Bursts, Pulses and Flickering: Wide-field monitoring of the dynamic radio sky


Name: Tzioumis, Tasso; Tingay, Steven
E-mail: tasso.tzioumis@csiro.au Affiliation: ATNF CSIRO; Swinburne University of Technology
Type of presentation: Oral
Title: eVLBI as a real-time response to transient phenomena
Abstract: eVLBI in Australia is developing the capability for fast response observations of transient phenomena at radio wavelengths, using an array of distributed antennas connected via optical fibre to supercomputers. Such a capability will complement fast, wide-field, sensitive, but low resolution transient source surveys with the extended New Technology Demonstrator (xNTD). Such a system could be analogous with certain operational modes of the SKA.

Name: Meyer, Leonhard
E-mail: leo@ph1.uni-koeln.de Affiliation: University of Cologne
Type of presentation: Oral
Title: The flaring activity of Sgr A*: An orbiting and expanding plasma blob?
Abstract: The supermassive black hole at the Galactic center, Sgr A*, shows frequent radiation outbursts, so-called flares. In the near-infrared some of these flares were reported to show intrinsic quasi-periodicities of 1813 min. In 2005 and 2006, we have carried out polarimetric observations of these QPOs in the K-band. These observations allow for a detailed investigation of Sgr A* within the hot spot model. In this model, inhomogeneities in the accretion flow are represented as confined orbiting material. By simultaneous fitting of the lightcurve fluctuations and the time-variable polarization angle, we address the question whether these changes are consistent with the hot spot model, in which the interplay of relativistic effects plays the major role. Considering the quality of the fit, we think that this model is favored. Our confidence contours give constraints to the spin-parameter and the inclination of the supermassive black hole associated with Sgr A*. Furthermore, by now there is some evidence that the linkage to the mm/radio-regime is provided by an adiabatic expansion of the blob.

Name: Law, Casey
E-mail: claw@science.uva.nl Affiliation: University of Amsterdam/LOFAR
Type of presentation: Oral
Title: Early Results from a Transient Survey with LOFAR-CS1
Abstract: We present preliminary results of a survey for radio transients with the first station of LOFAR, Core Station 1 (CS1). The observations were made at frequencies from 30 to 80 MHz and cover a roughly 60 degree patch of the sky for several days. The observations probe variability on time scales from tens of seconds to days. A full-day integration gives roughly Jansky-level sensitivity and half-degree spatial resolution.

Name: Spreeuw Hanno
E-mail: hspreeuw@science.uva.nl Affiliation: University of Amsterdam
Type of presentation: Poster
Title: Predictions for radio emission from extrasolar planets
Abstract: All strongly magnetized stars of the solar system are known to be sources of intense non-thermal radio emission. For close-in giant exoplanets ("Hot Jupiters"), the interaction of the planet with the stellar wind is believed to be much stronger than for planets at large orbital distances. This should result in radio emission much more intense than that of Jupiter. We present theoretical results concerning the detectability of such radio emission for all currently known extrasolar planets. In particular, we show estimates for the expected maximum emission frequency and for the radio flux.

Name: Miller-Jones, James
E-mail: jmiller@science.uva.nl Affiliation: Astronomical Institute 'Anton Pannekoek', University of Amsterdam
Type of presentation: Oral
Title: Low-frequency radio observations of Galactic microquasars
Abstract: With the advent of facilities enabling wide-field monitoring of the dynamic radio sky, new areas of parameter space will be opened up for exploration. Such monitoring will be done primarily at low frequencies, in order to maximise the available field of view. One class of radio sources known to be highly variable at GHz frequencies are the so-called `microquasars'. To date however, their low-frequency behaviour has not been well constrained by observations. I will present some of the first attempts to measure their low-frequency properties, showing wide-field images made from data taken with the 74-MHz system on the VLA and also the LFFEs, the new suite of low-frequency (117-175 MHz) receivers on the WSRT. I will show results including tracking the May 2006 outburst of Cygnus X-3 and the low-frequency spectrum of SS 433 and the surrounding W50 nebula.

Name: Gabanyi, Krisztina Eva
E-mail: krisztina.g@gmail.com Affiliation: HAS, Research Group for Physical Geodesy and Geodynamics, Budapest
Type of presentation: Oral
Title: A newly discovered highly variable IDV source
Abstract: J1128+592 is a newly found highly variable Intraday Variable (IDV) radio source, with observed timescales ranging between few hours and two days. At present the mixing ratio between source intrinsic and source extrinsic IDV is unclear. In the source extrinsic model of IDV, the variations are interpreted as scintillation of the radio waves in the turbulent ISM of the Milky Way. One of the strongest evidence in favor of a propagation induced IDV would be the annual modulation of the observed variability timescale caused by the Earth orbiting motion around the Sun. So far, the observations of J1128+592 suggested that the changes of its variability timescale may be attributed to annual modulation.

Name: Pandey Mamta
E-mail: mamtapan@gmail.com Affiliation: CEA, Saclay, France
Type of presentation: Poster
Title: Low frequency radio imaging of transient sources
Abstract: I will be presenting our results on low frequency imaging of transient XRBs monitored with the Giant Metrewave Radio Telescope.

Name: Scheers, Bart
E-mail: bscheers@science.uva.nl Affiliation: Astronomical Institute, University of Amsterdam
Type of presentation: Poster
Title: Low-frequency Radio View on GRBs with LOFAR
Abstract: The Low Frequency Array (LOFAR) will be a major multi-element, interferometric, imaging telescope designed for the 10-240 MHz frequency range, with unprecedented sensitivity and resolution at these frequencies. Detecting transient radio sources is one of the key science goals of LOFAR. Sophisticated detection algorithms will search for transients in logarithmically spaced time intervals ranging from 1 to 10000 seconds. This allows for searches of GRB prompt radio emission and radio flares at low frequencies. A catalogue of time series data of all observed sources is an excellent tool to study afterglows on timescales from seconds to years, constraining the physics of the blast wave during various stages of its evolution, and the properties of host galaxies of GRBs like star formation rates and its history.

Name: Ojha, Roopesh
E-mail: rojha@usno.navy.mil Affiliation: United States Naval Observatory
Type of presentation: Oral
Title: Milliarcsecond Structure of Microarcsecond Sources
Abstract: We present the key findings of an ongoing program of Very Long Baseline Interferometry (VLBI) observations of scintillating and non-scintillating flat-spectrum extragalactic radio sources whose scintillation status was determined by the Micro-Arcsecond Scintillation-Induced Variability (MASIV) survey. Both single frequency (8.4 GHz) observations to compare morphologies, and multi-frequency observations (from 330 MHz through 22 GHz) to study scattering behaviour have been carried out. Though scintillation probes the structure of quasars on scales of tens of microarcseconds, information at the milliarcsecond scale probed by these VLBI observations is proving invaluable in furthering our understanding of this phenomenon. Also, the common occurence of scintillation in compact radio sources might be the ultimate limitation for VLBI astrometry (which among other things defines the International Celestial Reference Frame) in the sense that the final precision of reference frame source positions are likely to be influenced by the presence of scintillation.

Name: Maitra, Dipankar
E-mail: dmaitra@science.uva.nl Affiliation: Astronomical Institute 'Anton Pannekoek', University of Amsterdam
Type of presentation: Oral
Title: Optical/near-IR detection and monitoring of LOFAR transients using SMARTS
Abstract: The Small and Moderate Aperture Research Telescope System (SMARTS) consortium has an ongoing program to routinely monitor X-ray binaries, simultaneously in optical and near-IR (OIR) wavelengths. I will discuss (a) our observing strategies, instrumental capabilities/limitations and (b) the possibility of OIR detection and follow-up of new transients found by the LOFAR Transient Key Project.

Name: Klein-Wolt, Marc
E-mail: klein@science.uva.nl Affiliation: Astronomical Institute University of Amsterdam
Type of presentation: Oral
Title: Identification of black hole power spectral components across all canonical states
Abstract: From a uniform analysis of a large (8.5 Ms) data set of RXTE observations of LMXBs, we present a complete classification of all the variability components found in the power spectra of black holes in their various states. The classification is based on the shifts in amplitude and frequency of the variability components observed as a source switches between canonical states, and uses a previous classification in the black hole low hard state as a starting point. It is supported by correlations between the frequencies of the variability components previously found to hold for black hole and neutron stars; we find the frequency-frequency correlations to hold for all black hole states as features change in frequency from state to state, but always following a fixed relation to other components. The implications of this relation are discussed in terms of the black hole canonical states characteristics such as the energy spectral- and radio properties.

Name: Meier, David
E-mail: dlm@sgra.jpl.nasa.gov Affiliation: Jet Propulsion Laboratory, California Institute of Technology
Type of presentation: Poster
Title: A Tale of Two Transients: LD GRBs and Variable ULXs
Abstract: A Tale of Two Transients: Long-duration GRBs without Supernova Signatures and ULX Sources in Star-Forming Regions I present simple models of two seemingly disparate transient sources that can both be explained by hyper- or super-critical accretion of gas from a relatively normal star onto a stellar-mass black hole (BH). In the case of LD GRBs that do not produce a detectable SN explosion, it is suggested that the event is driven by the merger of a BH/WD (white dwarf) binary --- i.e., ``Roche lobe overflow'' of the WD on a dynamical time scale. This gives the correct (few minute) time scale, and the engine itself is very similar in structure to that of a collapsar model, but does not produce a large Fe/Ni envelope whose radioactive decay would power a SN light curve. In the ULX case, the suggested underlying engine is a Cyg X-1 HMXB system in which the young O/B star undergoes supercritical accretion due to Roche lobe overflow on a nuclear (or possibly thermal) time scale at the rate of 10^{20-21} g/s. This feeds the companion black hole at a super-critical rate and drives an outflowing wind whose loss rate is equal to (\dot{M} - \dot{M}_{Edd}). The wind should behave similarly to that of a nova envelope, with the bolometric luminosity remaining near L_{Edd}, but with the color temperature fluctuating wildly with accretion/wind outflow rate. Specific detailed, but analytic, models show that it is the black hole's gravity alone that probably dominates the wind outflow structure, but that the last scattering surface of the wind could enclose the entire binary system (including the HMXB companion), creating a common envelope star in appearance, but not in physical structure.

Name: Bignall, Hayley
E-mail: bignall@jive.nl Affiliation: Joint Institute for VLBI in Europe
Type of presentation: Oral
Title: Rapid Interstellar Scintillation of Extragalactic Sources
Abstract: Some quasars and extragalactic megamasers have been found to exhibit rapid radio variability, on timescales of hours or less, consistent with interstellar scintillation in the weak scattering regime. I will discuss some recent observational results and implications for both the sources and the local interstellar medium responsible for the scattering.

Name: Dunn, Robert
E-mail: r.j.dunn@phys.soton.ac.uk Affiliation: University of Southampton
Type of presentation: Oral
Title: An X-ray study of the disc in GX339-4
Abstract: We present a detailed investigation into the X-ray emission from GX339-4. Using all data for GX339-4 in the RXTE archive, we perform a consistent analysis of the X-ray emission over a 10 year baseline. We will show our results into the emission from and evolution of the disc and its properties during outbursts. Using this thorough analysis, we focus especially on the Disc Temperature and iron line properties and how they are related to relativistic ejection events.

Name: Paragi, Zsolt (et al.)
E-mail: zparagi@jive.nl Affiliation: JIVE
Type of presentation: Poster
Title: Radio and optical interferometry observations of Algol
Abstract: We carried out e-EVN and CHARA interferometric observations of the Algol system in October and December 2006. These data provide unique information on the central binary orbital parameters but also on the astrophysical processes in the corona of the magnetically active K-companion star. We derive the separation of the inner ecplipsing binary by optical interferometry. We use the e-VLBI data together with optical photometry during a secondary minimum to measure the angle of the ascending node. The e-EVN and Westerbork Synthesis Array data show high level of circular polarization (CP) in the source in agreement with earlier observations, confirming the gyro-synchrotron nature of the radio emission. During the December 14 e-VLBI observations Algol exhibited a minor flare. It has been known that the flaring emission produces lower levels of CP. For the first time, we show that the circularly polarized emission and the flaring emission come from different physical locations in the system.

Name: Paragi, Zsolt (on behalf of the EXPReS group at JIVE)
E-mail: zparagi@jive.nl Affiliation: JIVE
Type of presentation: Oral
Title: Targeting transient phenomena with e-VLBI
Abstract: The European VLBI Network (EVN) routinely carries out e-VLBI science observations since 2006. The data from the radio telescopes are streamed into the correlator in realtime, and post-processed shortly after the observations. This gives a great flexibility for studying transient objects. With the data rate approaching 512 Mbps, and more telescopes joining the e-VLBI array during 2007, the e-EVN is becoming a powerful tool to observe e.g. faint, variable stellar objects, and the early phases of GRB afterglows at cm wavelengths. The e-VLBI developments at JIVE will be introduced in this talk along with the present and near future capabilities of the e-EVN. We describe strategies for calibration of the e-VLBI data in total intensity and polarization (including circular polarization). Some early science results will be presented as well.

Name: Marchili Nicola
E-mail: marchili@mpifr-bonn.mpg.de Affiliation: Max Planck Institute for Radioastronomy
Type of presentation: Oral
Title: Observations of IntraDay Variable sources with the Effelsberg and Urumqi Telescopes
Abstract: In 2005, in collaboration betweeen the Effelsberg and Urumqi Observatories, we started a regular monitoring project of some previously known and some new IntraDay Variable (IDV) radio sources. Several day long flux monitoring campaigns are performed at about 6 week time intervals through out the year. Main aim of the project, which is still ongoing, is testing the presence of annual modulation in the variability patterns of the IDV sources, as predicted by InterStellar Scintillation models. Here we present preliminary results from the analysis of the so far collected data, with particular emphasis on the annual modulation seen in new IDV source J1128+592, whose variability features resemble that of the few known fast scintillators. In contrast to this, other sources like e.g. 0716+71 and 0954+65, do not show any promiment evidence of such an effect.

Name: Markoff, Sera
E-mail: sera@science.uva.nl Affiliation: Astronomical Institute "Anton Pannekoek", University of Amsterdam
Type of presentation: Oral
Title: Low frequency constraints on weakly accreting black hole jets
Abstract: All accreting black holes produce associated jets at least some of the time. In stellar black holes accreting in X-ray binaries (XRBs), compact and steady jets are predominantly associated with the weakly (sub-Eddington) accreting hard state. These jets are apparently quenched at transition to the high luminosity state, thus jet production can be a cyclic phenomenon during outbursts. XRBs are therefore an ideal source population to study the physics of jet formation where many fundamental questions remain, such as the physics driving jet formation in the first place, or what jets comprise in terms of matter and electromagnetic fields. Using multiwavelength observations over the broadband spectrum, we have already made significant progress addressing some of these open questions. In the context of these results I will discuss how instruments probing the lowest end yet of the spectrum will specifically help us develop a better understanding of jet dynamics and energetics. I will also emphasize the importance of simultaneous observations at higher frequencies to allow stricter constraints.

Name: Cappallo, Roger
E-mail: rjc@haystack.mit.edu Affiliation: MIT Haystack Observatory
Type of presentation: Oral
Title: Transient Science with the MWA
Abstract: The Mileura Widefield Array is a radiotelescope consisting of an array of 500 dipole tiles, which is currently under construction in the outback of Western Australia. The MWA will cover the frequency band from 80 to 300 MHz, with an instantaneous processed bandwidth of 32 MHz. Its wide field of view (0.1 - 5 sr), excellent RFI environment, and novel software systems will allow unprecedented capabilities for searching for and observing transient radio sources. This talk will delineate the hardware and software features of the instrument, and show what they imply for sensitivity to various transient phenomena. We will also describe the structure of the MWA Transient Science Collaboration, a group which has been formed to organize our research in this exciting area.

Name: Tsarevsky Gregory
E-mail: tsar@lukash.asc.rssi.ru Affiliation: Astro Space Center, Lebedev Physical Institute, Moscow, Russia
Type of presentation: Oral
Title: Project ASTRAL: All-sky Space Telescope to Record Afterglow Locations
Abstract: ASTRAL is a project incorporating a wide-field optical telescopes onboard a small satellite dedicated to the whole-sky detection of a variety of rapid astronomical phenomena, particularly optical flashes associated with gamma ray bursts (GRB). Those flashes only visible optically (so called "orphans"), as well as those appeared in one time with associated GRBs, cannot be detected in the current triggering mode of the world wide GRB Coordinates Network (GCN). Hence ASTRAL would have a unique opportunity to trigger a follow-up multi-frequency study via GCN. ASTRAL consists of a set of 13 wide-field cameras (each with $FOV = {70^o}$) equipped with 4096x4096 CCDs. The detection method is based on the Digital Blink Comparator mode, with a template of a complete sample of $\sim2$ million stars down to $12^m$, precisely measured in the HIPPARCOS and TYCHO-2 missions. Supernovae, novae and nova-like explosions, fast variable AGNs, flare stars, and even new comets would be promptly detected as well. Thus ASTRAL would also be an original working prototype of the prospective major space mission to monitor all the sky for different types of optical transients - on-line.

Name: Tsarevsky Gregory
E-mail: tsar@lukash.asc.rssi.ru Affiliation: Astro Space Center, Lebedev Physical Institute, Moscow, Russia
Type of presentation: Oral
Title: The Flickering - What It Is?
Abstract: We show that massive all-sky variability surveys of the extragalactic radio sources taken at different frequencies display a prominent trend in the “Galactic Latitude - Modulation Index” (|b| - m) plot. Taken alone, it has a pretty small statistical significance due to various, quite understandable effects which scatter the plot. But as a pool, it proves directly the extrinsic, ISM scintillation origin of the variability, at least partly. To discriminate each other - the intrinsic and extrinsic parts - is a challenge for the scintillation theory.

Name: Lazaridis Kosmas
E-mail: klazarid@mpifr-bonn.mpg.de Affiliation: Max-Planck-Institut für Radioastronomie
Type of presentation: Poster
Title: Flux density spectrum of the magnetar AXP J1810-197
Abstract: As part of a simultaneous multi-telescope observing campaign, we performed multi frequency observations from July 2006 until March 2007 at 2.7, 4.9, 8.4, 14.6 and 32 GHz, with the 100-m Effelsberg radio telescope of the Max-Planck-Institut für Radioastronomie, in order to obtain flux density measurements and spectral features of the 5.5 sec radio emitting magnetar AXP XTE J1810-197. This magnetar consists of the main pulse (MP) and an interpulse (IP). We present the flux density spectrum of the average profile and of the separate pulse components of this first radio-emitting transient anomalous X-ray pulsar. We observe a decrease of the flux density of the order of 10 from July to December and also one of the two main components disappearing. Although the spectrum is generally flat with an average value for the spectral index of a = -0.26 +/- 0.08, we observe intense fluctuations of the latter with time. For that reason we finally make some measurements of modulation indices for individual pulses in order to investigate the true nature of these fluctuations.

Name: Spencer, Ralph
E-mail: res@jb.man.ac.uk Affiliation: The University of Manchester
Type of presentation: Poster
Title: Coherent Sources and New Generation Telescopes
Abstract: LOFAR and SKA are both designed to have wide fields of view, and one of their key science objectives is to study transient sources. At low frequencies of around 100 MHz we expect varying synchrotron sources to have long time constants (months) if constrained by inverse Compton losses. Rapid variations (seconds or less) require coherent radiation mechanisms. In this paper we look at constraints on the physical properties of sources set by the need for coherence, with the aim of finding out if such studies in extragalactic objects are feasible.

Name: Antonova, Antoaneta
E-mail: tan@arm.ac.uk Affiliation: Armagh Observatory
Type of presentation: Poster
Abstract: Recent observations have shown that ultracool dwarfs are capable of generating persistent levels of extremely bright, highly polarized (up to 100%), coherent emission that is best explained in the context of the electron cyclotron maser (ECM) instability. Until now, most of the radio surveys in the ultracool dwarfs (spectral type later than M8) have been conducted at 8.5 GHz. Since ECM emission from ultracool dwarfs is characterized by an upper cut-off frequency, associated with the maximum magnetic field strength in the magnetosphere of the dwarf. A detection of emission at 8.5 GHz would require a field strength of ~ 3 kG. Dwarfs, whose fields have strengths below that value would be undetected at that frequency, but could still be detected at lower frequencies. Taking into account the above considerations, we conducted a 4.5 GHz VLA survey of 8 ultracool dwarfs, covering the spectral range M8.5 - T6, that have been previously undetected at 8.5 GHz. As a result we report on the detection of radio emission from the L dwarf 2MASSW J0746425+200032, which is a binary system consisting of a very low mass star and a bona fide brown dwarf.

Name: Cimo, Giuseppe
E-mail: cimo@jive.nl Affiliation: JIVE
Type of presentation: Oral
Title: Monitoring the Interstellar Scintillation in a sample of Southern Blazars.
Abstract: I will provide a multifrequency description of the Intraday Variability phenomenon combining Australia Telescope Compact Array observations with data from the monitoring projects at the University of Tasmania. Some implications concerning the physics of compact structures and the characteristics of the interstellar medium will be discussed.

Name: Gregg Hallinan
E-mail: gregg@it.nuigalway.ie Affiliation: National University of Ireland Galway
Type of presentation: Oral
Title: Ultracool Dwarfs: A New Class of Pulsar
Abstract: We report the detection of periodic bursts of extremely bright, 100% circularly polarized coherent radio emission from three ultracool dwarfs. In the case of one of the dwarfs, TVLM 513-46546 (p = 1.96 hours), simultaneous photometric monitoring observations have established this periodicity to be the rotation period of the dwarf. These results confirm that ultracool dwarfs can generate persistent levels of broadband, coherent radio emission, associated with the presence of kG magnetic fields in a large-scale, stable configuration. Compact sources located at the magnetic polar regions produce highly beamed emission generated by the electron cyclotron maser instability, the same mechanism known to generate planetary coherent radio emission in our solar system. The narrow beams of radiation pass our line of sight as the dwarf rotates, producing the associated periodic bursts. The resulting radio light curves are analogous to the periodic light curves associated with pulsar radio emission highlighting these objects as a new class of transient radio source.

Name: Del Rizzo, David
E-mail: dave.delrizzo@nrc-cnrc.gc.ca Affiliation: National Research Council of Canada/DRAO
Type of presentation: Oral
Title: Searching for Variable Sources in the Canadian Galactic Plane Survey
Abstract: The Canadian Galactic Plane Survey (CGPS) radio continuum database is ideally suited to searches for radio variable sources, allowing a deep search for variability to be carried out on tens of thousands of compact radio sources in the Galactic Plane. As a consequence of the multi-day observing method used in the CGPS, sources with variations on time scales of hours, days and months, can be identified directly from the data. In this talk, we present a method of identifying intra-day variations from these data, and illustrate its application on survey regions.

Name: Koerding, Elmar
E-mail: elmar@phys.soton.ac.uk Affiliation: University of Southampton
Type of presentation: Oral
Title: Radio emission as a tracer of the accretion rate
Abstract: I will present a method to estimate the accretion rate and jet power from the core radio luminosity of jet emitting sources. Several applications will be highlighted: The bolometric luminosity of hard state objects as a function of the accretion rate can be observed. The findings suggest inefficient accretion both in stellar and supermassive black holes. Secondly, all soft state black holes seem to populate a plane in the space defined by the black hole mass, accretion rate and characteristic time scale. Using the presented technique this plane can be extended to hard state objects and neutron stars. Finally, I will use the jet power estimate to study the kinetic power output of active galactic nuclei.

Name: Baan, Willem
E-mail: baan@astron.nl Affiliation: ASTRON
Type of presentation: Oral
Title: Maser Variability
Abstract: Varibility of maser features has been detected in galactic and extragalactic sources. Some of this variability is intrinsic to the source and provides information on the physical process and the pumping schemes. Scintillation variability provides information on the size of the masering cell and varies with the amplifying gain of the cell. We will review observed variability and its implications for the physics of the masering regions.

Name: Swinbank, John
E-mail: swinbank Affiliation: University of Amsterdam
Type of presentation: Poster

Name: Swinbank, John
E-mail: swinbank@science.uva.nl Affiliation: University of Amsterdam
Type of presentation: Poster
Title: A transients detection pipeline for LOFAR
Abstract: LOFAR, the Low Frequency Array, will offer an unprecedented opportunity to monitor the northern sky for transient radio sources. The Transients Key Project is constructing an automatic software pipeline which will process the data from the telescope in real time, identifing and classifying variable sources and making the results available for immediate followup as well as later off-line analysis. Here, we outline the design and prototype implementation of this pipeline.

Name: Ray, Paul
E-mail: paul.ray@nrl.navy.mil Affiliation: Naval Research Laboratory
Type of presentation: Oral
Title: A Bursting Radio Transient in the Direction of Galactic Center
Abstract: The radio sky is poorly sampled for rapidly varying transients because of the narrow field-of-view of most imaging radio telescopes. This situation has begun to change and we have undertaken a series of wide-field monitoring observations and archival studies of the Galactic Center at 330 MHz. In this search, we discovered a transient, bursting, radio source in the direction of the Galactic Center, GCRT J1745-3009, with extremely unusual properties. Its flux and rapid variability imply a brightness temperature >10^12 K if it is at a distance >70 pc, implying that it is a coherent emitter. I will discuss the discovery of the source and the subsequent re-detections, as well as searches for counterparts at other wavelengths, and several proposed models.

Name: Russell, David
E-mail: davidr@phys.soton.ac.uk Affiliation: University of Southampton
Type of presentation: Oral
Title: Predicting radio activity in X-ray binaries with optical/infrared monitoring
Abstract: X-ray binaries undergo outbursts due to increased mass transfer towards the compact object, a black hole or neutron star. Recently, a picture has developed where the behaviour between the radio, optical/infrared and X-ray luminosities during these outbursts are correlated. Here, I review this picture and show how simple optical/infrared monitoring can predict radio flux densities. It is also possible to infer when the bright, optically thin jet flares are likely to occur in black hole systems. In the case of X-ray transients, bright optically thin outbursts can be predicted with a lead time on the order of days. These techniques may also be useful for neutron star systems, for which little radio observations have been made and the jet spectral slope is relatively unconstrained.

Name: Soleri, Paolo
E-mail: psoleri@science.uva.nl Affiliation: Astronomical Institute "A. Pannekoek", University of Amsterdam
Type of presentation: Oral
Title: Simultaneous X-ray/radio observations of Cir X-1
Abstract: We present an analysis of simultaneous X-ray/radio observations of the neutron star X-ray binary Cir X-1. The data were taken with ATCA (radio) and RXTE (X ray) during a survey carried out in October 2000 and December 2002. We identified Z branches in the X-ray hardness-intensity diagram and we studied the evolution of power density spectra along the branches. Moreover, in our data set, we associated to phase 0.0 of the orbital phase both radio flares and spectral/timing changes in the X-ray. While in black hole X-ray binaries there are clear spectral and timing signatures in the X-ray accompanying the radio flares, such compelling evidence is missing for neutron star X-ray binaries.

Name: Tudose, Valeriu
E-mail: vtudose@science.uva.nl Affiliation: Astronomical Institute, University of Amsterdam
Type of presentation: Oral
Title: Long-term radio behaviour of the X-ray binary Circinus X-1
Abstract: Circinus X-1 is a neutron star X-ray binary system with an interesting and at times puzzling behaviour over a broad range of frequencies, specifically in X-ray and radio. The system seems to harbour the most relativistic outflow (likely oriented close to the line of sight) observed so far within the Milky Way. It lies within a radio synchrotron nebula and has variable radio flux densities at cm wavelengths. The radio flares associated to the orbital phase zero reached up to 1 Jy in the late '70s, then have been observed at the tens of mJy level until recently; in 2007 January, Circinus X-1 seemed to have entered a very active radio flaring state. Here we present 4.8 and 8.6 GHz radio observations made with the Australia Telescope Compact Array, covering 10 years time period. The data set comprises 41 epochs, unequally spread in time between 1996 and 2006. We investigate the long-term changes in the brightness, morphology and spectrum of the radio structures. We have detected linear polarization in a third of the epochs and a good case for Faraday rotation in one epoch. In brief, the analysis reveals structural changes in the radio emission at time scales as short as days. Clear evidence for a counter-jet was found in a few epochs, and indications of "jumps" in the position angle of the jet. Possible observational campaigns with future radio networks (e.g. MWA, KAT) are briefly discussed.

Name: Roy Subhashis
E-mail: roy@astron.nl Affiliation: ASTRON
Type of presentation: Oral
Title: New Results on emission from the Transient Bursting Source GCRT J1745-3009
Abstract: GCRT J1745-3009 is a transient bursting radio source located about a degree away from Galactic center, discovered by Hyman et al. (2005) from 330 MHz VLA observations. We have made a new serendipitous detection of this source from GMRT observations in March 2004. From this burst lasting only 2 minutes, the spectral index is found to be extremely steep (-13 +/-3). From reanalysis of GMRT data taken in September 2003, we have detected high fraction of circularly polarised emission from this source. Since the emission is likely to be coherent, the emission mechanism is possibly electron cyclotron maser. Magnetic field required to produce such an emission at 330 MHz is ~120 Gauss, expected near stellar or planetary surfaces. Its non-detection in other wavebands, however, tend to preclude emission from any nearby magnetically dominated star. We consider different emission mechanisms and possible sources of emission including brown dwarf and extrasolar planet.

Name: Maccone Claudio
E-mail: clmaccon@libero.it Affiliation: INAF & International Academy of Astronautics
Type of presentation: Oral
Title: Innovative SETI by the KLT
Abstract: ABSTRACT. SETI searches are, by definition, the extraction of very weak radio signals out of the cosmic background noise. When SETI was born in 1959, it was “natural” to attempt this extraction by virtue of the only detection algorithm well known at the time: the Fourier Transform (FT). In fact: 1) SETI radio astronomers had adopted the viewpoint that a candidate ET signal would necessarily be a sinusoidal carrier, i.e. a very narrow-band signal. Over such a narrow band, the background noise is necessarily white. And so, the basic mathematical assumption behind the FT that the background noise must be white was “perfectly matched” to SETI for the next fifty years! 2) In addition, the Americans J. W. Cooley and J. W. Tukey discovered in April, 1965 that all FT computations could be speeded up by a factor of N/ln(N) (N is the number of numbers to be processed) by replacing the old FT with their own Fast Fourier Transform (FFT) algorithm. Then, SETI radio astronomers all over the world gladly, and unquestioningly, adopted the new FFT. In 1983, the French SETI radio astronomer, François Biraud, dared to challenge this view (ref. [3]). He argued that we only can make guesses about ET’s telecommunication systems, and that the shifting trend on Earth was from narrow-band to wide-band telecommunications. Thus, a new transform was needed that could detect signals over both narrow and wide bands, regardless of the colored noise distribution over this finite bandwidth. Such a transform had actually been pointed out as early as 1946 by the Finnish mathematician, Kari Karhunen and the French mathematician, Michel Loève, and is thus named KLT for them. In conclusion, François Biraud suggested to “look for the unknown in SETI” by adopting the KLT rather than the FFT. Starting 1987, this author also was “preaching the KLT”: first at the SETI Institute, then (since 1990) at the Italian CNR SETI facilities at Medicina, near Bologna. Their director, Stelio Montebugnoli, was willing to pay attention to him. Little by little, bright students succeeded in programming the KLT algorithm for the Medicina radio telescopes. Finally, by the year 2000, the advent of programmable cards, mastered by Montebugnoli, made the “miracle” happen. The KLT for SETI is now a reality at the SETI-Italia facilities and for the first time in history. This paper describes the KLT and how the KLT breakthrough for SETI was finally achieved, with special reference to the usefullness of installing the KLT on the SKA.

Name: Karastergiou, Aris
E-mail: aris@iram.fr Affiliation: IRAM
Type of presentation: Oral
Title: A new model for the beams of radio pulsars
Abstract: With the discovery of new classes of radio-emitting neutron stars, such as RRATS and the radio emitting magnetar, understanding the structure and geometry of pulsar beams is becoming central to the interpretation of the observations. We have developed a model, whereby radio emission at a particular frequency arises from a wide range of altitudes above the surface of the star, which can account for the large diversity found in the average profile shapes of pulsars. We demonstrate how a change in the range of emitting heights can account for the differences between pulse profiles of young, highly energetic pulsars and their older counterparts. Monte Carlo simulations are used to demonstrate the match of our model to real observations.

Name: Scaringi, Simone
E-mail: simo@astro.soton.ac.uk Affiliation: University of Southampton
Type of presentation:
Title: Data Mining INTEGRAL data.
Abstract: The International Gamma-Ray Astrophysics Laboratory (INTEGRAL) has been providing data since 2002 of the variable and persistent gamma-ray sky. To date there are over 30000 pointings for each of the defined 5 different energy channels in the energy range 20-300KeV. Since it's launch, different source identification techniques have been employed as a result of the exponential data growth. Here we will give a brief overview of the latest techniques (still testing) employed in order to compile the next gamma-ray catalogue for both transient and persistent sources. We will discuss the relevant timescales for source searching, the relevant variables employed in deciding source credibility and define a simple decision tree network in order to minimize the human intervention and subjectivity in compiling such catalogues.

Name: Nobuo, Matsumura
E-mail: nob-m@moegi.waseda.jp Affiliation: Institute for Astrophysics, Project Research Institutes, Comprehensive Research Organization, Waseda University
Type of presentation: Oral
Title: The 1 Jy class radio transients in Nasu 1.4 GHz wide-field survey
Abstract: We present the detection of radio transients in Nasu 1.4 GHz wide-field survey. The survey started at Nasu observatory, Japan, in 2003. In the survey, we use four pairs of the two element interferometer aligned east-west and simultaneously survey the region at +32 degree

Name: Dubois, Richard
E-mail: richard@slac.stanford.edu Affiliation: Stanford Linear Accelerator Center
Type of presentation: Oral
Title: GLAST Launch Status, Microquasars, Multiwavelength Opportunities and Public Access to Data
Abstract: The Gamma-ray Large Area Space Telescope (GLAST) is a next generation high energy gamma-ray observatory due for launch in late 2007. The primary instrument is the Large Area Telescope (LAT), which will measure gamma-ray flux and spectra from 20 MeV to > 300 GeV and is a successor to the highly successful EGRET experiment on CGRO. The LAT will have better angular resolution, greater effective area, wider field of view and broader energy coverage than any previous experiment in this energy range. This talk will present launch status and preparations for handling orbit data; performance estimates with particular emphasis on how these apply to studies of microquasars. The LAT's scanning mode will provide unprecedented unformity of sky coverage and permit measurements of light curves for any source. We will show results from recent detailed simulations that illustrate the potential of the LAT to observe microquasar variability and spectra, including source sensitivity and ability to detect orbital modulation. We will discuss efforts underway with GLAST to foster multiwavelength campaigns, and what data will be available for public consumption from the GLAST mission.

Name: Seradakis, John H.
E-mail: jhs@astro.auth.gr Affiliation: Aristotle University of Thessaloniki
Type of presentation: Oral
Title: The Antikythera Mechanism: An astronomical calculator
Abstract: The Antikythera Mechanism was found by chance, in a shipwreck, close to the small island of Antikythera (between Crete and Peloponnese) in April 1900, by sponge divers, who were stranded there, due to bad weather. The shipwreck was dated from between 86 and 67 B.C. (coins from Pergamon). The Mechanism was probably built in Rhodes and has been dated, by epigraphologists, around the second half of the 2nd century B.C. (100 – 150 B.C.). About this time the great Greek astronomer Hipparchos lived in Rhodes. He died there in 120 B.C. It was a portable (laptop-size), geared artefact which calculated and displayed, with high precision, the movement of the Sun and the Moon on the sky, the phase of the Moon for a given epoch and could predict eclipses. It had one dial on the front and two on the back. Its gears were driven by a manifold, with which the user could set a pointer to any particular epoch (at the front dial). While doing so, several pointers were synchronously driven by the gears, to show the above mentioned celestial phenomena on three accurately marked annuli. It contained an extensive user manual. The exact function of the gears has finally been decoded and a large portion of the manual has been read after 2000 years by a major new investigation, using state of the art equipment.

Name: Jean-Pierre Macquart
E-mail: jpm@astro.caltech.edu Affiliation: NRAO/CalTech
Type of presentation: Oral
Title: Limits on the detection of transients imposed by scattering
Abstract: I will discuss the limits imposed by (a) induced Compton scattering (b) induced Raman scattering and (c) temporal smearing due to scattering in the turbulent intergalactic medium on the detectability of transient sources in the range 30MHz-5GHz. I will also discuss what we will learn about the structure and energy input into the intergalactic medium using transients.

Name: Wijnands, Rudy
E-mail: rudy@science.uva.nl Affiliation: Astronomical Institute 'Anton Pannekoek', University of Amsterdam
Type of presentation: Oral
Title: Is there a connection between radio transients and very-faint X-ray transients?
Abstract: Very-faint X-ray transients are accreting neutron stars and black holes which have sub-luminous X-ray outbursts (several orders of magnitude fainter) compared to the ordinary, well-known and well-studied X-ray transients (with peak X-ray luminosities of 1E36 - 1E39 erg/s). The reason for such faint outbursts is currently not clear but might be related to the evolutionary phase of these systems. The few radio transients discovered so far have in general not been detected in the X-rays with typically upper limits on any X-ray emission of the order of 1E36 erg/s when they exhibited their radio outbursts. Therefore, it is quite possible that some fraction of the radio transients are part of the same family of sources as the very-faint X-ray transients. I will discuss the potential connection between the two different group of sources. If such a connection exists, then the planned radio monitoring instruments (e.g., LOFAR) might be excellent tools to find such enigmatic accreting neutron stars and black holes. They will be much more efficient in finding these sources than the current X-ray monitoring instruments which are typically not sensitive enough to detect the faint X-ray outbursts. I will discuss our plans to investigate this possible connection with approved RXTE and proposed Chandra, XMM, and Swift observations.

Name: Fender, Rob on behalf of the LOFAR Transients KSP
E-mail: rpf@phys.soton.ac.uk Affiliation: University of Southampton and Universiteit van Amsterdam
Type of presentation: Oral
Title: LOFAR Transients and the Radio Sky Monitor
Abstract: The detection and classification of transient radio phenomena is one of the four key science drivers for LOFAR, and is the remit of the Transients Key Science Project (KSP). In this presentation I shall outline the scientific remit of the Transients KSP, which includes black holes and neutron stars, coherent stellar phenomena, exoplanets, and the exploration of the unknown. I shall further describe the key innovative observing mode of LOFAR / Transients KSP, the "Radio Sky Monitor", which has the capability to survey a large fraction of the radio sky (more than 30%) daily to look for new transient radio phenomena.

Name: Kasper, Justin
E-mail: jck@mit.edu Affiliation: Massachusetts Institute of Technology
Type of presentation: Oral
Title: Light-curve monitoring with the MWA
Abstract: The Mileura Widefield Array (MWA) is an imaging radio array under construction in Western Australia with a large field of view, bandwidth, and sensitivity. MWA operates from 80-300 MHz, with 32 MHz of instantaneous bandwidth. These performance capabilities make MWA well-suited for searches of transient radio emission from galactic and extra-galactic sources. While the ideal transient program will be a blind search of the entire sky, I will describe a more modest first step in that direction. A component of the MWA processing pipeline has been designed to track approximately 1000 sources simultaneously within the field of view and generate full Stokes parameters at 100 kHz frequency resolution across the 32 MHz bandwidth at an eight second cadence. This system is used during the daytime to measure the magnetic field of the solar corona and inner heliosphere by tracking the Faraday rotation of polarized sources and at all times to correct polarization measurements for ionospheric effects. At night this system will be used for a targeted lightcurve monitoring campaign of candidate transient objects. I will discuss the anticipated performance of this system and potential scientific application.

Name: Lazio, Joseph
E-mail: Lazio@nrl.navy.mil Affiliation: Naval Research Laboratory
Type of presentation: Oral
Title: The Radio Transient Sky and the Long Wavelength Array
Abstract: Transient radio sources are necessarily compact and usually are the locations of explosive or dynamic events, therefore offering unique opportunities for probing fundamental physics and astrophysics. In addition, short-duration transients are powerful probes of intervening media owing to dispersion, scattering, and Faraday rotation that modify the signals. While radio astronomy has an impressive record obtaining high time resolution, usually it is achieved in quite narrow fields of view. Consequently, the dynamic radio sky is poorly sampled, in contrast to the situation in the X-ray and gamma-ray bands. Operating in the 20-80 MHz range, the Long Wavelength Array (LWA) is one of a suite of next-generation radio telescopes that will explore the radio transient sky. Composed of phased "stations" of dipoles, the LWA can probe the sky for transients on a range of angular and temporal scales, by using an individual station to scan much of the sky or correlating the signals from multiple stations to monitor possible transients. Numerous classes of radio transients, both known and hypothesized, are accessible to the LWA, ranging from cosmic ray air showers and Jovian emission, to bursts from extrasolar planets or other coherent emitters and prompt emission from gamma-ray bursts, to possible electromagnetic counterparts of gravitational wave burst sources. We summarize the scientific potential of radio transient observations with the LWA as well as some of the technical challenges, the most notable of which is the robust excision or avoidance of radio frequency interference (RFI). Basic research in radio astronomy at the NRL is supported by the Office of Naval Research.

Name: Spitkovsky, Anatoly
E-mail: anatoly@astro.princeton.edu Affiliation: Princeton University
Type of presentation: Oral
Title: Pulsar magnetospheres and emission
Abstract: I will discuss recent progress in modeling of pulsar magnetospheres and the strong connection that exists between the global magnetospheric physics and the physics leading to transient emission in all wavebands.

Name: Bower, Geoff
E-mail: gbower@astro.berkeley.edu Affiliation: UC Berkeley
Type of presentation: Oral
Title: Wide Field Surveys for Transients at Centimeter Wavelengths
Abstract: New technology is enabling systematic, blind surveys of the radio transient sky. The wide field of view of the Allen Telescope Array provides a powerful sky survey capability that will make it the leading telescope for radio transient surveys. I describe the Five GHz Sky Survey (FiGSS) to be conducted with the ATA, which will provide a systematic survey of the transient sky on time scales of days to months as well as a 5-GHz static counterpart to the NVSS, FIRST, and SDSS surveys. Finally, I will present the results of a search for radio transients in archival Very Large Array data at 5 and 8.4 GHz which discovered 10 new transients and has made the best estimate yet of the radio transient rate at milliJansky flux thresholds.

Name: Jauncey, David
E-mail: david.jauncey@csiro.au Affiliation: ATNF/CSIRO
Type of presentation: Oral
Title: Scintillation Surveys, Serendipitous, Systematic and MASIV; what do they tell us
Abstract: The discovery of IDV was made by Heeschen through a systematic source survey. Since then there have been a variety of surveys, both systematic and serendipitous, and each step has revealed new properties of both the population of compact, flat-spectrum sources and of the ISM.

Name: Lyne, Andrew
E-mail: andrew.lyne@manchester.ac.uk Affiliation: University of Manchester
Type of presentation: Oral
Title: RRATs and Intermittent Pulsars
Abstract: Two transient neutron star phenomena have been reported recently. RRATs were discovered in the Parkes Multibeam survey and produce very occasional pulses of emission which seem to come from rotating neutron stars. These ephemeral objects are only detectable radio sources for perhaps 0.1 second a day, but must represent a large galactic population. The second phenomenon is the class of Intermittent Pulsars which are regular pulsars for periods of time ranging from days to years, and then suddenly switch off completely for similar periods of time. When "ON" they slow down much more rapidly than when "OFF", indicating for the first time the role played by particle winds in the braking process. I will discuss the difficulties in discovering these objects and how they might be addressed in the future.

Name: Stappers, Ben
E-mail: stappers@astron.nl Affiliation: ASTRO/UvA
Type of presentation: Oral
Title: Radio Emitting Neutron Stars at Low Frequencies
Abstract: I will present new work from the WSRT at 100-170 MHz on a number of radio emitting neutron stars including pulsars, RRATs and Magnetars. These results will provide the basis of our expectations for how radio emitting neutron stars might show up in transient surveys especially where the inetgration time is much longer than the pulsation time. I will also present initial results of LOFAR-CS1 observations of pulsars.

Name: Osten, Rachel
E-mail: rosten@astro.umd.edu Affiliation: University of Maryland
Type of presentation: Oral
Title: Transient Emissions from Radio-Active Stars
Abstract: Nearby active stars can be the source of transient, but intense, bursts of radio radiation. Targeted studies have revealed that there are two main mechanisms producing powerful bursts at dm- and cm-wavelengths. I will review the current state of knowledge regarding observations and understanding of the phenomena, as well as provide some perspectives for the next generation of wide-field radio imaging telescopes.

Name: Dodson, Richard
E-mail: r.dodson@oan.es Affiliation: Observatorio Astronomico Nacional
Type of presentation: Oral
Title: Two decades of close monitoring the Vela pulsar glitches
Abstract: Pulsar glitches are transient events and the monitoring of the Vela pulsar by the Mt. Pleasant telescope provides the best tracing of these. The event probe the internal structure of pulsars, in a similar fashion to terrestrial earthquake studies.

Name: Rushton, Anthony
E-mail: anthony.rushton@postgrad.manchester.ac.uk Affiliation: Jodrell Bank Observatory
Type of presentation: Poster
Title: Adaptive eVLBI observations of weak radio emitting X-ray binaries
Abstract: Adaptive eVLBI is a new observing strategy for transient phenomena with the eEVN. Sixteen weak radio emitting X-ray binaries were observed on 30/01/07 in search of a radio jets. eVLBI allows the rapid production of images within hours of the observation, whereas disk recorded VLBI would take weeks. This allowed a second epoch, 48 hours after the observation, to fully observe a source that was been detected in the first epoch. Unfortunately during this experiment all the targets sources were below the sensitivity limit of ~ 0.5 mJy.

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