Radio Properties of Tidal Disruption Events

Radio observations of tidal disruption events (TDEs) probe material ejected by the disruption of stars by supermassive black holes (SMBHs), uniquely tracing the formation and evolution of jets and outflows, revealing details of the disruption hydrodynamics, and illuminating the environments around previously-dormant SMBHs. To date, observations reveal a surprisingly diverse population. A small fraction of TDEs (at most a few percent) have been observed to produce radio-luminous mildly relativistic jets. The remainder of the population are radio quiet, producing less luminous jets, non-relativistic outflows or, possibly, no radio emission at all. Here, we review the radio observations that have been made of TDEs to date and discuss possible explanations for their properties, focusing on detected sources and, in particular, on the two best-studied events: Sw J1644+57 and ASASSN-14li. We also discuss what we have learned about the host galaxies of TDEs from radio observations and review constraints on the rates of bright and faint radio outflows in TDEs. Upcoming X-ray, optical, near-IR, and radio surveys will greatly expand the sample of TDEs, and technological advances open the exciting possibility of discovering a sample of TDEs in the radio band unbiased by host galaxy extinction.Comment: Resubmitted for publication in Springer Space Science Reviews following referee comments. Chapter in ISSI review "The Tidal Disruption of Stars by Massive Black Holes" vol. 79. Table 2 is available in machine-readable format upon reques

Implications from Late-Time X-ray Detections of Optically Selected Tidal Disruption Events: State Changes, Unification, and Detection Rates

We present Chandra X-ray observations of four optically-selected tidal disruption events (TDEs) obtained 4-9 years after discovery. Three sources were detected with luminosities between 9X10^40 and 3X10^42 erg/s. The spectrum of PTF09axc is consistent with a power law of index 2.5+-0.1, whereas the spectrum of PTF09ge is very soft. The power law spectrum of PTF09axc and prior literature findings, provide evidence that TDEs transition from an early-time soft state to a late-time hard state many years after disruption. We propose that the time to peak luminosity for optical and X-ray emission may differ substantially in TDEs, with X-rays being produced or becoming observable later. This delay helps explain the differences in observed properties such as L_opt/L_ X of optically and X-ray selected TDEs. We update TDE rate predictions for the eROSITA instrument: it ranges from 3 per yr to 990 per yr, depending sensitively on the distribution of black hole spins and the time delay between disruption and peak X-ray brightness. We further predict an asymmetry in the number of retrograde and prograde disks in samples of optically and X-ray selected TDEs. The details of the observational biases can contribute to observed differences between optically and X-ray selected TDEs (with optically selected TDEs being fainter in X-rays for retrograde TDE disks).Comment: Accepted for publication to ApJ, 18 pages, 4 figure

Facilitating return to work through early specialist health-based interventions (FRESH): protocol for a feasibility randomised controlled trial

Background Over one million people sustain traumatic brain injury each year in the UK and more than 10 % of these are moderate or severe injuries, resulting in cognitive and psychological problems that affect the ability to work. Returning to work is a primary rehabilitation goal but fewer than half of traumatic brain injury survivors achieve this. Work is a recognised health service outcome, yet UK service provision varies widely and there is little robust evidence to inform rehabilitation practice. A single-centre cohort comparison suggested better work outcomes may be achieved through early occupational therapy targeted at job retention. This study aims to determine whether this intervention can be delivered in three new trauma centres and to conduct a feasibility, randomised controlled trial to determine whether its effects and cost effectiveness can be measured to inform a definitive trial. Methods/design Mixed methods study, including feasibility randomised controlled trial, embedded qualitative studies and feasibility economic evaluation will recruit 102 people with traumatic brain injury and their nominated carers from three English UK National Health Service (NHS) trauma centres. Participants will be randomised to receive either usual NHS rehabilitation or usual rehabilitation plus early specialist traumatic brain injury vocational rehabilitation delivered by an occupational therapist. The primary objective is to assess the feasibility of conducting a definitive trial; secondary objectives include measurement of protocol integrity (inclusion/exclusion criteria, intervention adherence, reasons for non-adherence) recruitment rate, the proportion of eligible patients recruited, reasons for non-recruitment, spectrum of TBI severity, proportion of and reasons for loss to follow-up, completeness of data collection, gains in face-to-face Vs postal data collection and the most appropriate methods of measuring primary outcomes (return to work, retention) to determine the sample size for a larger trial. Discussion To our knowledge, this is the first feasibility randomised controlled trial of a vocational rehabilitation health intervention specific to traumatic brain injury. The results will inform the design of a definitive trial

THE MAGNETIC FIELD AND POLARIZATION PROPERTIES OF RADIO GALAXIES IN DIFFERENT ACCRETION STATES

We use the integrated polarized radio emission at 1.4 GHz (P1.4 GHz) from a large sample of active galactic nuclei (AGN; 796 sources at redshifts z < 0.7) to study the large-scale magnetic field properties of radio galaxies in relation to the host galaxy accretion state. We find a fundamental difference in P1.4 GHz between radiative-mode AGN (i.e., high-excitation radio galaxies (HERGs) and radio-loud QSOs) and jet-mode AGN (i.e., low-excitation radio galaxies (LERGs)). While LERGs can achieve a wide range of P1.4 GHz (up to ∼30%), the HERGs and radioloud QSOs are limited to P1.4 GHz 15%. A difference in P1.4 GHz is also seen when the sample is divided at 0.5% of the total Eddington-scaled accretion rate, where the weakly accreting sources can attain higher values of P1.4 GHz. We do not find any clear evidence that this is driven by intrinsic magnetic field differences of the different radio morphological classes. Instead, we attribute the differences in P1.4 GHz to the local environments of the radio sources, in terms of both the ambient gas density and the magnetoionic properties of this gas. Thus, not only are different large-scale gaseous environments potentially responsible for the different accretion states of HERGs and LERGs, we argue that the large-scale magnetized environments may also be important for the formation of powerful AGN jets. Upcoming high angular resolution and broadband radio polarization surveys will provide the high-precision Faraday rotation measure and depolarization data required to robustly test this claim

Outcomes of patients with perforated colon cancer:A systematic review

Introduction: Perforated colon cancer (PCC) is a distinct clinical entity with implications for treatment and prognosis, however data on PCC seems scarce. The aim of this systematic review is to provide a comprehensive overview of the recent literature on clinical outcomes of PCC. Materials and methods: A systematic literature search of MEDLINE (PubMed), Embase, Cochrane library and Google scholar was performed. Studies describing intentionally curative treatment for patients with PCC since 2010 were included. The main outcome measures consisted of short-term surgical complications and long-term oncological outcomes. Results: Eleven retrospective cohort studies were included, comprising a total of 2696 PCC patients. In these studies, various entities of PCC were defined. Comparative studies showed that PCC patients as compared to non-PCC patients have an increased risk of 30-day mortality (8–33% vs 3–5%), increased post-operative complications (33–56% vs 22–28%), worse overall survival (36–40% vs 48–65%) and worse disease-free survival (34–43% vs 50–73%). Two studies distinguished free-perforations from contained perforations, revealing that free-perforation is associated with significantly higher 30-day mortality (19–26% vs 0–10%), lower overall survival (24–28% vs 42–64%) and lower disease-free survival (15% vs 53%) as compared to contained perforations. Conclusion: Data on PCC is scarce, with various PCC entities defined in the studies included. Heterogeneity of the study population, definition of PCC and outcome measures made pooling of the data impossible. In general, perforation, particularly free perforation, seems to be associated with a substantial negative effect on outcomes in colon cancer patients undergoing surgery. Better definition and description of the types of perforation in future studies is essential, as outcomes seem to differ between types of PCC and might require different treatment strategies.</p

The final season reimagined: 30 tidal disruption events from the ZTF-I survey

High Energy Astrophysic

Generalized Boltzmann Equation for Lattice Gas Automata

In this paper, for the first time a theory is formulated that predicts velocity and spatial correlations between occupation numbers that occur in lattice gas automata violating semi-detailed balance. Starting from a coupled BBGKY hierarchy for the $n$-particle distribution functions, cluster expansion techniques are used to derive approximate kinetic equations. In zeroth approximation the standard nonlinear Boltzmann equation is obtained; the next approximation yields the ring kinetic equation, similar to that for hard sphere systems, describing the time evolution of pair correlations. As a quantitative test we calculate equal time correlation functions in equilibrium for two models that violate semi-detailed balance. One is a model of interacting random walkers on a line, the other one is a two-dimensional fluid type model on a triangular lattice. The numerical predictions agree very well with computer simulations.Comment: 31 pages LaTeX, 12 uuencoded tar-compressed Encapsulated PostScript figures (`psfig' macro), hardcopies available on request, 78kb + 52k