An Optically Discovered Outburst from XTE J1859+226 Bellm, Eric C.; Wang, Yuankun; van Roestel, Jan ...
Astrophysical journal/The Astrophysical journal,
10/2023, Letnik:
956, Številka:
1
Journal Article
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Abstract
Using the Zwicky Transient Facility, in 2021 February we identified the first known outburst of the black hole X-ray transient XTE J1859+226 since its discovery in 1999. The outburst was ...visible at X-ray, UV, and optical wavelengths for less than 20 days, substantially shorter than its full outburst of 320 days in 1999, and the observed peak luminosity was 2 orders of magnitude lower. Its peak bolometric luminosity was only 2 × 10
35
erg s
−1
, implying an Eddington fraction of about 3 × 10
−4
. The source remained in the hard spectral state throughout the outburst. From optical spectroscopy measurements we estimate an outer disk radius of 10
11
cm. The low observed X-ray luminosity is not sufficient to irradiate the entire disk, but we observe a surprising exponential decline in the X-ray light curve. These observations highlight the potential of optical and infrared synoptic surveys to discover low-luminosity activity from X-ray transients.
Accreting compact object systems such as X-ray binaries (XRBs; neutron stars and black holes up to tens of solar masses) and active galactic nuclei (AGN; supermassive black holes up to 1e9 solar ...masses) exhibit variability in their luminosity on many timescales ranging from milliseconds to hundreds of days. Current studies on accretion disks seek to determine how the changes in black hole mass, the rate at which mass accretes onto the central black hole, and the internal and external disk environment affect the observed variability in various bandwidths of light. The fundamental structure of the accretion flow process itself, how it changes and results in the observed variability is not well known. This thesis employs novel methods from nonlinear dynamics to connect the ubiquitously complex variability of XRBs and AGN to the accretion properties and emission and probe commonalities across decades of mass. The methodologies used surpass the capabilities of traditional time series analysis techniques commonly used in astrophysics, such as the power density spectrum and other second order measures of variability, to probe the underlying dynamics. We study the longest light curves to date of XRBs by combining data from multiple all-sky monitors in the 2-20 keV bandpass; the most well-sampled and high precision optical light curves of AGN from the Kepler satellite; and the largest samples to date of long-term monitoring in the hard X-ray of AGN with the Swift/BAT telescope. We find evidence for chaos in a neutron star XRB connected to its superorbital period of 120 days and possibly related to a precession in the accretion disk. We similarly find higher levels of determinism correlate with specific spectral states of XRBs. Among AGN, we find that Type 1 AGN are more likely to exhibit nonlinear behavior than Type 2, obscured AGN are more likely to exhibit stochastic behavior than unobscured AGN, and radio loud sources are more deterministic than radio quiet, with a possible anti-correlation between increased luminosity and nonlinearity. Overall, we hypothesize that specific configurations of the accretion flow onto a compact object result in specific modulations of the emission that can be characterized as deterministic (e.g., possibly related to the presence of a jet-like process), nonlinear (e.g., due to a modulating warp or precession in the accretion disk), or stochastic (e.g., possibly related to the presence of strong outflows or hard X-ray coronal component).
The low-mass X-ray binary 4U1705-44 exhibits dramatic long-term X-ray time variability with a timescale of several hundred days. The All-Sky Monitor (ASM) aboard the Rossi X-ray Timing Explorer ...(RXTE) and the Japanese Monitor of All-sky X-ray Image (MAXI) aboard the International Space Station together have continuously observed the source from December 1995 through May 2014. The combined ASM-MAXI data provide a continuous time series over fifty times the length of the timescale of interest. Topological analysis can help us identify 'fingerprints' in the phase-space of a system unique to its equations of motion. The Birman-Williams theorem postulates that if such fingerprints are the same between two systems, then their equations of motion must be closely related. The phase-space embedding of the source light curve shows a strong resemblance to the double-welled nonlinear Duffing oscillator. We explore a range of parameters for which the Duffing oscillator closely mirrors the time evolution of 4U1705-44. We extract low period, unstable periodic orbits from the 4U1705-44 and Duffing time series and compare their topological information. The Duffing and 4U1705-44 topological properties are identical, providing strong evidence that they share the same underlying template. This suggests that we can look to the Duffing equation to help guide the development of a physical model to describe the long-term X-ray variability of this and other similarly behaved X-ray binary systems.
Using the Zwicky Transient Facility, in 2021 February we identified the first known outburst of the Black Hole X-ray Transient XTE J1859+226 since its discovery in 1999. The outburst was visible at ...X-ray, UV, and optical wavelengths for less than 20 days, substantially shorter than its 320-day full outburst in 1999, and the observed peak luminosity was two orders of magnitude lower. Its peak bolometric luminosity was only \(2\times 10^{35}\) erg s\(^{-1}\), implying an Eddington fraction of about \(3\times10^{-4}\). The source remained in the hard spectral state throughout the outburst. From optical spectroscopy measurements we estimate an outer disk radius of 10\(^{11}\) cm. The low observed X-ray luminosity is not sufficient to irradiate the entire disk, but we observe a surprising exponential decline in the X-ray lightcurve. These observations highlight the potential of optical and infrared (O/IR) synoptic surveys to discover low-luminosity activity from X-ray transients.
BackgroundLong-term survival after lung transplantation is limited compared with other organ transplants. The main cause is development of progressive immune-mediated damage to the lung allograft. ...This damage, which can develop via multiple immune pathways, is captured under the umbrella term chronic lung allograft dysfunction (CLAD). Despite the availability of powerful immunosuppressive drugs, there are presently no treatments proven to reverse or reliably halt the loss of lung function caused by CLAD. The aim of the E-CLAD UK trial is to determine whether the addition of immunomodulatory therapy, in the form of extracorporeal photopheresis (ECP), to standard care is more efficacious at stabilising lung function in CLAD compared with standard care alone.Methods and analysisE-CLAD UK is a Phase II clinical trial of an investigational medicinal product (Methoxsalen) delivered to a buffy coat prepared via an enclosed ECP circuit. Target recruitment is 90 bilateral lung transplant patients identified as having CLAD and being treated at one of the five UK adult lung transplant centres. Participants will be randomised 1:1 to intervention plus standard of care, or standard of care alone. Intervention will comprise nine ECP cycles spread over 20 weeks, each course involving two treatments of ECP on consecutive days. All participants will be followed up for a period of 24 weeks.The primary outcome is lung function stabilisation derived from change in forced expiratory volume in one second and forced vital capacity at 12 and 24 weeks compared with baseline at study entry. Other parameters include change in exercise capacity, health-related quality of life and safety. A mechanistic study will seek to identify molecular or cellular markers linked to treatment response and qualitative interviews will explore patient experiences of CLAD and the ECP treatment.A patient and public advisory group is integral to the trial from design to implementation, developing material to support the consent process and interview materials.Ethics and disseminationThe East Midlands—Derby Research Ethics Committee has provided ethical approval (REC 22/EM/0218). Dissemination will be via publications, patient-friendly summaries and presentation at scientific meetings.Trial registration numberEudraCT number 2022-002659-20; ISRCTN 10615985.
This paper outlines the ways in which the cohort born immediately following the Second World War illustrates changes in consumption patterns within their lives. The paper suggests that this cohort ...(often known as baby boomers) view themselves to be a 'bridging' generation between the 'old' ways of their own parents and the radically different views of the next generation. Now nearing or entering retirement and later life, the discussion considers the accounts of boomers themselves having experienced post-war consumer culture and shifting family relations. This paper focuses primarily on qualitative accounts from 150 detailed interviews followed by 30 in-depth interviews, and is framed by analysis of the English Longitudinal Study of Ageing. It explores central emergent themes in the accounts of respondents which demonstrate evidence for a 'bridging' identity maintained by baby boomers in relation to their consumption practices.
With an increasingly diverse ageing population, we need to understand how social divisions intersect to affect outcomes in later life. Gender and sexuality are recognised as key factors in ...determining a person’s experience of later life but little research has been done into how age, gender and sexualities work together and with other divisions, including ethnicity and class, to form a range of inequalities and opportunities for people as they age. The collection brings together an international group of researchers and writers from Australia, Brazil, Denmark, Israel, Italy, Spain, South Africa, Sweden, Taiwan, the UK, and the USA, who argue for multiple, complex contextualised and spatialized approaches to understanding intersections of ageing, gender and sexualities and uneven outcomes in later life. The book highlights new ways of engaging with and thinking through questions related to ageing, gender and sexualities.
This paper examines social and cultural constructions of first wave baby boomers, those born in the period 1945-1954. Boomers are depicted, variously, as bringing new lifestyles and attitudes to ...ageing and retirement; or heralding economic disaster; or placing fresh burdens on health and social care services. The paper seeks to explore narratives about the boomer generation, drawing on sociological studies, the mass media and cultural and social histories of the post-war period. The article provides a critical analysis of the construction of boomers as a ‘problem generation’, exploring this from the perspective of demography, consumption and politics. The paper concludes with a research agenda for further work around the boomer generation.
DNA vaccination is an invaluable approach for immune therapy in that it lacks vector interference and thus permits repeated vaccination boosts. However, by themselves, DNA-based vaccines are ...typically poor inducers of Ag-specific immunity in humans and non-human primates. Cytokines, such as IL-12 and IL-15, have been shown to be potent adjuvants for the induction and maintenance of cellular immune responses, in particular during HIV infection. In this study, we examined the ability of therapeutic vaccination with SIV-DNA+IL-12 or IL-15 as molecular adjuvants to improve DNA vaccine potency and to enhance memory immune responses in SIV-infected macaques. Our results demonstrate that incorporating IL-12 into the vaccine induces SIV-specific CD8 effector memory T cell (T(EM)) functional responses and enhances the capacity of IFN-gamma-producing CD8 T(EM) cells to produce TNF. Lower levels of PD-1 were expressed on T cells acquiring dual function upon vaccination as compared with mono-functional CD8 T(EM) cells. Finally, a boost with SIV-DNA+IL-15 triggered most T cell memory subsets in macaques primed with either DNA-SIV or placebo but only CD8 T(EM) in macaques primed with SIV-DNA+IL-12. These results indicate that plasmid IL-12 and IL-15 cytokines represent a significant addition to enhance the ability of therapeutic DNA vaccines to induce better immunity.
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