Using the SDSS and Pan-STARRS1 survey data, we found a likely companion of the recently discovered binary γ-ray radio-loud millisecond pulsar J0621+2514. Its visual brightness is about 22 mag. The broadband magnitudes and colours suggest that this is a white dwarf. Comparing the data with various white dwarfs evolutionary tracks, we found that it likely belongs to a class of He-core white dwarfs with a temperature of about 10 000 K and a mass of ≲ 0.5 M⊙. For a thin hydrogen envelope of the white dwarf, its cooling age is ≲ 0.5 Gyr which is smaller than the pulsar characteristic age of 1.8 Gyr. This may indicate that the pulsar age is overestimated. Otherwise, this may be explained by the presence of a thick hydrogen envelope or a low metallicity of the white dwarf progenitor.

Spherical coordinate systems, which are ubiquitous in astronomy, cannot be shown without distortion on flat, two-dimensional surfaces. This poses challenges for the two complementary phases of visual exploration—making discoveries in data by looking for relationships, patterns, or anomalies—and publication—where the results of an exploration are made available for scientific scrutiny or communication. This is a long-standing problem, and many practical solutions have been developed. Our allskyVR approach provides a workflow for experimentation with commodity virtual reality head-mounted displays. Using the free, open source s2plot programming library, and the A-Frame WebVR browser-based framework, we provide a straightforward way to visualise all-sky catalogues on a user-centred, virtual celestial sphere. The allskyVR distribution contains both a quickstart option, complete with a gaze-based menu system, and a fully customisable mode for those who need more control of the immersive experience. The software is available for download from https://github.com/cfluke/allskyVR.

The shaping of various morphological features of planetary nebulae is increasingly linked to the role of binary central stars. Identifying a binary within a planetary nebula offers a powerful tool with which to directly investigate the formation mechanisms behind these features. The Etched Hourglass Nebula, MyCn 18, is the archetype for several binary-linked morphological features, yet it has no identified binary nucleus. It has the fastest jets seen in a planetary nebula of 630 km s−1, a central star position offset from the nebula centre, and a bipolar nebula with a very narrow waist. Here we report on the Southern African Large Telescope High Resolution Spectrograph detection of radial velocity variability in the nucleus of MyCn 18 with an orbital period of 18.15 ± 0.04 d and a semi-amplitude of 11.0 ± 0.3 km s−1. Adopting an orbital inclination of 38 ± 5° and a primary mass of 0.6 ± 0.1 M⊙ yields a secondary mass of 0.19 ± 0.05 M⊙ corresponding to an M5V companion. The detached nature of the binary rules out a classical nova as the origin of the jets and the offset central star as hypothesised in the literature. Furthermore, scenarios that produce the offset central star during the AGB and that form narrow waist bipolar nebulae result in orbital separations 80–800 times larger than observed in MyCn 18. The inner hourglass and jets may have formed from part of the common envelope ejecta that remained bound to the binary system in a circumbinary disk, whereas the offset central star position may best be explained by proper motion. Detailed simulations of MyCn 18 are encouraged that are compatible with the binary nucleus to further investigate its complex formation history.

We communicate the discovery of a new globular cluster in the Galaxy that was first detected on WISE/2MASS images and is now confirmed with VVVX photometry. It is a Palomar-like cluster projected at ℓ = 359.15°, b = 5.73°, and may be related to the bulge. We derive an absolute magnitude of MV ≈ −3.3, thus being an underluminous globular cluster. Our analyses provide a reddening of E(B − V) = 1.08 ± 0.18 and a distance to the Sun d⊙ = 6.3 ± 1 kpc, which implies a current position in the bulge volume. The estimated metallicity is [Fe/H] = −1.5 ± 0.25. It adds to the recently discovered faint globular cluster (Minniti 22) and candidates found with VVV, building up expectations of ≈50 globular clusters yet to be discovered in the bulge. We also communicate the discovery of an old open cluster in the same VVVX tile as the globular cluster. The VVVX photometry provided E(B − V) = 0.62 ± 0.1, d⊙ = 7.6 ± 1 kpc, and an age of 1.5 ± 0.3 Gyr. With a height from the plane of ≈0.8 kpc, it adds to nine Gyr-class clusters recently discovered within 0.8 ⩽ Z ⩽ 2.2 kpc, as recently probed in the single VVV tile b201. We suggest that these findings may be disclosing the thick disk at the bulge, which so far has no open cluster counterpart, and hardly any individual star. Thus, the VVV and VVVX surveys are opening new windows for follow-up studies, to employ present and future generations of large aperture telescopes.

The luminosity function is a fundamental observable for characterising how galaxies form and evolve throughout the cosmic history. One key ingredient to derive this measurement from the number counts in a survey is the characterisation of the completeness and redshift selection functions for the observations. In this paper, we present GLACiAR, an open python tool available on GitHub to estimate the completeness and selection functions in galaxy surveys. The code is tailored for multiband imaging surveys aimed at searching for high-redshift galaxies through the Lyman-break technique, but it can be applied broadly. The code generates artificial galaxies that follow Sérsic profiles with different indexes and with customisable size, redshift, and spectral energy distribution properties, adds them to input images, and measures the recovery rate. To illustrate this new software tool, we apply it to quantify the completeness and redshift selection functions for J-dropouts sources (redshift z ~ 10 galaxies) in the Hubble Space Telescope Brightest of Reionizing Galaxies Survey. Our comparison with a previous completeness analysis on the same dataset shows overall agreement, but also highlights how different modelling assumptions for the artificial sources can impact completeness estimates.

We report the discovery of the ultra-luminous quasi-stellar object SMSS J215728.21−360215.1 with magnitude z = 16.9 and W4 = 7.42 at redshift 4.75. Given absolute magnitudes of M145, AB = −29.3, M300, AB = −30.12, and logLbol/Lbol, ⊙ = 14.84, it is the quasi-stellar object with the highest unlensed UV-optical luminosity currently known in the Universe. It was found by combining proper-motion data from Gaia DR2 with photometry from SkyMapper DR1 and the Wide-field Infrared Survey Explorer. In the GAIA database, it is an isolated single source and thus unlikely to be strongly gravitationally lensed. It is also unlikely to be a beamed source as it is not discovered in the radio domain by either NRAO-VLA Sky Survey or Sydney University Molonglo Southern Survey. It is classed as a weak-emission-line quasi-stellar object and possesses broad absorption line features. A lightcurve from ATLAS spanning the time from 2015 October to 2017 December shows little sign of variability.

We analyse observations of a saddle-like structure in the corona above the western limb of the Sun on 2017 July 18. The structure was clearly outlined by coronal loops with typical coronal temperature no more than 1 MK. The dynamics of loops showed convergence towards the centre of the saddle in the vertical direction and divergence in the horizontal direction. The event is a clear example of smooth coronal magnetic field reconnection. No heating manifestations in the reconnection region or magnetically connected areas were observed. Potential magnetic field calculations, which use as the boundary condition the SDO/HMI magnetogram taken on July 14, showed the presence of a null point at the height of 122 arcsec above the photosphere just at the centre of the saddle structure. The shape of field lines fits the fan-spine magnetic configuration above NOAA 2666.

We present orbit analysis for a sample of eight inner bulge globular clusters, together with one reference halo object. We used proper motion values derived from long time base CCD data. Orbits are integrated in both an axisymmetric model and a model including the Galactic bar potential. The inclusion of the bar proved to be essential for the description of the dynamical behaviour of the clusters. We use the Monte Carlo scheme to construct the initial conditions for each cluster, taking into account the uncertainties in the kinematical data and distances. The sample clusters show typically maximum height to the Galactic plane below 1.5 kpc, and develop rather eccentric orbits. Seven of the bulge sample clusters share the orbital properties of the bar/bulge, having perigalactic and apogalatic distances, and maximum vertical excursion from the Galactic plane inside the bar region. NGC 6540 instead shows a completely different orbital behaviour, having a dynamical signature of the thick disc. Both prograde and prograde–retrograde orbits with respect to the direction of the Galactic rotation were revealed, which might characterise a chaotic behaviour.

The dynamics of quantised vorticity in neutron star interiors is at the heart of most pulsar glitch models. However, the large number of vortices (up to ≈1013) involved in a glitch and the huge disparity in scales between the femtometre scale of vortex cores and the kilometre scale of the star makes quantum dynamical simulations of the problem computationally intractable. In this paper, we take a first step towards developing a mean field prescription to include the dynamics of vortices in large-scale hydrodynamical simulations of superfluid neutron stars. We consider a one-dimensional setup and show that vortex accumulation and differential rotation in the neutron superfluid lead to propagating waves, or ‘avalanches’, as solutions for the equations of motion for the superfluid velocities. We introduce an additional variable, the fraction of free vortices, and test different prescriptions for its advection with the superfluid flow. We find that the new terms lead to solutions with a linear component in the rise of a glitch, and that, in specific setups, they can give rise to glitch precursors and even to decreases in frequency, or ‘anti-glitches’.

We detail tentative detections of low-frequency carbon radio recombination lines from within the Orion molecular cloud complex observed at 99–129 MHz. These tentative detections include one alpha transition and one beta transition over three locations and are located within the diffuse regions of dust observed in the infrared at 100 μm, the Hα emission detected in the optical, and the synchrotron radiation observed in the radio. With these observations, we are able to study the radiation mechanism transition from collisionally pumped to radiatively pumped within the H ii regions within the Orion molecular cloud complex.

Astrophysical measurements regarding compact stars are just ahead of a big evolution jump, since the NICER experiment deployed on ISS on 2017 June 14. This will provide soon data that would enable the determination of compact star radius with less than 10% error. This can be further constrained by the new observation of gravitational waves originated from merging neutron stars, GW170817. This poses new challenges to nuclear models aiming to explain the structure of super dense nuclear matter found in neutron stars. Detailed studies of the QCD phase diagram show the importance of bosonic quantum fluctuations in the cold dense matter equation of state. Here we used a demonstrative model with one bosonic and one fermionic degree of freedom coupled by Yukawa coupling, we show the effect of bosonic quantum fluctuations on compact star observables such as mass, radius, and compactness. We have also calculated the difference in the value of compressibility which is caused by quantum fluctuations. The above-mentioned quantities are calculated in the mean field, one-loop, and in high order many loop approximation. The results show that the magnitude of these effects is in the range of 4–5%, which place it into the region where modern measurements may detect it. This forms a base for further investigations that how these results carry over to more complicated models.

Surface abundance observations of halo stars hint at the occurrence of r-process nucleosynthesis at low metallicity ([Fe/H] < -3), possibly within the first 108 yr after the formation of the first stars. Possible loci of early-Universe r-process nucleosynthesis are the ejecta of either black hole–neutron star or neutron star–neutron star binary mergers. Here, we study the effect of the inclination–eccentricity oscillations raised by a tertiary (e.g. a star) on the coalescence time-scale of the inner compact object binaries. Our results are highly sensitive to the assumed initial distribution of the inner binary semi-major axes. Distributions with mostly wide compact object binaries are most affected by the third object, resulting in a strong increase (by more than a factor of 2) in the fraction of fast coalescences. If instead the distribution preferentially populates very close compact binaries, general relativistic precession prevents the third body from increasing the inner binary eccentricity to very high values. In this last case, the fraction of coalescing binaries is increased much less by tertiaries, but the fraction of binaries that would coalesce within 108 yr even without a third object is already high. Our results provide additional support to the compact-binary merger scenario for r-process nucleosynthesis.

The recent observations in the high energy γ-ray band show that the extragalactic γ-ray sky is dominated by the emission from blazars. However, γ-ray emission from other types of AGNs, e.g., radiogalaxies, also have been detected. These sources were not considered as favored GeV emitters because the nonthermal emission from their jets is less Doppler boosted. Now, the γ-ray emission from more than 25 non-blazar AGNs has been already detected which opened a new window to have an insight into the particle acceleration and emission processes in different components of AGNs. Here, I will present the γ-ray variability of two well-known radiogalaxies, NGC 1275 and 3C 120, which show a rapid flux increase in the γ-ray band.

We present deep low radio frequency (230-470 MHz) observations from the Karl G. Jansky Very Large Array of the Perseus cluster, probing the non-thermal emission from the old particle population of the AGN outflows. Our observations of this nearby relaxed cool core cluster have revealed a multitude of new structures associated with the mini-halo, extending to hundreds of kpc in size. Its irregular morphology seems to have been influenced both by the AGN activity and by the sloshing motion of the cluster’ gas. In addition, it has a filamentary structure similar to that seen in radio relics found in merging clusters. These results illustrate the high-quality images that can be obtained with the new JVLA at low radio-frequencies.

We re-analyzed OJ287 in 120 Very Long Baseline Array (VLBA, MOJAVE) observations (at 15 GHz) covering the time span between Apr. 1995 and Apr. 2017. We find that the radio jet motion over the sky is consistent with a precessing and nutating jet source. The variability of the radio flux-density can be explained by Doppler beaming due to a change in the viewing angle. We suggest that part of the optical emission is due to synchrotron emission related to the jet radiation. We find a strikingly similar scaling for the timescales for precession and nutation as indicated for SS433 with a factor of roughly 50 times longer in OJ287.

An abundance of information about the magnetic (B) fields of relativistic AGN jets has been obtained through radio polarization observations made on a wide range of scales, from the parsec scales probed by Very Long Baseline Interferometry to the kiloparsec scales probed by instruments such as the the Jansky Very Large Array and e-MERLIN. The observed radio emission is synchrotron radiation, for which the linear polarization angles in optically thin regions is orthogonal to the local synchrotron B fields. The characteristic B field structures observed for these jets on parsec scales are described. A key question is whether B field structures observed in particular AGN jets come about primarily due to “global” effects such as the intrinsic B field of the jet itself, which is expected to be helical, or local phenomena such as shocks, shear and bending of the jets. Observational criteria that can be used to try to distinguish between various possible origins for observed B field structures are described. There is now considerable evidence that the relativistic jets of AGNs do indeed carry helical B fields, with the observed polarization also sometimes appreciably influenced by local effects. Patterns seen in the helical B field components, indicated for example by Faraday rotation observations, provide unique information about the processes involved in the generation of these helical B fields. The collected observations on parsec and kiloparsec scales provide weighty evidence that an important role is played by the action of a cosmic “battery” that acts to generate an inward current along the jet axis and an outward current in a more extended region surrounding the jet.

NGC 1275 is one of the best targets to study the high energy emission mechanism in radio galaxies and the accretion flow properties using a young re-started jet 3C 84 as a prober of subpc-to-pc scale environment. In this proceeding, we review the observation results from a series of our VLBI observations and discuss on the origin of gamma-ray emission and accretion flow properties. We also briefly present the preliminary results from our recent ALMA observations.

As revealed by the Fermi-LAT, blazars represent the dominant population of γ-ray emitters. An essential step for understanding blazar physics and the emission mechanisms is the investigation of a possible connection between the observed low- and high-energy emission. A number of works report on the existence of a significant correlation between radio emission and 0.1-100 GeV γ rays. How does this correlation evolve when very high energy (VHE, E > 0.1 TeV) γ rays are considered? The possible radio-VHE emission connection is still elusive mainly because of the lack of a homogeneous VHE sky coverage. In this work we explore the connection between the parsec-scale radio emission and GeV-TeV γ rays by using two unbiased blazar samples extracted from the 1FHL ( E > 10 GeV) and 2FHL (E > 50 GeV) Fermi catalogs. For comparison, we perform the same analysis by using the 3FGL 0.1-300 GeV γ-ray energy flux. Overall, we find out that there is no significant connection between radio and γ-ray emission above 10 GeV for all the blazar sub-classes with the exception of high synchrotron peaked objects. Conversely, when 0.1-300 GeV γ-ray energies are considered, a strong and significant correlation is found for all of the blazar sub-classes. We interpret these results within the context of the blazar spectral energy distribution properties.