , Goicoechea Luis J. , Gil-Merino Rodrigo 
Published: April 2012

AbstractWe present X-ray (Chandra), ultraviolet (Swift/UVOT; U band) and optical-infrared (Liverpool Telescope; griz bands) continuum light curves of Q0957+561 observed in the first half of 2010. A cross-correlation analysis of the light curves shows that the U-band fluctuation leads the other variations at higher and lower energies. The study constrains the geometry of the continuum emission regions in a distant radio-loud AGN for the first time. We note that our work opens a new window in echo-mapping of high-z AGNs with the use of lensed quasars, since the variability of some of the images of a given multiply-imaged quasar can be predicted in advance, provided there is a modest optical follow-up of the system.
Source Detection with Interferometric Datasets
Authors: Trott Cathryn M. , Wayth Randall B. , Macquart Jean-Pierre R. , Tingay Steven J. 
Published: April 2012

AbstractThe detection of sources in interferometric radio data typically relies on extracting information from images, formed by Fourier transform of the underlying visibility dataset, and CLEANed of contaminating sidelobes through iterative deconvolution. Variable and transient radio sources span a large range of variability timescales, and their study has the potential to enhance our knowledge of the dynamic universe. Their detection and classification involve large data rates and non-stationary PSFs, commensal observing programs and ambitious science goals, and will demand a paradigm shift in the deployment of next-generation instruments. Optimal source detection and classification in real time requires efficient and automated algorithms. On short time-scales variability can be probed with an optimal matched filter detector applied directly to the visibility dataset. This paper shows the design of such a detector, and some preliminary detection performance results.
Wide-Field Plate Database: Latest Results
Authors: Tsvetkov Milcho , Tsvetkova Katya 
Published: April 2012

AbstractWe present the Wide-Field Plate Database, a basic source of data and meta-data for astronomy's more than 2.4 million wide-field photographic images obtained with professional telescopes worldwide. The technology developed in Sofia for plate digitization with commercial high-quality flatbed scanners yields low-resolution digital images for quick visualization and easy online access, and optimal high-resolution ones for photometric and astrometric investigations.
The VLBA Fast Radio Transient Experiment: Progress and Early Results
Authors: Wayth Randall B. , Brisken Walter F. , Deller Adam T. , Majid Walid A. , Thompson David R. , Tingay Steven J. , Wagstaff Kiri L. 
Published: April 2012

AbstractMotivated by recent discoveries of isolated, dispersed radio pulses of possible extragalactic origin, we are performing a commensal search for short-duration (ms) continuum radio pulses using the Very Long Baseline Array (VLBA). The geographically separated antennæ of the VLBA make the system robust to local RFI and allow events to be verified and localised on the sky with milli-arcsec accuracy. We report sky coverage and detection limits from the experiment to date.
Around Gaia Alerts in 20 questions
Authors: Wyrzykowski Łukasz , Hodgkin Simon 
Published: April 2012

AbstractGaia is a European Space Agency (ESA) astrometry space mission, and a successor to the ESA Hipparcos mission. Gaia's main goal is to collect high-precision astrometric data (positions, parallaxes, and proper motions) for the 1 billion brightest objects in the sky. Those data, complemented with multi-band, multi-epoch photometric and spectroscopic data observed from the same observing platform, will allow astronomers to reconstruct the formation history, structure, and evolution of the Galaxy.Gaia will observe the whole sky for 5 years, providing a unique opportunity for the discovery of large numbers of transient and anomalous events such as supernovæ, novæ and microlensing events, GRB afterglows, fallback supernovæ, and other theoretical or unexpected phenomena. The Photometric Science Alerts team has been tasked with the early detection, classification and prompt release of anomalous sources in the Gaia data stream. In this paper we discuss the challenges we face in preparing to use Gaia to search for transient pheonomena at optical wavelengths.
Judicialversus‘natural’ selection of legal rules with an application to accident law
Authors: MICELI THOMAS J. 
Published: April 2012

Abstract:Law and economics scholars argue that the common law evolves toward efficiency. Invisible-hand theories suggest that the law is primarily driven by a selection process whereby inefficient laws are litigated more frequently than efficient laws, and hence are more likely to be overturned. However, the preferences of judges also necessarily affect legal change. This paper models the interaction of these two forces to evaluate the efficiency claim, and then applies the conclusions to the evolution of accident law in the United States beginning in the 19th century. Specifically, it attributes the persistence of negligence to its efficiency properties, despite its having been initially selected by judges for a different reason. The paper relates legal evolution to biological evolution by employing the concepts of natural and artificial selection, and the more recent concept of exaptation.
Integrated geophysical and hydrothermal models of flank degassing and fluid flow at Masaya volcano, Nicaragua
Authors: Pearson S. C. P. , Kiyosugi K. , Lehto H. L. , Saballos J. A. , Connor C. B. , Sanford W. E. 
Published: April 2012

We investigate geologic controls on circulation in the shallow hydrothermal system of Masaya volcano, Nicaragua, and their relationship to surface diffuse degassing. On a local scale (∼250 m), relatively impermeable normal faults dipping at ∼60° control the flowpath of water vapor and other gases in the vadose zone. These shallow normal faults are identified by modeling of a NE‐SW trending magnetic anomaly of up to 2300 nT that corresponds to a topographic offset. Elevated SP and CO2 to the NW of the faults and an absence of CO2 to the SE suggest that these faults are barriers to flow. TOUGH2 numerical models of fluid circulation show enhanced flow through the footwalls of the faults, and corresponding increased mass flow and temperature at the surface (diffuse degassing zones). On a larger scale, TOUGH2 modeling suggests that groundwater convection may be occurring in a 3–4 km radial fracture zone transecting the entire flank of the volcano. Hot water rising uniformly into the base of the model at 1 × 10−5 kg/m2s results in convection that focuses heat and fluid and can explain the three distinct diffuse degassing zones distributed along the fracture. Our data and models suggest that the unusually active surface degassing zones at Masaya volcano can result purely from uniform heat and fluid flux at depth that is complicated by groundwater convection and permeability variations in the upper few km. Therefore isolating the effects of subsurface geology is vital when trying to interpret diffuse degassing in light of volcanic activity.
Credible occurrence probabilities for extreme geophysical events: Earthquakes, volcanic eruptions, magnetic storms
Authors: Love Jeffrey J. 
Published: April 2012

Statistical analysis is made of rare, extreme geophysical events recorded in historical data – counting the number of events k with sizes that exceed chosen thresholds during specific durations of time τ.Under transformations that stabilize data and model‐parameter variances, the most likely Poisson‐event occurrence rate,k/τ, applies for frequentist inference and, also, for Bayesian inference with a Jeffreys prior that ensures posterior invariance under changes of variables. Frequentist confidence intervals and Bayesian (Jeffreys) credibility intervals are approximately the same and easy to calculate:
, where z is a parameter that specifies the width, z = 1 (z = 2) corresponding to 1σ, 68.3% (2σ, 95.4%). If only a few events have been observed, as is usually the case for extreme events, then these “error‐bar” intervals might be considered to be relatively wide. From historical records, we estimate most likely long‐term occurrence rates, 10‐yr occurrence probabilities, and intervals of frequentist confidence and Bayesian credibility for large earthquakes, explosive volcanic eruptions, and magnetic storms.