We evaluated ambipolar diffusion velocity in a magnetar. Previous studies concerning ambipolar diffusion ignored the presence of the crust, although a magnetar has both core and crust. We considered both core and crust and examined the influence of the crust in this study. We found that the crustal magnetic field can accelerate the ambipolar diffusion in its core.

Methanol and water masers indicate young stellar objects. They often exhibit flares, and a fraction shows periodic activity. Several mechanisms might explain this behavior but the lack of concurrent infrared (IR) data complicates the identification of its cause. Recently, 6.7 GHz methanol maser flares were observed, triggered by accretion bursts of high-mass YSOs which confirmed the IR-pumping of these masers. This suggests that regular IR changes might lead to maser periodicity. Hence, we scrutinized space-based IR imaging of YSOs associated with periodic methanol masers. We succeeded to extract the IR light curve from NEOWISE data for the intermediate mass YSO G107.298+5.639. Thus, for the first time a relationship between the maser and IR variability could be established. While the IR light curve shows the same period of ~34.6 days as the masers, its shape is distinct from that of the maser flares. Possible reasons for the IR periodicity are discussed.

Here we present a study of the radio frequency eclipses of the black widow pulsar J1810+1744 at low frequencies, where we are most sensitive to small deviations in the effects of material along the line of sight. Utilising the simultaneous dual beamforming and interferometric (imaging) mode of LOFAR High Band Antenna, pulsar flux variations throughout the orbit are compared for the two observing techniques to test for the presence of scattering and absorption at eclipse orbital phases. Dispersion measure and scattering variations are used as a sensitive probe into outermost edges of the eclipsing material surrounding the companion star. We find the eclipsing medium to be variable on timescales shorter than the 3.6 hr orbital period, and propose cyclotron-synchrotron absorption as the most likely primary eclipse mechanism.

The next generation of radio telescopes will have unprecedented sensitivity and time-resolution offering exciting new capabilities in time-domain science. However, this will result in very large numbers of pulsar and transient event candidates and the associated data rates will be technically challenging in terms of data storage and signal processing. Automated detection and classification techniques are therefore required and must be optimized to allow high-throughput data processing in real time. In this paper we provide a summary of the emerging machine learning techniques being applied to this problem.

Masers are becoming increasingly important probes of high-mass star formation, revealing details about the kinematics and physical conditions at the elusive, early stages of formation. Over the last decade significant investment has been made in a number of large-scale, sensitive maser surveys targeting transitions found in the vicinity of young, high-mass stars. Individually, these searches have led to valuable insights into maser populations, their associated star formation regions, and often revealed further details such as Galactic structure. In combination, they become even more powerful, especially when considered together with complementary multi-wavelength data. Another consequence of large maser surveys has been the identification of a number of especially interesting sources that have been the subject of subsequent detailed studies. I summarize the recent plethora of maser surveys, their results, and how they are contributing to our understanding of star formation. Ongoing searches will ensure a bright future of maser surveys in the decade to come.

Water megamaser emission is powerful in tracing the inner region of active nuclei, mapping accretion disks and providing important clues on their absorption properties. From the X-ray spectra of AGN it is possible to estimate the intrinsic power of the central engine and the obscuring column density. The synergy between X-ray and water maser studies allows us to tackle the AGN inner physics from different perspectives. For a complete sample of AGN selected in the 20-40 keV energy range, we have investigated the presence of water maser emission and its connection to the X-ray emission, absorption and accretion rate. The hard X-ray selection of the sample results in a water maser detection rate much higher than those obtained from optically-selected samples.

Through the observations and the analysis of maser polarization it is possible to measure the magnetic field in several astrophysical environments (e.g., star-forming regions, evolved stars). In particular from the linearly and circularly polarized emissions we can determine the orientation and the strength of the magnetic field, respectively. In these proceedings the implications, on observed data, of the new estimation of the Landé g-factors for the CH3OH maser are presented. Furthermore, some example of the most recent results achieved in observing the polarized maser emission from several maser species will also be reported.

Population of high quantum number states can differ from their LTE values at high densities (Ne ~106 − 108 cm−3) and temperatures of the order of 104 K. In this case, the intensity of recombination lines can be strongly amplified. The amount of amplification depends on density and temperature, and it is different for different quantum numbers, allowing the determination of the physical and kinematic conditions of the emitting region through the observation of recombination lines of different quantum numbers. This was the case of the massive binary system η Carinae. This system was observed with ALMA in the recombination lines H21α, H28α, H30α, H40α and H42α and the continuum at the frequencies of the corresponding lines. The continuum spectrum was characteristic of a compact HII region, becoming optically thin at around 300 GHz. From the intensity and width of the recombination lines we concluded that the not-resolved emission region, assumed spherically symmetric, is a shell of 40 AU radius and 4 AU width, expanding at velocities between 20 and 60 km s−1, with density of 107 cm−3 and temperature of 17000 K.

In this short overview we summarize our knowledge of twenty five pulsars showing GPS characteristics. Especially, we will focus on two objects. The first is PSR B1800–21 - a Vela-like GPS pulsar with a variable spectrum. The second is PSR J1740+1000 - a pulsar that shows high frequency turnover based on our most recent observations using the Giant Meterwave Radio Telescope and the Green Bank Telescope.

PSR B1828–11 is a young pulsar once thought to be undergoing free precession and recently found instead to be switching magnetospheric states in tandem with spin-down changes. Here we show the two extreme states of the mode-changing found for this pulsar and comment briefly on its interpretation.

The Central Molecular Zone (CMZ), the inner 450 pc of our Galaxy, is an exceptional region where the volume and column densities, gas temperatures, velocity dispersions, etc. are much higher than in the Galactic plane. It has been suggested that the formation of stars and clusters in this area is related to the orbital dynamics of the gas. The complex kinematic structure of the molecular gas was revealed by spectral line observations. However, these results are limited to the line-of-sight-velocities. To fully understand the motions of the gas within the CMZ, we have to know its location in 6D space (3D location + 3D motion). Recent orbital models have tried to explain the inflow of gas towards and its kinematics within this region. With parallax and proper motion measurements of masers in the CMZ we can discriminate among these models and constrain how our Galactic Center is fed with gas.

Transitional millisecond pulsars (tMSPs), which are systems that harbor a pulsar in the throes of the recycling process, have emerged as a new source class since the discovery of the first such system a decade ago. These systems switch between accretion-powered low-mass X-ray binary (LMXB) and rotation-powered radio millisecond pulsar (RMSP) states, and provide exciting avenues to understand the physical processes that spin-up neutron stars to millisecond periods. During the last decade, three tMSPs, as well as a candidate source, have been extensively probed using systematic, multi-wavelength campaigns. Here we review the observational highlights from these campaigns and our general understanding of tMSPs.

The discovery of pulsars was closely followed by the discovery of dispersion and scattering in the interstellar plasma (ionized interstellar medium - IISM). The rich phenomena of scattering and scintillation have since been successfully modelled as propagation through a statistically uniform plasma turbulence with an isotropic Kolmogorov spectrum of density. However, this enticingly simple model fails to explain the many recent observations, that show anisotropic scattering from highly localized regions of the IISM often referred to as phase screens. I summarize the recent evidence from pulsars and also from very compact AGN sources, which can exhibit rapid scintillation and occasionally ESEs. The unknown astrophysical origin of these phenomena includes thin current sheets, the diffuse remnants of old supernova shells, and plasma filaments surrounding ubiquitous molecular clumps near young hot stars.

The Square Kilometre Array (SKA) will be sensitive enough to discover all of the pulsars in the Milky Way that are beamed towards Earth. Already in the initial deployment, SKA Phase 1, it will make significant advances in pulsar science. In these proceedings I briefly overview what the SKA is, and describe its pulsar search and timing capabilities.

The Astronomical Observatory in Cagliari (OAC) is a growing facility with a group devoted to pulsar studies across the electromagnetic spectrum. Taking advantage of this expertise we have worked to provide a suite of multi-wavelength software and databases for the observations of pulsars and compact Galactic objects at the Sardinia Radio Telescope (SRT, Bolli et al. 2015, Prandoni et al. 2017).

Low-frequency pulsar observations are well suited for studying propagation effects caused by the interstellar medium (ISM). This is particularly important for millisecond pulsars (MSPs) that are part of high-precision timing applications such as pulsar timing arrays (PTA), which aim to detect nanoHertz gravitational waves. MSPs in the southern hemisphere will also be the prime targets for PTAs with the South African MeerKAT, and eventually with the SKA. The development of the Murchison Widefield Array (MWA) and the Engineering Development Array (EDA) brings excellent opportunities for low-frequency studies of MSPs in the southern hemisphere. They enable observations at frequencies from 50 MHz to 300 MHz, and can be exploited for a wide range of studies relating to pulsar emission physics and probing the ISM.

We initiated a long-term and highly frequent monitoring project toward 442 methanol masers at 6.7 GHz (Dec >−30 deg) using the Hitachi 32-m radio telescope in December 2012. The observations have been carried out daily, monitoring a spectrum of each source with intervals of 9–10 days. In September 2015, the number of the target sources and intervals were redesigned into 143 and 4–5 days, respectively. This monitoring provides us complete information on how many sources show periodic flux variations in high-mass star-forming regions, which have been detected in 20 sources with periods of 29.5–668 days so far (e.g., Goedhart et al. 2004). We have already obtained new detections of periodic flux variations in 31 methanol sources with periods of 22–409 days. These periodic flux variations must be a unique tool to investigate high-mass protostars themselves and their circumstellar structure on a very tiny spatial scale of 0.1–1 au.

The upgraded GMRT (uGMRT) with its unprecedented sensitivity and high figure of merit, is expected to result in the discovery of a large population of pulsars including pulsars of previously unknown type. In the phase-2 of the GMRT High Resolution Southern Sky (GHRSS) survey with the uGMRT we will reach 1/4th of sensitivity of the SKA Phase-1. In this paper we highlight the salient features of the survey of pulsars and fast transients with the uGMRT highlighting its discovery potential. The extended GMRT (eGMRT) equipped with wide field-of-view, increased collecting area will have unprecedented sensitivity in time-domain astronomy, reaching close to SKA-Phase1. Many fold increase in the number of elements, increase in the baseline length and addition of phased array feed will make eGMRT an excellent instrument for the survey of pulsars and transients with a promise of detecting large variety of pulsars and fast radio bursts.

The Sardinia Radio Telescope (SRT) is a modern, fully-steerable 64-m dish located in San Basilio, Sardinia (Italy). It is characterized by an active surface that allows it to cover a wide range of radio frequencies (300 MHz to 100 GHz). During SRT’s commissioning phase, we installed the hardware and software needed for pulsar observations. Since then, SRT has taken part in Large European Array for Pulsars and European Pulsar Timing Array observations for the purpose of gravitational wave detection. We have installed a new S-band receiver that will allow us to search for pulsars in the Galactic Center. We also plan to combine our efforts to search for Extraterrestrial Intelligence (SETI) with the search for pulsars and Fast Radio Bursts.

We have used LOFAR to perform targeted millisecond pulsar surveys of Fermi γ-ray sources. Operating at a center frequency of 135 MHz, the surveys use a novel semi-coherent dedispersion approach where coherently dedispersed trials at coarsely separated dispersion measures are incoherently dedispersed at finer steps. Three millisecond pulsars have been discovered as part of these surveys. We describe the LOFAR surveys and the properties of the newly discovered pulsars.