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1. Panchromatic HST/WFC3 Imaging Studies of Young, Rapidly Evolving Planetary Nebulae. I. NGC 6302

   https://doi.org/10.3847/1538-4357/ac51cd  

   Kastner, Joel H.; Moraga Baez, Paula; Balick, Bruce; Bublitz, Jesse; Montez, Rodolfo; Frank, Adam; Blackman, Eric (March 2022, The Astrophysical Journal)

   Abstract We present the results of a comprehensive, near-UV-to-near-IR Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) imaging study of the young planetary nebula (PN) NGC 6302, the archetype of the class of extreme bilobed, pinched-waist PNe that are rich in dust and molecular gas. The new WFC3 emission-line image suite clearly defines the dusty toroidal equatorial structure that bisects NGC 6302's polar lobes, and the fine structures (clumps, knots, and filaments) within the lobes. The most striking aspect of the new WFC3 image suite is the bright, S-shaped 1.64 μ m [Fe ii ] emission that traces the southern interior of the east lobe rim and the northern interior of the west lobe rim, in point-symmetric fashion. We interpret this [Fe ii ] emitting region as a zone of shocks caused by ongoing, fast (∼100 km s −1 ), collimated, off-axis winds from NGC 6302's central star(s). The [Fe ii ] emission and a zone of dusty, N- and S-rich clumps near the nebular symmetry axis form wedge-shaped structures on opposite sides of the core, with boundaries marked by sharp azimuthal ionization gradients. Comparison of our new images with earlier HST/WFC3 imaging reveals that the object previously identified as NGC 6302's central star is a foreground field star. Shell-like inner lobe features may instead pinpoint the obscured central star’s actual position within the nebula’s dusty central torus. The juxtaposition of structures revealed in this HST/WFC3 imaging study of NGC 6302 presents a daunting challenge for models of the origin and evolution of bipolar PNe. 

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2. MUSE crowded field 3D spectroscopy in NGC 300: IV. Planetary nebula luminosity function

   https://doi.org/10.1051/0004-6361/202244597  

   Soemitro, Azlizan A; Roth, Martin M; Weilbacher, Peter M; Ciardullo, Robin; Jacoby, George H; Monreal-Ibero, Ana; Castro, Norberto; Micheva, Genoveva (March 2023, Astronomy & Astrophysics)

   Aims.We perform a deep survey of planetary nebulae (PNe) in the spiral galaxy NGC 300 to construct its planetary nebula luminosity function (PNLF). We aim to derive the distance using the PNLF and to probe the characteristics of the most luminous PNe. Methods.We analysed 44 fields observed with MUSE at the VLT, covering a total area of ∼11 kpc². We find [O III]λ5007 sources using the differential emission line filter (DELF) technique. We identified PNe through spectral classification with the aid of the BPT diagram. The PNLF distance was derived using the maximum likelihood estimation technique. For the more luminous PNe, we also measured their extinction using the Balmer decrement. We estimated the luminosity and effective temperature of the central stars of the luminous PNe based on estimates of the excitation class and the assumption of optically thick nebulae. Results.We identify 107 PNe and derive a most-likely distance modulus $$ (m-M)_0 = 26.48^{+0.11}_{-0.26} $$ ($$ d = 1.98^{+0.10}_{-0.23} $$ Mpc). We find that the PNe at the PNLF cutoff exhibit relatively low extinction, with some high-extinction cases caused by local dust lanes. We present the lower limit luminosities and effective temperatures of the central stars for some of the brighter PNe. We also identify a few Type I PNe that come from a young population with progenitor masses > 2.5 M_⊙but do not populate the PNLF cutoff. Conclusions.The spatial resolution and spectral information of MUSE allow precise PN classification and photometry. These capabilities also enable us to resolve possible contamination by diffuse gas and dust, improving the accuracy of the PNLF distance to NGC 300. 

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3. JWST Observations of the Ring Nebula (NGC 6720). III. A Dusty Disk around Its Central Star

   https://doi.org/10.3847/1538-4357/adc91c  

   Sahai, Raghvendra; Van_de_Steene, Griet; van_Hoof, Peter_A M; Zijlstra, Albert; Volk, Kevin; Dinerstein, Harriet L; Barlow, Michael J; Peeters, Els; Manchado, Arturo; Matsuura, Mikako; et al (May 2025, The Astrophysical Journal)

   Abstract The planetary nebula NGC 6720, also known as the “Ring Nebula,” is one of the most iconic examples of nearby planetary nebulae whose morphologies present a challenge to our theoretical understanding of the processes that govern the deaths of most stars in the Universe that evolve on a Hubble time. We present new imaging with JWST of the central star of this planetary nebula (CSPN) and its close vicinity, in the near-to-mid-IR wavelength range. We find the presence of a dust cloud around the CSPN, both from the spectral energy distribution at wavelengths ≳5μm as well as from radially extended emission in the 7.7, 10, and 11.3μm images. From the modeling of these data, we infer that the CSPN has a luminosity of 310L_⊙and is surrounded by a dust cloud with a size of ∼2600 au, consisting of relatively small amorphous silicate dust grains (radius ∼0.01μm) with a total mass of 1.9 × 10⁻⁶M_⊕. However, our best-fit model shows a significant lack of extended emission at 7.7μm—we show that such emission can arise from a smaller (7.3 × 10⁻⁷M_⊕) but uncertain mass of (stochastically heated) ionized polycyclic aromatic hydrocarbon (PAHs). However, the same energetic radiation also rapidly destroys PAH molecules, suggesting that these are most likely being continuously replenished, via the outgassing of cometary bodies and/or the collisional grinding of planetesimals. We also find significant photometric variability of the central source that could be due to the presence of a close dwarf companion of mass ≤0.1M_⊙. 

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4. Physical Conditions of the Ionized Superwind in NGC 253 with VLT/MUSE

   https://doi.org/10.3847/1538-4357/add738  

   Cronin, Serena A; Bolatto, Alberto D; Congiu, Enrico; Donaghue, Keaton; Kreckel, Kathryn; Leroy, Adam K; Levy, Rebecca C; Veilleux, Sylvain; Walter, Fabian; Nolasco, Lenin (July 2025, The Astrophysical Journal)

   Abstract We present an analysis of the Hα-emitting ionized gas in the warm phase of the NGC 253 outflow using integral field spectroscopy from the Multi Unit Spectroscopic Explorer. In each spaxel, we decompose Hα, [Nii], and [Sii] emission lines into a system of up to three Gaussian components, accounting for the velocity contributions due to the disk and both intercepted walls of an outflow cone. In the approaching southern lobe of the outflow, we find maximum deprojected outflow velocities down to ∼−500 km s⁻¹. Velocity gradients of this outflowing gas range from ∼−350 to −550 km s⁻¹kpc⁻¹with increasing distance from the nucleus. Additionally, [Nii]/Hαand [Sii]/Hαintegrated line ratios are suggestive of shocks as the dominant ionization source throughout the wind. Electron densities, inferred from the [Sii] doublet, peak at 2100 cm⁻³near the nucleus and reach ≲50 cm⁻³in the wind. Finally, at an uncertainty of 0.3 dex on the inferred mass of 4 × 10⁵M_⊙, the mass-outflow rate of the Hα-emitting gas in the southern outflow lobe is ∼0.4M_⊙yr⁻¹. This yields a mass-loading factor ofη ∼ 0.1 and a ∼2% starburst energy efficiency. 

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5. Eruptive mass loss less than a year before the explosion of superluminous supernovae: I. The cases of SN 2020xga and SN 2022xgc

   https://doi.org/10.1051/0004-6361/202452357  

   Gkini, A; Fransson, C; Lunnan, R; Schulze, S; Poidevin, F; Sarin, N; Könyves-Tóth, R; Sollerman, J; Omand, C_M B; Brennan, S J; et al (February 2025, Astronomy & Astrophysics)

   We present photometric and spectroscopic observations of SN 2020xga and SN 2022xgc, two hydrogen-poor superluminous supernovae (SLSNe-I) atz = 0.4296 andz = 0.3103, respectively, which show an additional set of broad Mg IIabsorption lines, blueshifted by a few thousands kilometer second⁻¹with respect to the host galaxy absorption system. Previous work interpreted this as due to resonance line scattering of the SLSN continuum by rapidly expanding circumstellar material (CSM) expelled shortly before the explosion. The peak rest-frameg-band magnitude of SN 2020xga is −22.30 ± 0.04 mag and of SN 2022xgc is −21.97 ± 0.05 mag, placing them among the brightest SLSNe-I. We used high-quality spectra from ultraviolet to near-infrared wavelengths to model the Mg IIline profiles and infer the properties of the CSM shells. We find that the CSM shell of SN 2020xga resides at ∼1.3 × 10¹⁶cm, moving with a maximum velocity of 4275 km s⁻¹, and the shell of SN 2022xgc is located at ∼0.8 × 10¹⁶cm, reaching up to 4400 km s⁻¹. These shells were expelled ∼11 and ∼5 months before the explosions of SN 2020xga and SN 2022xgc, respectively, possibly as a result of luminous-blue-variable-like eruptions or pulsational pair instability (PPI) mass loss. We also analyzed optical photometric data and modeled the light curves, considering powering from the magnetar spin-down mechanism. The results support very energetic magnetars, approaching the mass-shedding limit, powering these SNe with ejecta masses of ∼7 − 9 M_⊙. The ejecta masses inferred from the magnetar modeling are not consistent with the PPI scenario pointing toward stars > 50 M_⊙He-core; hence, alternative scenarios such as fallback accretion and CSM interaction are discussed. Modeling the spectral energy distribution of the host galaxy of SN 2020xga reveals a host mass of 10^7.8M_⊙, a star formation rate of 0.96_−0.26^+0.47M_⊙yr⁻¹, and a metallicity of ∼0.2 Z_⊙. 

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