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ABSTRACT We present Hubble Space Telescope optical images, Keck-OSIRIS near-infrared (NIR) integral field spectroscopy data cubes and Keck-Near InfraRed Camera-2 (NIRC2) NIR images of nova V5668 Sgr from 2016 to 2019. The observations indicate enhanced emission at the polar caps and equatorial torus for low-ionization lines, and enhanced high-ionization emission lines only at the polar caps. The radial velocities are compatible with a homogeneous expansion velocity of v = 590 km s−1 and a system inclination angle of 24°. These values were used to estimate an expansion parallax distance of 1200 ± 400 pc. The NIRC2 data indicate the presence of dust in 2016 and 2017, but no dust emission could be detected in 2019. The observational data were used for assembling 3D photoionization models of the ejecta. The model results indicate that the central source has a temperature of 1.88 × 105 K and a luminosity of 1.6 × 1035 erg s−1 in August of 2017 (2.4 yr post eruption), and that the shell has a mass of 6.3 × 10−5 M⊙. The models also suggest anisotropy of the ionizing flux, possibly by the contribution from a luminous accretion disc.
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Transients obscured by dusty discs
ABSTRACT Dust absorption is invoked in a number of contexts for hiding a star that has survived some sort of transient event from view. Dust formed in a transient is expanding away from the star and, in spherical models, the mass and energy budgets implied by a high optical depth at late times make such models untenable. Concentrating the dust in a disc or torus can in principle hide a source from an equatorial observer using less mass and so delay this problem. However, using axisymmetric dust radiation transfer models with a range of equatorial dust concentrations, we find that this is quite difficult to achieve in practice. The polar optical depth must be either low or high to avoid scattering optical photons to equatorial observers. Most of the emission remains at wavelengths easily observed by JWST. The equatorial brightness can be significantly suppressed for very discy configurations with little polar optical depth – but only by a factor of ∼2 for polar optical depths of τp = 1 and ∼5 for τp = 0.1 even for a very high optical depth disc (τe = 1000) viewed edge-on. It is particularly difficult to hide a source with silicate dusts because the absorption feature near 10 µm frequently leads to the emission being concentrated just bluewards of the feature, near 8 µm.
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- Award ID(s):
- 2307385
- PAR ID:
- 10526450
- Publisher / Repository:
- Monthly Notices of the Royal Astronomical Society
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 529
- Issue:
- 3
- ISSN:
- 0035-8711
- Page Range / eLocation ID:
- 1958 to 1969
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/mnras/stae589
