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Astronomical colloquia.

These form an important part of a research facility, often as a sort of pre-publication 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 included in this section are the colloquia/seminars at the SAAO, NASSP, UWC and the Astrophysics, Cosmology and Gravity Centre at UCT, ACGC. Also 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.


Title: Nature or Nurture - Neutron Stars in Be/X-ray Binaries

Speaker: Prof Malcolm Coe (University of Southampton)

Venue: SAAO Auditorium

Date: 13 December 2012

Time: 11:00

Abstract: The population of Be/X-ray binaries in the Small Magellanic Cloud is proving a superb, homogeneous sample of this type of HMXBs. They are all at the same distance, the same extinction and probably born around the same time. As such we can use this sample of over 50 systems to explore evolution and accretion processes in these systems. In particular, recent results we have just published in Nature suggest the existence of two types of neutron stars, possibly linked to the two proposed types of SN explosions. So is it birth, or the environment, that is important in dictating how they behave when they are grown up?

Title: The IAU's Commitment to Education, Development and Public Outreach

Speaker: Sarah Reed (OAO) & Kevin Govender (OAD)

Venue: SAAO Auditorium

Date; 20 December 2012

Time: 11:00

Abstract: The IAU founded the Office of Astronomy for Development (OAD) in March 2011. Recent developments have further shown the IAU's commitment to education and public outreach (EPO). Firstly, at the IAU General Assembly in Beijing this summer, a restructuring of the organisation was approved, in which 'Education, Outreach and Heritage' is listed as one of seven new 'Divisions'. Furthermore, in September 2012, the IAU Office for Astronomy Outreach (OAO) was founded at the National Astronomical Observatory of Japan (NAOJ) in Tokyo, Japan, under the leadership of the IAU's new Astronomy Outreach Coordinator, Sarah Reed. In this talk, Kevin Govender and Sarah Reed will briefly outline the history and future plans of the OAD and OAO, respectively, and how the offices fit into the IAU's organisational structure. We will then present how the OAD and OAO plan to work together and share resources to support the missions of both global offices and ensure synergies between them.

Title: Unwinding the secrets of a dying star

Speaker: Shazrene Mohammed.

Venue: 1896 Building

Date: 17 January 2012

Time: 11:00

Abstract: The asymptoic giant branch star R Sculptoris is surrounded by a detached shell of dust and gas. The shell originates from a thermal pulse during which the star had a brief period of increased mass loss. It has hitherto been impossible to constrain the timescales and mass-loss properties during and after a thermal pulse parameters that determine the lifetime on the asymptotic giant branch and the amount of material returned to the interstellar medium. I will present Atacama Large Millimeter/submillimeter Array (ALMA) CO observations of the circumstellar envelope and shell around R Sculptoris. These high angular resolution observations revealed that the thin, clumpy shell contains a spiral structure. Spiral structures have been seen previously in the outflows of evolved stars and are associated with binary systems. I will discuss the formation of spiral sculpted outflows and how they can be used to conclude (by combining the ALMA data with hydrodynamic simulations) that R Sculptoris is a binary system that underwent a thermal pulse ~1800 years ago, lasting ~200 years.

Title: Binarity and final stages of massive star stellar evolution: The high spatial resolution view in the infrared.

Speaker: Olivier Chesneau (Observatoire de la Cote d'Azur)

Venue: 1896 Building

Date: 31 January 2012

Time: 11:00

Abstract: Progress in high angular resolution techniques in the infrared (Adaptive Optics and Optical Interferometry) provided a wealth of new observaions of the circumstellar environment of evolved stars in their immediate vicinity. I shall focus on the detection companions and examples of the deep influence of binarity on the fate of evolved stars. I shall present studies some spectral type thought to be directly connected to binarity (B[e] supergiants and dusty Wolf-Rayet stars). I will also discuss the rapidly growing field of intermediate luminosity transient phenomena.

Title: The Symbiotic path to SNe Ia

Speaker: Joanna Mikolajewska, N.

Copernicus Astron. Center

Venue: SAAO Auditorium

Date: 14 February

Time: 11:00

Abstract: Symbiotic stars are interacting binaries in which the first-formed white dwarf accretes and burns material from a red giant companion. I will present physical characteristics of these objects and discussing their possible link with progenitors of type Ia supernovae.

Title: Lumps and bumps in the early universe


Speaker: Mustafa Amin, Cambridge

Venue: M111, Maths Building, UCT

Date: 22 January 2013

Time: 13:00

Abstract: Our understanding of the universe between the end of inflation and production of light elements is incomplete. How did inflation end? What did the universe look like at the end of inflation? In this talk, I will discuss different end of inflation scenarios. I will concentrate on a particular case: the fragmentation of the inflaton into localized, long-lived excitations of the inflaton field (oscillons), which can end up dominating the energy density of the universe. I will argue that oscillons can be produced in a large class of well-motivated inflationary models that are consistent with CMB anisotropy measurements. I will discuss conditions for their existence, emergence and stability. Finally, I will discuss theoretical and possible observational consequences of different end of inflation scenarios in general as well as oscillons in particular in the early universe.

Title: Averaging the luminosity redshift relation: from theory to observations.

Speaker: Giovanni Marozzi

Venue: M111, Maths Building UCT.

Date: 5 February 2012

Time: 13:00

Abstract: I will show a general gauge invariant formalism for defining cosmological averages that are relevant for observations based on light-like signals. Such averages involve either null hypersurfaces corresponding to a family of past light-cones or compact surfaces given by their intersection with timelike hypersurfaces. Afterwards, using such formalism, together with adapted "geodesic light-cone" coordinates, I will show as backreaction effect emerges in the evaluation of observables related to the luminosity distance-redshit relation in an inhomogeneous Universe. To conclude, considering a realistic stochastic spectrum of inhomogeneities of primordial (inflationary) origin, I will show the magnitude and behaviour of such backreaction effects.


Title: Gravitational dynamics near the Galactic Centre

Speaker: Dr Jeandrew Brink.

Venue: RW James Lecture Hall C

Date: 13 Feb 2013

Time: 13:00

Abstract: There is substantial evidence for the existence of a quiescent super-massive black hole at the rotational centre of our Galaxy, denoted Sgr A*. The advent of the Square Kilometre Array, and gravitational wave detectors such as LIGO and LISA will enable us to experimentally probe the strong field region around Sgr A* with greater precision than ever before. With this information we should be able to test certain fundamental theorems that underlie our understanding of General Relativity such as the no-hair theorems. I discuss some of the theoretical and experimental infrastructure required to make a conclusive test of the cosmic censorship and causality conjectures on which these theorems are based. I also summarize a number of the experimental challenges that will need to be overcome before a conclusive measurement of the quadrupole moment of the black hole can be made.
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Title Annotation:colloquia
Publication:Monthly Notes of the Astronomical Society of Southern Africa
Geographic Code:1USA
Date:Feb 1, 2013
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