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1. New Observations of the IR Emission Corona from the 2019 July 2 Eclipse Flight of the Airborne Infrared Spectrometer

   https://doi.org/10.3847/1538-4357/ac6ce8  

   Samra, Jenna E.; Madsen, Chad A.; Cheimets, Peter; DeLuca, Edward E.; Golub, Leon; Marquez, Vanessa; Reyes, Naylynn Tañón (July 2022, The Astrophysical Journal)

   Abstract The Airborne Infrared Spectrometer (AIR-Spec) was commissioned during the 2017 total solar eclipse, when it observed five infrared coronal emission lines from a Gulfstream V research jet owned by the National Science Foundation and operated by the National Center for Atmospheric Research. The second AIR-Spec research flight took place during the 2019 July 2 total solar eclipse across the south Pacific. The 2019 eclipse flight resulted in seven minutes of observations, during which the instrument measured all four of its target emission lines: S xi 1.393 μ m, Si x 1.431 μ m, S xi 1.921 μ m, and Fe ix 2.853 μ m. The 1.393 μ m S xi line was detected for the first time, and probable first detections were made of Si xi 1.934 μ m and Fe x 1.947 μ m. The 2017 AIR-Spec detection of Fe ix was confirmed and the first observations were made of the Fe ix line intensity as a function of solar radius. Telluric absorption features were used to calibrate the wavelength mapping, instrumental broadening, and throughput of the instrument. AIR-Spec underwent significant upgrades in preparation for the 2019 eclipse observation. The thermal background was reduced by a factor of 30, providing a 5.5× improvement in signal-to-noise ratio, and the postprocessed pointing stability was improved by a factor of 5 to <10″ rms. In addition, two imaging artifacts were identified and resolved, improving the spectral resolution and making the 2019 data easier to interpret. 

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2. The Solar Minimum Eclipse of 2019 July 2. III. Inferring the Coronal T _e with a Radiative Differential Emission Measure Inversion

   https://doi.org/10.3847/1538-4357/acd10b  

   Boe, Benjamin; Downs, Cooper; Habbal, Shadia (July 2023, The Astrophysical Journal)

   Vishniac, E. (Ed.)

   Abstract Differential emission measure (DEM) inversion methods use the brightness of a set of emission lines to infer the line-of-sight (LOS) distribution of the electron temperature (T_e) in the corona. DEM inversions have been traditionally performed with collisionally excited lines at wavelengths in the extreme ultraviolet and X-ray. However, such emission is difficult to observe beyond the inner corona (1.5R_⊙), particularly in coronal holes. Given the importance of theT_edistribution in the corona for exploring the viability of different heating processes, we introduce an analog of the DEM specifically for radiatively excited coronal emission lines, such as those observed during total solar eclipses (TSEs) and with coronagraphs. This radiative-DEM (R-DEM) inversion utilizes visible and infrared emission lines that are excited by photospheric radiation out to at least 3R_⊙. Specifically, we use the Fex(637 nm), Fexi(789 nm), and Fexiv(530 nm) coronal emission lines observed during the 2019 July 2 TSE near solar minimum. We find that, despite a largeT_espread in the inner corona, the distribution converges to an almost isothermal yet bimodal distribution beyond 1.4R_⊙, withT_eranging from 1.1 to 1.4 in coronal holes and from 1.4 to 1.65 MK in quiescent streamers. Application of the R-DEM inversion to the Predictive Science Inc. magnetohydrodynamic simulation for the 2019 eclipse validates the R-DEM method and yields a similar LOST_edistribution to the eclipse data. 

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3. A JWST Near- and Mid-infrared Nebular Spectrum of the Type Ia Supernova 2021aefx

   https://doi.org/10.3847/2041-8213/acb4ec  

   Kwok, Lindsey A.; Jha, Saurabh W.; Temim, Tea; Fox, Ori D.; Larison, Conor; Camacho-Neves, Yssavo; Brenner Newman, Max J.; Pierel, Justin D.; Foley, Ryan J.; Andrews, Jennifer E.; et al (February 2023, The Astrophysical Journal Letters)

   Abstract We present JWST near-infrared (NIR) and mid-infrared (MIR) spectroscopic observations of the nearby normal Type Ia supernova (SN) SN 2021aefx in the nebular phase at +255 days past maximum light. Our Near Infrared Spectrograph (NIRSpec) and Mid Infrared Instrument observations, combined with ground-based optical data from the South African Large Telescope, constitute the first complete optical+NIR+MIR nebular SN Ia spectrum covering 0.3–14 μ m. This spectrum unveils the previously unobserved 2.5−5 μ m region, revealing strong nebular iron and stable nickel emission, indicative of high-density burning that can constrain the progenitor mass. The data show a significant improvement in sensitivity and resolution compared to previous Spitzer MIR data. We identify numerous NIR and MIR nebular emission lines from iron-group elements as well as lines from the intermediate-mass element argon. The argon lines extend to higher velocities than the iron-group elements, suggesting stratified ejecta that are a hallmark of delayed-detonation or double-detonation SN Ia models. We present fits to simple geometric line profiles to features beyond 1.2 μ m and find that most lines are consistent with Gaussian or spherical emission distributions, while the [Ar iii ] 8.99 μ m line has a distinctively flat-topped profile indicating a thick spherical shell of emission. Using our line profile fits, we investigate the emissivity structure of SN 2021aefx and measure kinematic properties. Continued observations of SN 2021aefx and other SNe Ia with JWST will be transformative to the study of SN Ia composition, ionization structure, density, and temperature, and will provide important constraints on SN Ia progenitor and explosion models. 

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4. The JWST View of Cygnus A: Jet-driven Coronal Outflow with a Twist

   https://doi.org/10.3847/1538-4357/adb71a  

   Ogle, Patrick M; Sebastian, B; Aravindan, A; McDonald, M; Canalizo, G; Ashby, M_L N; Azadi, M; Antonucci, R; Barthel, P; Baum, S; et al (April 2025, The Astrophysical Journal)

   Abstract We present first results from James Webb Space Telescope Near-Infrared Spectrograph, Mid-Infrared Instrument, and Keck Cosmic Webb Imager integral field spectroscopy of the powerful but highly obscured host galaxy of the jetted radio source Cygnus A. We detect 169 infrared emission lines at 1.7–27μm and explore the kinematics and physical properties of the extended narrow-line region (NLR) in unprecedented detail. The density-stratified NLR appears to be shaped by the initial blow-out and ongoing interaction of the radio jet with the interstellar medium, creating a multiphase bicone with a layered structure composed of molecular and ionized gas. The NLR spectrum, with strong coronal emission at kiloparsec scale, is well modeled by active galactic nucleus photoionization. We find evidence that the NLR is rotating around the radio axis, perhaps mediated by magnetic fields and driven by angular momentum transfer from the radio jet. The overall velocity field of the NLR is well described by 250 km s⁻¹outflow along biconical spiral flow lines, combining both rotation and outflow signatures. There is particularly bright [Feii]λ1.644μm emission from a dense, high-velocity dispersion, photoionized clump of clouds found near the projected radio axis. Outflows of 600–2000 km s⁻¹are found in bullets and streamers of ionized gas that may be ablated by the radio jet from these clouds, driving a local outflow rate of 40M_⊙yr⁻¹. 

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5. Physical Constraints on the Extended Interstellar Medium of the z = 6.42 Quasar J1148+5251: [C ii] _{158 μm} , [N ii] _{205 μm} , and [O i] _{146 μm} Observations

   https://doi.org/10.3847/1538-4357/ac4e94  

   Meyer, Romain A.; Walter, Fabian; Cicone, Claudia; Cox, Pierre; Decarli, Roberto; Neri, Roberto; Novak, Mladen; Pensabene, Antonio; Riechers, Dominik; Weiss, Axel (March 2022, The Astrophysical Journal)

   Abstract We report new Northern Extended Millimeter Array observations of the [C ii ] 158 μ m , [N ii ] 205 μ m , and [O i ] 146 μ m atomic fine structure lines (FSLs) and dust continuum emission of J1148+5251, a z = 6.42 quasar, which probe the physical properties of its interstellar medium (ISM). The radially averaged [C ii ] 158 μ m and dust continuum emission have similar extensions (up to θ = 2.51 − 0.25 + 0.46 arcsec , corresponding to r = 9.8 − 2.1 + 3.3 kpc , accounting for beam convolution), confirming that J1148+5251 is the quasar with the largest [C ii ] 158 μ m -emitting reservoir known at these epochs. Moreover, if the [C ii ] 158 μ m emission is examined only along its NE–SW axis, a significant excess (>5.8 σ ) of [C ii ] 158 μ m emission (with respect to the dust) is detected. The new wide-bandwidth observations enable us to accurately constrain the continuum emission, and do not statistically require the presence of broad [C ii ] 158 μ m line wings that were reported in previous studies. We also report the first detection of the [O i ] 146 μ m and (tentatively) [N ii ] 205 μ m emission lines in J1148+5251. Using FSL ratios of the [C ii ] 158 μ m , [N ii ] 205 μ m , [O i ] 146 μ m , and previously measured [C i ] 369 μ m emission lines, we show that J1148+5251 has similar ISM conditions compared to lower-redshift (ultra)luminous infrared galaxies. CLOUDY modeling of the FSL ratios excludes X-ray-dominated regions and favors photodissociation regions as the origin of the FSL emission. We find that a high radiation field (10 3.5–4.5 G 0 ), a high gas density ( n ≃ 10 3.5–4.5 cm −3 ), and an H i column density of 10 23 cm −2 reproduce the observed FSL ratios well. 

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