Flow Equations and Normal Ordering

In this paper we consider flow-equations where we allow a normal ordering which is adjusted to the one-particle energy of the Hamiltonian. We show that this flow converges nearly always to the stable phase. Starting out from the symmetric Hamiltonian and symmetry-broken normal ordering nearly always yields symmetry breaking below the critical temperature.Comment: 7 page

Radio observations of NGC 6388: an upper limit on the mass of its central black hole

We present the results of deep radio observations with the Australia Telescope Compact Array (ATCA) of the globular cluster NGC 6388. We show that there is no radio source detected (with a r.m.s. noise level of 27 uJy) at the cluster centre of gravity or at the locations of the any of the Chandra X-ray sources in the cluster. Based on the fundamental plane of accreting black holes which is a relationship between X-ray luminosity, radio luminosity and black hole mass, we place an upper limit of 1500 M_sun on the mass of the putative intermediate-mass black hole located at the centre of NGC 6388. We discuss the uncertainties of this upper limit and the previously suggested black hole mass of 5700 M_sun based on surface density profile analysis.Comment: 6 pages, 2 figures, accepted for publication in MNRA

The variability plane of accreting compact objects

Recently, it has been shown that soft-state black hole X-ray binaries and active galactic nuclei populate a plane in the space defined by the black hole mass, accretion rate and characteristic frequency. We show that this plane can be extended to hard-state objects if one allows a constant offset for the frequencies in the soft and the hard state. During a state transition the frequencies rapidly move from one scaling to the other depending on an additional parameter, possibly the disk-fraction. The relationship between frequency, mass and accretion rate can be further extended by including weakly accreting neutron stars. We explore if the lower kHz QPOs of neutron stars and the dwarf nova oscillations of white dwarfs can be included as well and discuss the physical implications of the found correlation.Comment: Accepted for publication in MNRA

Galactic X-ray binary jets

With their relatively fast variability time-scales, Galactic X-ray binaries provide an excellent laboratory to explore the physics of accretion and related phenomena, most notably outflows, over different regimes. After comparing the phenomenology of jets in black hole X-ray binary systems to that of neutron stars, here I discuss the role of the jet at very low Eddington ratios, and present preliminary results obtained by fitting the broadband spectral energy distribution of a quiescent black hole binary with a `maximally jet-dominated' model.Comment: Refereed version, accepted for publication in Astrophysics & Space Scienc

Magnetic field effects on neutrino production in microquasars

We investigate the effects of magnetic fields on neutrino production in microquasars. We calculate the steady particle distributions for the pions and muons generated in p-gamma and p-p interactions in the jet taking the effects of all energy losses into account. The obtained neutrino emission is significantly modified due to the synchrotron losses suffered by secondary pions and muons. The estimates made for neutrino fluxes arriving on the Earth imply that detection of high-energy neutrinos from the vicinity of the compact object can be difficult. However, in the case of windy microquasars, the interaction of energetic protons in the jet with matter of dense clumps of the wind could produce detectable neutrinos. This is because the pions and muons at larger distances from the compact object will not be affected by synchrotron losses.Comment: 12 pages, 11 figures, accepted for publication in A&

Studying the X-ray hysteresis in GX 339-4: the disc and iron line over one decade

We report on a comprehensive and consistent investigation into the X-ray emission from GX 339-4. All public observations in the 11 year RXTE archive were analysed. Three different types of model - single powerlaw, broken powerlaw and a disc + powerlaw - were fitted to investigate the evolution of the disc, along with a fixed gaussian component at 6.4 keV to investigate any iron line in the spectrum. We show that the relative variation in flux and X-ray colour between the two best sampled outbursts are very similar. The decay of the disc temperature during the outburst is clearly seen in the soft state. The expected decay is S_Disc \propto T^4; we measure T^4.75\pm0.23. This implies that the inner disc radius is approximately constant in the soft state. We also show a significant anti-correlation between the iron line significant width and the X-ray flux in the soft state while in the hard state the EW is independent of the flux. This results in hysteresis in the relation between X-ray flux and both line flux and EW. To compare the X-ray binary outburst to the behaviour seen in AGN, we construct a Disc Fraction Luminosity Diagram for GX 339-4, the first for an X-ray binary. The shape qualitatively matches that produced for AGN. Linking this with the radio emission from GX 339-4 the change in radio spectrum between the disc and power-law dominated states is clearly visible.Comment: Accepted for publication in MNRAS, 20 pages, 17 figures. For high-res version see http://www.astro.soton.ac.uk/~r.j.dunn/publications.htm

The completeness of electronic medical record data for patients with type 2 diabetes in primary care and its implications for computer modelling of predicted clinical outcomes.

Computer models predicting outcomes among patients with Type 2 Diabetes (T2D) can be used as disease management program evaluation tools. The clinical data required as inputs for these models include annually updated measurements such as blood pressure and glycated haemoglobin (HbA1c). These data can be extracted from primary care physician office systems but there are concerns about their completeness. This paper reports on the completeness of general practice records.Background: Computer models predicting outcomes among patients with Type 2 Diabetes (T2D) can be used as disease management program evaluation tools. The clinical data required as inputs for these models can include annually updated measurements such as blood pressure and glycated haemoglobin (HbA1c). These data can be extracted from primary care physician office systems but there are concerns about their completeness. Objectives/methods: This study addressed the completeness of routinely collected data extracted from 12 primary care practices in Australia. Data on annual availability of blood pressure, weight, total cholesterol, HDL-cholesterol and HbA1c values for regular patients were extracted in 2103 and analysed for temporal trends over the period 2000 to 2012. An ordinal logistic regression model was used to evaluate associations between patient characteristics and completeness of their records. Primary care practitioners were surveyed to identify barriers to recording data and strategies to improve its completeness. Results: Over the study period completeness of data improved substantially from less than 20% for some parameters up to a level of approximately 80% complete, except for the recording of weight. T2D patients with Ischaemic Heart Disease were more likely to have their blood pressure recorded (OR 1.6, p=0.02). Practitioners’ responses suggest they were not experiencing any major barriers to using their electronic medical record system but did agree with some suggested strategies to improve record completeness. Conclusion: The completeness of routinely collected data suitable for input into computerised predictive models is improving although other dimensions of data quality need to be addressed

An overview of jets and outflows in stellar mass black holes

In this book chapter, we will briefly review the current empirical understanding of the relation between accretion state and and outflows in accreting stellar mass black holes. The focus will be on the empirical connections between X-ray states and relativistic (`radio') jets, although we are now also able to draw accretion disc winds into the picture in a systematic way. We will furthermore consider the latest attempts to measure/order jet power, and to compare it to other (potentially) measurable quantities, most importantly black hole spin.Comment: Accepted for publication in Space Science Reviews. Also to appear in the Space Sciences Series of ISSI - The Physics of Accretion on to Black Holes (Springer Publisher

The balance of power: accretion and feedback in stellar mass black holes

In this review we discuss the population of stellar-mass black holes in our galaxy and beyond, which are the extreme endpoints of massive star evolution. In particular we focus on how we can attempt to balance the available accretion energy with feedback to the environment via radiation, jets and winds, considering also possible contributions to the energy balance from black hole spin and advection. We review quantitatively the methods which are used to estimate these quantities, regardless of the details of the astrophysics close to the black hole. Once these methods have been outlined, we work through an outburst of a black hole X-ray binary system, estimating the flow of mass and energy through the different accretion rates and states. While we focus on feedback from stellar mass black holes in X-ray binary systems, we also consider the applicability of what we have learned to supermassive black holes in active galactic nuclei. As an important control sample we also review the coupling between accretion and feedback in neutron stars, and show that it is very similar to that observed in black holes, which strongly constrains how much of the astrophysics of feedback can be unique to black holes.Comment: To be published in Haardt et al. Astrophysical Black Holes. Lecture Notes in Physics. Springer 201

Revisiting the radio/X-ray flux correlation in the black hole V404 Cyg: from outburst to quiescence

We report results of Chandra X-ray and VLA radio observations of the Galactic accreting black hole V404 Cyg (GS 2023+338) in its quiescent state. V404 Cyg is detected at its faintest level of radio and X-ray emission with a 0.5-10 keV unabsorbed luminosity of 8.3 x 10^32 (d/3.5 kpc)^2 erg/s. The X-ray spectrum fit with an absorbed power-law model yields a photon index of 2.17 +/- 0.13. Contrary to previous findings, this clearly indicates that V404 Cyg undergoes - like most black holes in quiescence - a softening of its X-ray spectrum at very low luminosity compared to the standard hard state. The quiescent radio emission is consistent with the presence of self-absorbed compact jets. We have also reanalyzed archival data from the decay of the 1989 outburst of V404 Cyg in order to quantify more precisely the correlation between radio and X-ray emission in the hard state of V404 Cyg. We show that this correlation extends over five decades in X-ray flux and holds down to the quiescent state of V404 Cyg. The index of this correlation (~0.5) may suggest that synchrotron self-Compton emission is the dominant physical process at high energy in V404 Cyg. However, this index is also consistent with scale invariant jet models coupled to an inefficiently radiating accretion disc. We discuss the properties of the quiescent state of black holes and highlight the fact that some of their properties are different from the standard hard state.Comment: 7 pages, Accepted for publication in MNRA