The ability to quickly detect transient sources in optical images and trigger multi-wavelength follow up is key for the discovery of fast transients. These include events rare and difficult to detect such as kilonovae, supernova shock breakout, and ‘orphan’ Gamma-ray Burst afterglows. We present the Mary pipeline, a (mostly) automated tool to discover transients during high-cadenced observations with the Dark Energy Camera at Cerro Tololo Inter-American Observatory (CTIO). The observations are part of the ‘Deeper Wider Faster’ programme, a multi-facility, multi-wavelength programme designed to discover fast transients, including counterparts to Fast Radio Bursts and gravitational waves. Our tests of the Mary pipeline on Dark Energy Camera images return a false positive rate of ~2.2% and a missed fraction of ~3.4% obtained in less than 2 min, which proves the pipeline to be suitable for rapid and high-quality transient searches. The pipeline can be adapted to search for transients in data obtained with imagers other than Dark Energy Camera.

We present a systematic evaluation of JPEG2000 (ISO/IEC 15444) as a transport data format to enable rapid remote searches for fast transient events as part of the Deeper Wider Faster programme. Deeper Wider Faster programme uses ~20 telescopes from radio to gamma rays to perform simultaneous and rapid-response follow-up searches for fast transient events on millisecond-to-hours timescales. Deeper Wider Faster programme search demands have a set of constraints that is becoming common amongst large collaborations. Here, we focus on the rapid optical data component of Deeper Wider Faster programme led by the Dark Energy Camera at Cerro Tololo Inter-American Observatory. Each Dark Energy Camera image has 70 total coupled-charged devices saved as a ~1.2 gigabyte FITS file. Near real-time data processing and fast transient candidate identifications—in minutes for rapid follow-up triggers on other telescopes—requires computational power exceeding what is currently available on-site at Cerro Tololo Inter-American Observatory. In this context, data files need to be transmitted rapidly to a foreign location for supercomputing post-processing, source finding, visualisation and analysis. This step in the search process poses a major bottleneck, and reducing the data size helps accommodate faster data transmission. To maximise our gain in transfer time and still achieve our science goals, we opt for lossy data compression—keeping in mind that raw data is archived and can be evaluated at a later time. We evaluate how lossy JPEG2000 compression affects the process of finding transients, and find only a negligible effect for compression ratios up to ~25:1. We also find a linear relation between compression ratio and the mean estimated data transmission speed-up factor. Adding highly customised compression and decompression steps to the science pipeline considerably reduces the transmission time—validating its introduction to the Deeper Wider Faster programme science pipeline and enabling science that was otherwise too difficult with current technology.

Observations of globular clusters in dwarf galaxies can be used to study a variety of topics, including the structure of dark matter halos and the history of vigorous star formation in low-mass galaxies. We report on the properties of the faint globular cluster (MV ~ −3.4) in the M31 dwarf galaxy Andromeda I. This object adds to the growing population of low-luminosity Local Group galaxies that host single globular clusters.

A radio polarization study of gamma-ray-detected pulsars reveals a surprising tendency for the magnetic and rotation axes to be relatively aligned. This provides tension with gamma-ray models, which disfavour such alignment. The lack of correlation between these findings and those derived from the gamma-ray light curves suggests problems in the models. To make the data consistent with a random orientation of the magnetic field the emission regions could be assumed to extend outside what is traditionally thought to be the open-field-line region in a magnetic inclination angle dependent way. Both acceptance and rejection of this hypothesis has important consequences. Finally, a unification scheme is proposed to explain the observational differences between gamma-ray loud and gamma-ray quiet radio pulsars. This unification scheme takes the orientation of the line of sight and the magnetic inclination angle to be key parameters affecting both the radio and gamma-ray light-curve morphology.

The Turner-Welch Object in the W3(OH) high-mass star forming complex drives a synchrotron jet, which is quite exceptional for a high-mass protostar, and is associated with a strongly polarized water maser source, W3(H2O), making it an optimal target to investigate the role of magnetic fields on the innermost scales of protostellar disk-jet systems. We report here full polarimetric VLBA observations of water masers. The linearly polarized emission from water masers provides clues on the orientation of the local magnetic field, while the measurement of the Zeeman splitting from circular polarization provides its strength. By combining the information on the measured orientation and strength of the magnetic field with the knowledge of the maser velocities, we infer that the magnetic field evolves from having a dominant component parallel to the outflow velocity in the pre-shock gas (with field strengths of the order of a few tens of mG), to being mainly dominated by the perpendicular component (of order of a few hundred of mG) in the post-shock gas where the water masers are excited. The general implication is that in the undisturbed (i.e. not-shocked) circumstellar gas, the flow velocities would follow closely the magnetic field lines, while in the shocked gas the magnetic field would be re-configured to be parallel to the shock front as a consequence of gas compression.

Since the discovery of periodic variability of Class II methanol masers associated with high-mass star formation, several possible driving mechanisms have been proposed to explain this phenomenon. Here the colliding wind binary (CWB) hypothesis is proposed to describe the periodic variability. It is shown that the recombination of a partially ionized gas describes the flare profiles remarkably well. In addition, the quiescent state flux density is also described remarkably well by the time-dependent change of the electron density. This suggests that the periodicity is caused by the time-dependent change in the radio free-free emission from the background HII regions against which the maser is projected.

We present multi–epoch VLBI observations of the methanol and water masers in the high–mass star formation region G 339.884−1.259, made using the Australian Long Baseline Array (LBA). Our sub–milliarcsecond precision measurements trace the proper motions of individual maser features in the plane of the sky. When combined with the direct line–of–sight radial velocity (vlsr), these measure the 3 D gas kinematics of the associated high–mass star formation region, allowing us to probe the dynamical processes to within 1000 AU of the core.

We observed single pulses from PSR J0034-0721 (B0031-07) simultaneously at the MWA (185 MHz) and the GMRT (610 MHz). Correlation analyses reveal that the phase difference of the average profiles at the two frequencies differs from the phase difference observed between individual subpulses, indicating that the individual emission columns above the pulsar’s rotating carousel of sparks do not evolve in frequency in the same way that the global magnetosphere does. This hints at a possible departure from the dipolar field geometry in this pulsar’s emission region. Moreover, the discrepancy depends on the drift mode, suggestive of a way to constrain the emission heights associated with each drift mode.

Recent studies of interstellar scattering frequency evolution indicate, that for a large number of pulsars the measured scatter time to frequency scaling does not follow predictions based upon simple scattering models. The number of such deviations suggests, that what was previously known as “anomalous scattering” is actually quite normal for a large subset of the pulsar population. New observations are needed, especially at low frequencies, to study the scattering of low-DM objects. In this regard even small telescopes, such as single LOFAR stations - like PL-612 in Bałdy, near Olsztyn, Poland - can be extremely helpful.

Both the physics of the pulsar emission mechanism and free-free absorption in the intervening interstellar medium can be tested with the pulsar radio spectra. We have built on our previous work on describing LOFAR population of millisecond pulsars (MSPs; Kondratiev et al. 2016) and HBA census of slow pulsars (Bilous et al. 2016) and present the study of radio spectra of the MSPs with a special attention on the low-frequency turnover. Using LOFAR timing data allowed us to measure flux densities of many MSPs over time span of up to three years in the frequency range 110–188 MHz. This provided more reliable estimates of mean flux densities and spectra reducing the influence of refractive scintillation, ionosphere and other factors on a single flux measurement. Together with published data at other radio frequencies we constructed pulsars’ spectra and fitted them with single or broken power-laws. We discuss the obtained spectra and their fits, paying special attention to the low-frequency turnover, and compare broadband radio spectra of MSPs to those of normal pulsars.

Circumstellar SiO masers can be observed in red giant evolved stars throughout the Galaxy. Since stellar masers are not affected by non-gravitational forces, they serve as point-mass probes of the gravitational potential and form an excellent sample for studies of the Galactic structure and dynamics. Compared to optical studies, the non-obscured masers are in particular valuable when observed close to the highly obscured Galactic Bulge and Plane. Their line-of-sight velocities can easily be obtained with high accuracy, proper motions can be measured and distances can be estimated. Furthermore, when different mass and metallicity effects can be accounted for, such a large sample will highlight asymmetries and evolutionary traces in the sample. In our Bulge Asymmetries and Dynamic Evolution (BAaDE) survey we have searched 20,000 infrared selected evolved stars for 43 GHz SiO masers with the VLA in the northern Bulge and Plane and are in the process of observing another 10,000 stars for 86 GHz SiO masers with ALMA in the southern Bulge. Our instantaneous detection rate in the Bulge is close to 70%, both at 43 and 86 GHz, with occasionally up to 7 simultaneous SiO transitions observed in a single star. Here we will outline the BAaDE survey, its first results and some of the peculiar maser features we have observed. Furthermore we will discuss the prospects for obtaining proper motions and parallaxes for individual maser stars to reconstruct individual stellar orbits.

In August 2017 a new radio telescope, the Ghana Radio Astronomy Observatory (GRAO), was officially inaugurated at Kuntunse, Ghana. The GRAO is a former satellite Earth station and now the first operational station in the African VLBI Network (AVN). The Jodrell Bank Centre for Astrophysics (JBCA), supported by the UK’s STFC/Newton Fund, has developed a new pulsar timing system (Hebe) for the GRAO. We present some aspects of the design of Hebe and an outline of the first pulsar detection at GRAO.

The first few binary pulsars revealed the richness of evolution possible in binary systems containing neutron stars. Products of different evolutionary routes, in high and low mass binaries, as well as examples of evolution affected by the pulsar wind were among the first ten objects discovered. This article presents a historical review of the impact of binary pulsars on the early development of ideas regarding the evolution of neutron stars in binary systems.

We study the possibility of two types of inhomogeneous phases in core of neutron stars: one is the Coulomb crystal, which is known as quark-hadron pasta structures, and another one is chiral crystal. In the Coulomb crystal, the inhomogeneous phase appears as the result of the balance between the surface tension and the Coulomb interaction. In chiral crystal, we study the inhomogeneous chiral condensate, which has spatial modulation. In the simple model in 1+1 dimensions, this condensate has the same feature with the FFLO state, which is well known in the condensed matter physics.

Thanks to a detailed pulse phase spectroscopy of archival XMM–Newton observations, we discovered narrow and strongly phase-dependent absorption features in the X-ray spectra of two X-ray dim isolated neutron stars (XDINSs), RX J0720.4-3125 and RX J1308.6+2127. The spectral lines show similar properties: they are detected in only 20% of the rotational cycle with an energy of ~ 740 eV and appear to be stable over the timespan covered by the observations. The strong dependence on the pulsar rotation and the narrow width suggest that the features are most likely due to proton cyclotron resonant scattering in a confined magnetic structure close to the stellar surface. The inferred magnetic field in such a loop is of the order of ~ 1014 G, higher than the surface dipolar magnetic field (~ 1 – 3.5 × 1013 G for the XDINSs).

We report progress on research relating to 36.2 GHz extragalactic class I methanol masers, including a review of published work and new observations at high angular resolution. These observations reveal that extragalactic class I masers are excited in shocked gas and maybe associated with starbursts, galactic-scale outflows from active galactic nuclei (AGNs) feedback, or the inner-end region of the galactic bar. The current observational results suggests that extragalactic class I methanol masers provide a new probe for starbursts and feedback in active galaxies.