High-energy astrophysics teleconference
13th October 2006

Files and links at http://www.ph.unimelb.edu.au/~duncang/heat

Present: Andrew Melatos, Christine Chung  & Duncan Galloway  (UMelb);
Stefan Dieters (UTas); Bryan Gaensler, Zdenka Kuncic, Shami Chatterjee &
Gemma Anderson (USyd); Ravi Sood & Sean Farrell (ADFA) & Geoff Bicknell
(RSAA)

Apologies: Gavin Rowell, Aimee McNamara, Jasmina Lazendic & John Greenhill.

Introductions:

Andrew Melatos - research interests include relativistic winds from
pulsars, gravitational waves, accretion disks, superfluid hydrodynamics.

Christine Chung - first year PhD working with Andrew M. and Duncan,
looking at gravity wave sources (accreting MSPs/SNRs) and superfluids in
neutron stars.

Andrew: Update on Texas 2006
- Abstracts due in by October 15. See website (http://www.texas06.com) for
  the program outline, speaker list, and what to do if your computer
  doesn't write abstracts in Arial font size 12 (!).
- Also of interest is "Didjeridu - A Triumph of Mind Over Matter" on
  Tues 12 December, presented by Lloyd Holenberg (UMelb) and musicians.
  Contact the organisers if you are interested.

Bryan & Gemma: Interesting talks from the recent HEAD meeting
- Quasi-periodic oscillations during magnetar flares (Anna Watts & Todd
  Strohmayer)

- Transient X-ray bursts in the galactic centre (Michael Muno). There is
  an over-abundance (by a factor of 20 per unit stellar mass) of faint
  (<10^36 ergs/s) transients in the central parsec around Sgr A* as compared
  to 1-20 pc away from the galactic centre.

Discussion: There must therefore be exchanges in the galactic centre,
forming these objects, e.g. interactions between black holes in a cluster
around the central supermassive black hole can produce LMXBs. Also
detectable would be X-rays from bowshocks.

Papers referenced in Muno's talk:
 * Morris, 1993, ApJ, 408, 496
 * Miralda-Escude & Gould, 2000, ApJ, 545, 847 (the one that Bryan read)
 * Pfahl & Loeb, 2004, ApJ, 615, 253
 * Muno et al., 2005, ApJL, 622, L113
 * Muno et al., 2005, ApJ, 633, 228
 * Porquet et al., 2005, A&A, 430, L9
 * Porquet et al., 2005, A&A, 443, 571


- Radio lobes around X-ray binaries as a tool to study microquasar jets
  (Sebastian Heinz)

A list of all abstracts is available online at
http://www.abstractsonline.com/viewer/browseOptions.asp?MKey={27F17723-CCC9-4AEF-89DC-E18425D56297}&AKey={AAF9AABA-B0FF-4235-8AEC-74F22FC76386}

Duncan: Summary of his recent paper (astro-ph/0609693)
- The paper discusses the behaviour of the 7th discovered accreting
  millisecond pulsar (MSP). MSPs are thought to be the progenitors of
  millisecond radio pulsars. Normally MSPs have recurring outbursts every >2
  years lasting ~ a few weeks, in which persistent pulsations and
  thermonuclear X-ray bursts are detectable. However this particular source
  has remained active for ~1.5 years, and has non-persistent pulsations
  which vary in amplitude and seem to be triggered by X-ray bursts. Is this
  the first MSP/LMXB crossover?

Discussion: Why do pulsations in LMXBs necessarily indicate the presence
of a magnetic field?

Geoff: Summary of his upcoming paper with Ralph Sutherland
- Have been running simulations of jets propagating through a homogeneous
  medium and are writing up the 3D case. Found that a jet propagating
  through a turbulent disk looks like a gigahertz peak spectrum (GPS)
  source. These are sources which are described by a power law with a turn
  around at ~ a gigahertz. Early stages of simulation shows bubbles forming
  on either side, and the jet piercing the bubble.

Gemma: CHICCAGO
- stands for CHasing the Identity of Compact and Complex extrAGalactic Objects
- submitted an XMM proposal

Bryan: RRAT
- stands for Rotating RAdio Transients, which are pulsars that are mostly
  quiet, but display bursts of radio emission about once a day. Timing
  gaps in the bursts have a common denominator. The most active one (a burst
  every 2 hours) was observed with Chandra and has a normal NS spectrum,
  evidence that RRATs are neutron stars and not a separate class of source. 

Reminder: 5th Stromlo Symposium (http://www.mso.anu.edu.au/5SS/)