Accreting millisecond pulsars: one on each hand

We report on the X-ray aperiodic timing analysis of two accreting millisecond pulsars: XTE J1807-294 and IGR J00291+5934. On the one hand, we discovered in XTE J1807-294 seven pairs of simultaneous kilohertz quasi-periodic oscillations (kHz QPOs) separated in frequency by nearly the spin frequency of the neutron star. This confirms the suspected dichotomy in the frequency separation of kHz QPOs: sometimes once and sometimes half the spin frequency. On the other hand, we found an extreme behavior in the power spectra of IGR J00291+5934: very strong variability at very low frequencies. Namely, the fractional amplitude of the variability was ~50%, the highest value found so far in a neutron star system.Comment: To appear in the proceedings of the conference `The Multicoloured Landscape of Compact Objects and their Explosive Origins' (Cefalu, Sicily, June 2006), AI

Spectral Softening Between Outburst and Quiescence In The Neutron Star Low-Mass X-Ray Binary SAX J1750.8-2900

Tracking the spectral evolution of transiently accreting neutron stars between outburst and quiescence probes relatively poorly understood accretion regimes. Such studies are challenging because they require frequent monitoring of sources with luminosities below the thresholds of current all-sky X-ray monitors. We present the analysis of over 30 observations of the neutron star low-mass X-ray binary SAX J1750.8-2900 taken across four years with the X-ray telescope aboard Swift. We find spectral softening with decreasing luminosity both on long ($\sim$1 year) and short ($\sim$days to week) timescales. As the luminosity decreases from $4\times10^{36}$ erg s$^{-1}$ to $\sim1\times10^{35}$ erg s$^{-1}$ (0.5-10 keV), the power law photon index increases from from 1.4 to 2.9. Although not statistically required, our spectral fits allow an additional soft component that displays a decreasing temperature as the luminosity decreases from $4 \times 10^{36}$ to $6 \times 10^{34}$ erg s$^{-1}$. Spectral softening exhibited by SAX J1750.8-2900 is consistent both with accretion emission whose spectral shape steepens with decreasing luminosity and also with being dominated by a changing soft component, possibly associated with accretion onto the neutron star surface, as the luminosity declines.Comment: 11 pages, 9 figures, 3 Tables. Resubmitted to The Astrophysical Journal after incorporating comments from the refere

The 26.3-h orbit and multiwavelength properties of the 'redback' millisecond pulsar PSR J1306-40

We present the discovery of the variable optical and X-ray counterparts to the radio millisecond pulsar (MSP) PSR J1306–40, recently discovered by Keane et al. We find that both the optical and X-ray fluxes are modulated with the same period, which allows us to measure for the first time the orbital period Porb = 1.097¿16[6] d. The optical properties are consistent with a main-sequence companion with spectral type G to mid K and, together with the X-ray luminosity (8.8¿×¿1031¿erg¿s-1 in the 0.5–10¿keV band, for a distance of 1.2¿kpc), confirm the redback classification of this pulsar. Our results establish the binary nature of PSR J1306–40, which has the longest Porb among all known compact binary MSPs in the Galactic disc. We briefly discuss these findings in the context of irradiation and intrabinary shock emission in compact binary MSPs.Postprint (published version

Timing the accretion flow around accreting millisecond pulsars

At present, ten years after they were first discovered, ten accreting millisecond pulsars are known. I present a study of the aperiodic X-ray variability in three of these systems, which led to the discovery of simultaneous kHz quasi periodic oscillations in XTE J1807-294 and extremely strong broadband noise at unusually low variability frequencies in IGR J00291+5934. Furthermore, we classified SWIFT J1756.9-2508 as an atoll source and measured in its 2007 outburst spectral and variability properties typical of the extreme island state. I also give detailed estimates of the total fluence during the studied outbursts.Comment: To be published in the proceedings of the workshop 'A Decade of Accreting Millisecond X-ray pulsars' (Amsterdam 14-18 April 2008; Eds. Wijnands et al.

Las revistas científicas desde sus nexos con la responsabilidad social. Reflexiones

This research debate convenes this article aims to show the importance of scientific journals in the field of communication of research results, premised on the social responsibility as a specific and necessary analysis. It is accurate as at present the informative concept in scientific journals is ethically responsible. Journals objective analysis as demonstrated in the discussion are committed to social responsibility that affects them, as communication channel and cohesion vehicle with scientific, technological and environmental guidelines that society provides for its development, being an intangible product communicative , affects the ability of the progress of society.El presente debate investigativo al que convoca este artículo, pretende evidenciar la importancia de las revistas científicas en el ámbito de la comunicación de resultados de investigación, sustentándose en la responsabilidad social como un análisis específico y necesario. Se precisa como en la actualidad la concepción divulgativa en las revistas científicas es éticamente responsable. Las revistas científicas como objetivo de análisis demuestra en el debate, como se comprometen con la responsabilidad social que les atañe, como canal comunicativo y vehículo en cohesión con los lineamientos científicos, tecnológicos y medioambientales que estipula la sociedad para su desarrollo, siendo un producto comunicativo intangible, incide la capacidad de progreso de la sociedad

Discovery of the near-infrared counterpart to the luminous neutron-star low-mass X-ray binary GX 3+1

Using the High Resolution Camera onboard the Chandra X-ray Observatory, we have measured an accurate position for the bright persistent neutron-star X-ray binary and atoll source GX 3+1. At a location that is consistent with this new position we have discovered the near-infrared (NIR) counterpart to GX 3+1 in images taken with the PANIC and FourStar cameras on the Magellan Baade Telescope. The identification of this K_s=15.8+-0.1 mag star as the counterpart is based on the presence of a Br-gamma emission line in a NIR spectrum taken with the FIRE spectrograph on the Baade Telescope. The absolute magnitude derived from the best available distance estimate to GX 3+1 indicates that the mass donor in the system is not a late-type giant. We find that the NIR light in GX 3+1 is likely dominated by the contribution from a heated outer accretion disk. This is similar to what has been found for the NIR flux from the brighter class of Z sources, but unlike the behavior of atolls fainter (Lx ~ 1e36 to 1e37 erg/s) than GX 3+1, where optically-thin synchrotron emission from a jet probably dominates the NIR flux.Comment: Accepted for publication in Ap

Experiences of poverty amongst low-income older adults living in a high-income country: A qualitative study

Aim: To understand the experience of low-income older adults living in poverty in a high-income country. Design: A qualitative study based on Gadamer's hermeneutic phenomenology. Methods: A convenience sample of twenty-seven low-income older adults were interviewed in-depth between September 2021 and January 2022. Fleming's method for conducting phenomenological qualitative studies was followed and ATLAS.ti software was used for data analysis. Results: Three main themes were extracted from the analysis: (i) ‘living in the shadow of poverty’, (ii) ‘unprotected by the ‘social shield’ of the welfare state’ (iii) ‘the struggle to attain good health’. Conclusion: Living in poverty affects all spheres of life. Older adults living in poverty feel excluded from social support policies and laws. This has a negative impact on the older adults' mental health and can lead to social isolation. Implications for the Profession and/or Patient Care: Nursing interventions to promote health amongst older adults living in poverty should include an assessment of the patient's social determinants and a focus on increasing social participation. Older people living in poverty experience difficulties accessing formal social support so nurses should implement patient navigation interventions that aim to help them overcome the complexities of the system. Nursing interventions to improve mental health amongst older adults living in poverty are much needed. Impact: Living in poverty increases older adults' vulnerability. Older adults living in poverty suffer from mental health issues as they live under constant pressure to meet their basic needs and lack formal social support. These findings are important for nurses, who play a pivotal role in the design, implementation and evaluation of policies and interventions that promote health equity. Reporting Method: The study has been conducted following the COREQ guidelines. Patient or Public Contribution: There has been no public or patient involvement in the design or development of the study.Knowledge Transfer Programme from the University of Almería, Grant/Award Number: TRFE-SI-2021/00