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Abstract A range of stellar explosions, including supernovae (SNe), tidal disruption events (TDE), and fast blue optical transients (FBOTs), can occur in dusty environments initially opaque to transients’ optical/UV light, becoming visible only once the dust is destroyed by transients’ rising luminosity. We present axisymmetric, time-dependent radiation transport simulations of dust-shrouded transients withAthena++and tabulated gray opacities, predicting the light curves of the dust-reprocessed infrared (IR) radiation. The luminosity and timescale of the IR light curve depend on whether the transient rises rapidly or slowly compared to the light-crossing time of the photosphere,tlc. For slow-rising transients (trise ≫ tlc) like SNe, the reprocessed IR radiation diffuses outward through the dust shell faster than the shell sublimates; the IR light curve therefore begins rising prior to the escape of UV/optical light, but peaks on a timescale ∼triseshorter than the transient duration. By contrast, for fast-rising transients (trise ≪ tlc) such as FBOTs and some TDEs, the finite light-travel time results in the reprocessed radiation arriving as an “echo” lasting much longer than the transient itself. We explore the effects of the system geometry by considering a torus-shaped distribution of dust. The IR light curves seen by observers in the equatorial plane of the torus resemble those for a spherical dust shell, while polar observers see faster-rising, brighter, and shorter-lived emission. We successfully model the IR excess seen in AT2018cow as a dust echo, supporting the presence of an opaque dusty medium surrounding FBOTs prior to explosion.
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Unraveling the Dusty Environment around RT Vir
Abstract Infrared (IR) studies of asymptotic giant branch (AGB) stars are critical to our understanding of the formation of cosmic dust. In this investigation, we explore the mid- to far-IR emission of the oxygen-rich AGB star RT Virginis. This optically thin dusty environment has unusual spectral features when compared to other stars in its class. To explore this enigmatic object we use the one-dimensional radiative transfer modeling code DUSTY. Modeled spectra are compared with observations from the Infrared Space Observatory, InfraRed Astronomical Satellite, the Herschel Space Observatory, and a host of other sources to determine the properties of RT Vir's circumstellar material. Our models suggest a set of two distant and cool dust shells at low optical depths (τV,inner= 0.16,τV,outer= 0.06), with inner dust temperaturesT1= 330 K,T3= 94 K. Overall, these dust shells exhibit a chemical composition consistent with dust typically found around O-rich AGB stars. However, the distribution of materials differs significantly. The inner shell consists of a mixture of silicates, Al2O3, FeO, and Fe, while the outer shell primarily contains crystalline Al2O3polymorphs. This chemical change is indicative of two distinct epochs of dust formation around RT Vir. These changes in dust composition are driven by either changes in the pressure–temperature conditions around the star or by a decrease in the C/O ratio due to hot-bottom burning.
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- Award ID(s):
- 2106926
- PAR ID:
- 10568910
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 979
- Issue:
- 2
- ISSN:
- 0004-637X
- Format(s):
- Medium: X Size: Article No. 242
- Size(s):
- Article No. 242
- Sponsoring Org:
- National Science Foundation
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