Dust formation in massive stars and their explosive ends
I. Cherchneff
备注：
10 pages, 3 figures, to appear in 'Hot And Cool: Bridging Gaps in Massive Star Evolution', Eds. C. Leitherer, P.D. Bennett, P.W. Morris and J.T. van Loon, ASP Conf. Ser. 2009
We review the observational evidence for dust formation in Wolf-Rayet binary systems and in Type II Supernova ejecta. Existing theoretical models describing the condensation of solids in carbon-rich Wolf-Rayet stars and in Supernovae close by and at high redshift are discussed. We describe new modeling of carbon- and oxygen-based grain nucleation using a chemical kinetic approach applied to the ejecta of massive pair-instability Supernovae in the early universe. Finally, dust formation processes in colliding wind regions of WC binary systems are discussed.
The winds of cool luminous AGB stars are commonly assumed to be driven by radiative acceleration of dust grains which form in the extended atmospheres produced by pulsation-induced shock waves. The dust particles gain momentum by absorption or scattering of stellar photons, and they drag along the surrounding gas particles through collisions, triggering an outflow. This scenario, here referred to as Pulsation-Enhanced Dust-DRiven Outflow (PEDDRO), has passed a range of critical observational tests as models have developed from empirical and qualitative to increasingly self-consistent and quant…
We report 1.2 mm polarized continuum emission observations carried out with the Atacama Large Millimeter/submillimeter Array (ALMA) toward the high-mass star formation region G5.89-0.39. The observations show a prominent 0.2 pc north-south filamentary structure. The UCHII in G5.89-0.39 breaks the filament in two pieces. Its millimeter emission shows a dusty belt with a mass of 55-115 M$_{\odot}$ and 4,500 au in radius, surrounding an inner part comprising mostly ionized gas with a dust emission only accounting about 30% of the total millimeter emission. We also found a lattice of convex arches…
We present the first set of a new generation of models of massive stars of solar composition extending between 13 and 120 \msun, computed with and without the effects of rotation. We included two instabilities induced by rotation, namely the meridional circulation and the shear instability. We implemented two alternative schemes to treat the transport of the angular momentum: the advection-diffusion formalism and the simpler purely diffusive one. The full evolution from the Pre Main Sequence up to the presupernova stage is followed in detail with a very extended nuclear network. The explosive …
The first molecules detected at infrared wavelengths in the ejecta of a Type II supernova, namely SN1987A, consisted of CO and SiO. Since then, confirmation of the formation of these two species in several other supernovae a few hundred days after explosion has been obtained. However, supernova environments appear to hamper the synthesis of large, complex species due to the lack of microscopically-mixed hydrogen deep in supernova cores. Because these environments also form carbon and silicate dust, it is of importance to understand the role played by molecules in the depletion of elements and …
The envelope of the red supergiant VY CMa has long been considered an extreme example of episodic mass loss that is possibly taking place in other cool and massive evolved stars. Recent submm observations of the envelope revealed massive dusty clumps within 800 mas from the star which reinforce the picture of drastic mass-loss phenomena in VY CMa. We present new ALMA observations at an angular resolution of 0.1" and at an unprecedented sensitivity that reveal further details about the dusty clumps. We resolve more discrete features and identify a submm counterpart of a more distant Clump SW kn…
We present high-resolution infrared (2--18 micron) images of the archetypal periodic dust-making Wolf-Rayet binary system WR140 (HD 193793) taken between 2001 and 2005, and multi-colour (J -- [19.5]) photometry observed between 1989 and 2001. The images resolve the dust cloud formed by WR140 in 2001, allowing us to track its expansion and cooling, while the photometry allows tracking the average temperature and total mass of the dust. The combination of the two datasets constrains the optical properties of the dust. The most persistent dust features, two concentrations at the ends of a `bar' o…
Core collapse supernovae (CCSNe) are important sources of interstellar dust, potentially capable of producing one solar mass of dust in their explosively expelled ejecta. However, unlike other dust sources, the dust has to survive the passage of the reverse shock, generated by the interaction of the supernova blast wave with its surrounding medium. Knowledge of the net amount of dust produced by CCSNe is crucial for understanding the origin and evolution of dust in the local and high-redshift universe. Our aim is to identify the dust destruction mechanisms in the ejecta, and derive the net amo…
(ABRIDGED) The canonical picture of a supernova impostor is a -11 < M_V < -14 optical transient from a massive (M > 40Msun) star during which the star ejects a dense shell of material. Dust formed in the ejecta then obscures the star. In this picture, the geometric expansion of the shell leads to clear predictions for the evolution of the optical depths and hence the evolution of the optical through mid-IR emissions. Here we review the theory of this standard model and then examine the impostors SN1954J, SN1997bs, SN1999bw, SN2000ch, SN2001ac, SN2002bu, SN2002kg and SN2003gm, as well as the po…
About a year after core collapse supernova, dust starts to condense in the ejecta. In meteorites, a fraction of C-rich presolar grains (e.g., silicon carbide (SiC) grains of Type-X and low density graphites) are identified as relics of these events, according to the anomalous isotopic abundances. Several features of these abundances remain unexplained and challenge the understanding of core-collapse supernovae explosions and nucleosynthesis. We show, for the first time, that most of the measured C-rich grain abundances can be accounted for in the C-rich material from explosive He burning in co…
This brief review describes some of the observed properties of the populations of massive asymptotic giant branch (AGB) stars and red supergiants (RSGs) found in nearby galaxies, with a focus on their luminosity functions, mass-loss rates and dust production. I do this within the context of their role as potential supernova (SN) progenitors, and the evolution of SNe and their remnants. The paper ends with an outlook to the near future, in which new facilities such as the James Webb Space Telescope offer a step change in our understanding of the evolution and fate of the coolest massive stars i…
A new link in the causal mapping between massive stars and potentially fatal explosive transients opened with the 2008 discovery of the dust-obscured progenitors of the luminous outbursts in NGC 6946 and NGC 300. Here we carry out a systematic mid-IR photometric search for massive, luminous, self-obscured stars in four nearby galaxies: M33, NGC 300, M81, and NGC 6946. For detection, we use only the 3.6 micron and 4.5 micron IRAC bands, as these can still be used for multi-epoch Spitzer surveys of nearby galaxies (=<10 Mpc). We combine familiar PSF and aperture-photometry with an innovative app…
Binary mass transfer via Roche-lobe overflow (RLOF) is a key channel for producing stripped-envelope Wolf-Rayet (WR) stars and may be critical to account for SN Ib/c progenitors. RY Scuti is an extremely rare example of a massive binary star caught in this brief but important phase. Its toroidal nebula indicates equatorial mass loss during RLOF, while the mass-gaining star is apparently embedded in an opaque accretion disk. RY Scuti's toroidal nebula has two components: an inner ionised double-ring system, and an outer dust torus that is twice the size of the ionised rings. We present two epoc…
The rapid neutron-capture process, creating about half of the heaviest elements in the Solar System was believed to be unique. Many recent studies have shown that this does not include the formation of lighter elements (in particular 38 < Z < 48). Among those, palladium (Pd) and especially silver (Ag) are expected to be key indicators of a possible second r-process, but until recently they have been studied only in a few stars. Therefore we target Pd and Ag in a large sample of stars and compare these abundances to those of Sr, Y, Zr, Ba and Eu produced by the slow (s-) and rapid (r-) neutron-…
We carry out radiation hydrodynamical simulations of the formation of massive stars in the super-Eddington regime including both their radiative feedback and protostellar outflows. The calculations start from a prestellar core of dusty gas and continue until the star stops growing. The accretion ends when the remnants of the core are ejected, mostly by the force of the direct stellar radiation in the polar direction and elsewhere by the reradiated thermal infrared radiation. How long the accretion persists depends on whether the protostellar outflows are present. We set the mass outflow rate t…
Star clusters larger than $\sim 10^{3}$ $M_\odot$ contain multiple hot stars that launch fast stellar winds. The integrated kinetic energy carried by these winds is comparable to that delivered by supernova explosions, suggesting that at early times winds could be an important form of feedback on the surrounding cold material from which the star cluster formed. However, the interaction of these winds with the surrounding clumpy, turbulent, cold gas is complex and poorly understood. Here we investigate this problem via an accounting exercise: we use empirically determined properties of four wel…
We couple star cluster formation and feedback simulations of a Carina-like star forming region with 1D disc evolutionary models to study the impact of external photoevaporation on disc populations in massive star forming regions. To investigate the effect of shielding of young stellar objects by star forming material, we track the FUV field history at each star in the cluster with two methods: i) Monte Carlo radiative transfer accounting for the shielding of stars from the FUV by the star forming cloud ii) Geometric dilution of the radiation from other stars which ignores shielding effects. We…
Massive stars die an explosive death as a core-collapse supernova (CCSN). The exact physical processes that cause the collapsing star to rebound into an explosion are not well-understood, and the key in resolving this issue may lie in the measurement of the shape of CCSNe ejecta. Spectropolarimetry is the only way to perform this measurement for CCSNe outside of the Milky Way and Magellanic Clouds. We present an infrared (IR) spectropolarimetric detection of a CCSN, enabled by the new highly sensitive WIRC+Pol instrument at Palomar Observatory, that can observe CCSNe (M = -17 mags) out to 20 M…
SPIRITS---SPitzer InfraRed Intensive Transients Survey---is an ongoing survey of nearby galaxies searching for infrared (IR) transients with Spitzer/IRAC. We present the discovery and follow-up observations of one of our most luminous ($M_{[4.5]} = -17.1\pm0.4$ mag, Vega) and red ($[3.6] - [4.5] = 3.0 \pm 0.2$ mag) transients, SPIRITS 15c. The transient was detected in a dusty spiral arm of IC 2163 ($D\approx35.5$ Mpc). Pre-discovery ground-based imaging revealed an associated, shorter-duration transient in the optical and near-IR (NIR). NIR spectroscopy showed a broad ($\approx 8400$ km s$^{-…
