Variable OH/IR stars are Asymptotic Giant Branch (AGB) stars with an optically thick circumstellar envelope that emit strong OH 1612 MHz emission. They are commonly observed throughout the Galaxy but also in the LMC and SMC. Hence, the precise inference of the distances of these stars will ultimately result in better constraints on their mass range in different metallicity environments. Through a multi-year long-term monitoring program at the Nancay Radio telescope (NRT) and a complementary high-sensitivity mapping campaign at the eMERLIN and JVLA to measure precisely the angular diameter of the envelopes, we have been re-exploring distance determination through the phase-lag method for a sample of stars, in order to refine the poorly-constrained distances of some and infer the currently unknown distances of others. We present here an update of this project.

The majority of fast radio bursts (FRBs) are poorly localised, hindering their potential scientific yield as galactic, intergalactic, and cosmological probes. LOFT-e, a digital backend for the U.K.’s e-MERLIN seven-telescope interferometer will provide commensal search and real-time detection of FRBs, taking full advantage of its field of view (FoV), sensitivity, and observation time. Upon burst detection, LOFT-e will store raw data offline, enabling the sub-arcsecond localisation provided by e-MERLIN and expanding the pool of localised FRBs. The high-time resolution backend will additionally introduce pulsar observing capabilities to e-MERLIN.

With luminosities between those of typical Galactic OH masers and more distant OH megamasers, the masers in the nearby galaxy M82 are an interesting population which can be used to probe the physical conditions in the central starburst region of this irregular galaxy. Following on from previous low spatial resolution studies, here we present the initial results of two high-resolution observations separated by eight years. We find that some of the maser spots are resolved into multiple spatial components when observed with the EVN, as predicted by our previous studies, but that significantly less flux is recovered that that seen with the previous VLA observations. We conclude that some of this flux difference is likely due to variability but that, in common with the results seen in Arp220, there may also be a significant diffuse component.

Over the last fifty years since the discovery of pulsars, our understanding of where and how pulsars emit the radiation we observe has undergone significant revision. The location and mechanisms of high-energy radiation are intimately tied to the sites of particle acceleration. The evolution of emission models has paralleled the development of increasingly more sensitive telescopes, especially at high energies. I will review the history of pulsar emission modeling, from the early days of gaps at the polar caps, to outer gaps and slot gaps in the outer magnetosphere, to the present era of global magnetosphere simulations that locate most acceleration and high-energy emission in the current sheets.

Simultaneous measurements of the radius and mass of neutron stars (NSs) are expected from the new generation of X-ray telescopes, potentially constraining the NS equation of state (EoS). However using ‘non-unified’ EoSs with the ones for the core and the crust not based on the same nuclear model can introduce an uncertainty on the radius as large as the precision expected from these instruments. I present two solutions to this problem: a large collection of unified EoSs and an approximate and yet precise approach that, with no need of a crust EoS, provides the relation between the NS mass and radius. I discuss correlations between the NS radius and nuclear parameters, possibly allowing to constrain the NS radius with experiments on Earth. Finally, I show that in spite of the observation of massive NSs, one can not exclude that hyperons appear at high densities in NSs due to the scarcity of the available experimental data.

We present observational results of the submillimeter H2O and SiO lines toward a candidate high-mass young stellar object Orion Source I using ALMA. The spatial structures of the high excitation lines at lower-state energies of >2500 K show compact structures consistent with the circumstellar disk and/or base of the northeast-southwest bipolar outflow with a 100 au scale. The highest excitation transition, the SiO (v=4) line at band 8, has the most compact structure. In contrast, lower-excitation transitions are more extended than 200 au tracing the outflow. Almost all the line show velocity gradients perpendicular to the outflow axis suggesting rotation motions of the circumstellar disk and outflow. While some of the detected lines show broad line profiles and spatially extended emission components indicative of thermal excitation, the strong H2O lines at 321 GHz, 474 GHz, and 658 GHz with brightness temperatures of >1000 K show clear signatures of maser action.

The Low Frequency Array (LOFAR) is ideally suited to pulsar scattering studies, providing broad bands at low frequencies where the imprints of the ionized Interstellar Medium (IISM) are exaggerated. We analyse a set of sources at 110–190 MHz, and find unexpectedly shallow dependencies of pulse scatter broadening on frequency. These anomalous scattering values are discussed by considering evidence for anisotropic scattering and small scattering clouds.

Cepheus A is the second nearest high mass star-forming region after Orion. It is characterized by the presence of several phenomena, such as a complex molecular outflow, and multiple radio continuum sources, known as HW sources. The radio continuum and water maser emission have been detected toward HW2, HW3b and HW3d regions, and all of them are considered harboring young stellar objects. In 2014, we performed KaVA observations and detected a new bright maser feature, ~700 mas apart from HW3d, which has not been detected with previous VLBI observations. The relative proper motion of the new maser feature is faster than other regions. It can be a clue for a newly forming star. Alternatively, it may be caused by outflow shock from the star-forming regions such as HW3d or HW3c.

Mode changing is a phenomenon where a pulsar’s emission abruptly changes between two or more quasi-stable modes. We have discovered mode changing in the Black Widow Pulsar (PSR B1957+20), a first detection of mode changing in a millisecond pulsar. On average, a mode change occurs every 1.7 seconds. Multiple components across the pulse profile participate in the mode changing, indicating that this is likely caused by a global change in the pulsar’s magnetosphere.

Pulsars were discovered on the basis of their individual pulses, first by Jocelyn Bell and then by many others. This was chart-recorder science as computers were not yet in routine use. Single pulses carry direct information about the emission process as revealed in the detailed properties of their polarization characteristics. Early analyses of single pulses proved so dizzyingly complex that attention shifted to study of average profiles. This is turn led to models of pulsar emission beams—in particular the core/double-cone model—which now provides a foundation for understanding single-pulse sequences. We mention some of the 21stC single-pulse surveys and conclude with a brief discussion of our own recent analyses leading to the identification of the pulsar radio-emission mechanism of both slow and millsecond pulsars.

Studies of Galactic LPVs based on astrometric VLBI are presented. We use a VLBI array, “VERA”, to measure parallaxes and calibrate the K-band period luminosity relation (PLR) of the Galactic Miras. Since the PLR offers a distance indicator, its calibration is crucial to reveal their spatial distribution. Parallaxes of dozens of LPVs are presented. For the longer period stars, the mass-loss is high and the stars are obscured and recognized as OH/IR stars. We estimated mid-infrared absolute magnitudes of dozens of OH/IR stars and found that they show a loose concentration around −14 mag at λ of 11.6 μm, indicating an existence of PLR for OH/IR stars. Astrometry of OH/IR stars will also help us to study non-steady spiral arms as proposed from the latest simulation study of the galactic dynamics. We will start astrometric VLBI observation of two OH/IR stars NSV25875 and OH127.8+0.0 at 43 GHz with VERA.

The standard shock acceleration model of pulsar wind nebulae (PWNe) does not account for the hard spectrum in radio wavelengths. The origin of the radio-emitting particles is also important to determine the pair production efficiency in the pulsar magnetosphere. Here, we propose a possible resolution for the particle energy distribution in PWNe; the radio-emitting particles are not accelerated at the pulsar wind termination shock but are stochastically accelerated by turbulence inside PWNe. We upgrade our past one-zone spectral evolution model including the energy diffusion, i.e., the stochastic acceleration, and apply to the Crab Nebula. For a particle injection to the stochastic acceleration process, we consider the continuous injection from the supernova ejecta or the impulsive injection associated with supernova explosion. The observed broadband spectrum and the decay of the radio flux are reproduced by tuning the amount of the particle injected to the stochastic acceleration process. Our results imply that some unveiled mechanisms, such as back reaction to the turbulence, are required to make the energies of stochastically and shock accelerated particles comparable.

The Square Kilometre Array (SKA), reaching a collecting area of one square kilometre, will be the world’s largest radio telescope. Even in its first stage of deployment (SKA1, whose construction will be completed in 2026) it will enable transformational science on a very broad range of scientific objectives. Amongst them, there is the investigation of several Galactic and extra-galactic Masers. In this paper I will present the status of the SKA project and I will describe the capabilities of the SKA, with a focus on those that are more relevant for Maser science.

Observations of the masers in the course of RadioAstron mission yielded detections of fringes for a number of sources in both water and hydroxyl maser transitions. Several sources display numerous ultra-compact details. This proves that implementation of the space VLBI technique for maser studies is possible technically and is not always prevented by the interstellar scattering, maser beaming and other effects related to formation, transfer, and detection of the cosmic maser emission. For the first time, cosmic water maser emission was detected with projected baselines exceeding Earth Diameter. It was detected in a number of star-forming regions in the Galaxy and two megamaser galaxies NGC 4258 and NGC 3079. RadioAstron observations provided the absolute record of the angular resolution in astronomy. Fringes from the NGC 4258 megamaser were detected on baseline exceeding 25 Earth Diameters. This means that the angular resolution sufficient to measure the parallax of the water maser source in the nearby galaxy LMC was directly achieved in the cosmic maser observations. Very compact features with angular sizes about 20\muas\, have been detected in star-forming regions of our Galaxy. Corresponding linear sizes are about 5-10 million kilometers. So, the major step from milli- to micro-arcsecond resolution in maser studies is achieved by the RadioAstron mission. The existence of the features with extremely small angular sizes is established. Further implementations of the space–VLBI maser instrument for studies of the nature of cosmic objects, studies of the interaction of extremely high radiation field with molecular material and studies of the matter on the line of sight are planned.

The ongoing Green Bank North Celestial Cap pulsar survey is using the Green Bank Telescope to search for pulsars and transients over 85% of the celestial sphere. The survey has resulted in over 150 new pulsars, among which are high-precision millisecond pulsars, several binary pulsars, including at least one relativistic double neutron star system, nulling pulsars, and several nearby millisecond pulsars. We find no fast radio bursts in the survey to date. We present these results and discuss the future prospects for the survey.

We identified gigahertz-peaked spectra behavior from our radio interferometric observations at low frequencies using the Giant Metrewave Radio Telescope. We modeled the turnover spectra based on thermal free-free absorption in the interstellar medium. The free-free absorption is believed to be responsible for the inverted spectrum. Using the model, we were able to put some observational constrains on the physical parameters of the absorbing matter, which allows us to distinguish between the possible sources of absorption.

We present Kitty, an unprecedented and near simultaneous flaring event in ten transitions (6 hydroxyl, 1 water and 3 methanol), that began on 1 January 2015 in the massive star-forming region NGC6334F located in the Cat’s Paw Nebula. The brightest components in each transition increased by factors of 20 to 70 in line with a factor of ~70 increase in dust emission luminosity for the source MM1. We also report the detection of only the fifth known 4.660 GHz hydroxyl maser and that it varied in a correlated fashion with 1.720, 6.031, and 6.035 GHz hydroxyl counterparts. We postulate that if Kitty, and two historical flares in 1965 & 1999, are accretion events and are caused by the successive passages of a secondary star disrupting the accretion disk, where the frequency of occurrence is cycling down at a rate of ~2.2, it is possible another event will occur in 2022.

Pulsar glitches are thought to be probes of the superfluid interior of neutron stars. These sudden jumps in frequency observed in many pulsars are generally assumed to be the macroscopic manifestation of superfluid vortex motion on a microscopic scale. Resolving and modelling such phenomena on the scale of a neutron star is, however, a challenging problem which still remains open, fifty years after the discovery of pulsars. In this article I will review recent theoretical progress, both on the microscopic level and on the macroscopic level, and discuss which constraints on the models can be provided by observations.

We present results from long-term optical photometric observations of the Pre-Main Sequence (PMS) stars, located in the star formation region around the bright nebula NGC 7129. Using the long-term light curves and spectroscopic data, we tried to classify the PMS objects in the field and to define the reasons for the observed brightness variations. Our main goal is to explore the known PMS stars and discover new, young, variable stars. The new variable PMS star 2MASS J21403576+6635000 exhibits unusual brightness variations for very short time intervals (few minutes or hours) with comparatively large amplitudes (ΔI = 2.65 mag).

The first periodic Class II methanol maser was reported on in 2003. Since that time, a number of different monitoring programmes have found periodic masers, as well as other modes of variability. In a few cases, periodicity has been found in other maser species such as formaldehyde and water. Several distinct characteristics of light curves have been noted, possibly pointing to different underlying mechanisms for periodicity if one assumes a linear response to incoming radiation. I will give a brief overview of the known periodic sources, discuss current theories, and present new results obtained from monitoring mainline hydroxyl masers using the seven-element Karoo Array Telescope (KAT-7) during its science verification phase.