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IRAS 15099-5856 in the young supernova remnant (SNR) MSH 15-52 is the first and only SNR-associated object with crystalline silicate dust detected so far, although its nature and the origin of the crystalline silicate are still unclear. In this paper, we present high-resolution mid-infrared (MIR) imaging observations of the bright central compact source IRS1 of IRAS 15099-5856 to study the spatial distributions of gas and dust and the analysis of its Spitzer MIR spectrum to explore the origin of IRS1. The MIR images obtained with the T-ReCS attached on the Gemini South telescope show a complicated, inhomogeneous morphology of IRS1 with bright clumps and diffuse emission in [Ne II] 12.81 $\mu$m and Qa 18.30 $\mu$m, which confirms that IRS1 is an extended source externally heated by the nearby O star Muzzio 10, a candidate for the binary companion of the progenitor star. The Spitzer MIR spectrum reveals several ionic emission lines including a strong [Ne II] 12.81 $\mu$m line, but no hydrogen line is detected. We model the spectrum using the photoionization code CLOUDY with varying elemental composition. The elemental abundance of IRS1 derived from the model is close to that of SN ejecta with depleted hydrogen and enhanced metals, particularly neon, argon, and iron. Our results imply that IRS1 originates from the SN ejecta and suggest the possibility of the formation of crystalline silicate in newly-formed SN dust., Comment: 18 pages, 9 figures, accepted for publication in The Astrophysical Journal

Most stars form in multiple star systems. For a better understanding of their formation processes, it is important to resolve the individual protostellar components and the surrounding envelope and disk material at the earliest possible formation epoch because the formation history can be lost in a few orbital timescales. Here we present the ALMA observational results of a young multiple protostellar system, IRAS 04239+2436, where three well-developed large spiral arms were detected in the shocked SO emission. Along the most conspicuous arm, the accretion streamer was also detected in the SO$_2$ emission. The observational results are complemented by numerical magneto-hydrodynamic simulations, where those large arms only appear in magnetically weakened clouds. The numerical simulations also suggest that the large triple spiral arms are the result of gravitational interactions between compact triple protostars and the turbulent infalling envelope., Comment: Accepted for publication in ApJ

We investigate the effects of winds on the observational properties of Type Ib and Ic supernova (SN Ib/Ic) progenitors using spectral models constructed with the non-LTE stellar atmospheric code CMFGEN. We consider SN Ib/Ic progenitor models of the final mass range of 2.16 -- 9.09~$M_\odot$ having different surface temperatures and chemical compositions, and calculate the resulting spectra for various wind mass-loss rates and wind terminal velocities. We find that the progenitors having an optically thick wind would become brighter in the optical for a higher mass-loss rate (or a lower wind terminal velocity), because of the formation of the photosphere in the extended wind matter and the contribution from free-free and line emissions from the wind. As a result, for the standard Wolf-Rayet wind mass-loss rate, helium-deficient compact SN Ic progenitors would be brighter in the optical by $\sim$3 mag compared to the case without the wind effects. We also find that the color dependence on the photospheric temperature is non-monotonic because of the wind effects. Our results imply that inferring the progenitor mass, bolometric luminosity and effective temperature from the optical observation using the standard stellar evolution model prediction can be misleading. By comparing our fiducial model predictions with the detection limits of the previous SN Ib/Ic progenitor searches, we conclude that a deep search with an optical absolute magnitude larger than $\sim -4$ is needed to directly identify most of the ordinary SN Ib/Ic progenitors. We discuss implications of our results for the observed SN Ib/Ic progenitor candidates for iPTF13bvn, SN 2019yvr and SN 2017ein., Comment: 32 pages, 18 figures, 5 tables ; accepted for publication in ApJ

Cassiopeia A is a nearby young supernova remnant that provides a unique laboratory for the study of core-collapse supernova explosions. Cassiopeia A is known to be a Type IIb supernova from the optical spectrum of its light echo, but the immediate progenitor of the supernova remains uncertain. Here we report results of near-infrared, high-resolution spectroscopic observations of Cassiopeia A where we detected the pristine circumstellar material of the supernova progenitor. Our observations revealed a strong emission line of iron (Fe) from a circumstellar clump that has not yet been processed by the supernova shock wave. A comprehensive analysis of the observed spectra, together with an HST image, indicates that the majority of Fe in this unprocessed circumstellar material is in the gas phase, not depleted onto dust grains as in the general interstellar medium. This result is consistent with a theoretical model of dust condensation in material that is heavily enriched with CNO-cycle products, supporting the idea that the clump originated near the He core of the progenitor. It has been recently found that Type IIb supernovae can result from the explosion of a blue supergiant with a thin hydrogen envelope, and our results support such a scenario for Cassiopeia A., Comment: 18 pages, 7 figures

We present a long-exposure (~10 hr) image of the supernova (SN) remnant Cassiopeia A (Cas A) obtained with the UKIRT 3.8-m telescope using a narrow band filter centered at 1.644 um emission. The passband contains [Fe II] 1.644 um and [Si I] 1.645 um lines, and our `deep [Fe II]+[Si I] image' provides an unprecedented panoramic view of Cas A, showing both shocked and unshocked SN ejecta together with shocked circumstellar medium at subarcsec (~0.7 arcsec or 0.012 pc) resolution. The diffuse emission from the unshocked SN ejecta has a form of clumps, filaments, and arcs, and their spatial distribution correlates well with that of the Spitzer [Si II] infrared emission, suggesting that the emission is likely due to [Si I] line not [Fe II] line as in shocked material. The structure of the optically-invisible western area of Cas A is clearly seen for the first time. The area is filled with many Quasi-Stationary Flocculi (QSFs) and fragments of the disrupted ejecta shell. We suggest that the anomalous radio properties in this area could be due to the increased number of such dense clumps. We identified 309 knots in the deep [Fe II]+[Si I] image and classified them into QSFs and fast-moving knots (FMKs). The total H+He mass of QSFs is ~0.23 Msun, implying that the mass fraction of dense clumps in the progenitor's red-supergiant wind is 4--13%. The spatial distribution of QSFs suggests that there had been a highly asymmetric mass loss $10^4$--$10^5$ yr before the SN explosion. The mass of the [Fe II] line-emitting, shocked dense Fe ejecta is ~3x$10^{-5}$ Msun. The comparison with the ionic S-line dominated Hubble Space Telescope WFC3/IR image suggests that the outermost FMKs in the southeastern area are Fe-rich., Comment: 36 pages, 13 figures, ApJ in press

We present a parsec-scale molecular hydrogen (H$_2$ 1-0 S(1) at 2.12~\micron) outflow discovered from the UKIRT Widefield Infrared Survey for H$_2$. The outflow is located in the infrared dark cloud core MSXDC G053.11+00.05 MM1 at 1.7 kpc and likely associated with two young stellar objects (YSOs) at the center. The overall morphology of the outflow is bipolar along the NE-SW direction with a brighter lobe to the southwest, but the detailed structure consists of several flows and knots. With the total length of $\sim$1 pc, the outflow luminosity is fairly high with $L_{\rm H_{2}} > 6~L_{\sun}$, implying a massive outflow-driving YSO if the entire outflow is driven by a single source. The two putative driving sources, located at the outflow center, show photometric variability of $\gtrsim$1 mag in {\it H}- and {\it K}-bands. This, with their early evolutionary stage from spectral energy distribution (SED) fitting, indicates that both are capable of ejecting outflows and may be eruptive variable YSOs. The YSO masses inferred from SED fitting are $\sim$10~$M_{\sun}$ and $\sim$5~$M_{\sun}$, suggesting the association of the outflow with massive YSOs. The geometrical morphology of the outflow is well explained by the lower mass YSO by assuming a single source origin, but without kinematic information, the contribution from the higher mass YSO cannot be ruled out. Considering star formation process by fragmentation of a high-mass core into several lower mass stars, we also suggest the possible presence of another, yet-undetected driving source deeply embedded in the core., Comment: 28 pages, 8 figures, accepted for publication in the Astrophysical Journal