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Multi-epoch Chandra and XMM-Newton observations of the symbiotic system R Aquarii (R Aqr) spanning 22 yr are analysed by means of a reflection model produced by an accretion disc. This methodology helps dissecting the contribution from different components in the X-ray spectra of R Aqr: the soft emission from the jet and extended emission, the heavily-extinguished plasma component of the boundary layer and the reflection contribution, which naturally includes the 6.4 keV Fe fluorescent line. The evolution with time of the different components is studied for epochs between 2000 Sep and 2022 Dec, and it is found that the fluxes of the boundary layer and that of the reflecting component increase as the stellar components in R Aqr approach periastron passage, a similar behaviour is exhibited by the shocked plasma produced by the precessing jet. Using publicly available optical and UV data we are able to study the evolution of the mass-accretion rate $\dot{M}_\mathrm{acc}$ and the wind accretion efficiency $\eta$ during periastron. These exhibit a small degree of variability with median values of $\dot{M}_\mathrm{acc}$=7.3$\times10^{-10}$ M$_\odot$ yr$^{-1}$ and $\eta$=7$\times10^{-3}$. We compare our estimations with predictions from a modified Bondi-Hoyle-Lyttleton accretion scenario., Comment: 17 pages, 15 figures, 4 tables; accepted to MNRAS

We present an analysis of high-dispersion spectroscopic observations of the symbiotic system R Aquarii (R Aqr) obtained with the Manchester Echelle Spectrograph (MES) at the 2.1 m telescope of the San Pedro M\'artir Observatory (Mexico). An interpretation of these data is presented by means of the shape software to disclose the morpho-kinematics of the nebulosities associated with R Aqr. The best model that reproduces narrow-band images and position-velocity diagrams is composed by three structures: an outer (large) hourglass structure surrounding an inner bipolar with a spiral-like filament entwined around the later. Different expansion velocity patterns are predefined for each structure, which predict kinematic ages of $\tau_{1}$=450$\pm$25 yr (outer hourglass), $\tau_{2}$=240$\pm$20 yr (inner bipolar) and $\tau_{3}$=215$\pm$20 yr (spiral-like filament). We suggest that the spiral-like filament is tracing the regions of interaction of the precessing jet with the circumstellar material, which simultaneously carves the inner bipolar structure. If a similar process created the large hourglass structure, it means that the action of the jet ceased for about 230 yr. We discuss the implication for other unresolved symbiotic systems detected in X-rays., Comment: 10 pages, 8 figures. Accepted for publication in MNRAS

We present the analysis of archival Very Large Telescope (VLT) MUSE and multi-epoch Hubble Space Telescope (HST) WFPC2 and WFC3/UVIS narrow-band observations of the remnant associated with the ejecta of the mid-nineteenth century outburst of the recurrent nova T Pyx. These data sets are used to investigate its true 3D physical structure and the nebular expansion patterns along the line of sight and on the plane of the sky. The VLT MUSE emission line maps and 3D visualisations based on position-position-velocity diagrams reveal T Pyx as a bipolar nebula, with a knotty toroidal structure at its waist best seen in H$\beta$ and two open bowl-shaped bipolar lobes (a diabolo) best revealed by the [OIII] emission lines. The comparison of multi-epoch HST WFPC2 and WFC3/UVIS narrow-band images and VLT MUSE emission line maps of T Pyx reveals the angular expansion of the remnant through the proper motion of individual knots and nebular features. The angular expansion is confirmed to be homologous in the period from 1994.2 to 2007.4 before the recent 2011 outburst, but there is suggestive evidence that the inner knots have experienced a higher expansion rate since then., Comment: 18 pages, 15 figures. Accepted for publication in MNRAS

The acquisition of high-quality deep images of planetary nebulae (PNe) has allowed the detection of a wealth of small-scale features, which highlight the complexity of the formation history and physical processes shaping PNe. Here we present the discovery of three groups of clumps embedded within the nebular shell of the evolved PN NGC3587, the Owl Nebula, that had escaped previous detections. The analysis of multi-wavelength GEMINI GMOS, NOT ALFOSC, Aristarchos Andor optical, CFHT WIRCam and Spitzer IRAC and MIPS infrared (IR) images indicates that these clumps are formed by material denser and colder than the surrounding nebula, with a notable content of molecular H2, but negligible or null amounts of dust. The presence of H2-rich pockets embedded within the ionized shell of this evolved PN is suggestive of the survival of high-density condensations of material created at the onset of the PN stage., Comment: 8 pages, 6 figures, 1 tables. Accepted for publication in MNRAS

The emission of hard X-rays associated with white dwarfs (WD) can be generated by the presence of a stellar companion either by the companion's coronal emission or by an accretion disk formed by material stripped from the companion. Recent studies have suggested that a Jupiter-like planet can also be donor of material whose accretion onto the WD can generate hard X-rays. We use the {\sc guacho} code to reproduce the conditions of this WD-planet scenario. With the example of the hard X-ray WD KPD\,0005+5106, we explore different terminal wind velocities and mass-loss rates of a donor planet for a future network of simulations to investigate the luminosity and the spectral and temporal properties of the hard X-ray emission in WD-planet systems. Our simulations show that the material stripped from the planet forms a disk and accretes onto the WD to reach temperatures high enough to generate hard X-rays as usually seen in X-ray binaries with low-mass companions. For high terminal wind velocities, the planet material does not form a disk, but it rather accretes directly onto the WD surface. The simulations reproduce the X-ray luminosity of another X-ray accreting WD (G\,29$-$38), and only for some times reaches the hard X-ray luminosity of KPD\,0005+5106. The X-ray variability is stochastic and does not reproduce the period of KPD\,0005+5106, suggesting that additional physical processes (e.g., hot spots resulting from magnetic channelling of the accreting material) need to be explored., Comment: 16 pages, 13 figures

We present the analysis of spatially-resolved spectroscopic observations of the born-again planetary nebula (PN) A 78 that are used to investigate the chemistry and physical properties of its three main morphological components, namely the inner knots, its eye-like structure, and the low surface-brightness outer nebula. The H-poor chemical abundances of the inner knots confirm the born-again nature of A 78, with a N/O abundances ratio consistent with the predictions of very late thermal pulses (VLTP). On the other hand, the high Ne/O is not expected in VLTP events, which prompts a possible different evolutionary path may be involving a binary system. The low N/O ratio and He/H abundances of the outer shell are indicative of a low-mass progenitor, whereas the chemical abundances of the eye-like structure, which results from the interaction between the H-poor born-again material and the outer nebula, evidence their mixture. Unlike previous works, the extinction is found to be inhomogeneous, being much higher towards the H-poor inner knots, where the presence of large amounts of C-rich dust has been previously reported. Dust-rich material seems to diffuse into outer nebular regions, resulting in zones of enhanced extinction., Comment: 18 pages, 6 Tables, 5 Figures; accepted to MNRAS

We present the analysis of archival XMM-Newton and Chandra observations of CH Cyg, one of the most studied symbiotic stars (SySts). The combination of the high-resolution XMM-Newton RGS and Chandra HETG X-ray spectra allowed us to obtain reliable estimates of the chemical abundances and to corroborate the presence of multi-temperature X-ray-emitting gas. Spectral fitting of the medium-resolution XMM-Newton MOS (MOS1+MOS2) spectrum required the use of an additional component not seen in previous studies in order to fit the 2.0-4.0 keV energy range. Detailed spectral modelling of the XMM-Newton MOS data suggests the presence of a reflection component, very similar to that found in active galactic nuclei. The reflection component is very likely produced by an ionised disk (the accretion disk around the white dwarf) and naturally explains the presence of the fluorescent Fe emission line at 6.4 keV while also contributing to the soft and medium energy ranges. The variability of the global X-ray properties of CH Cyg are discussed as well as the variation of the three Fe lines around the 6-7 keV energy range. We conclude that reflection components are needed to model the hard X-ray emission and may be present in most $\beta/\delta$-type SySt., Comment: 12 pages, 7 figures, 5 tables; To appear in MNRAS

We present the first 3D radiation-hydrodynamic simulations of the formation of planetary nebulae (PNe) emerging from 3D spiral patterns. We use the GUACHO code to create 3D spiral structures as a consequence of the distortions on the geometry of the intrinsically isotropic wind of an asymptotic giant branch (AGB) star produced by a companion star in a circular orbit. We found that the orbital period of the binary producing the 3D spiral pattern has consequences on the formation and shaping of the PN itself. Stellar systems with longer period create less entwined 3D spirals, producing PNe with rounder inner cavities, and prevent the expansion of jet towards the polar directions. The spiral fitting procedure used in the literature to predict the binary's orbital period may be misleading in the case of proto-PNe and PNe as spiral patterns are diluted by their own thermal expansion down to the average AGB density profile within a few hundred years and are further disrupted by the action of jets. By adopting a phase of jet ejections between the AGB and post-AGB stages, we are able to recover the morphologies of proto-PNe and PNe that exhibit ring-like structures in their halos., Comment: 12 pages, 12 figures, 1 table; Accepted to MNRAS

A recent analysis of Chandra X-ray data of the metal-polluted white dwarf (WD) G29-38 has revealed X-ray emission that can be attributed to the accretion of debris from a planetary body. In the light of this detection we revisit here archival XMM-Newton observations of G29-38 from which only an upper limit was derived in the past due to the presence of a relatively bright nearby X-ray source. An analysis of these data in multiple energy bands allows disentangling the X-ray emission at the location of G29-38 from that of the nearby source. The similar spectral properties of the source in the XMM-Newton and Chandra observations and their spatial shift, consistent with the proper motion of G29-38 between these observations, strengthen the origin of that X-ray emission from G29-38. The X-ray luminosities from both observations are consistent within 1-$\sigma$ uncertainties, so too are the best-fit plasma temperatures. Although the count number is small, there is tantalizing evidence for line emission in the 0.7-0.8 keV energy band from an optically-thin hot plasma. The most likely candidate for this line emission would be the Fe complex at 16 \r{A}., Comment: 6 pages, 4 figures, 1 table; accepted to ApJL

We present the analysis of archival XMM-Newton observations of the symbiotic stars HM Sge, NQ Gem, and PU Vul. The EPIC-pn spectra hint at the presence of emission lines, which are further confirmed in the 1st order RGS spectra of the three sources. Spectral modeling of the EPIC-pn data disclose unprecedented characteristics, for instance, the best fit to the EPIC-pn spectrum of the $\beta$-type symbiotic star PU Vul reveals the presence of two plasma components. We report the discovery of an extremely soft spectral component in the EPIC-pn spectrum of the $\beta$-type symbiotic star HM Sge which we suggest is produced by periodic mass ejections such as jets. Consequently, we suggest that a simple $\beta$-type classification no longer applies to HM Sge. Finally, the spectrum of the $\beta/\delta$-type symbiotic star NQ Gem can not be fitted by a two-temperature plasma model as performed by previous authors. The model requires extra components to fit the 1.0-4.0 keV energy range. More sophisticated models to $\beta/\delta$-type symbiotic stars are needed in order to peer into the accretion process from such systems., Comment: 9 pages, 2 Tables, 3 Figures; Accepted to ApJ

Theory predicts that the temperature of the X-ray-emitting gas ($\sim$10$^{6}$ K) detected from planetary nebulae (PNe) is a consequence of mixing or thermal conduction when in contact with the ionized outer rim ($\sim$10$^{4}$ K). Gas at intermediate temperatures ($\sim$10$^{5}$ K) can be used to study the physics of the production of X-ray-emitting gas, via C IV, N V and O VI ions. Here we model the stellar atmosphere of the CSPN of NGC 1501 to demonstrate that even this hot H-deficient [WO4]-type star cannot produce these emission lines by photoionization. We use the detection of the C IV lines to assess the physical properties of the mixing region in this PNe in comparison with its X-ray-emitting gas, rendering NGC 1501 only the second PNe with such characterization. We extend our predictions to the hottest [WO1] and cooler [WC5] spectral types and demonstrate that most energetic photons are absorbed in the dense winds of [WR] CSPN and highly ionized species can be used to study the physics behind the production of hot bubbles in PNe. We found that the UV observations of NGC 2452, NGC 6751 and NGC 6905 are consistent with the presence mixing layers and hot bubbles, providing excellent candidates for future X-ray observations., Comment: To appear in MNRAS; 14 pages, 10 figures, 6 tables

We present GTC MEGARA high-dispersion integral field spectroscopic observations of the nova remnant QU\,Vul, which provide a comprehensive 3D view of this nova shell. The tomographic analysis of the H$\alpha$ emission reveals a complex physical structure characterized by an inhomogeneous and clumpy distribution of the material within this shell. The overall structure can be described as a prolate ellipsoid with an axial ratio of 1.4$\pm$0.2, a major axis inclination with the line of sight of $12^{\circ}\pm6^{\circ}$, and polar and equatorial expansion velocities $\approx$560 km~s$^{-1}$ and 400$\pm$60 km s$^{-1}$, respectively. The comparison of the expansion velocity on the plane of the sky with the angular expansion implies a distance of 1.43$\pm$0.23 kpc. The ionized mass is found to be $\approx 2\times 10^{-4}$ M$_\odot$, noting that the information on the 3D distribution of material within the nova shell has allowed us to reduce the uncertainty on its filling factor. The nova shell is still in its free expansion phase, which can be expected as the ejecta mass is much larger than the swept-up circumstellar medium mass. The 3D distribution and radial velocity of material within the nova shell provide an interpretation of the so-called "castellated" line profiles observed in early optical spectra of nova shells, which can be attributed to knots and clumps moving radially along different directions., Comment: 10 pages, 6 figures

We present a comprehensive study of the ionization structure and kinematics of the planetary nebula (PN) NGC40 (a.k.a. the Bow-tie Nebula). A set of narrow-band images obtained with the ALhambra Faint Object Spectrograph and Camera (ALFOSC) at the Nordic Optical Telescope (NOT) are used to study the turbulent distribution of gas in the main cavity, the ionization stratification and the density of this PN. High-resolution Manchester Echelle Spectrograph (MES) observations obtained at 2.1m telescope of the San Pedro M\'{a}rtir (SPM) Observatory are used to unveil in great detail the kinematic signatures of all morphological features in NGC40. The images and spectra suggest that NGC40 had multiple mass ejections in its recent formation history. We found 4 jet-like ejections not aligned with the main axis of NGC40 (PA=20$^{\circ}$), some of them having pierced the main cavity along the SW-NE direction as well as the southern lobe. Using a tailor-made morpho-kinematic model of NGC40 produced with SHAPE we found that the main cavity has a kinematic age of 6,500 yr and the two pairs of lobes expanding towards the N and S directions have an averaged age of 4,100$\pm$550 yr. NGC40 thus adds to the group of PNe with multiple ejections along different axes that challenge the models of PN formation., Comment: 11 pages, 9 figures, 3 tables; Accepted to MNRAS

We present the analysis of Multi-Espectr\'ografo en GTC de Alta Resoluci\'on para Astronom\'ia (MEGARA) high-dispersion integral field spectroscopic observations of the bipolar planetary nebula (PN) M 3-38. These observations unveil the presence of a fast outflow aligned with the symmetry axis of M 3-38 that expands with a velocity up to $\pm$225 km s$^{-1}$. The deprojected space velocity of this feature can be estimated to be $\approx$320$^{+130}_{-60}$ km s$^{-1}$, which together with its highly collimated morphology suggests that it is one of the fastest jet detected in a PN. We have also used Kepler observations of the central star of M 3-38 to unveil variability associated with a dominant period of 17.7 days. We attribute this to the presence of a low-mass star with an orbital separation of $\approx$0.12-0.16 au. The fast and collimated ejection and the close binary system point towards a common envelope formation scenario for M 3-38., Comment: 9 pages, 5 figures, Accepted ApJ Letter

We present the analysis of the optical variability of the early, nitrogen-rich Wolf-Rayet (WR) star WR7. The analysis of multi-sector Transiting Exoplanet Survey Satellite (TESS) light curves and high-resolution spectroscopic observations confirm multi-periodic variability that is modulated on time-scales of years. We detect a dominant period of $2.6433 \pm 0.0005$ d in the TESS sectors 33 and 34 light curves in addition to the previously reported high-frequency features from sector 7. We discuss the plausible mechanisms that may be responsible for such variability in WR7, including pulsations, binarity, co-rotating interacting regions (CIRs) and clumpy winds. Given the lack of strong evidence for the presence of a stellar or compact companion, we suggest that WR7 may pulsate in quasi-coherent modes in addition to wind variability likely caused by CIRs on top of stochastic low-frequency variability. WR7 is certainly a worthy target for future monitoring in both spectroscopy and photometry to sample both the short ($\lesssim 1$ d) and long ($\gtrsim 1000$ d) variability time scales., Comment: 9 pages, 5 Figures, 1 Table; Accepted to MNRAS

Winds from massive stars have recently been deemed promising sites for investigating relativistic particle acceleration. Particularly, the resulting bow shock from the interaction of the winds of runaway stars with interstellar matter has been observed at multiple wavelengths. Here we investigate the O4If star, BD+433654, the bow shock of which is, so far, the only one proven to radiate both thermally and non-thermally at radio frequencies. We also consider NGC7635 as a bow shock candidate and examine its apex for indications of thermal and non-thermal radio emission. We observed both sources with the VLA at 4-8 GHz and 8-12 GHz, and with the Effelsberg telescope at 4-8 GHz. We analysed data from both telescopes individually and combined, obtained their spectral index maps and calculated their Spectral Energy Distributions. We present the first high-resolution maps of radio emission from NGC7635. We find that both emit non-thermal emission in the radio regime, with the clearest evidence for NGC7635. Our results are less conclusive for BD+433654, as the emission from its bow shock becomes weaker and fainter at higher radio frequencies. Our results extend the previous radio results for the BD+433654 bow shock to higher frequencies. Modelling of our data for both sources shows that accelerated electrons at the wind termination shock are a plausible source for the non-thermal radio emission, but energetics arguments suggest that any non-thermal X-ray and $\gamma$-ray emission could be significantly below existing upper limits. Enhanced synchrotron emission from compressed Galactic cosmic rays in the radiative bow shock could also explain the radio emission from the BD+433654 bow shock but not NGC7635. Non-detection of point-like radio emission from BD+433654 puts an upper limit on the mass-loss rate of the star that is lower than values quoted in the literature. [abridged], Comment: 17 pages, 13 figures

Born-again planetary nebulae (PNe) are extremely rare cases in the evolution of solar-like stars. It is commonly accepted that their central stars (CSPN) experienced a very late thermal pulse (VLTP), ejecting H-deficient material inside the evolved H-rich PN. Given the short duration of this event and the fast subsequent evolution of the CSPN, details of the mass ejection are unknown. We present the first morpho-kinematic model of the H-deficient material surrounding a born-again PN, namely A30. New San Pedro M\'{a}rtir observations with the Manchester Echelle Spectrograph were recently obtained to map the inner region of A30 which are interpreted by means of the software SHAPE in conjunction with HST WFC3 images. The SHAPE morpho-kinematic model that best reproduces the observations is composed by a disrupted disk tilted $37^\circ$ with respect to the line of sight and a pair of orthogonal opposite bipolar ejections. We confirm previous suggestions that the structures closer to the CSPN present the highest expansion velocities, that is, the disrupted disk expands faster than the farther bipolar features. We propose that the current physical structure and abundance discrepancy of the H-deficient clumps around the CSPN of A30 can be explained by a common envelope phase following the VLTP event. Our proposed scenario is also compared with other known born-again PNe (A58, A78, HuBi1 and the Sakurai's Object)., Comment: 9 pages, 6 figures, 1 table; Accepted to MNRAS

We present a 3D mapping of the Wolf-Rayet (WR) nebula M1-67 around WR124. We obtained high-resolution San Pedro M\'{a}rtir (SPM) Manchester Echelle Spectrograph (MES) observations along 17 long-slit positions covering all morphological features in M1-67. We are able to unveil the true morphology of M1-67 and its kinematics by interpreting the SPM MES observations by means of the 3D modelling tool for Astrophysics SHAPE. Our SHAPE model that best reproduces the SPM MES data includes three concentric bipolar structures composed by a hollow ellipsoidal structure and a torus. In addition, the model requires the presence of expanding jets and broken blisters in order to reproduce specific spectral features. Our results are consistent with the idea that M1-67 and its progenitor star WR124 have formed through a common envelope scenario that occurred 11.8$^{+4.6}_{-0.8}$ kyr ago. Our bipolar model strongly questions previous suggestions of the presence of a bow shock structure surrounding M1-67. We interpret that the bright structures detected in the spectra extracted from the central regions are produced by wind compression at the receding region of the innermost structure in M1-67. Furthermore, WR124 is moving through a low-density region above the Galactic plane that has negligibly affected the formation history of M1-67., Comment: 9 pages, 7 figures, 2 tables; Accepted to MNRAS

We present the analysis of Very Large Telescope (VLT) Multi Unit Spectroscopic Explorer (MUSE) observations of the planetary nebula (PN) IC 4406. MUSE images in key emission lines are used to unveil the presence of at least 5 ring-like structures North and South of the main nebula of IC 4406. MUSE spectra are extracted from the rings to unambiguously assess for the first time in a PN their physical conditions, electron density (ne) and temperature (Te). The rings are found to have similar Te than the rim of the main nebula, but smaller ne. Ratios between different ionic species suggest that the rings of IC 4406 have a lower ionization state than the main cavity, in contrast to what was suggested for the rings in NGC6543, the Cat's Eye Nebula., Comment: 8 pages, 5 figures, 2 tables. Accepted for publication in MNRAS

We present long-slit intermediate-dispersion spectroscopic observations and narrow-band direct imaging of four classical nova shells, namely TAur, HRDel, DQHer and QUVul, and the nova-like source CKVul. These are used to construct models of their nebular remnants using the morpho-kinematic modelling tool Shape to reveal their 3D shape. All these nova remnants but CKVul can be described by prolate ellipsoidal shells with different eccentricity degree, from the spherical QUVul to the highly elongated shell with an equatorial component HRDel. On the other hand, CKVul shows a more complex structure, with two pairs of nested bipolar lobes. The spatio-kinematic properties of the ellipsoidal nova shells derived from our models include their true axial ratios. This parameter is expected to correlate with the expansion velocity and decline time C3 (i.e., their speed class) of a nova as the result the interaction of the ejecta with the circumstellar material and rotation speed and magnetic field of the white dwarf. We have compared these three parameters including data available in the literature for another two nova shells, V533 Her and FH Ser. There is an anti-correlation between the expansion velocity and the axial ratio and decline time C3 for nova remnants with ellipsoidal morphology, and a correlation between their axial ratios and decline times C3, confirming theoretical expectations that the fastest expanding novae have the smallest axial ratios. We note that the high expansion velocity of the nova shell HRDel of 615 km/s is inconsistent with its long decline time C3 of 250 days., Comment: 12 pages, 7 figures, 1 Appendix + 1 figure, 3 tables. Accepted for publication in MNRAS

The central star of the planetary nebula (PN) HuBi\,1 has been recently proposed to have experienced a very late thermal pulse (VLTP), but the dilution of the emission of the recent ejecta by that of the surrounding H-rich old outer shell has so far hindered confirming its suspected H-poor nature. We present here an analysis of the optical properties of the ejecta in the innermost regions of HuBi\,1 using MEGARA high-dispersion integral field and OSIRIS intermediate-dispersion long-slit spectroscopic observations obtained with the 10.4m Gran Telescopio de Canarias. The unprecedented tomographic capability of MEGARA to resolve structures in velocity space allowed us to disentangle for the first time the H$\alpha$ and H$\beta$ emission of the recent ejecta from that of the outer shell. The recent ejecta is found to have much higher extinction than the outer shell, implying the presence of large amounts of dust. The spatial distribution of the emission from the ejecta and the locus of key line ratios in diagnostic diagrams probe the shock excitation of the inner ejecta in HuBi\,1, in stark contrast with the photoionization nature of the H-rich outer shell. The abundances of the recent ejecta have been computed using the {\sc mappings v} code under a shock scenario. They are found to be consistent with a born-again ejection scenario experienced by the progenitor star, which is thus firmly confirmed as a new "born-again" star., Comment: 14+4 pages, 21+2 figures, including supplementary information

The Nearby Evolved Stars Survey (NESS) is a volume-complete sample of $\sim$850 Galactic evolved stars within 3\,kpc at (sub-)mm wavelengths, observed in the CO $J = $ (2$-$1) and (3$-$2) rotational lines, and the sub-mm continuum, using the James Clark Maxwell Telescope and Atacama Pathfinder Experiment. NESS consists of five tiers, based on distances and dust-production rate (DPR). We define a new metric for estimating the distances to evolved stars and compare its results to \emph{Gaia} EDR3. Replicating other studies, the most-evolved, highly enshrouded objects in the Galactic Plane dominate the dust returned by our sources, and we initially estimate a total DPR of $4.7\times 10^{-5}$ M$_\odot$ yr$^{-1}$ from our sample. Our sub-mm fluxes are systematically higher and spectral indices are typically shallower than dust models typically predict. The 450/850 $\mu$m spectral indices are consistent with the blackbody Rayleigh--Jeans regime, suggesting a large fraction of evolved stars have unexpectedly large envelopes of cold dust., Comment: 20 pages, 13 figures, 5 tables, accepted for publications in MNRAS

We present a multi-wavelength characterisation of the planetary nebula (PN) NGC 6905 and its [Wolf-Rayet]-type ([WR]) central star (CSPN) HD 193949. Our Nordic Optical Telescope (NOT) Alhambra Faint Object Spectrograph and Camera (ALFOSC) spectra and images unveil in unprecedented detail the high-ionization structure of NGC 6905. The high-quality spectra of HD 193949 allowed us to detect more than 20 WR features including the characteristic O-bump, blue bump and red bump, which suggests a spectral type no later than a [WO2]-subtype. Moreover we detect the Ne VII and Ne VIII broad emission lines, rendering HD 193949 yet another CSPN with $T_\mathrm{eff}\lesssim150$ kK exhibiting such stellar emission lines. We studied the physical properties ($T_\mathrm{e}$ and $n_\mathrm{e}$) and chemical abundances of different regions within NGC 6905 including its low-ionization clumps; abundances are found to be homogeneous. We used the PoWR stellar atmosphere code to model the spectrum of HD 193949, which is afterwards used in a photoionization model performed with Cloudy that reproduces the nebular and dust properties for a total mass in the 0.31-0.47 M$_{\odot}$ range and a mass of C-rich dust of $\sim$2 $\times10^{-3}$ M$_{\odot}$. Adopting a current stellar mass of 0.6 M$_{\odot}$, our model suggests an initial mass $\sim$1 M$_\odot$ for HD 193949, consistent with the observations., Comment: To appear in MNRAS; 17 pages, 9 figures, 10 tables

We present the first instalment of a deep imaging catalogue containing 58 True, Likely and Possible extended PNe detected with the Isaac Newton Telescope Photometric H$\alpha$ Survey (IPHAS). The three narrow-band filters in the emission lines of H$\alpha$, [N II] $\lambda$6584 \r{A} and [O III] $\lambda$5007 \r{A} used for this purpose allowed us to improve our description of the morphology and dimensions of the nebulae. In some cases even the nature of the source has been reassessed. We were then able to unveil new macro-and micro-structures, which will without a doubt contribute to a more accurate analysis of these PNe. It has been also possible to perform a primary classification of the targets based on their ionization level. A Deep Learning classification tool has also been tested. We expect that all the PNe from the IPHAS catalogue of new extended planetary nebulae will ultimately be part of this deep H$\alpha$, [N II] and [O III] imaging catalogue., Comment: 19 pages, 15 figures, 4 tables; accepted to MNRAS

We present a comprehensive analysis of the compact planetary nebula M2-31 investigating its spectral properties, spatio-kinematical structure and chemical composition using GTC MEGARA integral field spectroscopic observations and NOT ALFOSC medium-resolution spectra and narrow-band images. The GTC MEGARA high-dispersion observations have remarkable tomographic capabilities, producing an unprecedented view of the morphology and kinematics of M2-31 that discloses a fast spectroscopic bipolar outflow along position angles 50$^\circ$ and 230$^\circ$, an extended shell and a toroidal structure or waist surrounding the central star perpendicularly aligned with the fast outflows. These observations also show that the C II emission is confined in the central region and enclosed by the [N II] emission. This is the first time that the spatial segregation revealed by a 2D map of the C II line implies the presence of multiple plasma components. The deep NOT ALFOSC observations allowed us to detect broad WR features from the central star of M2-31, including previously undetected broad O VI lines that suggest a reclassification as a [WO4]-type star., Comment: 12 pages, 8 figures, 3 tables; accepted to MNRAS

We present a characterization of the dust in the Wolf-Rayet (WR) nebula RCW 58 around the WN8h star WR 40 using archival infrared (IR) observations from WISE and Herschel and radio observations from ATCA. We selected two clumps, free from contamination from material along the line of sight and located towards southern regions in RCW 58, as representative of the general properties of this WR nebula. Their optical, IR and radio properties are then modelled using the photoionization code Cloudy, which calculates a self-consistent spatial distribution of dust and gas properties. Two populations of dust grains are required to model the IR SED: a population of small grains with sizes 0.002-0.01 $\mu$m, which is found throughout the clumps, and a population of large grains, with sizes up to 0.9 $\mu$m, located further from the star. Moreover, the clumps have very high dust-to-gas ratios, which present a challenge for their origin. Our model supports the hypothesis that RCW 58 is distributed in a ring-like structure rather than a shell, and we estimate a mass of $\sim$2.5 M$_\odot$. This suggests that the mass of the progenitor of WR 40 was about $\approx40^{+2}_{-3}$ M$_\odot$. The ring morphology, low nebular mass, large dust grain size and high dust-to-gas ratio lead us to propose that RCW 58 has formed through a common envelope channel, similar to what has been proposed for M 1-67., Comment: 17 pages, 8 figures, 7 tables; accepted to MNRAS

We present the first 3D radiation-hydrodynamic simulations on the formation and evolution of born-again planetary nebulae (PNe), with particular emphasis to the case of HuBi1, the inside-out PN. We use the extensively-tested GUACHO code to simulate the formation of HuBi1 adopting mass-loss and stellar wind terminal velocity estimates obtained from observations presented by our group. We found that, if the inner shell of HuBi1 was formed by an explosive very late thermal pulse (VLTP) ejecting material with velocities of $\sim$300 km s$^{-1}$, the age of this structure is consistent with that of $\simeq$200 yr derived from multi-epoch narrow-band imaging. Our simulations predict that, as a consequence of the dramatic reduction of the stellar wind velocity and photon ionizing flux during the VLTP, the velocity and pressure structure of the outer H-rich nebula are affected creating turbulent ionized structures surrounding the inner shell. These are indeed detected in Gran Telescopio Canarias MEGARA optical observations. Furthermore, we demonstrate that the current relatively low ionizing photon flux from the central star of HuBi1 is not able to completely ionize the inner shell, which favors previous suggestions that its excitation is dominated by shocks. Our simulations suggest that the kinetic energy of the H-poor ejecta of HuBi1 is at least 30 times that of the clumps and filaments in the evolved born-again PNe A30 and A78, making it a truly unique VLTP event., Comment: 9 pages, 10 figures, no tables; accepted to MNRAS

We present an infrared (IR) characterization of the born-again planetary nebulae (PNe) A30 and A78 using IR images and spectra. We demonstrate that the carbon-rich dust in A30 and A78 is spatially coincident with the H-poor ejecta and coexists with hot X-ray-emitting gas up to distances of 50$''$ from the central stars (CSPNs). Dust forms immediately after the born-again event and survives for 1000 yr in the harsh environment around the CSPN as it is destroyed and pushed away by radiation pressure and dragged by hydrodynamical effects. Spitzer IRS spectral maps showed that the broad spectral features at 6.4 and 8.0 $\mu$m, attributed to amorphous carbon formed in H-deficient environments, are associated with the disrupted disk around their CSPN, providing an optimal environment for charge exchange reactions with the stellar wind that produces the soft X-ray emission of these sources. Nebular and dust properties are modeled for A30 with Cloudy taking into account different carbonaceous dust species. Our models predict dust temperatures in the 40-230 K range, five times lower than predicted by previous works. Gas and dust masses for the born-again ejecta in A30 are estimated to be $M_\mathrm{gas}=(4.41^{+0.55}_{-0.14})\times10^{-3}$ M$_\odot$ and $M_\mathrm{dust}=(3.20^{+3.21}_{-2.06})\times10^{-3}$ M$_\odot$, which can be used to estimate a total ejected mass and mass-loss rate for the born-again event of $(7.61^{+3.76}_{-2.20})\times10^{-3}$ M$_{\odot}$ and $\dot{M}=[5-60]\times10^{-5}$ M$_{\odot}$ yr$^{-1}$, respectively. Taking into account the carbon trapped into dust grains, we estimate that the C/O mass ratio of the H-poor ejecta of A30 is larger than 1, which favors the very late thermal pulse model over the alternate hypothesis of a nova-like event., Comment: 14 pages, 11 Figures, 1 Table; Accepted to MNRAS

Jets (fast collimated outflows) are claimed to be the main shaping agent of the most asymmetric planetary nebula (PNe) as they impinge on the circumstellar material at late stages of the asymptotic giant branch (AGB) phase. The first jet detected in a PN was that of NGC 2392, yet there is no available image because its low surface brightness contrast with the bright nebular emission. Here we take advantage from the tomographic capabilities of GTC MEGARA high-dispersion integral field spectroscopic observations of the jet in NGC 2392 to gain unprecedented details of its morphology and kinematics. The jet of NGC 2392 is found to emanate from the central star, break through the walls of the inner shell of this iconic PN and extend outside the nebula's outermost regions with an S-shaped morphology suggestive of precession. At odds with the fossil jets found in mature PNe, the jet in NGC 2392 is currently being collimated and launched. The high nebular excitation of NGC 2392, which implies a He$^{++}$/He ionization fraction too high to be attributed to the known effective temperature of the star, has been proposed in the past to hint at the presence of a hot white dwarf companion. In conjunction with the hard X-ray emission from the central star, the present-day jet collimation would support the presence of such a double-degenerate system where one component undergoes accretion from a remnant circumbinary disk of the common envelope phase., Comment: 12 pages, 9 figures, accepted for publication in The Astrophysical Journal

We present the analysis of XMM-Newton European Photon Imaging Camera (EPIC) observations of the nova shell IPHASX J210204.7$+$471015. We detect X-ray emission from the progenitor binary star with properties that resemble those of underluminous intermediate polars such as DQ Her: an X-ray-emitting plasma with temperature of $T_\mathrm{X}=(6.4\pm3.1)\times10^{6}$ K, a non-thermal X-ray component, and an estimated X-ray luminosity of $L_\mathrm{X}=10^{30}$ erg s$^{-1}$. Time series analyses unveil the presence of two periods, the dominant with a period of $2.9\pm0.2$ hr, which might be attributed to the spin of the white dwarf, and a secondary of $4.5\pm0.6$ hr that is in line with the orbital period of the binary system derived from optical observations. We do not detect extended X-ray emission as in other nova shells probably due to its relatively old age (130-170 yr) or to its asymmetric disrupted morphology which is suggestive of explosion scenarios different to the symmetric ones assumed in available numerical simulations of nova explosions., Comment: 6 pages and 5 Figures; Accepted to MNRAS

We present the analysis of archival Very Large Telescope (VLT) Multi Unit Spectroscopic Explorer (MUSE) observations of the interacting galaxies NGC 4038/39 (a.k.a. the Antennae) at a distance of 18.1 Mpc. Up to 38 young star-forming complexes with evident contribution from Wolf-Rayet (WR) stars are unveiled. We use publicly available templates of Galactic WR stars in conjunction with available photometric extinction measurements to quantify and classify the WR population in each star-forming region, on the basis of its nearly Solar oxygen abundance. The total estimated number of WR stars in the Antennae is 4053 $\pm$ 84, of which there are 2021 $\pm$ 60 WNL and 2032 $\pm$ 59 WC-types. Our analysis suggests a global WC to WN-type ratio of 1.01 $\pm$ 0.04, which is consistent with the predictions of the single star evolutionary scenario in the most recent BPASS stellar population synthesis models., Comment: 20 pages, 16 figures, 5 tables; accepted to MNRAS

We present a detailed analysis of the new planetary nebula (PN) IPHASX J193718.6+202102 using deep imaging and intermediate- and high resolution spectroscopy that are interpreted through morpho-kinematic and photoionisation modelling. The physical structure of the nebula consists of a fragmented torus and an extremely faint orthogonal bipolar outflow, contrary to the pinched waist PN morphology suggested by its optical image. Our kinematic analysis indicates that the torus is expanding at 25$\pm$5 km s$^{-1}$ and is gradually breaking up. At an estimated distance of 7.1$_{-0.3}^{+0.8}$ kpc, the corresponding kinematic age of $\sim$26000 years is consistent with a faint and disintegrating PN. The intermediate-resolution spectra reveal an excited PN with chemical abundances typical of Type II PNe. Based on the latter we also estimate an initial mass for the progenitor in the range 2--3 M$_{\odot}$ and a central star (CSPN) mass $M_\mathrm{CSPN}\sim$0.61 M$_{\odot}$. The Spitzer MIPS 24 $\mu$m emission that closely follows the fragmented torus could be attributed to the emission of [O IV] at 25.9 $\mu$m rather than to dust emission. All the results coherently point towards an evolved moderately massive bipolar Type II PN on the brink of dissolving into the interstellar medium., Comment: 12 pages, 9 figures, accepted for publication in MNRAS

HuBi 1 has been proposed to be member of the rare class of born-again planetary nebulae (PNe), i.e., its central star experienced a very late thermal pulse and ejected highly-processed material at high speeds inside the old hydrogen-rich PN. In this letter we present GTC MEGARA integral field spectroscopic observations of the innermost regions of HuBi 1 at high spectral resolution $\simeq16$ km s$^{-1}$ and multi-epoch sub-arcsec images obtained $\simeq 12$ yr apart. The analysis of these data indicates that the inner regions of HuBi 1 were ejected $\simeq200$ yr ago and expand at velocities $\simeq300$ km s$^{-1}$, in excellent agreement with the born-again scenario. The unprecedented tomographic capabilities of the GTC MEGARA high-dispersion observations used here reveal that the ejecta in HuBi 1 has a shell-like structure, in contrast to the disrupted disk and jet morphology of the ejecta in other born-again PNe., Comment: 7 pages, 5 Figures; accepted to ApJL

We present the first detailed study of the bipolar planetary nebula (PN) IPHASX J191104.8$+$060845 (PN G040.6$-$01.5) discovered as part of the Isaac Newton Telescope Photometric H$\alpha$ Survey of the Northern Galactic plane (IPHAS). We present Nordic Optical Telescope (NOT) narrow-band images to unveil its true morphology. This PN consists of a main cavity with two newly uncovered extended low-surface brightness lobes located towards the NW and SE directions. Using near-IR WISE images we unveiled the presence of a barrel like structure, which surrounds the main cavity, which would explain the dark lane towards the equatorial regions. We also use Gran Telescopio de Canarias (GTC) spectra to study the physical properties of this PN. We emphasise the potential of old PNe detected in IPHAS to study the final stages of the evolution of the circumstellar medium around solar-like stars., Comment: 9 pages, 8 Figures, 3 Tables; Accepted to MNRAS

We present a comprehensive infrared (IR) study of the iconic Wolf-Rayet (WR) wind-blown bubble NGC6888 around WR136. We use Wide-field Infrared Survey Explorer (WISE), Spitzer IRAC and MIPS and Herschel PACS IR images to produce a sharp view of the distribution of dust around WR136. We complement these IR photometric observations with Spitzer IRS spectra in the 5-38 $\mu$m wavelength range. The unprecedented high-resolution IR images allowed us to produce a clean spectral energy distribution, free of contamination from material along the line of sight, to model the properties of the dust in NGC6888. We use the spectral synthesis code Cloudy to produce a model for NGC6888 that consistently reproduces its optical and IR properties. Our best model requires a double distribution with the inner shell composed only of gas, whilst the outer shell requires a mix of gas and dust. The dust consists of two populations of grain sizes, one with small sized grains $a_\mathrm{small}$=[0.002-0.008] $\mu$m and another one with large sized grains $a_\mathrm{big}$=[0.05-0.5] $\mu$m. The population of big grains is similar to that reported for other red supergiants stars and dominates the total dust mass, which leads us to suggest that the current mass of NGC6888 is purely due to material ejected from WR136, with a negligible contribution of swept up interstellar medium. The total mass of this model is 25.5$^{+4.7}_{-2.8}$ M$_{\odot}$, a dust mass of $M_\mathrm{dust}=$0.14$^{+0.03}_{-0.01}$ M$_{\odot}$, for a dust-to-gas ratio of $5.6\times10^{-3}$. Accordingly, we suggest that the initial stellar mass of WR136 was $\lesssim$50 M$_{\odot}$, consistent with current single stellar evolution models., Comment: 13 pages, 11 figures, 6 tables; Accepted to MNRAS

The Wolf-Rayet nebula M1-67 around WR124 is located above the Galactic plane in a region mostly empty of interstellar medium, which makes it the perfect target to study the mass-loss episodes associated with the late stages of massive star evolution. Archive photometric observations from WISE, Spitzer (MIPS) and Herschel (PACS and SPIRE) are used to construct the spectral energy distribution (SED) of the nebula in the wavelength range of 12-500$\mu$m. The infrared (photometric and spectroscopic) data and nebular optical data from the literature are modeled simultaneously using the spectral synthesis code Cloudy, where the free parameters are the gas density distribution and the dust grain size distribution. The infrared SED can be reproduced by dust grains with two size distributions: a MRN power-law distribution with grain sizes between 0.005 and 0.05$\mu$m and a population of large grains with representative size 0.9$ \mu$m. The latter points towards an eruptive origin for the formation of M1-67. The model predicts a nebular ionized gas mass of $M_\mathrm{ion} = 9.2^{+1.6}_{-1.5}~\mathrm{M}_\odot$ and the estimated mass-loss rate during the dust-formation period is $\dot{M} \approx 6 \times 10^{-4} \mathrm{M}_\odot$yr$^{-1}$. We discuss the implications of our results in the context of single and binary stellar evolution and propose that M1-67 represents the best candidate for a post-common envelope scenario in massive stars., Comment: 15 pages, 11 Figures, 7 Tables; accepted for MNRAS

We present the analysis of the planetary nebula (PN) NGC 2371 around the [Wolf-Rayet] ([WR]) star WD 0722$+$295. Our Isaac Newton Telescope (INT) Intermediate Dispersion Spectrograph (IDS) spectra, in conjunction with archival optical and UV images, unveil in unprecedented detail the high-ionisation of NGC 2371. The nebula has an apparent multipolar morphology, with two pairs of lobes protruding from a barrel-like central cavity, a pair of dense low-ionisation knots misaligned with the symmetry axis embedded within the central cavity, and a high excitation halo mainly detected in He II. The abundances from the barrel-like central cavity and dense knots agree with abundance determinations for other PNe with [WR]-type CSPNe. We suggest that the densest knots inside NGC 2371 are the oldest structures, remnant of a dense equatorial structure, whilst the main nebular shell and outer lobes resulted from a latter ejection that ended the stellar evolution. The analysis of position-velocity diagrams produced from our high-quality spectra suggests that NGC 2371 has a bipolar shape with each lobe presenting a double-structure protruding from a barrel-like central region. The analysis of the spectra of WD 0722$+$295 results in similar stellar parameters as previously reported. We corroborate that the spectral sub-type corresponds with a [WO1] type., Comment: 15 pages, 12 figures, 5 tables; accepted to MNRAS

We present an analysis of archival Chandra and XMM-Newton observations of the magnetically-active cataclysmic variable DQ Her and the shell around it ejected in a nova event in 1934. A careful revision of the Chandra observations confirms previous claims on the presence of extended X-ray emission around DQ Her and reveals that it actually corresponds to a bipolar jet-like structure extending $\simeq$32$''$ along a direction from NE to SW. Therefore, this X-ray emission extends beyond the optical nova shell and is perpendicular to its major axis. The XMM-Newton observations confirm the presence of the extended X-ray emission detected by Chandra, suggesting the additional presence of a diffuse X-ray emission from a hot bubble filling the nova shell. This hot bubble was very likely produced by the explosion that created the nebular shell detected in optical images. The bipolar feature can be modelled by the combination of an optically thin plasma emission component with temperature $T\approx2\times10^{6}$ K and a power law component with a photon index of $\Gamma=1.1\pm0.9$. Its X-ray luminosity in the 0.3 - 5 keV energy range is $L_\mathrm{X}=(2.1\pm1.3)\times10^{29}$ erg s$^{-1}$, for an electron density $n_\mathrm{e}\approx2$ cm$^{-3}$ and a mass $m_\mathrm{X}\approx 3\times10^{-6}$ M$_{\odot}$. We suggest that the X-ray bipolar structure in DQ Her is a jet and interpret its non-thermal X-ray emission in terms of a magnetized jet., Comment: 8 pages, 4 figures, 1 table; accepted to MNRAS

We present a detailed comparative study of the arcs and fragmented ring-like features in the haloes of the planetary nebulae (PNe) NGC 6543, NGC 7009, and NGC 7027 and the spiral pattern around the carbon star AFGL 3068 using high-quality multi-epoch HST images. This comparison allows us to investigate the connection and possible evolution between the regular patterns surrounding AGB stars and the irregular concentric patterns around PNe. The radial proper motion of these features, ~15 km/s, are found to be consistent with the AGB wind and their linear sizes and inter-lapse times (500-1900 yr) also agree with those found around AGB stars, suggesting a common origin. We find evidence using radiative-hydrodynamic simulations that regular patterns produced at the end of the AGB phase become highly distorted by their interactions with the expanding PN and the anisotropic illumination and ionization patterns caused by shadow instabilities. These processes will disrupt the regular (mostly spiral) patterns around AGB stars, plausibly becoming the arcs and fragmented rings observed in the haloes of PNe., Comment: 13 pages, 9 figures, accepted for publication in MNRAS

The ACIS-S camera on board the Chandra X-ray Observatory has been used to discover a hot bubble in the planetary nebula (PN) IC4593, the most distant PN detected by Chandra so far. The data are used to study the distribution of the X-ray-emitting gas in IC 4593 and to estimate its physical properties. The hot bubble has a radius of ~2$^{\prime\prime}$ and is found to be confined inside the optically-bright innermost cavity of IC 4593. The X-ray emission is mostly consistent with that of an optically-thin plasma with temperature $kT\approx0.15$ keV (or $T_\mathrm{X}\approx1.7\times10^{6}$ K), electron density $n_\mathrm{e}\approx15$ cm$^{-3}$, and intrinsic X-ray luminosity in the 0.3-1.5 keV energy range $L_\mathrm{X}=3.4\times10^{30}$ erg s$^{-1}$. A careful analysis of the distribution of hard ($E>$0.8 keV) photons in IC 4593 suggests the presence of X-ray emission from a point source likely associated with its central star (CSPN). If this were the case, its estimated X-ray luminosity would be $L_\mathrm{X,CSPN}=7\times10^{29}$ erg s$^{-1}$, fulfilling the log$(L_\mathrm{X,CSPN}/L_\mathrm{bol})\approx-7$ relation for self-shocking winds in hot stars. The X-ray detection of the CSPN helps explain the presence of high-ionisation species detected in the UV spectra as predicted by stellar atmosphere models., Comment: 6 pages, 4 figures; Accepted to MNRAS

We present a multiwavelength study of the iconic Bubble Nebula (NGC 7635) and its ionising star BD$+$60$^{\circ}$2522. We obtained XMM-Newton EPIC X-ray observations to search for extended X-ray emission as in other similar wind-blown bubbles around massive stars. We also obtained San Pedro M\'{a}rtir spectroscopic observations with the Manchester Echelle Spectrometer to study the dynamics of the Bubble Nebula. Although our EPIC observations are deep, we do not detect extended X-ray emission from this wind-blown bubble. On the other hand, BD$+$60$^{\circ}$2522 is a bright X-ray source similar to other O stars. We used the stellar atmosphere code PoWR to characterise BD$+$60$^{\circ}$2522 and found that this star is a young O-type star with stellar wind capable of producing a wind-blown bubble that in principle could be filled with hot gas. We discussed our findings in line with recent numerical simulations proposing that the Bubble Nebula has been formed as the result of the fast motion of BD$+$60$^{\circ}$2522 through the medium. Our kinematic study shows that the Bubble Nebula is composed by a series of nested shells, some showing blister-like structures, but with little signatures of hydrodynamical instabilities that would mix the material producing diffuse X-ray emission as seen in other wind-blown bubbles. Its morphology seems to be merely the result of projection effects of these different shells., Comment: 10 Figures, 1 Table; Accepted to MNRAS

Nova shells can provide us with important information on their distance, their interactions with the circumstellar and interstellar media, and the evolution in morphology of the ejecta. We have obtained narrow-band images of a sample of five nova shells, namely DQHer, FHSer, TAur, V476Cyg, and V533Her, with ages in the range from 50 to 130 years. These images have been compared with suitable available archival images to derive their angular expansion rates. We find that all the nova shells in our sample are still in the free expansion phase, which can be expected, as the mass of the ejecta is 7-45 times larger than the mass of the swept-up circumstellar medium. The nova shells will keep expanding freely for time periods up to a few hundred years, reducing their time dispersal into the interstellar medium., Comment: 8 pages, 2 figures, 3 tables. Accepted for publication in ApJ

We report the detection of 7 new Wolf-Rayet (WR) star locations in M81 using the Multi-Object Spectrograph of the OSIRIS instrument at Gran Telescopio Canarias. These detections are the result of a follow-up of an earlier study using the same instrumental set-up that resulted in the detection of 14 WR locations. We analyse the entire sample of 21 spectra to classify them to one of the known WR sub-types using template spectra of WR stars in the Large Magellanic Cloud (LMC), with similar metallicity to M81. Taking into consideration the dispersion in the strengths of the bumps for a given WR sub-type, we found that 19 of the 21 locations correspond to individual stars, including all the 7 new detections, of sub-types: WNL, WNE, WCE and the transitional WN/C. None of the detections correspond to WCL or WO types. The positions of these stars in the red bump vs blue bump luminosity diagram agrees well with an evolutionary path according to the Conti scenario. Based on this, we propose this diagram as a straightforward tool for spectral classification of extragalactic WR sources. The detection of individual WR stars in M81, which is at a distance of 3.6 Mpc, opens up a new environment for testing the massive star evolutionary models., Comment: 15 pages, 7 figures, 6 tables; accepted to MNRAS

A significant fraction of planetary nebulae (PNe) exhibit collimated outflows, distinct narrow kinematical components with notable velocity shifts with respect to the main nebular shells typically associated with low-ionization compact knots and linear or precessing jet-like features. We present here a spatio-kinematical investigation of a sample of twelve PNe with morphologies in emission lines of low-ionization species suggestive of collimated outflows. Using archival narrow-band images and our own high-dispersion long-slit echelle spectra, we confirm the presence of collimated outflows in Hen 2-429, J 320, M 1-66, M 2-40, M 3-1, and NGC 6210 and possibly in NGC 6741, for which the spatio-kinematical data can also be interpreted as a pair of bipolar lobes. The presence of collimated outflows is rejected in Hen 2-47, Hen 2-115, M 1-26, and M 1-37, but their morphology and kinematics are indicative of the action of supersonic outflows that have not been able to pierce through the nebular envelope. In this sense, M 1-66 appears to have experienced a similar interaction between the outflow and nebular envelope, but, as opposed to these four PNe, the outflow has been able to break through the nebular envelope. It is suggested that the PNe without collimated outflows in our sample are younger or descend from lower mass progenitors than those that exhibit unambiguous collimated outflows., Comment: 14 pages, 12 figures, ACCEPTED

We present the discovery of extended X-ray emission from the planetary nebula (PN) NGC 5189 around the [WO1]-type WD 1330-657 with XMM-Newton. The X-ray-emitting gas fills the cavities detected in the Hubble Space Telescope [O III] narrow-band image and presents a limb-brightened morphology towards the outer edges of the east and west lobes. The bulk of the X-ray emission is detected in the soft (0.3 - 0.7 keV) band with the XMM-Newton EPIC spectra dominated by the C VI Ly$\alpha$ line at 0.37 keV (=33.7 \AA). Spectral analysis resulted in carbon and neon abundances 38 and 6 times their solar values, with a plasma temperature of $kT=0.14\pm0.01$ keV ($T=1.6\times10^{6}$ K) and X-ray luminosity of $L_\mathrm{X}=(2.8\pm0.8)\times10^{32}$ erg s$^{-1}$. NGC 5189 is an evolved and extended PN ($\lesssim$0.70 pc in radius), thus, we suggest that the origin of its X-ray emission is consistent with the born-again scenario in which the central star becomes carbon-rich through an eruptive very late thermal pulse, subsequently developing a fast, carbon-rich wind powering the X-ray emission as suggested for A30 and A78., Comment: 9 pages; 5 figures and 1 table; Accepted to ApJ

We present a study of the diffuse X-ray emission from the star forming region LMC-N 57 in the Large Magellanic Cloud (LMC). We use archival XMM-Newton observations to unveil in detail the distribution of hot bubbles in this complex. X-ray emission is detected from the central superbubble (SB) DEM L 229, the supernova remnant (SNR) 0532$-$675 and the Wolf-Rayet (WR) bubble DEM L 231 around the WR star Br 48. Comparison with infrared images unveils the powerful effect of massive stars in destroying their nurseries. The distribution of the hot gas in the SNR and the SB display their maxima in regions in contact with the filamentary cold material detected by IR images. Our observations do not reveal extended X-ray emission filling DEM L 231, although several point-like sources are detected in the field of view of this WR nebula. The X-ray properties of Br 48 are consistent with a binary WN4$+$O as proposed by other authors. We modeled the X-ray emission from the SB and found that its X-ray emission can be simply explained by pressure-driven wind model, that is, there is no need to invoke the presence of a SN explosion as previously suggested. The pressure calculations of the hot gas confirms that the dynamical evolution of the SB DEM L 229 is dominated by the stellar winds from the star cluster LH 76., Comment: 14 pages, 7 figures, 2 tables; accepted for publication in ApJ

We present the analysis of infrared (IR) observations of the planetary nebula NGC 40 together with spectral analysis of its [WC]-type central star HD 826. Spitzer IRS observations were used to produce spectral maps centred at polycyclic aromatic hydrocarbons (PAH) bands and ionic transitions to compare their spatial distribution. The ionic lines show a clumpy distribution of material around the main cavity of NGC 40, with the emission from [Ar II] being the most extended, whilst the PAHs show a rather smooth spatial distribution. Analysis of ratio maps shows the presence of a toroidal structure mainly seen in PAH emission, but also detected in a Herschel PACS 70 mic image. We argue that the toroidal structure absorbs the UV flux from HD 826, preventing the nebula to exhibit lines of high-excitation levels as suggested by previous authors. We discuss the origin of this structure and the results from the spectral analysis of HD 826 under the scenario of a late thermal pulse., Comment: 10 pages, 10 figures; Accepted to MNRAS

Among different types of massive stars in advanced evolutionary stages is the enigmatic WN8h type. There are only a few Wolf-Rayet (WR) stars with this spectral type in our Galaxy. It has long been suggested that WN8h-type stars are the products of binary evolution that may harbor neutron stars (NS). One of the most intriguing WN8h stars is the runaway WR124 surrounded by its magnificent nebula M1-67. We test the presence of an accreting NS companion in WR124 using 100 ks long observations by the Chandra X-ray observatory. The hard X-ray emission from WR124 with a luminosity of $L_\mathrm{X}$= 10$^{31}$ erg s$^{-1}$ is marginally detected. We use the non-LTE stellar atmosphere code PoWR to estimate the WR wind opacity to the X-rays. The wind of a WN8-type star is effectively opaque for X-rays, hence the low X-ray luminosity of WR124 does not rule out the presence of an embedded compact object. We suggest that, in general, high opacity WR winds could prevent X-ray detections of embedded NS, and be an explanation for the apparent lack of WR+NS systems., Comment: 7 pages; 1 Table; 3 Figures; to appear in ApJ Letters

The parallax expansion and kinematics of a nova shell can be used to assess its age and distance, and to investigate the interaction of the ejecta with the circumstellar medium. These are key to understand the expansion and dispersal of the nova ejecta in the Galaxy. Multi-epoch images and high-dispersion spectroscopic observations of the recently discovered classical nova shell IPHASXJ210204.7+471015 around a nova-like system have been used to derive a present day expansion rate of 0.100 arcsec/yr and an expansion velocity of 285 km/s. These data are combined to obtain a distance of 600 pc to the nova. The secular expansion of the nova shell place the event sometime between 1850 and 1890, yet it seems to have been missed at that time. Despite its young age, 130-170 yrs, we found indications that the ejecta has already experienced a noticeable deceleration, indicating the interaction of this young nova shell with the surrounding medium., Comment: 8 pages, 5 figures, Accepted for publication in MNRAS