Andreas Ritter

This study was motivated by the search for planetary nebulae (PNe) and open cluster (OCs) associations. Only five PNe are currently in Galactic OCs among the previous ∼4800 OCs known. They are valuable because as cluster members their properties can be linked to their progenitor stars, something no possible for general field PNe. Since the GAIA astrometric satellite first data release, thousands of new OC candidates have been identified. This offers fresh motivation to search them as hosts for known PNe. Statistically we expect 30 OC-PN pairs to be present. We searched these GAIA candidate OCs, found by E. L. Hunt & S. Reffert, for known central stars of PNe (CSPNe) as a practical proxy for the PNe themselves and one suited to automated searches. We identified 1 potential CSPN (IRAS 15127-5811) of “likely” PN [GKF2010] MN18 in the HASH database, as a claimed member of the putative cluster HSC 2686. A second cluster (Lynga 3) with similar parameters and in very close angular proximity could also be a potential host. Here we reclassify CSPN IRAS 15127-5811 as a blue supergiant with a surrounding bipolar nebular. Nevertheless, we collected all available information on proposed member stars for both these clusters. We conclude that neither claimed cluster is real. Our results shed considerable doubt on the veracity of many newly identified OCs that have modest numbers of stellar members.

Context. The identification of the nebula HaTr 5 with the shell remnant of the historic Nova Sco 1437 around the low-accretion rate cataclysmic variable 2MASS J17022815-4306123 has been used in the framework of the hibernation scenario to set an upper limit of ≤580 yr on the transition time from a nova-like binary to a dwarf nova. Aims. This work is aimed at clarifying the nature of HaTr 5, which has also been deemed a possible planetary nebula in previous works. Methods. We obtained intermediate- and high-dispersion long-slit spectra of HaTr 5 and analyzed them in conjunction with archival optical and infrared images to investigate its spectral properties using photoionization models. In addition, we sought to derive its Hα flux and ionized mass and determine its spatio-kinematic by means of 3D models to clarify its true nature. Results. The Hα flux of HaTr 5 implies an ionized mass of 0.059 M_⊙ at the 0.99 kpc distance of 2MASS J17022815-4306123, namely, ∼1000 times the typical ejecta of a nova. If HaTr 5 were actually an unrelated planetary nebula, its Hα flux would imply a distance of 2.25 kpc and an ionized mass of 0.47 M_⊙. The expansion velocity of HaTr 5 is found to be ≃27 km s⁻¹, with a heliocentric radial velocity of −1 km s⁻¹. Conclusions. The ionized mass of HaTr 5 and its expansion velocity (and associated kinematic age) are clearly inconsistent with those expected for a nova remnant, all strongly support a planetary nebula nature. The association of 2MASS J17022815-4306123 with HaTr 5 is further called into question based on their differing radial velocities and almost orthogonal motions on the plane of the sky. We have concluded that HaTr 5 is an old, evolved planetary nebula unrelated to the remnant of Nova Sco 1437 or to the cataclysmic variable 2MASS J17022815-4306123, with the latter being by chance projected onto HaTr 5.

This work presents emission line flux and kinematic structure mapping based on IFU data of the planetary nebulae Abell 30 (A30). The IFU has a field of view (FoV) of 16" x 12.3" and was used to partially cover knots J1 and J2, and completely cover knots J3 and J4 of A30. Our emission line flux map shows recombination species C II, C III, He I, O II as well as forbidden line species [O III], [Ne III] and [Ne IV] of high excitation level are all distributed in different parts of the knots. The kinematic structure shows considerable variation in both the velocities and spatial locations of these knots with positive and negative velocity excursions from the systematic value. Forbidden line species [O III], [Ne III] are distributed in both knots J3 and J4 but they are travelling at different speeds in opposite directions. Despite variation in distribution of the species, the velocities of [Ne IV] and [O III] are similar and travelling in the same direction while the other species [Ne III], He I, and O II share similar velocity of 200kms−1 up in the opposite direction. The complexity of distribution and kinematic structure of the knots revealed in this work indicates a strong tendency towards the hypothesis of multiple triggering events in the past history of A30.

The observation of the low-energy γ-ray (0.1 to 30 MeV) sky has been significantly limited since the COMPTEL instrument aboard the Compton Gamma Ray Observatory (CGRO) satellite was decommissioned in 2000. The exploration of γ-ray photons within this energy band, often referred to as the MeV gap, is crucial to address numerous unresolved mysteries in high-energy and multi-messenger astrophysics. Although several large MeV γ-ray missions have been proposed (e.g., e-ASTROGAM, AMEGO, and COSI), most of these are in the planning phase, with launches not expected until the next decade, at the earliest. Recently, there has been a surge in proposed CubeSat missions as cost-effective and rapidly implementable pathfinder alternatives. An MeV CubeSat dedicated to γ-ray astronomy could serve as a valuable demonstrator for large-scale future MeV payloads. This paper proposes a γ-ray payload design with a silicon-based tracker and a cesium iodide-based calorimeter. We report the results of a simulation study to assess the performance of this payload concept and compare the results with those of previous γ-ray instruments. As part of the performance assessment and comparison, we show that with our proposed payload design, a sensitivity better than IBIS can be achieved for energies between 0.1 and 10 MeV, and for energies up to around 1 MeV, the achieved sensitivity is comparable to COMPTEL, therefore opening up a window toward cost-effective observational astronomy with comparable performance to past missions.

On August 25 2013 Dana Patchick from the “Deep Sky Hunters” (DSH) amateur astronomer group discovered a diffuse nebulosity in the Wide-field Infrared Survey Explorer (WISE) mid-IR image archive that had no optical counterpart but appeared similar to many Planetary Nebulae (PNe) in WISE. As his 30th discovery he named it Pa 30 and it was added to the HASH PN database as a new PN candidate. Little did he know how important his discovery would become. 10 years later this object is the only known bound remnant of a violent double WD merger accompanied by a rare Type Iax SN, observed and recorded by the ancient Chinese and Japanese in 1181 AD. This makes Pa 30 and its central star IRAS 00500+6713 (WD J005311) the only SN Iax remnant in our Galaxy, the only known bound remnant of any SN, and based on the central star’s spectrum the only Wolf-Rayet star known that neither has a massive progenitor nor is the central star of a Planetary Nebula. We cover this story and our key role in it.

We report observations of a remarkable major axes alignment nearly parallel to the Galactic plane of 5σ significance for a subset of bulge "planetary nebulae" (PNe) that host, or are inferred to host, short period binaries. Nearly all are bipolar. It is solely this specific PNe population that accounts for the much weaker statistical alignments previously reported for the more general bulge PNe. It is clear evidence of a persistent, organised process acting on a measurable parameter at the heart of our Galaxy over perhaps cosmologically significant periods of time for this very particular PNe sample. Stable magnetic fields are currently the only plausible mechanism that could affect multiple binary star orbits as revealed by the observed major axes orientations of their eventual PNe. Examples are fed into the current bulge planetary nebulae population at a rate determined by their formation history and mass range of their binary stellar progenitors.

We report observations of a remarkable major axes alignment nearly parallel to the Galactic plane of 5σ significance for a subset of bulge “planetary nebulae” (PNe) that host, or are inferred to host, short-period binaries. Nearly all are bipolar. It is solely this specific PN population that accounts for the much weaker statistical alignments previously reported for the more general bulge PNe. It is clear evidence of a persistent, organized process acting on a measurable parameter at the heart of our galaxy over perhaps cosmologically significant periods of time for this very particular PN sample. Stable magnetic fields are currently the only plausible mechanism that could affect multiple binary star orbits as revealed by the observed major axes orientations of their eventual PNe. Examples are fed into the current bulge PN population at a rate determined by their formation history and mass range of their binary stellar progenitors.

We report observations and modeling of the stellar remnant and presumed double-degenerate merger of Type Iax supernova Pa 30, which is the probable remnant of SN 1181 AD. It is the only known bound stellar SN remnant and the only star with Wolf–Rayet features that is neither a planetary nebula central star nor a massive Population I progenitor. We model the unique emission-line spectrum with broad, strong O vi and O viii lines as a fast stellar wind and shocked, hot gas. Non-LTE wind modeling indicates a mass-loss rate of ∼10⁻⁶ M _⊙ yr⁻¹ and a terminal velocity of ∼15,000 km s⁻¹, consistent with earlier results. O viii lines indicate shocked gas temperatures of T ≃ 4 MK. We derive a magnetic field upper limit of B < 2.5 MG, below earlier suggestions. The luminosity indicates a remnant mass of 1.0–1.65 M _⊙ with ejecta mass 0.15 ± 0.05 M _⊙. Archival photometry suggests the stellar remnant has dimmed by ∼0.5 mag over 100 yr. A low Ne/O < 0.15 argues against an O-Ne white dwarf in the merger. A cold dust shell is only the second detection of dust in an SN Iax and the first of cold dust. Our ejecta mass and kinetic energy estimates of the remnant are consistent with Type Iax extragalactic sources.