bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Dynamic Radio Sky
Authors: Cordes James M. 
Published: April 2012

AbstractThe radio band is known to be rich in variable and transient sources, but exploration of it has only begun only in the last few years. Relevant time scales are as small as a fraction of a nanosecond (giant pulses from the Crab pulsar). Short transients (less than one second, say) have signal structure in the time-frequency plane at the very least because of interstellar plasma propagation effects (dispersion and scattering), and in some cases due to emission structure. Optimal detection requires handling a range of signal types in the time-frequency plane. Short bursts by necessity have very large effective radiation brightness temperatures associated with coherent emission processes. This paper surveys relevant source classes and summarizes propagation effects that must be considered to optimize detection in large-scale surveys. Scattering horizons for the interstellar and intergalactic media are defined, and the role of the radio band in panchromatic and multimessenger studies is discussed.
Systematically Bridging the Gap between Novæ and Supernovæ
Authors: Kasliwal Mansi M. 
Published: April 2012

AbstractUntil recently, the venerable field of cosmic explosions has been plagued with a glaring six-magnitude luminosity gap between the brightest novæ and the faintest supernovæ. A key science driver of the Palomar Transient Factory was a systematic search for optical transients that are fainter, faster and rarer than supernovæ. Theorists predict a variety of mechanisms to produce transients in that “gap”, and observers have the best chance of finding them in the local universe. The talk presented the discoveries and the unique physics of cosmic explosions which bridge that gap between novæ and supernovæ. As Fig. 1 illustrates, there is now evidence of multiple, distinct populations of rare transients in the “gap”.
Supernovæ and Transients with Euclid and the European ELT
Authors: Hook Isobel 
Published: April 2012

AbstractThe prospects are described for studies of large samples of supernovæ and other variable objects with two proposed future facilities: (1) the European Extremely Large Telescope, a general-purpose 40-m-class ground-based optical-IR telescope, and (2) Euclid, an M-class mission within ESA's Cosmic Vision programme, primarily for cosmology. The capabilities and status of the two facilities are briefly described. Their suitability for the study of time-varying objects in general, and of supernovæ in particular, is discussed. It is shown that Euclid has the potential for NIR imaging of a few thousand Type Ia supernovæ to intermediate z, while the E-ELT will be capable of spectroscopic and classification measurements of Type Ia supernovæ to z=4.
Search for Electromagnetic Counterparts to LIGO-Virgo Candidates: Expanded Very Large Array Observations
Authors: Lazio Joseph , Keating Katie , Jenet F. A. , Kassim N. E. 
Published: April 2012

AbstractThis paper summarizes a search for radio-wavelength counterparts to candidate gravitational-wave events. The identification of an electromagnetic counterpart could provide a more complete understanding of a gravitational-wave event, including such characteristics as the location and the nature of the progenitor. We used the Expanded Very Large Array (EVLA) to search six galaxies which were identified as potential hosts for two candidate gravitational-wave events. We summarize our procedures and discuss preliminary results.
Spectroscopic Binaries: Towards the 100-Year Time Domain
Authors: Griffin R. F. 
Published: April 2012

AbstractGood measurements of visual binary stars (position angle and angular separation) have been made for nearly 200 years. Radial-velocity observers have exhibited less patience; when the orbital periods of late-type stars in the catalogue published in 1978 are sorted into bins half a logarithmic unit wide, the modal bin is the one with periods between 3 and 10 days. The same treatment of the writer's orbits shows the modal bin to be the one between 1000 and 3000 days. Of course the spectroscopists cannot quickly catch up the 200 years that the visual observers have been going, but many spectroscopic orbits with periods of decades, and a few of the order of a century, have been published. Technical developments have also been made in ‘visual’ orbit determination, and orbits with periods of only a few days have been determined for certain ‘visual’ binaries. In principle, therefore, the time domains of visual and spectroscopic binaries now largely overlap. Overlap is essential, as it is only by combining both techniques that orbits can be determined in three dimensions, as is necessary for the important objective of determining stellar masses accurately. Nevertheless the actual overlap—objects with accurate measurements by both techniques—remains disappointingly small. There have, however, been unforeseen benefits from the observation of spectroscopic binaries that have unconventionally long orbital periods, not a few of which have proved to be interesting and significant objects in their own right. It has also been shown that binary membership is more common than was once thought (orbits have even been determined for some of the IAU standard radial-velocity stars!); a recent study of the radial velocities of K giants that had been monitored for 45 years found a binary incidence of 30%, whereas a figure of 13.7% was given as recently as 2005 for a similar group.
Sines, Steps and Droplets: Semi-parametric Bayesian Modelling of Arrival Time Series
Authors: Loredo Thomas J. 
Published: April 2012

AbstractI describe ongoing work developing Bayesian methods for flexible modelling of arrival-time-series data without binning. The aim is to improve the detection and measurement of X-ray and gamma-ray pulsars and of pulses in gamma-ray bursts. The methods use parametric and semi-parametric Poisson point process models for the event rate, and by design have close connections to conventional frequentist methods that are currently used in time-domain astronomy.
Variable Stellar Object Detection and Light Curves from the Solar Mass Ejection Imager (SMEI)
Authors: Hounsell R. A. , Bode M. F. , Darnley M. J. , Harman D. J. , Hick P. P , Buffington A. , Jackson B. V. , Clover J. M. , Shafter A. W. 
Published: April 2012

AbstractWith the advent of surveys such as the Catalina Real-Time Transient Survey, the Palomar Transient Factory, Pan-STARRS and Gaia, the search for variable objects and transient events is rapidly accelerating. There are, however important existing data-sets from instruments not originally designed to find such events. One example of such an instrument is the Solar Mass Ejection Imager (SMEI), an all-sky space-based differential photometer which is able to produce light curves of bright objects (m ≤ 8) with a 102-minute cadence. In this paper we discuss the use of such an instrument for investigations of novæ, and outline future plans to find other variable objects with this hitherto untapped resource.
Surveying the Bright Sky
Authors: Henden Arne A. 
Published: April 2012

AbstractThe AAVSO is initiating a new survey of the sky. It will cover the entire visible sky, both north and south, on a daily basis, in two colours, and with a limiting magnitude of V = 17. This will be a perfect complement to LSST, but will be available years earlier and will continue into the indefinite future. The photometry will be publicly available within 24 hours through our website. Some details of the hardware and operations are described.
High Time-Resolution Astronomy on the 10-m SALT
Authors: Welsh Barry , Anderson David , McPhate Jason , Vallerga John , Siegmund Oswald H. W. , Buckley David , Gulbis Amanda , Kotze Marissa , Potter Stephen 
Published: April 2012

AbstractWe present a brief description of the Berkeley Visible Imaging Tube (BVIT) detector system, which is a user instrument on the 10-m Southern African Large Telescope (SALT), and include some preliminary observational results gained in mid-2011. The data show that BVIT is capable of revealing emission features occurring on time-scales of < 0.1 sec, thus opening up for the general user a window of high time-resolution astronomy at visible wavelengths.
Charting the Transient Radio Sky on Sub-Second Time-Scales with LOFAR
Authors: Hessels J. W. T. ,   the LOFAR Transients Key Science Project
Published: April 2012

SummaryThe LOw Frequency ARray (LOFAR) is a radio interferometric telescope that promises to open a largely unexplored window on transient sources in the “radio sky”, from time-scales of nanoseconds to years. An important aspect of this will be the study of radio-emitting neutron stars in their various incarnations: slow pulsars, young pulsars, millisecond pulsars, magnetars, rotating radio transients, intermittent pulsars, et cetera. Pulsars and their brethren are the prototype of the more general “fast transients”: sub-second, dispersed radio bursts which point the way to extreme, and potentially still unknown, phenomena. For instance, prompt radio bursts from supernovæ and other extra-galactic bursts have been hypothesized; these could prove to be powerful cosmological probes.This talk discussed LOFAR's impressive ability to observe pulsars and to enlarge greatly the discovery space for (even rarer) fast transients. It also presented the latest pulsar observations made during LOFAR's commissioning period. These are demonstrating powerful observing techniques that will be crucial for the next generation of radio telescopes as well as the effort to increase our understanding of the dynamic nature of the Universe.An expanded version of the talk can be found at http://adsabs.harvard.edu/abs/2011A
On Rapid Interstellar Scintillation of Quasars: PKS 1257-326 Revisited
Authors: Bignall Hayley E. , Hodgson Jeffrey A. 
Published: April 2012

AbstractThe line of sight towards the compact, radio loud quasar PKS 1257–326 passes through a patch of scattering plasma in the local Galactic ISM that causes large and rapid, intra-hour variations in the received flux density at centimetre wavelengths. This rapid interstellar scintillation (SS) has been occurring for at least 15 years, implying that the scattering “screen” is at least 100 AU in physical extent. Through observations of the ISS we have measured microarcsecond-scale “core shifts” in PKS 1257-326, corresponding to changing opacity during an intrinsic outburst. Recent analysis of VLA data of a sample of 128 quasars found 6 sources scintillating with a characteristic time-scale of < 2 hours, suggesting that nearby scattering screens in the ISM may have a covering fraction of a few percent. That is an important consideration for proposed surveys of the transient and variable radio sky.
Sonification of Astronomical Data
Authors: Diaz-Merced Wanda L. , Candey Robert M. , Brickhouse Nancy , Schneps Matthew , Mannone John C. , Brewster Stephen , Kolenberg Katrien 
Published: April 2012

AbstractThis document presentsJava-based software calledxSonifythat uses a sonification technique (the adaptation of sound to convey information) to promote discovery in astronomical data. The prototype is designed to analyze two-dimensional data, such as time-series data. We demonstrate the utility of the sonification technique with examples applied to X-ray astronomy and solar data. We have identified frequencies in theChandraX-Ray observations of EX Hya, a cataclysmic variable of the intermediate polar type. In another example we study the impact of a major solar flare, with its associated coronal mass ejection (CME), on the solar wind plasma (in particular the solar wind between the Sun and the Earth), and the Earth's magnetosphere.
Pulsars, SKA and Time-Domain Studies in the Future
Authors: Kramer Michael 
Published: April 2012

AbstractPulsars are a classical example for time-domain astronomy. Using just the precisely measured arrival time of pulses from pulsars, we can study a wide range of physics, and in particular probe the validity of theories of gravity. Despite huge success, pulsar astrophysics will completely change with the Square Kilometre Array (SKA), lifting pulsar science into a new era of time-domain astronomy. I will review the applications using pulsars and the prospects for the SKA.
The Future of the Time Domain with LSST
Authors: Walkowicz Lucianne M. 
Published: April 2012

SummaryIn the coming decade LSST's combination of all-sky coverage, consistent long-term monitoring and flexible criteria for event identification will revolutionize studies of a wide variety of astrophysical phenomena. Time-domain science with LSST encompasses objects both familiar and exotic, from classical variables within our Galaxy to explosive cosmological events. Increased sample sizes of known-but-rare observational phenomena will quantify their distributions for the first time, thus challenging existing theories. Perhaps most excitingly, LSST will provide the opportunity to sample previously untouched regions of parameter space. LSST will generate ‘alerts’ within 60 seconds of detecting a new transient, permitting the community to follow up unusual events in greater detail. However, follow-up will remain a challenge as the volume of transients will easily saturate available spectroscopic resources. Characterization of events and access to appropriate ancillary data (e.g. from prior observations, either in the optical or in other passbands) will be of the utmost importance in prioritizing follow-up observations. The incredible scientific opportunities and unique challenges afforded by LSST demand organization, forethought and creativity from the astronomical community. To learn more about the telescope specifics and survey design, as well as obtaining a overview of the variety of the scientific investigations that LSST will enable, readers are encouraged to look at the LSST Science Book: http://www.lsst.org/lsst/scibook. Organizational details of the LSST science collaborations and management may be found at http://www.lsstcorp.org.
Next-Generation X-Ray Astronomy
Authors: White Nicholas E. 
Published: April 2012

AbstractThis review of future timing capabilities in X-ray astronomy includes missions in implementation (astro-h, gems, srg and astrosat), those under study (currently nicer, athena and loft), and new technologies that may be the seeds for future missions, such as lobster-eye optics. Those missions and technologies will offer exciting new capabilities that will take X-ray Astronomy into a new generation of achievements.
Swift: Opportunities, Capabilities and Data Handling
Authors: Starling Rhaana 
Published: April 2012

AbstractA focus session was held for those wanting to familiarise themselves with the Swift satellite and to consider its exploitation for specific scientific goals. An overview was presented, with questions throughout. Proposal preparation and and the automated science products from the X-ray Telescope were discussed. This account summarises the information given in the presentation and in the answers to the questions which were raised.
Gravitational Waves and Time-Domain Astronomy
Authors: Centrella Joan , Nissanke Samaya , Williams Roy 
Published: April 2012

AbstractThe gravitational-wave window onto the universe will open in roughly five years, when Advanced LIGO and Virgo achieve the first detections of high-frequency gravitational waves, most likely coming from compact binary mergers. Electromagnetic follow-up of these triggers, using radio, optical, and high energy telescopes, promises exciting opportunities in multi-messenger time-domain astronomy. In the decade, space-based observations of low-frequency gravitational waves from massive black hole mergers, and their electromagnetic counterparts, will open up further vistas for discovery. This two-part workshop featured brief presentations and stimulating discussions on the challenges and opportunities presented by gravitational-wave astronomy. Highlights from the workshop, with the emphasis on strategies for electromagnetic follow-up, are presented in this report.
Light Echoes
Authors: Bond Howard E. , Bentz Misty C. , Clayton Geoffrey C. , Rest Armin 
Published: April 2012

AbstractThe first “light echo”—scattered light from a stellar outburst arriving at the Earth months or years after the direct light from the event—was detected more than 100 years ago, around Nova Persei 1901. Renewed interest in light echoes has come from the spectacular echo around V838 Monocerotis, and from discoveries of light echoes from historical and prehistorical supernovæ in the Milky Way and Large Magellanic Cloud as well as from the 19th-century Great Eruption of η Carinae. A related technique is reverberation mapping of active galactic nuclei. This report of a workshop on Light Echoes gives an introduction to light echoes, and summarizes presentations on discoveries of light echoes from historical and prehistorical events, light and shadow echoes around R CrB stars, and reverberation mapping.
Astrotomography
Authors: Horne Keith , Baptista Raymundo , Bentz Misty C. , Steeghs Danny 
Published: April 2012

AbstractAstrotomography refers to a suite of indirect imaging techniques that achieve micro-arcsecond angular resolution by measuring projections obtained from time-resolved spectroscopic observations. The projections arise from Doppler shifts, eclipses or time delays, combined with rotation of the star or binary system being imaged. At our workshop we reviewed and discussed state-of-the-art methods for imaging the surfaces and magnetic fields of rapidly rotating stars, the accretion flows in compact binary star systems and the broad emission-line regions in active galactic nuclei.
Data Management, Infrastructure and Archiving for Time-Domain Astronomy
Authors: Schade David 
Published: April 2012

AbstractThe workshop on Data Management issues for Time-Domain Astronomy was conceived as a forward-looking discussion of the primary issues that need to be addressed for science in the time domain. The very broad diversity of the science areas presented in the main Symposium made it clear that most of the general issues for astronomy data management—for example, large data volumes, the need for timely processing and network performance—would be pertinent in the time domain. In addition, there might be other tight time constraints on data processing when the output was required to trigger rapid follow-up observations, while science based on very long time-baselines might require careful consideration of long-term data preservation and availability issues. But broadly speaking, data management challenges in the time domain are not at variance to any significant degree with those for astronomy or data-intensive research in general. The workshop framed and debated a number of questions: What is the biggest challenge faced by future projects? How do grid and cloud computing figure in data management plans? Is the Virtual Observatory important to future projects? How are the issues of data life cycle being addressed?
Workshop on Radio Transients
Authors: Croft Steve , Gaensler Bryan 
Published: April 2012

SummaryWe are entering a new era in the study of variable and transient radio sources. This workshop discussed the instruments and the strategies employed to study those sources, how they are identified and classified, how results from different surveys can be compared, and how radio observations tie in with those at other wavelengths. The emphasis was on learning what common ground there is between the plethora of on-going projects, how methods and code can be shared, and how best practices regarding survey strategy could be adopted.The workshop featured the four topics below. Each topic commenced with a fairly brief introductory talk, which then developed into discussion. By way of preparation, participants had been invited to upload and discuss one slide per topic to a wiki ahead of the workshop.1. Telescopes, instrumentation and survey strategy. New radio facilities and on-going projects (including upgrades) are both studying the variability of the radio sky, and searching for transients. The discussion first centred on the status of those facilities, and on projects with a time-domain focus, both ongoing and planned, before turning to factors driving choices of instrumentation, such as phased array versus single pixel feeds, the field of view, spatial and time resolution, frequency and bandwidth, depth, area, and cadence of the surveys.2. Detection, pipelines, and classification. The workshop debated (a) the factors that influence decisions to study variability in the (u,v) plane, in images, or in catalogues, (b) whether, and how much, pipeline code could potentially be shared between one project and another, and which software packages are best for different approaches, (c) how data are stored and later accessed, and (d) how transients and variables are defined and classified.3. Statistics, interpretation, and synthesis. It then discussed how (i) the choice of facility and strategy and (ii) detection and classification schemes influence what is seen (in terms of types of object and rates) by different surveys, (iii) how results from different surveys could be compared, and (iv) how what we know from existing surveys drives choices (i) and (ii), particularly as regards finding new classes of object.4. Multiwavelength approaches. The workshop concluded by discussing what information is needed from wavelengths other than radio in order to classify transients and variables adequately and predict their rates as a function of topics (1), (2) and (3). It asked what the constraints are on responding to, and issuing triggers for, follow-up observations, and how that might feed back into considerations for designing our telescopes and surveys.
Modulated Light Curves of Multiperiodic Stars
Authors: Benkő József M. , Szabó Róbert , Paparó Margit 
Published: April 2012

AbstractWe modelled the light curves of modulated multiperiodically pulsating stars by a simple double-mode pulsation with combined amplitude and frequency modulations. The synthetic light curves and their spectra show similar features to those we found and discussed for monoperiodic stars. Comparing the synthetic light curves and their spectra with the observed ones helps us to classify the modulations and to distinguish between long-period modulation (Blazhko effect) and the other types of amplitude and/or period changes.
Fermi LAT Flare Advocate Activity
Authors: Ciprini Stefano , Gasparrini Dario , Bastieri Denis 
Published: April 2012

AbstractThe Fermi Flare Advocate (also known as Gamma-ray Sky Watcher, FA-GSW) service provides a daily quick-look analysis and review of the high-energy gamma-ray sky seen by the Fermi Gamma-ray Space Telescope. The duty offers alerts for potentially new gamma-ray sources, interesting transients and flares. A weekly digest containing the highlights about the GeV gamma-ray sky is published in the web-based Fermi Sky Blog. During the first 3 years of all-sky survey, more than 150 Astronomical Telegrams, several alerts to the TeV Cherenkov telescopes, and targets of opportunity to Swift and other observatories, were realized. That increased the rate of simultaneous multi-frequency observing campaigns and the level of international cooperation. Many gamma-ray flares from blazars (such as extraordinary outbursts of 3C 454.3, intense flares of PKS 1510-089, 4C 21.35, PKS 1830-211, AO 0235+164, PKS 1502+106, 3C 279, 3C 273, PKS 1622-253), short/long flux duty cycles, unidentified transients near the Galactic plane (like J0910-5041, J0109+6134, the Galactic center region), flares associated with Galactic sources (like the Crab nebula, the nova V407 Cyg, the microquasar Cyg X-3), emission of the quiet and active sun, were observed by Fermi and communicated by FA-GSWs.