We present HST/WFC3 ultraviolet imaging in the F275W and F336W bands of the Type IIb SN 2001ig at an age of more than 14 years. A clear point source is detected at the site of the explosion, with ...mF275W = 25.39 0.10 and mF336W = 25.88 0.13 mag. Despite weak constraints on both the distance to the host galaxy NGC 7424 and the line-of-sight reddening to the supernova, this source matches the characteristics of an early B-type main-sequence star with 19,000 < Teff < 22,000 K and . A BPASS v2.1 binary evolution model, with primary and secondary masses of 13 M and 9 M , respectively, is found to simultaneously resemble, in the Hertzsprung-Russell diagram, both the observed location of this surviving companion, and the primary star evolutionary endpoints for other Type IIb supernovae. This same model exhibits highly variable late-stage mass loss, as expected from the behavior of the radio light curves. A Gemini/GMOS optical spectrum at an age of 6 years reveals a narrow He ii λ4686 emission line, indicative of continuing interaction with a dense circumstellar medium at large radii from the progenitor. We review our findings on SN 2001ig in the context of binary evolution channels for stripped-envelope supernovae. Owing to the uncrowded nature of its environment in the ultraviolet, this study of SN 2001ig represents one of the cleanest detections to date of a surviving binary companion to a Type IIb supernova.
The mysteries of the interior structures of stars are being tackled with asteroseismology. The observable parameters of the surface pulsations of stars inform
us of the interior characteristics of ...numerous classes of stars. The main-sequence gamma Doradus stars, just a little hotter than the Sun, offer the
potential of determining stellar structure right down to the core. To determine the structural profile of a star, the observed frequencies and a full geometric
description must be determined. This is only possible with long-term spectroscopic monitoring and careful analysis of the pulsation signature in spectral
lines. This work seeks to identify the pulsational geometry of several gamma Doradus stars and to identify areas of improvement for current observation,
analysis and modelling techniques. More than 4500 spectra were gathered on five stars for this purpose. For three stars a successful multi-frequency and mode
identification solution was determined and significant progress has been made towards the understanding of a binary system involving a gammaDoradus star. A
hybrid gamma Doradus/\delta Scuti pulsator was also intensely monitored and results from this work raise important questions about the classification of
this type of star. Current analysis techniques were found to be fit-for-purpose for pure gamma Doradus stars, but stars with complexities such as hybrid
pulsations and/or fast rotation require future development of the current models.
We present HST/WFC3 ultraviolet imaging in the F275W and F336W bands of the Type IIb SN 2001ig at an age of more than 14 years. A clear point source is detected at the site of the explosion having ...\(m_{\rm F275W}=25.39 \pm 0.10\) and \(m_{\rm F336W}=25.88 \pm 0.13\) mag. Despite weak constraints on both the distance to the host galaxy NGC 7424 and the line-of-sight reddening to the supernova, this source matches the characteristics of an early B-type main sequence star having \(19,000 < T_{\rm eff} < 22,000\) K and \(\log (L_{\rm bol}/L_{\odot})=3.92 \pm 0.14\). A BPASS v2.1 binary evolution model, with primary and secondary masses of 13 M\(_{\odot}\) and 9 M\(_{\odot}\) respectively, is found to resemble simultaneously in the Hertzsprung-Russell diagram both the observed location of this surviving companion, and the primary star evolutionary endpoints for other Type IIb supernovae. This same model exhibits highly variable late-stage mass loss, as expected from the behavior of the radio light curves. A Gemini/GMOS optical spectrum at an age of 6 years reveals a narrow He II emission line, indicative of continuing interaction with a dense circumstellar medium at large radii from the progenitor. We review our findings on SN 2001ig in the context of binary evolution channels for stripped-envelope supernovae. Owing to the uncrowded nature of its environment in the ultraviolet, this study of SN 2001ig represents one of the cleanest detections to date of a surviving binary companion to a Type IIb supernova.
We present improvement and confirmation of identified frequencies and
pulsation modes for the $\gamma$ Doradus star HD 189631. This work improves
upon previous studies by incorporating a significant ...number of additional
spectra and precise determination of frequencies. Four frequencies were
identified for this star: $1.6774 \pm 0.0002$ d$^{-1}$, $1.4174 \pm 0.0002$
d$^{-1}$, $0.0714 \pm 0.0002$ d$^{-1}$, and $1.8228 \pm 0.0002$ d$^{-1}$ which
were identified with the modes ($l$,$m$) = ($1,+1$), ($1,+1$), ($2,-2$), and
($1,+1$) respectively. These findings are in agreement with the most recent
literature. The prevalence of ($l$,$m$) = ($1,+1$) modes in $\gamma$ Doradus
stars is starting to become apparent and we discuss this result.
We present improvement and confirmation of identified frequencies and pulsation modes for the \(\gamma\) Doradus star HD 189631. This work improves upon previous studies by incorporating a ...significant number of additional spectra and precise determination of frequencies. Four frequencies were identified for this star: \(1.6774 \pm 0.0002\) d\(^{-1}\), \(1.4174 \pm 0.0002\) d\(^{-1}\), \(0.0714 \pm 0.0002\) d\(^{-1}\), and \(1.8228 \pm 0.0002\) d\(^{-1}\) which were identified with the modes (\(l\),\(m\)) = (\(1,+1\)), (\(1,+1\)), (\(2,-2\)), and (\(1,+1\)) respectively. These findings are in agreement with the most recent literature. The prevalence of (\(l\),\(m\)) = (\(1,+1\)) modes in \(\gamma\) Doradus stars is starting to become apparent and we discuss this result.
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