Dirk Froebich

Univ Kent

Title: The Kent Globular Cluster Search Program - An Update

Abstract: The talk presents a summary of our long term efforts to identify and classify so far unknown stellar clusters in the Milky Way. The first part of the talk will briefly describe our cluster sample and how it was obtained. In the main part of the talk I will concentrate on our (and other groups) efforts made so far to determine more detailed cluster parameters (distance, age, metallicity, reddening) for objects from our list. This includes the possible discovery of 4 new globular clusters and 5 old open clusters with ages of more than 1Gyr.

Thibaut Lery

Eurpean Science Foundation

Title: The European Science Foundation, towards the Global Research Area

Abstract: Dr. Thibaut LERY, presently the Science Officer of the Physical and Engineering Sciences (PESC) Unit in the European Science Foundation, will present the structure and instruments of the ESF. He will show several highlights and results of 2007, including a survey on European Researchers' Requirements for e-Infrastructure. A discussion on the role of ESF in the emerging European Research Area (and GLOREA) will follow.

Gregg Hallinan

NUI Galway

Title: Looking for a Pulse: The Search for Radio Emission from Brown Dwarfs and Extrasolar Planets

Abstract: In the last number of years it has been confirmed that brown dwarfs and very low mass stars near the substellar boundary can be bright sources of radio emission. The high luminosity of the radio emission was a particular source of surprise, especially in light of the low Halpha and X-ray luminosities of evolved 'ultracool dwarfs'. Initially, it was postulated that this radio emission was incoherent gyrosynchrotron radiation of the same nature as that detected from stellar coronae. However, our recent observations of a number of these dwarfs have disproved this model. We have detected periodic bursts of extremely, bright 100% polarized radio emission from 3 dwarfs located at or below the stellar/substellar boundary. These bursts are conclusively coherent in nature and are produced at the magnetic polar regions 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 dwarfs as a new class of transient radio source. For all three dwarfs, the detected emission requires the presence of extremely strong kilogauss magnetic fields in a large-scale stable configuration. Such high magnetic field strengths are of the same order as those confirmed for the most magnetically active dMe flare stars, confirming that a very efficient dynamo can operate in the fully convective interiors possessed by brown dwarfs. In light of the low Halpha and X-ray luminosities of brown dwarfs, the study of this pulsed radio emission represents the best observational window on the nature of magnetic activity in the mass gap between low mass stars and planets. Indeed, observations commencing in February will extend the search for radio emission directly into the exoplanetary regime with deep low frequency pointings of 'Hot Jupiters' in the Solar neighbourhood.

Hansruedi Maurer

ETH Zurich

Title: Optimized design of geolectrical experiments

Abstract: tba.

Paul Dempsey

DIAS

cancelled

Abstract: tba.

Alexander Lutovinov

Space research Institute (IKI), Moscow

Title: Survey of the galactic and extragalactic sources in hard X-rays with the INTEGRAL observatory

Abstract: Some results of five years observations of the INTEGRAL observatory are presented. About 150 new hard X-ray sources as galactic as extragalactic nature were discovered, particularly new classes of highly absorbed sources and fast X-ray transients. A significant enlargement of a number of sources allowed us to compare their distribution with the Galaxy spiral structure and show that there is a displacement between position of spiral arms and maximums of a HMXBs distribution. From extragalactic sources a special attention was dedicated to the study of a hard X-ray emission from the Coma cluster. The temperature map of the cluster central part (~30-40 arcmin) shows variations of the gas temperature from ~7.5 to ~10.5 keV with most hot region (~11.5 keV) in the south-west extension. We found that the hard non-thermal X-ray emission is not significantly detected from the cluster and showed that it is very unlikely that IC emission in hard X-rays can reach the flux level comparable with the INTEGRAL/ISGRI sensitivity for the magnetic fields of few 0.1 muG (as it was estimated for Coma).

Masha Chernyakova

DIAS

Title: Multiwavelength properties of gamma loud binary systems

Abstract: Despite the variety of the X-ray binary systems, there are only three firmly established gamma-ray loud binary systems, namely PSR B1259-63, LSI +61 303 and LS 5039. In my talk I will discuss what can we learn from the timing and spectral properties of the broad band emission (from radio to TeV) from these systems.

Stefano Gabici

DIAS

Title: Gamma rays from Ultra-High-Energy-Cosmic-Ray Sources

Abstract: The origin of the highest energy cosmic rays (E > 10^20 eV per particle) is still an open issue. The difficulty in identifying the sources of such particles is twofold:
1) even the most extreme astrophysical objects we know might have problems in accelerating particles up to that huge energy,
2) the deflection of cosmic rays in the intergalactic magnetic field might prevent us to do "cosmic ray astronomy".

I will discuss the possibility of observing ultra high energy cosmic ray sources in high energy gamma rays. Protons propagating away from their accelerators produce secondary electrons during interactions with cosmic microwave background photons. These electrons start an electromagnetic cascade that results in a broad band gamma ray emission. I will show that in a magnetized Universe (B > 10-12 G) such emission is likely to be too extended to be detected above the diffuse background. A more promising possibility comes from the detection of synchrotron photons from the extremely energetic secondary electrons. Although this emission is produced in a rather extended region of size ~ 10Mpc, it is expected to be point-like and detectable at GeV energies if the intergalactic magnetic field is at the nanogauss level.

Stephane Dudzinski & IT staff

DIAS

Title: IT Services in DIAS - Edition 2007

Abstract: We will be presenting what has changed on the DIAS network, presenting also the new network in Fitzwilliam and addressing some issues with support and how/where to find the information.

Mark Dieckmann

Ruhr-University Bochum

Title: The forming of a relativistic partially electromagnetic planar plasma shock

Abstract: Relativistically colliding plasma is modelled by PIC simulations in one and two spatial dimensions, taking an ion-to-electron mass ratio of 400 and a temperature of 100 keV. The energy of an initial quasi-parallel magnetic field is one percent of the plasma kinetic energy. Energy dissipation by a growing wave pulse of mixed polarity, probably an oblique whistler wave, and different densities of the colliding plasma slabs results in the forming of an energetic electromagnetic structure during milliseconds. The structure, which develops for an initial collision speed of 0.9 c, accelerates electrons to Lorentz factors of several hundred. A downstream region forms, separating the forward and reverse shocks. In this region, the plasma approaches an energy equi-partition between electrons, ions and the magnetic field. The electron energy spectrum resembles a power-law at high energies with an exponent close to -2.7. The magnetic field reflects upstream ions, which form a beam and drag the electrons along to preserve the plasma quasi-neutrality. The forward and reverse shocks are asymmetric due to the unequal slab densities. The forward shock may be representative for the internal shocks of gamma ray bursts.