RAS Specialist Discussion Meeting on Accretion States

April 10, 2015 at the Royal Astronomical Society

Organisers: Rob Fender (Oxford), Steve Balbus (Oxford), Chris Done (Durham), Christian Knigge (Southampton)


Distinct accretion "states", distinguished by their spectral and
temporal properties, which in turn reflect the geometry, optical depth
and radiative efficiency of the accretion flows, have been clearly
identified in white dwarfs, stellar-mass black holes and neutron stars.
These states have been clearly linked to modes of kinetic and radiative
feedback in complex but repeatable ways. They have also probably been
identified in supermassive black holes, and understanding the duration
and luminosity of a state in any given time period may be the key to
understanding feedback from AGN over cosmological time. In this meeting
we will summarize and discuss the state of the art in our empirical
understanding of these accretion states and associated feedback, and
some of the underlying theories for their origin.

The morning session of the meeting will discuss the evidence for accretion states in a range of objects, including black holes of all masses, neutron stars and white dwarfs, and discuss whether they are really the same phenomena.


10:00-10:30 COFFEE and TEA

10:30-13:00 Morning session: Observational evidence for accretion states
Chair: McHardy [Southampton]

10:30 BH XRB States and feedback / Fender [Oxford] (15+5)
10:50 NS XRB States / Munoz-Darias [IAC Tenerife] (12+3)
11:10 States in AGN? the case of 3C120 / Lohfink [Cambridge] (12+3)
11:25 States in AGN? AGN QPOs / Alston [Cambridge] (12+3)
11:40 States in AGN? AGN radio loudness and populations / Mingo [Leicester] (12+3)
11:55 States in CVs? / Knigge [Southampton] (12+3)
12:10 States in ULX? / Roberts [Durham] (12+3)
12:25 States in flip-flopping pulsars? / Breton [Manchester] (12+3)

12:40 Discussion: Observationally: are these states all the same?
Panel: Phil Uttley, Chris Reynolds, Christian Knigge, Matt Middleton, Ian McHardy

13:00-13:45 LUNCH

13:45-15:30 Afternoon session: Theoretical interpretation of states
Chair: D’Angelo [Leiden]

13:45 Accretion disc instability models / Dubus [Grenonble] (20+5)
14:10 A physical model for black hole binary variabilty / Ingram [Amsterdam] (12+3)
14:25 Magnetic models for states and hysteresis / Reynolds [Maryland] (15+5)
14:45 A new type of accretion disc instability / Potter [Oxford] (12+3)

15:00 Discussion: What’s behind these states?
Panel: Steve Balbus, Guillaume Dubus, Jean-Pierre Lasota, Caroline D’Angelo

15:30 CLOSE / TEA


Wasutep Luangtip (Durham)
Abigail Stevens (Amsterdam)
Chelsea McLeod (ROE)
Lucy Heil (Amsterdam)
Ranjan Vasudevan (Cambridge)