Bow shocks generated by pulsars moving through weakly ionised interstellar medium (ISM) produce emission dominated by non-equilibrium atomic transitions. These bow shocks are primarily observed as Hα nebulae. We developed a package, named Shu, that calculates non-LTE intensity maps in more than 150 spectral lines, taking into account geometrical properties of the pulsars’ motion and lines of sight. We argue here that atomic (C I, N I, O I) and ionic (S II, N II, O III, Ne IV) transitions can be used as complementary and sensitive probes of ISM. We perform self-consistent 2D relativistic hydrodynamic calculations of the bow shock structure and generate non-LTE emissivity maps, combining global dynamics of relativistic flows, and detailed calculations of the non-equilibrium ionisation states. We find that though typically Hα emission is dominant, spectral fluxes in [O III], [S II] and [N II] may become comparable for relatively slowly moving pulsars. Overall, morphology of non-LTE emission, especially of the ionic species, is a sensitive probe of the density structures of the ISM.

Petabytes of archival high time resolution observations have been captured with the Murchison Widefield Array. The search for Fast Radio Bursts within these using established software has been limited by its inability to scale on supercomputing infrastructure, necessary to meet the associated computational and memory requirements. Hence, past searches used a coarse integration time, in the scale of seconds, or analysed an insufficient number of hours of observations. This paper introduces BLINK, a novel radio interferometry imaging software for low-frequency FRB searches to be run on modern supercomputers. It is implemented as a suite of software libraries executing all computations on GPU, supporting both AMD and NVIDIA hardware vendors. These libraries are designed to interface with each other and to define the BLINK imaging pipeline as a single executable program. Expensive I/O operations between imaging stages are not necessary because the stages now share the same memory space and data representation. BLINK is the first imaging pipeline implementation able to fully run on GPUs as a single process, further supporting AMD hardware and enabling Australian researchers to take advantage of Pawsey’s Setonix supercomputer. In the millisecond-scale time resolution imaging test case illustrated in this paper, representative of what is required for FRB searches, the BLINK imaging pipeline achieves a 3687x speedup compared to a traditional MWA imaging pipeline employing WSClean.

The outer solar system is theoretically predicted to harbour an undiscovered planet, often referred to as Planet Nine. Simulations suggest that its gravitational influence could explain the unusual clustering of minor bodies in the Kuiper Belt. However, no observational evidence for Planet Nine has been found so far, as its predicted orbit lies far beyond Neptune, where it reflects only a faint amount of Sunlight. This work aims to find Planet Nine candidates by taking advantage of two far-infrared all-sky surveys, which are IRAS and AKARI. The epochs of these two surveys were separated by 23 years, which is large enough to detect Planet Nine’s ∼ 3′/year orbital motion. We use a dedicated AKARI Far-Infrared point source list for the purpose of our Planet Nine search — AKARI-FIS Monthly Unconfirmed Source List (AKARI-MUSL), which includes sources detected repeatedly only in hours timescale, but not after months. AKARI-MUSL is more advantageous than the AKARI Bright Source Catalogue (AKARI-BSC) for detecting moving and faint objects like Planet Nine with a twice-deeper flux detection limit. We search for objects that moved slowly between IRAS and AKARI detections given in the catalogues. First, we estimated the expected flux and orbital motion of Planet Nine by assuming its mass, distance, and effective temperature to ensure it can be detected by IRAS and AKARI, then applied the positional and flux selection criteria to narrow down the number of sources from the catalogues. Next, we produced all possible candidate pairs including one IRAS source and one AKARI source whose angular separations were limited between 42′ and 69.6′, corresponding to the heliocentric distance range of 500 – 700 AU and the mass range of 7 – 17M⊕. There are 13 candidate pairs obtained after the selection criteria. After image inspection, we found one good candidate, of which the IRAS source is absent from the same coordinate in the AKARI image after 23 years and vice versa. However, AKARI and IRAS detections are not enough to determine the full orbit of this candidate. This issue leads to the need for follow-up observations, which will determine the Keplerian motion of our Planet Nine candidate.

We introduce a new approach to quantifying dust in galaxies by combining information from the Balmer decrement (BD) and the dust mass (Md). While there is no explicit correlation between these two properties, they jointly probe different aspects of the dust present in galaxies. We explore two new parameters that link BD with Md by using star formation rate sensitive luminosities at several wavelengths (ultraviolet, Hα, and far-infrared). This analysis shows that combining the BD and Md in these ways provides new metrics that are sensitive to the degree of optically thick dust affecting the short wavelength emission. We show how these new “dust geometry” parameters vary as a function of galaxy mass, star formation rate, and specific star formation rate. We demonstrate that they are sensitive probes of the dust geometry in galaxies, and that they support the “maximal foreground screen” model for dust in starburst galaxies.

The potential of a galaxy to host habitable planets is one of the most important questions in astrobiology. It is tightly connected to the evolution of galaxy-scale properties and the underlying cosmological processes. Using the improved cosmological simulation IllustrisTNG, we revisit the claim that a population of small, metal-rich, star-forming galaxies (“Cloudlet”), forms a local peak on the mass-metallicity relation, reflecting an enhanced galactic habitability potential. We refine the earlier analysis by applying updated filtering criteria to identify a more refined sample, further selecting objects based on their history. This process resulted in a confirmed sample of 97 dwarf galaxies, alongside 519 additional structures of uncertain origin, potentially comprising both numerical artefacts and unrecognized physical systems. Under these stricter conditions, the proposed bimodality in galactic habitability is strongly diminished. However, the astrobiological potential of metal-rich dwarfs, most of which are compact remnants of more massive galaxies that underwent tidal stripping, is a thrilling area of exploration. Although dense stellar environments are traditionally seen as inhospitable, recent studies highlight the role of dynamic environments in enhancing the distribution of biological material. Furthermore, the potential habitability of tidal structures formed in the aftermath of galactic interactions is a fascinating possibility. Our findings suggest that non-traditional structures support conditions favourable for life, opening up exciting new avenues for astrobiological research. This research underscores the need for a holistic approach to studying habitability that moves beyond planetary and stellar-focused frameworks to incorporate the broader galactic environment. Understanding the interactions between galaxies, their evolution, and the influence of their surroundings is essential to developing a more comprehensive model of how and where life might emerge and persist across the Universe.

An unusual orbital element clustering of Kuiper belt objects (KBOs) has been observed. The most promising dynamic solution is the presence of a giant planet in the outer Solar system, Planet Nine. However, due to its extreme distance, intensive searches in optical have not been successful. We aim to find Planet Nine in the far-infrared, where it has the peak of the black body radiation, using the most sensitive all-sky far-infrared survey to date, AKARI. In contrast to optical searches, where the energy of reflected sunlight decreases by $d^{4}$, thermal radiation in the infrared decreases with the square of the heliocentric distance $d^{2}$. We search for moving objects in the AKARI Single Scan Detection List. We select sources from a promising region suggested by an N-body simulation from Millholland and Laughlin 2017: $30^{\circ}\lt$ R.A. $\lt50^{\circ}$ and $-20^{\circ}\lt$ Dec. $\lt20^{\circ}$. Known sources are excluded by cross-matching AKARI sources with 9 optical and infrared catalogues. Furthermore, we select sources with small background strength to avoid sources in the cirrus. Since Planet Nine is stationary in a timescale of hours but moves on a monthly scale, our primary strategy is to select slowly moving objects that are stationary in 24 h but not in six months, using multiple single scans by AKARI. The selected slowly moving AKARI sources are scrutinised for potential contamination from cosmic rays. Our analysis reveals two possible Planet Nine candidates whose positions and flux are within the theoretical prediction ranges. These candidates warrant further investigation through follow-up observations to confirm the existence and properties of Planet Nine.

We measured the harmonic-space power spectrum of galaxy clustering auto-correlation from the Evolutionary Map of the Universe Pilot Survey 1 data (EMU PS1) and its cross-correlation with the lensing convergence map of cosmic microwave background (CMB) from Planck Public Release 4 at the linear scale range from l = 2 to 500. We applied two flux density cuts at 0.18 and 0.4mJy on the radio galaxies observed at 944MHz and considered two source detection algorithms. We found the auto-correlation measurements from the two algorithms at the 0.18mJy cut to deviate for l ≳ 250 due to the different criteria assumed on the source detection and decided to ignore data above this scale. We report a cross-correlation detection of EMU PS1 with CMB lensing at ∼5.5σ, irrespective of flux density cut. In our theoretical modelling we considered the SKADS and T-RECS redshift distribution simulation models that yield consistent results, a linear and a non-linear matter power spectrum, and two linear galaxy bias models. That is a constant redshift-independent galaxy bias b(z) = bg and a constant amplitude galaxy bias b(z) = bg/D(z). By fixing a cosmology model and considering a non-linear matter power spectrum with SKADS, we measured a constant galaxy bias at 0.18mJy (0.4mJy) with and a constant amplitude bias with . When σ8 is a free parameter for the same models at 0.18mJy (0.4mJy) with the constant model we found , while with the constant amplitude model we measured , respectively. Our results agree at 1σ with the measurements from Planck CMB and the weak lensing surveys and also show the potential of cosmology studies with future radio continuum survey data.

Before a binary system enters into a common envelope (CE) phase, accretion from the primary star onto the companion star through Roche Lobe overflow (RLOF) will lead to the formation of an accretion disk, which may generate jets. Accretion before and during the CE may alter the outcome of the interaction. Previous studies have considered different aspects of this physical mechanism. Here we study the properties of an accretion disk formed via 3D hydrodynamic simulations of the RLOF mass transfer between a 7 M⊙, red supergiant star and a 1.4 M⊙, neutron star companion. We simulate only the volume around the companion for improved resolution. We use a 1D implicit MESA simulation of the evolution of the system during 30 000 years between the on-set of the RLOF and the CE to guide the binary parameters and the mass-transfer rate, while we simulate only 21 years of the last part of the RLOF in 3D using an ideal gas quasi-isothermal equation of state. We expect that a pre-CE disk under these parameters will have a mass of ∼ 5 × 10–3 M⊙ and a radius of ∼40 R⊙ with a scale height of ∼5 R⊙. The temperature profile of the disk is shallower than that predicted by the formalism of Shakura and Sunyaev, but more reasonable cooling physics would need to be included. We stress test these results with respect to a number of physical and numerical parameters, as well as simulation choices, and we expect them to be reasonable within a factor of a few for the mass and 15% for the radius. We also contextualise our results within those presented in the literature, in particular with respect to the dimensionality of simulations and the adiabatic index. We discuss the measured accretion rate in the context of the Shakura and Sunyaev formalism and debate the viscous mechanisms at play, finishing with a list of prospects for future work.

The scatter in global atomic hydrogen (Hi) scaling relations is partly attributed to differences in how Hi and stellar properties are measured, with Hi reservoirs typically extending beyond the inner regions of galaxies where star formation occurs. Using pilot observations from the Widefield ASKAP L-band Legacy All-sky Blind Survey (WALLABY), we present the first measurements of Hi mass enclosed within the stellar-dominated regions of galaxies for a statistical sample of 995 local gas-rich systems, investigating the factors driving its variation. We examine how global Hi scaling relations change when measurements are restricted to $R_{\text{25}}$ and $R_{\text{24}}$ – the isophotal radii at 25 and 24 mag arcsec$^{-2}$ in the i-band – and explore how the fraction of Hi mass and Hi surface density within these radii correlate with other galaxy properties. On average, 68% of the total Hi mass is enclosed within $R_{\text{25}}$ and 54% within $R_{\text{24}}$, though significant variation exists between galaxies, ranging from $\sim$20% to 100%. The fraction of Hi mass within $R_{\text{25}}$ shows a mild correlation with stellar properties, with galaxies of higher stellar mass, greater stellar surface density, or redder colours enclosing a larger fraction of their Hi reservoirs. These correlations do not significantly strengthen when considering $R_{\text{24}}$. Conversely, global Hi surface densities show no significant correlation with stellar mass or stellar surface density, but trends start emerging when these are measured within the inner regions of galaxies. The strongest correlation is observed with optical colour, with bluer galaxies having higher average Hi surface densities within $R_{\text{25}}$. This trend of the average Hi surface density with optical colour strengthens when we restrict from $R_{\text{25}}$ to $R_{\text{24}}$, suggesting a closer connection between inner Hi reservoirs and star formation. This study underscores the value of (at least marginally) resolved Hi surveys of statistical samples for advancing our understanding of the gas-star formation cycle in galaxies.

Post-asymptotic giant branch (post-AGB) binaries are surrounded by dusty circumbinary disks, and exhibit unexpected orbital properties resulting from poorly understood binary interaction processes. Re-accreted gas from the circumbinary disk alters the photospheric chemistry of the post-AGB star, producing a characteristic underabundance of refractory elements that correlates with condensation temperature – a phenomenon known as chemical depletion. This work investigates how re-accretion from a disk drives chemical depletion, and the impact accreted matter has on post-AGB evolution. We used the MESA code to evolve 0.55 and 0.60 M⊙ post-AGB stars with the accretion of refractory element-depleted gas from a circumbinary disk. Our study adopts observationally-constrained initial accretion rates and disk masses to reproduce the chemical depletion patterns of six well-studied post-AGB binary stars: EP Lyr, HP Lyr, IRAS 17038-4815, IRAS 09144-4933, HD 131356, and SX Cen. We find high accretion rates (> 10–7 M⊙ yr–1) and large disk masses (≳ 10–2 M⊙) necessary to reproduce observed depletion, particularly in higher-mass, hotter post-AGB stars (Teff ≳ 6000 K). A slower evolution (lower core mass) is required to reproduce cooler (Teff ≲ 5000 K) depleted post-AGB stars. Rapid accretion significantly impacts post-AGB evolution, stalling stars at cooler effective temperatures and extending post-AGB lifetimes by factors of around 3 to 10. Despite this, extended post-AGB timescales remain within or below the planetary nebula (PN) visibility timescale, suggesting accretion cannot account for the observed lack of ionised PNe in post-AGB binaries. Our findings constrain accretion-flow parameters and advance our understanding of disk-binary interactions in post-AGB systems.

New far ultraviolet imaging of the galaxy NGC 205 is presented, which shows the emission is significantly offset ($\sim5^{\prime\prime}$ NW) from the optical and infrared centers of the galaxy. Spectral energy distribution (SED) modelling is applied to investigate the spatial dependence of the star formation history (SFH) of NGC 205, using data from far ultraviolet to far infrared. The SED model includes young and old stellar populations, gas emission, dust emission and dust absorption. The old stellar population has a total mass of $1.1\times10^8$ M$_{\odot}$ whereas the young population has a much smaller total mass of 3 200 M$_{\odot}$. The best forms of SFH for old and young stars are found to be exponentially declining bursts with start times $t_0$ yr ago and e-folding times $\tau$ yr. The old stellar population has uniform $t_0$ = 9.5 Gyr, with $\tau$ decreasing with radius from 1 Gyr to 500 Myr. The young stellar population has $t_0$ = 900 Myr and $\tau$ = 800 Myr, both uniform across NGC 205. The young and old stellar mass surface densities are exponential in radius with scale lengths of 40 and 110 pc, respectively. The dust heating has a $\sim$ 40% contribution from young stars and $\sim$ 60% from old stars.

We identify an axis connecting two opposite ‘ears’ in the supernova remnant W49B and morphological signatures of three arcs around this axis that we claim are sections of full circum-jet rings. Based on recent identifications of morphological signatures of jets in core-collapse supernovae (CCSNe), including ejecta-rich axes, we re-examine images of W49B and identify a heavy element-rich protrusion (ear) as a jet-inflated structure. We identify the opposite ear and a clump at its tip as the signature of the opposite jets. The line connecting the two clumps at the tips of the two opposite ears forms the main jet axis of W49B. We compare the three arcs around the main jet axis in W49B to the circum-jet rings of the jets in the Cygnus A galaxy and deduce that these arcs are sections of full circum-jet rings in W49B. In W49B, the jets are long gone, as in some planetary nebulae with circum-jet rings. Identifying the main jet axis is incompatible with a type Ia supernova. It leaves two possibilities: that jets exploded W49B as a CCSN, i.e. the jittering jets explosion mechanism where the pair of jets we identify is one of many that exploded the star, or that the explosion was a common envelope jet supernova with a thermonuclear outburst, i.e. both the pair of jets and thermonuclear outburst exploded the core of a red supergiant star as a pre-existing neutron star tidally destroyed it.

We study the late-time evolution of the compact Type IIb SN 2001ig in the spiral galaxy NGC 7424, with new and unpublished archival data from the Australia Telescope Compact Array and the Australian Square Kilometre Array Pathfinder. More than two decades after the SN explosion, its radio luminosity is showing a substantial re-brightening: it is now two orders of magnitude brighter than expected from the standard model of a shock expanding into a uniform circumstellar wind (i.e. with a density scaling as $R^{-2}$). This suggests that the SN ejecta have reached a denser shell, perhaps compressed by the fast wind of the Wolf–Rayet progenitor or expelled centuries before the final stellar collapse. We model the system parameters (circumstellar density profile, shock velocity, and mass loss rate), finding that the denser layer was encountered when the shock reached a distance of $\approx 0.1$ pc; the mass-loss rate of the progenitor immediately before the explosion was $\dot{M}/v_{w} \sim 10^{-7} {\rm M}_\odot {\mathrm {~yr}}^{-1} {\mathrm {km}}^{-1} {\mathrm {s}}$. We compare SN 2001ig with other SNe that have shown late-time re-brightenings, and highlight the opposite behaviour of some extended Type IIb SNe which show instead a late-time flux cut-off.

We present the results of a detailed high-resolution spectroscopic analysis (SUBARU/HDS spectra, R$\sim$50 000) of three faint high-latitude carbon stars HE 1104$-$0957, HE 1205$-$0521, and HE 1244$-$3036. Our estimated metallicity for these objects is $-$2.96, $-$2.63, and $-$2.49, respectively. The surface chemical compositions of the objects are found to be characterised by enhanced carbon and heavy elements, such as Y, Ba, La, and Ce. Using the classification criteria for carbon-enhanced metal-poor (CEMP) stars the objects HE 1104$-$0957 and HE 1205$-$0521 could not be classified into any known CEMP sub-classes, whereas the object HE 1244$-$3036 is found to be likely a CEMP-s star. The observed abundance patterns in HE 1244$-$3036 are also found to match well with the yields of a 2 M$_{\odot}$ AGB star with [Fe/H] = $-$2.50. Although our kinematic analysis indicates that the objects belong to the halo population, the elemental abundance ratios of HE 1104$-$0957 and HE 1205$-$0521 do not match well with those of typical halo objects. Estimated elemental abundances are presented, and kinematic properties of the stars are discussed.

Advancements in VLBI instrumentation, driven by the geodetic community’s goal of achieving positioning accuracy of 1 mm and stability of 0.1 mm/y, have led to the development of new broadband systems. Here, we assess the potential of these new capabilities for space weather monitoring. These enhanced VLBI capabilities were used to investigate interplanetary scintillation (IPS), a phenomenon caused by the scattering of radio waves due to density irregularities in the solar wind. Compact radio sources near the Sun were observed using the AuScope VLBI array in Australia, which consists of 12-m telescopes at Hobart, Katherine, and Yarragadee. The baseline lengths between these telescopes are approximately 3 400 km (Hobart–Katherine), 3 200 km (Hobart–Yarragadee), and 2 400 km (Katherine–Yarragadee). The observations covered solar elongations from 6.5$^\circ$ to 11.3$^\circ$ and frequencies between 3 and 13 GHz. The study focused on phase scintillation as an indicator of turbulence in the solar wind. As the solar elongation decreased, we observed an increase in the phase scintillation index, consistent with theoretical models. Importantly, the broadband system also detected IPS using relatively weak radio sources. Additionally, the phase scintillation increased with baseline length, in agreement with Kolmogorov turbulence with an index of 11/3. These findings demonstrate the effectiveness of geodetic broadband VLBI in capturing detailed features of the solar wind. This capability enables continuous space weather monitoring and advances our understanding of solar and interplanetary dynamics.

The radio telescopes of the European VLBI Network (EVN) and the University of Tasmania (UTAS) conducted an extensive observation campaign of the European Space Agency’s (ESA) Mars Express (MEX) spacecraft between 2013 and 2020. The campaign, carried out under the Planetary Radio Interferometry and Doppler Experiment (PRIDE) framework, aimed to study interplanetary phase scintillation and assess the noise budget in the closed-loop Doppler observations. The average closed-loop Doppler noise was determined to be approximately 10 mHz at a 10-s integration time, reaffirming the technique’s suitability for radio science experiments. We evaluated how different observational parameters such as the solar elongation, antenna size, and elevation angle impact the Doppler noise. A key part of the analysis involved comparing results from co-located telescopes to investigate system noise effects. Co-located telescopes at both Wettzell and Hobart provided highly consistent results, with any deviations serving as diagnostic tools to identify station-dependent issues. Additionally, the use of phase calibration tones during spacecraft tracking showed that the instrumental noise contribution is of the order of 5$\%$ of the total noise. This study provides a detailed noise budget for closed-loop Doppler observations with VLBI telescopes while emphasizing the effectiveness of the co-location method in isolating system-level noise. These findings are important for optimizing future radio science and VLBI tracking missions using stations outside the the Deep Space Network (DSN) and European Space Tracking (ESTRACK) network.

The Lyman alpha (Ly$\alpha$) forest in the spectra of $z\gt5$ quasars provides a powerful probe of the late stages of the epoch of reionisation (EoR). With the recent advent of exquisite datasets such as XQR-30, many models have struggled to reproduce the observed large-scale fluctuations in the Ly$\alpha$ opacity. Here we introduce a Bayesian analysis framework that forward-models large-scale lightcones of intergalactic medium (IGM) properties and accounts for unresolved sub-structure in the Ly$\alpha$ opacity by calibrating to higher-resolution hydrodynamic simulations. Our models directly connect physically intuitive galaxy properties with the corresponding IGM evolution, without having to tune ‘effective’ parameters or calibrate out the mean transmission. The forest data, in combination with UV luminosity functions and the CMB optical depth, are able to constrain global IGM properties at percent level precision in our fiducial model. Unlike many other works, we recover the forest observations without invoking a rapid drop in the ionising emissivity from $z\sim7$ to 5.5, which we attribute to our sub-grid model for recombinations. In this fiducial model, reionisation ends at $z=5.44\pm0.02$ and the EoR mid-point is at $z=7.7\pm0.1$. The ionising escape fraction increases towards faint galaxies, showing a mild redshift evolution at fixed UV magnitude, $M_\textrm{UV}$. Half of the ionising photons are provided by galaxies fainter than $M_\textrm{UV} \sim -12$, well below direct detection limits of optical/NIR instruments including $\textit{ JWST}$. We also show results from an alternative galaxy model that does not allow for a redshift evolution in the ionising escape fraction. Despite being decisively disfavoured by the Bayesian evidence, the posterior of this model is in qualitative agreement with that from our fiducial model. We caution, however, that our conclusions regarding the early stages of the EoR and which sources reionised the Universe are more model-dependent.

Interstellar hydrogen atoms (H atoms) penetrate into the heliosphere through the region of the solar wind interaction with the interstellar plasma due to their large mean free path. Resonant charge exchange of H atoms with protons has been considered as the main interaction process between the components. In the majority of models, other processes like elastic H-H and H-p collisions are not included. Moreover, it has been assumed that the velocities of the colliding particles remain unchanged during charge exchange. This corresponds to the scattering on the angle of $\pi$ in the centre mass rest frame. The goal of this paper is to explore effects of the elastic H-H and H-p collisions as well as the angular scattering during charge exchange on the distribution of the interstellar atoms in the heliosphere and at its boundary. We present results of simple (and therefore, easily repeatable) kinetic model of the interstellar atom penetration through the region of the solar and interstellar winds interaction into the heliosphere. As a result of the model, we compute the distribution function of the interstellar atoms at different heliospheric distances. Further, this distribution function is used to compute its moments and potentially observable features such as absorption and backscattered spectra in the Lyman-alpha line. Results show that there are differences in the behaviour of the distribution function when considering elastic collisions and the changes in the moments of the distribution achieve 10%. Therefore, in cases where precise calculation of H atom parameters is essential, such as in the modelling of backscattered Lyman-$\alpha$ emission, elastic collisions must be considered.

In this work, we studied the broadband temporal and spectral properties of the flat-spectrum radio quasar Ton 599. We collected the long-term data from January 2019 to August 2024 when the source was in a long flaring episode. We used the Bayesian block methodology to identify the various flux states, including three flares. The broadband fractional variability is estimated during two flaring states. The F$_{\text{var}}$ variation with respect to frequency shows a nearly double hump structure similar to broadband SED. The power spectral density shows a pink-noise kind of stochastic variability in the light curve, and we do not see any break in the power spectrum, suggesting a much longer characteristic timescale is involved in gamma-ray variability. The flux distribution is well-fitted with a double log-normal flux distribution, suggesting the variability of non-linear in nature. The gamma-ray, optical, and X-ray emissions were found to be highly correlated with a zero time lag, suggesting a co-spatial origin of their emissions. We used the one-zone leptonic model to reproduce the broadband spectrum in the energy range from the IR to very high-energy gamma rays. The increase in the magnetic field and the Doppler factor were found to be the main causes for high flux states. The XMM-Newton spectra taken during one of the flaring durations exhibit a signature of thermal black body emission from the accretion disc, suggesting a possible disc-jet coupling. This has also been indicated by the gamma-ray flux distribution, which shows the distribution as non-linear in nature, which is mostly seen in galactic X-ray binaries or active galactic nuclei, where the accretion disc dominates the emission.

Spectra have been obtained with the multi-fibre instrument 2dF on the Anglo-Australian Telescope of 89 candidate main sequence stars in the globular cluster M55 (NGC 6809). Radial velocities and Gaia proper motions confirm 72 candidates as cluster members. Among these stars one stands out as having a substantially stronger G-band (CH) than the rest of the member sample. The star is a dwarf carbon star that most likely acquired the high carbon abundance ([C/Fe] $\approx$ 1.2 $\pm$ 0.2) via mass transfer from a $\sim$1$-$3 M$_{\odot}$ binary companion (now a white dwarf) during its AGB phase of evolution. Interestingly, M55 also contains a CH-star that lies on the cluster red giant branch – the low central concentration/low density of this cluster presumably allows the survival of binaries that would otherwise be disrupted in denser systems. The existence of carbon stars in six other globular clusters is consistent with this hypothesis, while the origin of the carbon-enhanced star in M15 (NGC 7078) is attributed to a merger process similar to that proposed for the origin of the carbon-rich R stars.