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IRAS 22568+6141 has been classified as a low-ionisation planetary nebula (PN) and presents non-thermal radio continuum emission, which could be a signature of nascent PNe. We present intermediate-resolution long-slit spectra obtained in 2021 and 2023, high-resolution long-slit spectra taken in 2023, and a light curve at the $r$-filter between 1953 and 2019, that reveal changes in IRAS 22568+6141 with timescales of decades and a few years. The object underwent an energetic event around 1990 that suddenly increased its brightness which has been fading since then. A comparison with a published spectrum from 1988 shows an increase of the H$\beta$ flux in 2021 by factor of $\simeq$6 and the [O III] emission lines that were absent in 1988. Between 2021 and 2023 the H$\beta$ flux decreased by a factor of $\simeq$1.7, and the [O III] emission lines almost vanished. These results and the variability observed in other emission lines indicate that IRAS 22568+6141 is recombining and cooling down between 2021 and 2023, and probably since 2005, as suggested by archival radio continuum and mid-IR observations. The intermediate- and high-resolution spectra show that the excitation of the emission lines is dominated by shocks in 2021 and 2023, and, probably, also in 1988, which may be related to the non-thermal radio continuum emission from the object. Although the variability might be due to changes in the physical conditions in the shocks or in a nova-like eruption, it accommodates better to that expected from a late thermal pulse, which is further suggested by a comparison with other similar objects. New observations and monitoring in the coming years are crucial to corroborate the origin of the variability., Comment: 11 pages, 8 figures, 6 tables. Accepted for publication in A&A

We report confirmation of a large, evolved, bipolar planetary nebula and its blue, white dwarf central star as a member of the ~500 Myr old Galactic open star cluster M37 (NGC 2099). This is only the third known example of a planetary nebula in a Galactic open cluster and was found via our on-going program of identifying and studying planetary nebulae - open cluster associations. High confidence in the association comes from the consistent radial velocities and proper motions for the confirmed central star and cluster stars from Gaia, reddening agreement and location of the planetary nebula well within the tidal cluster boundary. Interestingly, all three Galactic examples have bipolar morphology and likely Type I chemistry, both characteristics of higher mass progenitors. In this case the progenitor star mass is in the mid-range of ~2.8 Msun. It provides a valuable, additional point on the key stellar initial-to-final mass relation independent of cluster white dwarf estimates and also falls in a gap in the poorly sampled mass region. This planetary nebula also appears to have the largest kinematical age ever determined and implies increased visibility lifetimes when they are located in clusters., Comment: 11 pages, 5 figures, 1 table

We present high-resolution, long-slit optical spectra and images of the planetary nebula NGC1514. The position velocity maps of the [OIII] emission line reveal complex kinematics with multiple structures. A morpho-kinematical analysis suggests an inner shell, originally spherical and now distorted by several bubbles, and an attached outer shell. The two well-defined, mid-infrared rings of NGC1514 are not detected in our high-resolution, long-slit spectra, which prevented us from doing a kinematical analysis of them. Based exclusively on their morphology, we propose a barrel-like structure to explain the rings. Several ejection processes have been possibly involved in the formation of the nebula although a time sequence is difficult to establish with the current data. We also analyze intermediate-resolution, long-slit spectra with the goal of studying the physical parameters and chemical abundances of NGC1514. The nebular spectra reveal a moderate-excitation nebula with weak emission lines of [ArIII], [NeIII], HeI and HeII. No [NII] neither other low-excitation emission lines are detected. We found an electron temperature around 14000K in the gas and an electron density in the range of 2000 and 4000 cm$^{-3}$., Comment: Accepted for publication in MNRAS. 12 pages, 8 figures, 3 tables

We present new narrow-band Ha, [N II], and [O III] high-resolution images of the quadrupolar planetary nebula (PN) NGC 6309 that show in great detail its bipolar lobes and reveal new morphological features. New high- and low-dispersion long-slit spectra have been obtained to help in the investigation of the new nebular components. The images and spectra unveil two diffuse blobs, one of them located at 55 arcsec from the central star along the NE direction (PA= +71) and the other at 78 arcsec in the SW direction (PA= -151). Therefore, these structures do not share the symmetry axes of the inner bipolar outflows. Their radial velocities relative to the system are quite low: +3 and -4 km/s, respectively. Spectroscopic data confirm a high [O III] to Ha ratio, indicating that the blobs are being excited by the UV flux from the central star. Our images convincingly show a spherical halo 60 arcsec in diameter encircling the quadrupolar nebula. The expansion velocity of this shell is low, 66 km/s. The software SHAPE has been used to construct a morpho-kinematic model for the ring and the bipolar flows that implies an age of 4,000 yrs, the expansion of the halo sets a lower limit for its age 46,000 yrs, and the very low expansion of the blobs suggests they are part of a large structure corresponding to a mass ejection that took place 150,000 yrs ago. In NGC 6309 we have direct evidence of a change in the geometry of mass-loss, from spherical in the halo to axially-symmetric in the two pairs of bipolar lobes., Comment: 8 pages, 7 figures, Accepted for publication in MNRAS

NGC 6369 is a double-shell PN with a filamentary outer shell or envelope and faint bipolar extensions. We have used ground- and space-based narrowband optical and near-IR images, broadband mid-IR images, optical long-slit echelle spectra, and mid-IR spectra to investigate its physical structure. The observations confirm a bipolar structure for the inner shell of NGC 6369, but they also reveal evidence for H2 and strong polycyclic aromatic hydrocarbons (PAHs) emission from a photo-dissociation region (PDR) with molecular inclusions located outside the bright inner shell., Comment: Published in the proceedings of the IAU Symp. 283: Planetary Nebulae: An Eye to the Future 2 pages, 2 figures

Once classified as an emission line source, the planetary nebula (PN) nature of the source Kn 26 has been only recently recognized in digital sky surveys. To investigate the spectral properties and spatio-kinematical structure of Kn 26, we have obtained high spatial-resolution optical and near-IR narrow-band images, high-dispersion long-slit echelle spectra, and intermediate-resolution spectroscopic observations. The new data reveal an hourglass morphology typical of bipolar PNe. A detailed analysis of its morphology and kinematics discloses the presence of a second pair of bipolar lobes, making Kn 26 a new member of the subclass of quadrupolar PNe. The time-lap between the ejection of the two pairs of bipolar lobes is much smaller than their dynamical ages, implying a rapid change of the preferential direction of the central engine. The chemical composition of Kn 26 is particularly unusual among PNe, with a low N/O ratio (as of type II PNe) and a high helium abundance (as of type I PNe), although not atypical among symbiotic stars. Such an anomalous chemical composition may have resulted from the curtail of the time in the Asymptotic Giant Branch by the evolution of the progenitor star through a common envelope phase., Comment: 9 pages, 5 figures, accepted for publication in A&A

We have analysed optical, near-, and mid-IR images of the bright planetary nebula (PN) IC 418. These images probe unambiguously for the first time a number of low surface brightness structures and shells around the bright main nebula, including radial filaments or rays, a system of three concentric rings, and two detached haloes with sizes ~ 150" and 220"\times250", respectively. The main nebula is slightly off-centered with respect to the elliptical outer halo. The time-lapse between the two haloes is 10,000-50,000 yr, whereas the time-lapse between the three concentric rings is ~ 630 yr. We emphasize the advantages of near- and mid-IR imaging for the detection of faint structures and shells around optically bright nebulae., Comment: 9 pages, 5 figures, accepted for publication in MNRAS

High-resolution Hubble Space Telescope (HST) archive imaging and high-dispersion spectroscopy are used to study the complex morphological and kinematical structure of the planetary nebula, NGC 2818. We analyze narrow band H{\alpha}, [O III], [N II], [S II] and He II images, addressing important morphological features. Ground-based longslit echelle spectra were obtained crossing NGC 2818 at five different positions to precisely determine kinematical features in the structure of the nebula. A distance of 2.5 kpc was used to determine physical scales. Constructing models to fit the data with modern computational tools, we find NGC 2818 is composed by: (1) a non-uniform bipolar structure with a semi-major axis of 0.92 pc (75 arcsec), possibly deformed by the stellar wind, (2) a 0.17 pc (14 arcsec) diameter central region, which is potentially the remnant of an equatorial enhancement, and (3) a great number of cometary knots. These knots are preferentially located inside a radius of 0.24 pc (20 arcsec) around the central star. The ma jor axis of the main structure is oriented at i \simeq 60\degree with respect to the line-of-sight and at PA = +89\degree on the plane of the sky. Expansion velocities of this nebula are Vpol = 105 km/s and Veq = 20 km/s, which lead to our estimate of the kinematical age of {\tau}k \simeq 8,400 \pm 3, 400 yr (assuming homologous expansion). Our observations do not support the idea that high velocity collimated ejections are responsible for the formation of microstructures inside the nebula. We determine the systemic velocity of NGC 2818 to be VHEL = +26 \pm 2 km/s., Comment: 20 pages, 6 figures

NGC 6369 is a double-shell planetary nebula (PN) consisting of a bright annular inner shell with faint bipolar extensions and a filamentary envelope. We have used ground- and space-based narrow-band optical and near-IR images, broad-band mid-IR images, optical long-slit echelle spectra, and mid-IR spectra to investigate its physical structure. These observations indicate that the inner shell of NGC 6369 can be described as a barrel-like structure shape with polar bubble-like protrusions, and reveal evidence for H2 and strong polycyclic aromatic hydrocarbons (PAHs) emission from a photo-dissociative region (PDR) with molecular inclusions located outside the bright inner shell. High-resolution HST narrow-band images reveal an intricate excitation structure of the inner shell and a system of "cometary" knots. The knotty appearance of the envelope, the lack of kinematical evidence for shell expansion and the apparent presence of emission from ionized material outside the PDR makes us suggest that the envelope of NGC 6369 is not a real shell, but a flattened structure at its equatorial regions. We report the discovery of irregular knots and blobs of diffuse emission in low-excitation and molecular line emission that are located up to 80" from the central star, well outside the main nebular shells. We also show that the filaments associated to the polar protrusions have spatial extents consistent with post-shock cooling regimes, and likely represent regions of interaction of these structures with surrounding material., Comment: 14 pages, 13 figures. Accepted for publication in MNRAS

The fundamental parameters of reddening, metallicity, age, and distance are presented for the poorly studied open clusters Be~89, Ru~135, and Be~10, derived from their CCD UBVRI photometry. By fitting the appropriate isochrones to the observed sequences of the clusters in five different color--magnitude diagrams, the weighted averages of distance moduli and heliocentric distances ($(V_0$--$M_{V}), d$(kpc)) are $(11\fm90\pm 0\fm06, 2.4\pm 0.06$) for Be~89, $(9\fm58\pm 0\fm07, 0.81\pm 0.03$) for Ru~135, and $(11\fm16\pm 0\fm06, 1.7 \pm 0.05$) for Be~10, and the weighted averages of the ages $(\log(A), A$(Gyr)) are $(9.58\pm 0.06, 3.8\pm 0.6)$ for Be~89, $(9.58\pm 0.06, 3.8\pm 0.7)$ for Ru~135, and $(9.06\pm 0.05, 1.08\pm 0.08)$ for Be~10., Comment: accepted to RevMexAA

We present narrow-band optical images, VLA-A 3.6 cm continuum and H92alpha emission line data and high resolution long-slit [N II] spectra of Hu 2-1. The formation of Hu 2-1 appears dominated by anisotropic mass ejection during the late AGB stage of its progenitor and by variable, ``precessing'' collimated bipolar outflows during the proto-PN and/or early PN phases. The data strongly support the existence of a binary central star at center of Hu 2-1: (1) the brightness distribution of the bipolar lobes and inner shell is point-symmetric, and the bipolar lobes show departures from axial symmetry; (2) the position of the central star is off-center; (3) mass ejection towards the equatorial plane is detected; (4) ``precessing'' collimated outflows are present. Besides all this circumstantial evidences, the analysis of the kinematics shows that the systemic velocity of the bipolar outflows does not coincide with the systemic velocity of the nebula. We propose that this velocity difference is a direct evidence of orbital motion of the ejection source in a binary system. Assuming a reasonable range of masses for the progenitor stars, the orbital velocity of ~10 km/s corresponds to a semi-major axis of 9-27 AU and to a period of 25-80 yr. The formation of Hu 2-1 is analyzed within current scenarios of PN formation with binary central stars., Comment: 18 pages, 9 figures, to be published in MNRAS