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Colloquia and seminars.

These form an important part of a research facility, often as a sort of prepublication discussion or a discussion of an individual's current research, and as such it is virtually impossible to "publish" this material. However by recording the topics discussed in the form below does indicate to those, who are unable to attend, what current trends are and who has visited to do research: it keeps everyone 'in the loop' so to speak

Also in this section are the colloquia/seminars at the SAAO, NASSP, UWC and the Astrophysics, Cosmology and Gravity Centre at UCT, ACGC. Included are the SAAO Astro-coffees which are 15-20min informal discussions on just about any topic including but not limited to: recent astro-ph papers, seminal/classic publications, education/outreach ideas and initiatives, preliminary results, student progress reports, conference/workshop feedback and skills-transfer [Editor].

SAAO

Title: Long-term monitoring of the optical polarization in the TeV blazar PKS 2155-304

Speaker: Nikki Pekeur (Visiting from North-West University)

Venue: SAAO Auditorium

Date: 12 December 2013

Time: 11h00

Abstract: Blazars are radio-loud active galactic nuclei (AGN) that are characterized by intense and rapid variability across the electromagnetic spectrum. The observed emission from these objects is generally believed to originate from synchrotron processes in its relativistic jet. Multi-band polarimetric measurements are therefore an important tool to investigate the nature of the components that are responsible for the observed variability. In this work, a study of the temporal evolution of the optical polarization of the archetypal blazar PKS 2155-305 is presented. The source was monitored with the HIgh Speed Photo-Polarimter (HIPPO) of the SAAO and the SPOL imaging spectropolarimeter of the Steward Observatory between 2008 and 2013. Fluctuations in both the internight and intranight polarization is investigated. The frequency dependence of the polarization during an increased state of activity is also examined.

Title: MeerLICHT: Simultaneous optical-radio observations of astrophysical transients

Speaker: Patrick Woudt

Venue: SAAO Auditorium

Date: 23 January

Time: 11h00

Abstract: ThunderKAT is the MeerKAT Large Survey Project (LSP) for incoherent (synchrotron) radio transients. A nominal amount of 3000 h has been allocated for dedicated MeerKAT observations of X-ray binaries, tidal disruption events, cataclysmic variables, supernovae and gamma-ray bursts over the first five years of science operation of MeerKAT. In addition, ThunderKAT will make use of a dedicated 'transient data spigot' to search all MeerKAT LSP imaging data for astrophysical transients on time scales in excess of 0.1-1 sec, monitoring the transient radio universe in real time for unusual events (e.g. Fast Radio Bursts, Thornton et al. 2013).

In this talk I will present details of the MeerLICHT project: time-scales, optical design and the primary science case for simultaneous optical-radio observations of astrophysical transients. MeerLICHT is the [simultaneous and real-time] optical extension of ThunderKAT's commensal search for radio transients. The MeerLICHT telescope, to be housed in Sutherland, will be a fully robotic 0.65-m telescope with an instantaneous field of view of 2 square degrees, matching the field of view of MeerKAT. The telescope will receive its pointing input from the MeerKAT telescope, ensuring simultaneous optical-radio coverage for all night-time MeerKAT observations.

Title: X-ray Transients from Supersoft to Halo Black-Hole Systems

Speaker: Phil Charles

Venue: SAAO Auditorium

Date: 23 January

Time: 11h00

Abstract: I will discuss the nature of X-ray transient outbursts from both HMXBs and LMXBs. In the former, we have identified an X-ray flash that, in spite of its high luminosity, we interpret as a white dwarf compact object. Whereas in the latter, there is growing evidence for a new class of high latitude, very short period, black-hole systems.

ACGC

Title: Gravitational Waves: a portrait of the early universe

Speaker: Joao Morais (CENTRA, Instituto Superior Tecnico, Lisbon Portugal)

Venue: M111, Maths Building, UCT

Date: 10 December 2013

Time: 12h00

Abstract: The cosmological gravitational waves (GWs), when detected, could provide us with an invaluable picture of the dynamics of the early universe. By implementing the method of the Bogoliubov coefficients to compute the energy spectrum of the GWs as would be measured today, we can look for imprints of the early evolution of the universe. In particular, we can look for potential signs of a primordial bounce. We apply these ideas to modified theories of gravity: (i) generalised theories of the kind f(R); (ii) a loop quantum Cosmology setup where the modification with respect to GR is due to the quantization of space-time.

Title: Gamma-Ray Constraints on Self Annihilating Dark Matter

Speaker: Chris Gordon (University of Canterbury--New Zealand)

Venue: M111, Maths Building, UCT

Date: 21 January

Time: 12h00

Abstract: One of the main candidates for dark matter (DM) is the weakly interacting massive particle (WIMP). The WIMP model predicts that DM particles should pair annihilate into standard model particles. This allows the DM to be a thermal relic of the big bang and the weak scale interaction strength leads to the observed dark matter abundance. The standard model particles produced by the WIMP annihilation typically have weak scale energies and so by a process of pion decay, bremsstrahlung, or inverse Compton scattering, can lead to gamma-ray emission. This residual gamma-ray emission is being searched for with the Fermi Large Area Telescope (LAT) and HESS telescope. Regions, such as Milky Way satellite galaxies, galaxy clusters and the inner Galaxy are the most promising targets. The Fermi-LAT is starting to rule out the lighter WIMP models which have a thermal relic cross-section. There are some excess gamma rays observed in the Galactic Center but these are probably due to an unresolved population of millisecond pulsars.

Title: Geometry of Abelian Higgs Vortices

Speaker: Prof. Nicholas Manton (University of Cambridge--UK)

Venue: M111, Maths Building, UCT

Date: 4 February

Time: 12h00

Abstract: Vortices in the Abelian Higgs model are related to magnetic flux vortices in superconductors, but they can also be regarded as solitonic particles in two dimensions. The first order BPS equations for vortices in the plane or on a curved surface reduce to Taubes' equation, a nonlinear scalar PDE that is close to Liouville's equation. Solutions have an elegant, geometry-preserving character, as observed by Baptista. Moving vortices on a surface have an effective mass that depends on the local curvature. They behave approximately as point particles, but the effect of their finite size has recently been clarified by Dorigoni, Dunajski and the speaker.

UWC

Title: Detecting planets around evolved pulsating stars using the timing method

Speaker: Enrico Olivier (UWC)

Venue: Room 1.35 of the Physics Department, UWC

Date: 6 December 2013

Time: 14h00

Abstract: I met up with the EXOTIME group at the Osservatorio Astrofisico di Torino during October this year to learn more about their data analysis method. The primary goal of the EXOTIME project is to use the timing method to detect exoplanets around evolved pulsating stars such as subdwarf B (sdB) stars and white dwarfs. This talk will cover the timing method, the EXOTIME project itself and the wider context of the project in exoplanet and stellar research. I will also discuss one of the project's southern targets, the sdB star EC09582-1137 originally discovered by Dave Kilkenny.

Title: Testing Bell's Inequality with Cosmic Photons

Speaker: Jason Gallicchio from the University of Chicago

Venue: Room 1.35 of the Physics Department, UWC

Date: 13 December 2013

Time: 14h00

Abstract: A practical scheme to use photons from causally disconnected cosmic sources to set the detectors in an experimental test of Bell's inequality will be discussed. In current experiments, with settings determined by quantum random number generators, only a small amount of correlation between detector settings and local hidden variables, established less than a millisecond before each experiment, would suffice to mimic the predictions of quantum mechanics. By setting the detectors using pairs of quasars or patches of the Cosmic Microwave Background, observed violations of Bell's inequality would require any such coordination to have existed for billions of years--an improvement of 20 orders of magnitude.

AIMS

Title: Dark Matter and Pulsar Model Constraints from Galactic Center Fermi-LAT Gamma Ray Observations

Speaker: Chris Gordon (University of Canterbury--New Zealand).

Venue: The Hall, AIMS research centre

Date: 27 January

Time: 12h00

Abstract: Employing Fermi-LAT gamma ray observations, several independent groups have found excess extended gamma ray emission at the Galactic Center (GC). Both, annihilating dark matter (DM) or a population of about 1000 unresolved millisecond pulsars (MSPs) are regarded as well motivated possible explanations. However, there is significant uncertainties in the diffuse galactic background that need to be accounted for. We have performed a revaluation of the DM and MSP models for the extended gamma ray source at the GC by accounting for the systematic uncertainties of the Galactic diffuse emission model. We also marginalized over point source and diffuse background parameters in the region of interest. We showed that the excess emission is significantly more extended than a point source. We found that the DM (or pulsars population) signal is larger than the systematic errors and therefore proceeded to determine the sectors of parameter space that provided an acceptable fit to the data. We found that a population of order 1000 MSPs with parameters consistent with the average spectral shape of Fermi-LAT measured MSPs was able to fit the GC excess emission. For DM, we found that a pure tau+tau- annihilation channel is not a good fit to the data. But a mixture of tau+ tau- and b bbar with a ov of order the thermal relic value and a DM mass of around 20 to 60 GeV provides an adequate fit.

Title: Three applied statistical problems

Speaker: Ian Durbach (University of Capetown, Department of Statistical Sciences).

Venue: The Hall, AIMS research centre

Date: 12 February

Time: 12h00

Abstract: This talk briefly describes three applied problems. The first involves estimating the ages of long-living trees in arid areas in order to infer recruitment events--mass births generally triggered by abiotic factors and occurring at intervals of several years--using a combination of distribution fitting, simulation and bootstrap resampling. The second describes an application of Bayesian change-point models (or product partition models) to retrospectively identify changes in time series, in the area of consumer behavior. The third investigates the extent of the "wisdom of the crowd" in sports betting data, and shows how this is dependent on the loss function used to evaluate individual bets.

Astro-coffee

Title: Latest pulsar results from LOFAR

Speaker: Joeri van Leeuwen

Date: 16 January

Venue: 2nd Floor Auditorium SKA SA building, Pinelands

Time: 13h00

Abstract: The Dutch/European Low Frequency Array LOFAR provides exceptional collecting area and bandwidth. In the commissioning phase and the first cycle of open-time observing, LOFAR collected much high-quality data. I will describe some of the initial results, on low-frequency behaviour in M87; deep LOFAR epoch of reionization observations toward the north celestial pole; recombination lines; and our ionosphere. I will then present in some more detail the results from our two complementary pilot pulsar surveys, and several other LOFAR pulsar projects--mostly on neutron-star magnetospheres. Finally I will sketch the current dedicated and open-time projects, focusing on the search for new pulsars and fast transients.

Title: Mapping the distant universe with emission line galaxies and quasars

Speaker: Jean Paul Kneib Professor - ERC Advanced Grant Laureate--Project "Light on the Dark"

Laboratoire d'Astrophysique Ecole Polytechnique Federale de Lausanne (EPFL)

Date: 21 January

Venue: 2nd Floor Auditorium SKA SA building, Pinelands

Time: 13h00

Abstract: In this presentation, I will explain why and how astronomers will map the distant Universe (0.7<z<3) using Emission Line Galaxies (ELG) and Quasars in order to probe cosmology using BAO and RSD techniques. I will show results from recent pilot project conducted on SDSS/BOSS and VLT/FORS demonstrating the feasibility of targeting these new tracers. Finally, I will present how these new tracers are implemented in the new Sloan Cosmology project eBOSS and how they will be used in future cosmology project such as DESI and PFS.
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Publication:Monthly Notes of the Astronomical Society of Southern Africa
Article Type:List
Geographic Code:4EUUK
Date:Feb 1, 2014
Words:1969
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