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<jats:title>Abstract</jats:title> <jats:p>We present wide-field multiwavelength observations of <jats:italic>γ</jats:italic> Cassiopeiae (or <jats:italic>γ</jats:italic> Cas for short) in order to study its feedback toward the interstellar environment. A large expanding cavity is discovered toward <jats:italic>γ</jats:italic> Cas in the neutral hydrogen (H <jats:sc>i</jats:sc>) images at a systemic velocity of about −10 km s<jats:sup>−1</jats:sup>. The measured dimension of the cavity is roughly 2.°0 × 1.°4 (or 6.0 pc × 4.2 pc at a distance of 168 pc), while the expansion velocity is ∼5.0 ± 0.5 km s<jats:sup>−1</jats:sup>. The CO observations reveal systematic velocity gradients in IC 63 (∼20 km s<jats:sup>−1</jats:sup> pc<jats:sup>−1</jats:sup>) and IC 59 (∼30 km s<jats:sup>−1</jats:sup> pc<jats:sup>−1</jats:sup>), two cometary globules illuminated by <jats:italic>γ</jats:italic> Cas, proving fast acceleration of the globules under stellar radiation pressure. The gas kinematics indicate that the cavity is opened by strong stellar wind, which has high potential to lead to the peculiar X-ray emission observed in <jats:italic>γ</jats:italic> Cas. Our result favors a new scenario that emphasizes the roles of stellar wind and binarity in the X-ray emission of the <jats:italic>γ</jats:italic> Cas stars.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This work presents a first attempt to apply fuzzy cluster analysis (FCA) to analyzing stellar spectra. FCA is adopted to categorize line indices measured from LAMOST low-resolution spectra, and automatically remove the least metallicity-sensitive indices. The FCA-processed indices are then transferred to the artificial neural network (ANN) to derive metallicities for 147 very metal-poor (VMP) stars that have been analyzed by high-resolution spectroscopy. The FCA-ANN method could derive robust metallicities for VMP stars, with a precision of ∼0.2 dex compared with high-resolution analysis. The recommended FCA threshold value <jats:italic>λ</jats:italic> for this test is between 0.9965 and 0.9975. After reducing the dimension of the line indices through FCA, the derived metallicities are still robust, with no loss of accuracy, and the FCA-ANN method performs stably for different spectral quality from [Fe/H] ∼ −1.8 down to −3.5. Compared with traditional classification methods, FCA considers ambiguity in groupings and noncontinuity of data, and is thus more suitable for observational data analysis. Though this early test uses FCA to analyze low-resolution spectra, and feeds the input to the ANN method to derive metallicities, FCA should be able to, in the large data era, also analyze slitless spectroscopy and multiband photometry, and prepare the input for methods not limited to ANN, in the field of stellar physics for other studies, e.g., stellar classification, identification of peculiar objects. The literature-collected high-resolution sample can help improve pipelines to derive stellar metallicities, and systematic offsets in metallicities for VMP stars for three published LAMOST catalogs have been discussed.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The tidal perturbation of embedded protoplanets on their natal disks has been widely attributed to be the cause of gap-ring structures in submillimeter images of protoplanetary disks around T Tauri stars. Numerical simulations of this process have been used to propose scaling of characteristic dust-gap width/gap-ring distance with respect to planet mass. Applying such scaling to analyze observed gap samples yields a continuous mass distribution for a rich population of hypothetical planets in the range of several Earth to Jupiter masses. In contrast, the conventional core-accretion scenario of planet formation predicts a bimodal mass function due to (1) the onset of runaway gas accretion above ∼20 Earth masses and (2) suppression of accretion induced by gap opening. Here, we examine the dust disk response to the tidal perturbation of eccentric planets as a possible resolution of this paradox. Based on simulated gas and dust distributions, we show the gap-ring separation of Neptune-mass planets with small eccentricities might become comparable to that induced by Saturn-mass planets on circular orbits. This degeneracy may obliterate the discrepancy between the theoretical bimodal mass distribution and the observed continuous gap width distribution. Despite damping due to planet–disk interaction, modest eccentricity may be sustained either in the outer regions of relatively thick disks or through resonant excitation among multiple super Earths. Moreover, the ring-like dust distribution induced by planets with small eccentricities is axisymmetric even in low viscosity environments, consistent with the paucity of vortices in Atacama Large Millimeter/submillimeter Array images.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The distribution of orbital energies imparted into stellar debris following the close encounter of a star with a supermassive black hole is the principal factor in determining the rate of return of debris to the black hole, and thus in determining the properties of the resulting lightcurves from such events. We present simulations of tidal disruption events for a range of <jats:italic>β</jats:italic> ≡ <jats:italic>r</jats:italic> <jats:sub>t</jats:sub>/<jats:italic>r</jats:italic> <jats:sub>p</jats:sub> where <jats:italic>r</jats:italic> <jats:sub>p</jats:sub> is the pericenter distance and <jats:italic>r</jats:italic> <jats:sub>t</jats:sub> the tidal radius. We perform these simulations at different spatial resolutions to determine the numerical convergence of our models. We compare simulations in which the heating due to shocks is included or excluded from the dynamics. For <jats:italic>β</jats:italic> ≲ 8, the simulation results are well-converged at sufficiently moderate-to-high spatial resolution, while for <jats:italic>β</jats:italic> ≳ 8, the breadth of the energy distribution can be grossly exaggerated by insufficient spatial resolution. We find that shock heating plays a non-negligible role only for <jats:italic>β</jats:italic> ≳ 4, and that typically the effect of shock heating is mild. We show that self-gravity can modify the energy distribution over time after the debris has receded to large distances for all <jats:italic>β</jats:italic>. Primarily, our results show that across a range of impact parameters, while the shape of the energy distribution varies with <jats:italic>β</jats:italic>, the width of the energy spread imparted to the bulk of the debris is closely matched to the canonical spread, <jats:inline-formula> <jats:tex-math> <?CDATA ${\rm{\Delta }}E={{GM}}_{\bullet }{R}_{\star }/{r}_{{\rm{t}}}^{2}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="normal">Δ</mml:mi> <mml:mi>E</mml:mi> <mml:mo>=</mml:mo> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic">GM</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>•</mml:mo> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⋆</mml:mo> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:msubsup> <mml:mrow> <mml:mi>r</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">t</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac2ee8ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, for the range of <jats:italic>β</jats:italic> we have simulated.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The gravitational wave event GW170817 with a macronova/kilonova shows that a merger of two neutron stars ejects matter with radioactivity including <jats:italic>r</jats:italic>-process nucleosynthesis. A part of the ejecta inevitably falls back to the central object, possibly powering long-lasting activities of a short gamma-ray burst (sGRB), such as extended and plateau emissions. We investigate fallback accretion with <jats:italic>r</jats:italic>-process heating by performing one-dimensional hydrodynamic simulations and developing a semi-analytical model. We show that the usual fallback rate <jats:italic>dM</jats:italic>/<jats:italic>dt</jats:italic> ∝ <jats:italic>t</jats:italic> <jats:sup>−5/3</jats:sup> is halted by the heating because pressure gradients accelerate ejecta beyond an escape velocity. The suppression is steeper than Chevalier’s power-law model through Bondi accretion within a turn-around radius. The characteristic halting timescale is ∼10<jats:sup>4</jats:sup>–10<jats:sup>8</jats:sup> s for the GW170817-like <jats:italic>r</jats:italic>-process heating, which is longer than the typical timescale of the long-lasting emission of sGRBs. The halting timescale is sensitive to the uncertainty of the <jats:italic>r</jats:italic>-process. Future observations of fallback halting could constrain the <jats:italic>r</jats:italic>-process heating on the scale of a year.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We have surveyed magnetic field data from the Ulysses spacecraft and found examples of magnetic waves with the expected characteristics that point to excitation by newborn pickup He<jats:sup>+</jats:sup>. With interstellar neutrals as the likely source for the pickup ions, we have modeled the ion production rates and used them to produce wave excitation rates that we compare to the background turbulence rates. The source ions are thought to be always present, but the waves are seen when growth rates are comparable to or exceed the turbulence rates. With the exception of the fast latitude scans, and unlike the waves excited by newborn interstellar pickup H<jats:sup>+</jats:sup>, the waves are seen throughout the Ulysses orbit.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present and analyze a near-infrared (NIR) spectrum of the underluminous Type Ia supernova SN 2020qxp/ASASSN-20jq obtained with NIRES at the Keck Observatory, 191 days after <jats:italic>B</jats:italic>-band maximum. The spectrum is dominated by a number of broad emission features, including the [Fe <jats:sc>ii</jats:sc>] at 1.644 <jats:italic>μ</jats:italic>m, which is highly asymmetric with a tilted top and a peak redshifted by ≈2000 km s<jats:sup>−1</jats:sup>. In comparison with 2D non-LTE synthetic spectra computed from 3D simulations of off-center delayed-detonation Chandrasekhar-mass (<jats:italic>M</jats:italic> <jats:sub>ch</jats:sub>) white dwarf (WD) models, we find good agreement between the observed lines and the synthetic profiles, and are able to unravel the structure of the progenitor’s envelope. We find that the size and tilt of the [Fe <jats:sc>ii</jats:sc>] 1.644 <jats:italic>μ</jats:italic>m profile (in velocity space) is an effective way to determine the location of an off-center delayed-detonation transition (DDT) and the viewing angle, and it requires a WD with a high central density of ∼4 × 10<jats:sup>9</jats:sup> g cm<jats:sup>−3</jats:sup>. We also tentatively identify a stable Ni feature around 1.9 <jats:italic>μ</jats:italic>m characterized by a “pot-belly” profile that is slightly offset with respect to the kinematic center. In the case of SN 2020qxp/ASASSN-20jq, we estimate that the location of the DDT is ∼0.3<jats:italic>M</jats:italic> <jats:sub>WD</jats:sub> off center, which gives rise to an asymmetric distribution of the underlying ejecta. We also demonstrate that low-luminosity and high-density WD SN Ia progenitors exhibit a very strong overlap of Ca and <jats:sup>56</jats:sup>Ni in physical space. This results in the formation of a prevalent [Ca <jats:sc>ii</jats:sc>] 0.73 <jats:italic>μ</jats:italic>m emission feature that is sensitive to asymmetry effects. Our findings are discussed within the context of alternative scenarios, including off-center C/O detonations in He-triggered sub-<jats:italic>M</jats:italic> <jats:sub>Ch</jats:sub> WDs and the direct collision of two WDs. Snapshot programs with Gemini/Keck/Very Large Telescope (VLT)/ELT-class instruments and our spectropolarimetry program are complementary to mid-IR spectra by the James Webb Space Telescope (JWST).</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We perform a detailed theoretical study of the atomic structure of ions with <jats:italic>ns</jats:italic> <jats:sup>2</jats:sup> <jats:italic>np</jats:italic> <jats:sup> <jats:italic>m</jats:italic> </jats:sup> ground configurations and focus on departures from <jats:italic>LS</jats:italic> coupling, which directly affect the Landé <jats:italic>g</jats:italic> factors of magnetic dipole lines between levels of the ground terms. Particular emphasis is given to astrophysically abundant ions formed in the solar corona (those with <jats:italic>n</jats:italic> = 2,3) with M1 transitions spanning a broad range of wavelengths. Accurate Landé <jats:italic>g</jats:italic> factors are needed to diagnose coronal magnetic fields using measurements from new instruments operating at visible and infrared wavelengths, such as the Daniel K. Inouye Solar Telescope. We emphasize an explanation of the dynamics of atomic structure effects for nonspecialists.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Detailed analyses of high-redshift galaxies are challenging because these galaxies are faint, but this difficulty can be overcome with gravitational lensing, in which the magnification of the flux enables spectroscopy with a high signal-to-noise ratio (S/N). We present the rest-frame ultraviolet (UV) Keck Echellette Spectrograph and Imager (ESI) spectrum of the newly discovered <jats:italic>z</jats:italic> = 2.79 lensed galaxy SDSS J1059+4251. With an observed magnitude F814W = 18.8 and a magnification factor <jats:italic>μ</jats:italic> = 31 ± 3, J1059+4251 is both highly magnified and intrinsically luminous, about two magnitudes brighter than <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{\mathrm{UV}}^{* }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>UV</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>*</mml:mo> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac24a2ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> at <jats:italic>z</jats:italic> ∼ 2–3. With a stellar mass <jats:italic>M</jats:italic> <jats:sub>*</jats:sub> = (3.22 ± 0.20) × 10<jats:sup>10</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, star formation rate SFR = 50 ± 7 M<jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup>, and stellar metallicity <jats:italic>Z</jats:italic> <jats:sub>*</jats:sub> ≃ 0.15–0.5 <jats:italic>Z</jats:italic> <jats:sub>⊙</jats:sub>, J1059+4251 is typical of bright star-forming galaxies at similar redshifts. Thanks to the high S/N and the spectral resolution of the ESI spectrum, we are able to separate the interstellar and stellar features and derive properties that would be inaccessible without the aid of the lensing. We find evidence of a gas outflow with speeds up to −1000 km s<jats:sup>−1</jats:sup>, and of an inflow that is probably due to accreting material seen along a favorable line of sight. We measure relative elemental abundances from the interstellar absorption lines and find that <jats:italic>α</jats:italic>-capture elements are overabundant compared to iron-peak elements, suggestive of rapid star formation. However, this trend may also be affected by dust depletion. Thanks to the high data quality, our results represent a reliable step forward in the characterization of typical galaxies at early cosmic epochs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report on a discovery of an X-ray emitting circumstellar material (CSM) knot inside the synchrotron dominant supernova remnant RX J1713.7−3946. This knot was previously thought to be a Wolf–Rayet star (WR 85), but we realized that it is in fact ∼40″ away from WR 85, indicating no relation to WR 85. We performed high-resolution X-ray spectroscopy with the Reflection Grating Spectrometer (RGS) on board XMM-Newton. The RGS spectrum clearly resolves a number of emission lines, such as N Ly<jats:italic>α</jats:italic>, O Ly<jats:italic>α</jats:italic>, Fe <jats:sc>xviii</jats:sc>, Ne <jats:sc>x</jats:sc>, Mg <jats:sc>xi</jats:sc>, and Si <jats:sc>xiii</jats:sc>. The spectrum can be well represented by an absorbed thermal-emission model with a temperature of <jats:italic>k</jats:italic> <jats:sub>B</jats:sub> <jats:italic>T</jats:italic> <jats:sub>e</jats:sub> = 0.65 ± 0.02 keV. The elemental abundances are obtained to be <jats:inline-formula> <jats:tex-math> <?CDATA ${\rm{N}}/{\rm{H}}=3.5\pm 0.8{\left({\rm{N}}/{\rm{H}}\right)}_{\odot }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="normal">N</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> <mml:mo>=</mml:mo> <mml:mn>3.5</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.8</mml:mn> <mml:msub> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mi mathvariant="normal">N</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac2c00ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, <jats:inline-formula> <jats:tex-math> <?CDATA ${\rm{O}}/{\rm{H}}=0.5\pm 0.1{\left({\rm{O}}/{\rm{H}}\right)}_{\odot }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="normal">O</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0.5</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.1</mml:mn> <mml:msub> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mi mathvariant="normal">O</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac2c00ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>, <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{Ne}/{\rm{H}}=0.9\pm 0.1{\left(\mathrm{Ne}/{\rm{H}}\right)}_{\odot }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>Ne</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0.9</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.1</mml:mn> <mml:msub> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mi>Ne</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac2c00ieqn3.gif" xlink:type="simple" /> </jats:inline-formula>, <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{Mg}/{\rm{H}}=1.0\pm 0.1{\left(\mathrm{Mg}/{\rm{H}}\right)}_{\odot }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>Mg</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> <mml:mo>=</mml:mo> <mml:mn>1.0</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.1</mml:mn> <mml:msub> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mi>Mg</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac2c00ieqn4.gif" xlink:type="simple" /> </jats:inline-formula>, <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{Si}/{\rm{H}}=1.0\pm 0.2{\left(\mathrm{Si}/{\rm{H}}\right)}_{\odot }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>Si</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> <mml:mo>=</mml:mo> <mml:mn>1.0</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.2</mml:mn> <mml:msub> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mi>Si</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac2c00ieqn5.gif" xlink:type="simple" /> </jats:inline-formula>, and <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{Fe}/{\rm{H}}=1.3\pm 0.1{\left(\mathrm{Fe}/{\rm{H}}\right)}_{\odot }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>Fe</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> <mml:mo>=</mml:mo> <mml:mn>1.3</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.1</mml:mn> <mml:msub> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mi>Fe</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac2c00ieqn6.gif" xlink:type="simple" /> </jats:inline-formula>. The enhanced N abundance with others being about the solar values allows us to infer that this knot is CSM ejected when the progenitor star evolved into a red supergiant. The abundance ratio of N to O is obtained to be <jats:inline-formula> <jats:tex-math> <?CDATA ${\rm{N}}/{\rm{O}}={6.8}_{-2.1}^{+2.5}{\left({\rm{N}}/{\rm{O}}\right)}_{\odot }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="normal">N</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="normal">O</mml:mi> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>6.8</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2.1</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>2.5</mml:mn> </mml:mrow> </mml:msubsup> <mml:msub> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mi mathvariant="normal">N</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="normal">O</mml:mi> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac2c00ieqn7.gif" xlink:type="simple" /> </jats:inline-formula>. By comparing this to those in outer layers of red supergiant stars expected from stellar evolution simulations, we estimate the initial mass of the progenitor star to be 15 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> ≲ <jats:italic>M</jats:italic> ≲ 20 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>.</jats:p>