The innermost jet in the hidden ultra-luminous X-ray source Cygnus X-3

Cygnus X-3 is a high-mass X-ray binary with a compact object accreting matter from a Wolf-Rayet donor star. Recently, it has been revealed by the Imaging X-ray Polarimetry Explorer (IXPE) as a hidden Galactic ultra-luminous X-ray (ULX) source with a luminosity above the Eddington limit along the direction of a narrow (opening angle <~32 degree) funnel. In between the IXPE observations, we observed Cyg X-3 with the European VLBI (very long baseline interferometry) Network at 22 GHz and the NICER X-ray instrument. To probe possible relations between the X-ray funnel and the potential radio jet from the ULX, we analyzed the simultaneous multi-wavelength data. Our high-resolution VLBI image reveals an elongated structure with a position angle of -3.2+/-0.4 degree, accurately perpendicular to the direction of the linear X-ray polarization. Because Cyg X-3 was in the radio quiescent state on 2022 November 10, we identify the mas-scale structure as the innermost radio jet. The finding indicates that the radio jet propagates along and within the funnel. Moreover, the jet is marginally resolved in the transverse direction. This possibly results from the strong stellar winds and the rapid orbital motion of the binary system.Comment: 7 pages, 8 figures, accepted for publication in MNRAS Letter

A New Statistical Approach to the Optical Spectral Variability in Blazars

We present a spectral variability study of a sample of about 25 bright blazars, based on optical spectroscopy. Observations cover the period from the end of 2008 to mid 2015, with an approximately monthly cadence. Emission lines have been identified and measured in the spectra, which permits us to classify the sources into BL Lac-type or FSRQs, according to the commonly used EW limit. We have obtained synthetic photometry and produced colour-magnitude diagrams which show different trends associated with the object classes: generally, BL Lacs tend to become bluer when brighter and FSRQs become redder when brighter, although several objects exhibit both trends, depending on brightness. We have also applied a pattern recognition algorithm to obtain the minimum number of physical components which can explain the variability of the optical spectrum. We have used NMF (Non-Negative Matrix Factorization) instead of PCA (Principal Component Analysis) to avoid un-realistic negative components. For most targets we found that 2 or 3 meta-components are enough to explain the observed spectral variability

Outflow Legacy Accretion Survey: unveiling the wind driving mechanism in BHXRBs

Transient black-hole X-ray binaries viewed at high inclinations display blue-shifted absorption lines in their X-ray spectra. These features are the signatures of powerful, hot and equatorial accretion disk winds being driven from these systems in their luminous soft states. Remarkably, blue-shifted absorption lines have recently also been discovered in optical and NIR recombination lines and ultraviolet resonance features. These features must also be produced in an outflow, but the physical conditions traced by these outflows are different. Despite this, the characteristic Doppler velocities of all three types of signatures are comparable, yet they have never been observed simultaneously. It is therefore completely unclear if they are associated with distinct outflows (e.g. driven by different mechanisms) or simply with different regions/phases within the same outflow. Here, we propose to answer this question by carrying out simultaneous time-resolved spectroscopy of a high-inclination system in the X-ray, ultraviolet and optical bands, in its two distinct physical configurations (hard- and soft-states). This will allow us to test if the three types of wind features are present simultaneously, and, if so, whether they display correlated variability and/or velocity structure

A shared accretion instability for black holes and neutron stars

Accretion disks around compact objects are expected to enter an unstable phase at high luminosity1. One instability may occur when the radiation pressure generated by accretion modifies the disk viscosity, resulting in the cyclic depletion and refilling of the inner disk on short timescales2. Such a scenario, however, has only been quantitatively verified for a single stellar-mass black hole3,4,5. Although there are hints of these cycles in a few isolated cases6,7,8,9,10, their apparent absence in the variable emission of most bright accreting neutron stars and black holes has been a continuing puzzle11. Here we report the presence of the same multiwavelength instability around an accreting neutron star. Moreover, we show that the variability across the electromagnetic spectrum—from radio to X-ray—of both black holes and neutron stars at high accretion rates can be explained consistently if the accretion disks are unstable, producing relativistic ejections during transitions that deplete or refill the inner disk. Such a new association allows us to identify the main physical components responsible for the fast multiwavelength variability of highly accreting compact objects.The authors thank the referees for the constructive comments which improved the manuscript. The interpretation of the FV thank R. Arcodia, P. Casella, G. Marcel, G. Mastroserio, N. Scepi and L. Stella for insightful discussions. The interpretation of the results benefited from discussions held during the meeting ‘Looking at the disc-jet coupling from different angles’ held at the International Space Science Institute in Bern, Switzerland. FV was supported by the NASA awards 80NSSC19K1456, 80NSSC21K0526 and from grant FJC2020-043334-I financed by MCIN/AEI/10.13039/501100011033 and NextGenerationEU/PRTR. JN acknowledges support by the SAO award GO1-22036X. AJT acknowledges support for this work was provided by NASA through the NASA Hubble Fellowship grant #HST–HF2–51494.001 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5–26555. D.A. and N.C.S. acknowledges support from the Science and Technology Facilities Council (STFC) grant ST/V001000/1. FV, MAP and VC acknowledge support from the Spanish Ministry of Science and Innovation research project PID2020-120323GB-I00. MAP acknowledges support from the Consejería de Economía, Conocimiento y Empleo del Gobierno de Canarias and the European Regional Development Fund (ERDF) under grant with reference ProID2021010132 ACCISI/FEDER, UE. TMB acknowledges financial contribution from the agreement ASI-INAF n.2017- 14-H.0 and from PRIN-INAF 2019 N.15. TMD acknowledges support from the Spanish Ministry of Science and Innovation project PID2021-124879NB-I00, and the Europa Excelencia grant (EUR2021-122010). TDR acknowledge financial contribution from the agreement ASIINAF n.2017-14-H.0.Peer ReviewedPostprint (author's final draft

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Multi-wavelength studies of accretion and outflows in compact binaries

The study of interacting compact binaries invokes a wide variety of astrophysical concepts, ranging from the physics of compact objects, accretion, stellar atmospheres and interiors, stellar and binary evolution. These systems host a stellar remnant, i.e. a white dwarf, neutron star or black hole – which produce a wide variety of exotic phenomena observable across the entire electromagnetic spectrum. Essentially all accreting systems exhibit evidence of mass-loss in the form of jets and disc winds, representing key mechanisms by which they interact with their environment. In this thesis, multi-wavelength (MW) observations encompassing different techniques and a wide range of timescales are used to investigate the accretion flow, outflows and evolution of two accreting compact binaries. In Chapter 2, the first comprehensive study on V341 Ara is presented, a 10th magnitude star recently identified as a cataclysmic variable star. The analysis of long-term and high resolution light curves allows the identification of both, the negative super-humps, and the super-orbital modulation of a tilted accretion disc that ultimately causes them. A recently developed disc instability model acting in a tilted disc is proposed as the underlying mechanism responsible of the eventual fading episodes observed in this source. The system’s mass ratio is obtained from time-resolved spectroscopy and the wind mass loss rate is constrained using spatially resolved [OIII] emission produced by a bow-shock. In Chapter 3, an overview of a major MW campaign is presented. One of the key ingredients of this campaign is the coordination of many of the major Earth- and space-based observatories from X-ray to radio, including near-infrared optical and ultraviolet time resolved spectroscopy and photometry of an extremely flaring low-mass X-ray binary. Chapter 4 is focused on the detection and implications of accretion disc winds in the ultraviolet spectrum we obtained during the campaign. In this research time-tagged far-ultraviolet spectroscopy is used to demonstrate that the absorption troughs are associated with a non-variable component of the spectrum, showing that flares and outflows are driven by different mechanisms; it also illustrates how wind signatures can be masked by flaring emission, even if the outflow is present all the time. This is crucial for the correct interpretation of all wind signatures. In Chapter 5, archival and new data is analysed to determine the properties of the companion star and line-of-sight absorption, to discuss the intrinsic luminosity and evolutionary stage of Swift J1858. All this is summarised in Chapter 6 along with future lines of research in these topics