The CHIME telescope (the Canadian Hydrogen Intensity Mapping Experiment) recently built in Penticton, Canada, is currently being commissioned. Originally designed as a cosmology experiment, it was soon recognized that CHIME has the potential to simultaneously serve as an incredibly useful radio telescope for pulsar science. CHIME operates across a wide bandwidth of 400–800 MHz and will have a collecting area and sensitivity comparable to that of the 100-m class radio telescopes. CHIME has a huge field of view of ~250 square degrees. It will be capable of observing 10 pulsars simultaneously, 24-hours per day, every day, while still accomplishing its missions to study Baryon Acoustic Oscillations and Fast Radio Bursts. It will carry out daily monitoring of roughly half of all pulsars in the northern hemisphere, including all NANOGrav pulsars employed in the Pulsar Timing Array project. It will cycle through all pulsars in the northern hemisphere with a range of cadence of no more than 10 days.

We discuss the impact of mixing and rotation along the red-giant branch (RGB) on the properties of horizontal-branch (HB) stars with emphasis on two problems: the nature of the unexpected blue HB population in the metal-rich globular clusters (GCs) NGC 6388 and NGC 6441 and the cause of the low gravities in the blue HB stars. New stellar models indicate that the sloped HBs in NGC 6388 and NGC 6441 might arise from a spread in metallicity, implying that these GCs may be metal-rich analogues of ω Cen. The low gravity problem can be largely explained by the radiative levitation of Fe in the atmospheres of the blue HB stars. We show that the onset of radiative levitation and the drop in HB rotation velocities at Teff ≈ 11,000 K coincide with the disappearance of surface convection. The low rotation velocities of the hotter HB stars may be due to the spin down of the surface layers by a weak stellar wind induced by the radiative levitation of Fe. We conclude that the impact of mixing and rotation on the HB remains to be clearly established.

We present spectroscopic and photometric observational evidence for abundance stratification in stellar atmospheres. Attention is given to chemically peculiar (Ap) stars in which magnetic fields stabilize the atmosphere, allowing diffusion processes to establish abundance stratification during the early stages of star's life. The results of recent empirical modelling of chemically stratified atmospheres are briefly discussed, and a comparison is given with the predictions of self-consistent atmospheric models which include radiative diffusion.

The importance of abundance stratification analysis is demonstrated for rapidly oscillating (roAp) stars in which the amplitudes of the radial velocity pulsations are different for the lines of different elements in different ionization stages. We also demonstrate that chemical stratification has important effects on the Zeeman Stokes IQUV profiles of Ap stars, indicating that stratification must be taken into account in detailed modelling of their magnetic fields.

We describe a programme that aims to increase the known sample of massive young stellar objects (MYSOs) by an order of magnitude. About 2000 candidates colour-selected from the MSX survey are being followed up at radio, mm and IR wavelengths to identify genuine MYSOs from the UCHII regions and other contaminants. Results so far indicate that the strategy does indeed deliver a significant fraction of luminous YSOs that will provide the basis for future galaxy-wide systematic studies.

Most evidence on X-ray emission from the vicinity of Be stars concerns the Be/X-ray binaries. Presently some 20 of these systems are known, making them the most numerous class of massive X-ray binaries. Evidence for the binary nature of these systems comes from (i) Doppler modulation of X-ray pulse periods, (ii) periodic X-ray flaring behavior, and (iii) correlated optical and X-ray variability. The correlation between X-ray pulse period and orbital period found by Corbet (1984) can potentially provide important information on the densities and velocities in the circumstellar disks of Be stars.

Evolutionary models indicate that the Be/X-ray binaries represent a later stage in the evolution of normal close binaries with initial primary masses predominantly in the the range 8 to 15 M⊙ . These models indicate that also a class of slightly less massive Be star binaries should exist in which the compact companions are white dwarfs. Be-type blue stragglers in galactic clusters may be such systems.

The size of the core is one of the main diagnostics of the evolutionary state of a globular cluster. Much has been learned over the last few years about the behavior of the core radius during and after core collapse, under a variety of different conditions related to the presence or absence of large numbers of binaries. An overview is presented of the basic physical principles that can be used to estimate the core radius. Four different situations are discussed, and expressions are presented for the ratio rc/rh of core radius to half mass radius. The regimes are: deep collapse in the absence of primordial binaries; steady post-collapse evolution after primordial binaries have been burned up; chaotic post-collapse evolution under the same conditions; and post-collapse evolution in the presence of primordial binaries. In addition, modifications to all of these cases are indicated for the more realistic situation where effects of the galactic tidal field are taken into account.

Generalizations of the Schwarzschild and Kerr black holes are discussed in an astrophysically viable generalized theory of gravity, which includes higher curvature corrections in the form of the Gauss-Bonnet term, coupled to a dilaton. The angular momentum of these black holes can slightly exceed the Kerr bound. The location and the orbital frequency of particles in their innermost stable circular orbits can deviate significantly from the respective Kerr values. Study of the quasinormal modes of the static black holes gives strong evidence that they are mode stable against polar and axial perturbations. Future gravitational wave observations should improve the current bound on the Gauss-Bonnet coupling constant, based on observations of the low-mass x-ray binary A 0620-00.

This personal perspective on the development of archaeoastronomy over the last thirty years focuses on interpretative and methodological issues, picking up for example from the debate between Schaefer and Aveni at Oxford VII. How far we have actually progressed in the last three decades? Are we at last starting to achieve the correct fusion between the social science questions that our discipline addresses and the ‘hard science’ methods that are often involved in tackling them? In this paper I argue that the need for our hypotheses to be solidly grounded in social theory, which has rightly been recognised by most archaeoastronomers in recent years, is not an excuse for avoiding the need to be scientifically rigorous in assessing them against the actual evidence. I conclude that identifying robust methodologies for weighing together the different types of data with which the cultural astronomer is faced in different sitations, so as to infer the ‘best’ interpretation, remains at once the most challenging and the most pressing issue facing our ‘interdiscipline’ in the future.

A new non-parametric method based on Gaussian Processes (GP) was proposed recently to measure the Hubble constant H0. The freedom in this approach comes in the chosen covariance function, which determines how smooth the process is and how nearby points are correlated. We perform coverage tests with a thousand mock samples within the ΛCDM model in order to determine what covariance function provides the least biased results. The function Matérn(5/2) is the best with sligthly higher errors than other covariance functions, although much more stable when compared to standard parametric analyses.

Since the construction of the first specialized submillimeter telescopes nearly a decade ago, there has been extensive mapping of astronomical sources in the previously difficult to observe ground-state fine-structure transition of [C I] at 492 GHz. We discuss recent CSO observations of [C I] and 13CO (2 → 1) lines toward bright photon-dominated regions (PDRs). These observations have revealed an interesting effect. In many sources and over a broad range of column densities, the observed intensity of the [C I] line is proportional to that of the 13CO (2 → 1) line with exceptions mainly in dense, active star-forming regions, where C I appears to be under-abundant relative to 13CO. In this paper we quantitatively display this effect.

As we prepare to undertake the observational search for extrasolar terrestrial planets, theoretical modeling studies can help to prepare us for the likely diversity of the extrasolar terrestrial planets. This diversity may arise as a function of planetary system architecture and formation history, which results in a variety of initial planetary properties, as well as stellar, planetary and biological evolutionary processes. Modeling of the physical and chemical processes of the planetary environment, and their interaction with the parent star, allows us to understand the nature of the planetary characteristics that indicate habitability and life, and how these manifest in the planetary spectra. Here we present disk-averaged spectra of planets in our own solar system, and models of the Earth through several eons to understand the types of planetary characteristics that are likely to be observed by planned planet detection and characterization missions.

Recent studies have claimed the existence of very massive stars (VMS) up to 300 M⊙ in the local Universe. As this finding may represent a paradigm shift for the canonical stellar upper-mass limit of 150 M⊙, it is timely to discuss the status of the data, as well as the far-reaching implications of such objects. We held a Joint Discussion at the General Assembly in Beijing to discuss (i) the determination of the current masses of the most massive stars, (ii) the formation of VMS, (iii) their mass loss, and (iv) their evolution and final fate. The prime aim was to reach broad consensus between observers and theorists on how to identify and quantify the dominant physical processes.

The Galaxy Zoo project has provided quantitative visual morphologies for over a million galaxies, and has been part of a reinvigoration of interest in the morphologies of galaxies and what they reveal about galaxy evolution. Morphological information collected by GZ has shown itself to be a powerful tool for studying galaxy evolution, and GZ continues to collect classifications - currently serving imaging from DECaLS in its main site, and running a variety of related projects hosted by the Zooniverse; the citizen science platform which came out of the early success of GZ. I highlight some of the results from the last twelve years, with a particular emphasis on linking morphology and dynamics, look forward to future projects in the GZ family, and provide a quick start guide for how you can easily make use of citizen science techniques to analysis your own large and complex data sets.

The Magnetism in Massive Stars (MiMeS) project represents the largest systematic survey of stellar magnetism ever undertaken. Based on a sample of over 550 Galactic B and O-type stars, the MiMeS project has derived the basic characteristics of magnetism in hot, massive stars. Herein we report preliminary results.

This document presents Java-based software called xSonify that uses a sonification technique (the adaptation of sound to convey information) to promote discovery in astronomical data. The prototype is designed to analyze two-dimensional data, such as time-series data. We demonstrate the utility of the sonification technique with examples applied to X-ray astronomy and solar data. We have identified frequencies in the Chandra X-Ray observations of EX Hya, a cataclysmic variable of the intermediate polar type. In another example we study the impact of a major solar flare, with its associated coronal mass ejection (CME), on the solar wind plasma (in particular the solar wind between the Sun and the Earth), and the Earth's magnetosphere.

Microprobe two-step laser mass spectrometry (μL2MS) is a new mass spectrometric method in which the two essential steps of any mass spectrometric analysis, vaporization and ionization, are carried out using two independent laser sources. In the first step, the output of a pulsed infrared laser is focused on the sample to cause rapid heating in the spot area illuminated, which is typically 40 μm by 40 μm. In the second step, the output of a pulsed ultraviolet laser causes (1+1) resonance-enhanced multiphoton ionization (REMPI) of those desorbed neutral molecules that (1) are able to absorb this UV wavelength and (2) whose ionization potential is less than the energy of two photons of this UV wavelength. The resulting ions are then mass analyzed in a reflectron time-of-flight apparatus. Under suitable conditions fragmentation can be avoided in both the vaporization and ionization steps so that μL2MS can be applied to the analysis of a mixture of molecules. Applications of μL2MS to meteorite samples are presented as a means of detecting trace amounts of certain organic molecules present in complex materials without prior sample preparation, extraction, purification, and separation steps. Moreover, this analysis can be carried out with micrometer spatial resolution so that in favorable cases the presence or absence of certain molecules can be correlated to mineralogical features of the sample.

The theory of line formation in a magnetic field is reviewed. It is shown how the formulations by Unno, Beckers, Stepanov and Rachkovsky are related to each other. The general treatment of true absorption, anomalous dispersion, radiative scattering and level-crossing interference is discussed. Special attention is paid to the inhomogeneous nature of the solar atmosphere. The properties of magnetic filaments are reviewed. It is shown how a filamentary structure will drastically influence the interpretation of magnetograph observations. The treatment of line formation in a turbulent magnetic field is also discussed.

The fine structure of the solar atmosphere will influence different types of magnetographs in entirely different ways. The relation between the observed magnetic field and the resolution of the instrument is discussed for a Babcock-type, Evans-type and a transversal magnetograph. Finally some suggestions for future work in this field are listed.

We present here evidence for the existence of a citation advantage within astrophysics for papers that link to data. Using simple measures based on publication data from NASA Astrophysics Data System we find a citation advantage for papers with links to data receiving on the average significantly more citations per paper than papers without links to data. Furthermore, using INSPEC and Web of Science databases we investigate whether either papers of an experimental or theoretical nature display different citation behavior.

The different methods which have been used, or which may be used in the future, to measure solar magnetic fields are described and discussed. Roughly these can be divided into three groups (a) those which use the influence of the magnetic field on the electromagnetic radiation, (b) those which use the influence of the field on the structure of the solar atmosphere (MHD effects), and (c) those which use theoretical arguments. The former include the Zeeman effect, the Hanle effect, the gyro and synchrotron radiations and the Faraday rotation of radiowaves. The second includes the alignment of details at all levels of the solar atmosphere, and the calcium network, and the third makes use, for example, of the assumption of equipartition between magnetic and kinetic energy density.