Accreting Millisecond X-Ray Pulsars

Accreting Millisecond X-Ray Pulsars (AMXPs) are astrophysical laboratories without parallel in the study of extreme physics. In this chapter we review the past fifteen years of discoveries in the field. We summarize the observations of the fifteen known AMXPs, with a particular emphasis on the multi-wavelength observations that have been carried out since the discovery of the first AMXP in 1998. We review accretion torque theory, the pulse formation process, and how AMXP observations have changed our view on the interaction of plasma and magnetic fields in strong gravity. We also explain how the AMXPs have deepened our understanding of the thermonuclear burst process, in particular the phenomenon of burst oscillations. We conclude with a discussion of the open problems that remain to be addressed in the future.Comment: Review to appear in "Timing neutron stars: pulsations, oscillations and explosions", T. Belloni, M. Mendez, C.M. Zhang Eds., ASSL, Springer; [revision with literature updated, several typos removed, 1 new AMXP added

Black hole spin-orbit misalignment in the x-ray binary MAXI J1820+070

If a black hole is in a close enough binary system with a star, it rips material off the companion. As that material falls into the black hole, it forms an accretion disk that is hot enough to emit optical and x-ray radiation. Poutanen et al. used optical polarimetry to determine the orbital axis of a black hole x-ray binary (see the Perspective by Patat and Mapelli). Combining these observations with previous measurements of the black hole spin showed that the two are misaligned by at least 40 degrees. This high misalignment must have been generated during the formation of the black hole, because accretion always brings the two axes closer together. —KT

The intermediate polar cataclysmic variable GK Persei 120 years after the nova explosion: a first dynamical mass study

We present a dynamical study of the intermediate polar and dwarf nova cataclysmic variable GK Persei (Nova Persei 1901) based on a multisite optical spectroscopy and R-band photometry campaign. The radial velocity curve of the evolved donor star has a semi-amplitude K-2 = 126.4 +/- 0.9 km s(-1) and an orbital period P = 1.996872 +/- 0.000009 d. We refine the projected rotational velocity of the donor star to v(rot) sin i = 52 +/- 2 km s(-1) that, together with K-2, provides a donor star to white dwarf mass ratio q = M-2/M-1 = 0.38 +/- 0.03. We also determine the orbital inclination of the system by modelling the phase-folded ellipsoidal light curve and obtain i = 67 degrees +/- 5 degrees. The resulting dynamical masses are M-1 = 1.03(-0.11)(+0.16) M-circle dot and M-2 = 0.39(-0.06)(+0.07) M-circle dot at 68 per cent confidence level. The white dwarf dynamical mass is compared with estimates obtained by modelling the decline light curve of the 1901 nova event and X-ray spectroscopy. The best matching mass estimates come from the nova light curve models and an X-ray data analysis that uses the ratio between the Alfven radius in quiescence and during dwarf nova outburst

Hard-state Accretion Disk Winds from Black Holes: The Revealing Case of MAXI J1820+070

We report on a detailed optical spectroscopic follow-up of the black hole (BH) transient MAXI J1820+070 (ASASSN-18ey). The observations cover the main part of the X-ray binary outburst, when the source alternated between hard and soft states following the classical pattern widely seen in other systems. We focus the analysis on the He I emission lines at 5876 and 6678 angstrom, as well as on H alpha. We detect clear accretion disk wind features (P-Cyg profiles and broad emission line wings) in the hard state, both during outburst rise and decay. These are not witnessed during the several months long soft state. However, our data suggest that the visibility of the outflow might be significantly affected by the ionization state of the accretion disk. The terminal velocity of the wind is above similar to 1200 km s(-1), which is similar to outflow velocities derived from (hard-state) optical winds and (soft-state) X-ray winds in other systems. The wind signatures, in particular the P-Cyg profiles, are very shallow, and their detection has only been possible thanks to a combination of source brightness and intense monitoring at very high signal-to-noise. This study indicates that cold, optical winds are most likely a common feature of BH accretion, and therefore, that wind-like outflows are a general mechanism of mass and angular momentum removal operating throughout the entire X-ray binary outburst

An update of the Worldwide Integrated Assessment (WIA) on systemic insecticides. Part 2: impacts on organisms and ecosystems

New information on the lethal and sublethal effects of neonicotinoids and fipronil on organisms is presented in this review, complementing the previous WIA in 2015. The high toxicity of these systemic insecticides to invertebrates has been confirmed and expanded to include more species and compounds. Most of the recent research has focused on bees and the sublethal and ecological impacts these insecticides have on pollinators. Toxic effects on other invertebrate taxa also covered predatory and parasitoid natural enemies and aquatic arthropods. Little, while not much new information has been gathered on soil organisms. The impact on marine coastal ecosystems is still largely uncharted. The chronic lethality of neonicotinoids to insects and crustaceans, and the strengthened evidence that these chemicals also impair the immune system and reproduction, highlights the dangers of this particular insecticidal classneonicotinoids and fipronil. , withContinued large scale – mostly prophylactic – use of these persistent organochlorine pesticides has the potential to greatly decreasecompletely eliminate populations of arthropods in both terrestrial and aquatic environments. Sublethal effects on fish, reptiles, frogs, birds and mammals are also reported, showing a better understanding of the mechanisms of toxicity of these insecticides in vertebrates, and their deleterious impacts on growth, reproduction and neurobehaviour of most of the species tested. This review concludes with a summary of impacts on the ecosystem services and functioning, particularly on pollination, soil biota and aquatic invertebrate communities, thus reinforcing the previous WIA conclusions (van der Sluijs et al. 2015)