### Classical Nova Carinae 2018: Discovery of circumbinary iron and oxygen

Monthly Notices of the Royal Astronomical Society Oxford University Press 494:1 (2020) 743-749

#### Authors:

Dominic McLoughlin, Katherine Blundell, Steven Lee

#### Abstract:

We present time-lapse spectroscopy of a classical nova explosion commencing 9 days after discovery. These data reveal the appearance of a transient feature in Fe ii and [O i]. We explore different models for this feature and conclude that it is best explained by a circumbinary disc shock-heated following the classical nova event. Circumbinary discs may play an important role in novae in accounting for the absorption systems known as THEA, the transfer of angular momentum, and the possible triggering of the nova event itself.

### GG Carinae: Orbital parameters and accretion indicators from phase-resolved spectroscopy and photometry

Monthly Notices of the Royal Astronomical Society 501:4 (2021) 5554-5574

#### Authors:

A Porter, D Grant, K Blundell, S Lee

#### Abstract:

© 2021 2020 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society. B[e] supergiants are a rare and unusual class of massive and luminous stars, characterized by opaque circumstellar envelopes. GG Carinae is a binary whose primary component is a B[e] supergiant and whose variability has remained unsatisfactorily explained. Using photometric data from ASAS, OMC, and ASAS-SN and spectroscopic data from the Global Jet Watch and FEROS to study visible emission lines, we focus on the variability of the system at its ∼31-d orbital period and constrain the stellar parameters of the primary. There is one photometric minimum per orbital period and, in the emission line spectroscopy, we find a correlation between the amplitude of radial velocity variations and the initial energy of the line species. The spectral behaviour is consistent with the emission lines forming in the primary's wind, with the variable amplitudes between line species being caused by the less energetic lines forming at larger radii on average. By modelling the atmosphere of the primary, we are able to model the radial velocity variations of the wind lines in order to constrain the orbit of the binary. We find that the binary is even more eccentric than previously believed (e = 0.5 ± 0.03). Using this orbital solution, the system is brightest at periastron and dimmest at apastron, and the shape of the photometric variations at the orbital period can be well described by the variable accretion by the secondary of the primary's wind. We suggest that the evolutionary history of GG Carinae may need to be re-evaluated in a binary context.

### GG Carinae: Discovery of orbital phase dependent 1.583-day periodicities in the B[e] supergiant binary

Monthly Notices of the Royal Astronomical Society Oxford University Press

#### Authors:

Augustus Porter, Katherine Blundell, Philipp Podsiadlowski, steven lee

### Uncovering the orbital dynamics of stars hidden inside their powerful winds: application to $η$ Carinae and RMC 140

Monthly Notices of the Royal Astronomical Society Oxford University Press 494:1 (2020) 17-35

#### Authors:

David Grant, Katherine Blundell, James Matthews

#### Abstract:

Determining accurate orbits of binary stars with powerful winds is challenging. The dense outflows increase the effective photospheric radius, precluding direct observation of the Keplerian motion; instead the observables are broad lines emitted over large radii in the stellar wind. Our analysis reveals strong, systematic discrepancies between the radial velocities extracted from different spectral lines: the more extended a line's emission region, the greater the departure from the true orbital motion. To overcome these challenges, we formulate a novel semi-analytical model which encapsulates both the star's orbital motion and the propagation of the wind. The model encodes the integrated velocity field of the out-flowing gas in terms of a convolution of past motion due to the finite flow speed of the wind. We test this model on two binary systems. (1), for the extreme case $\eta$ Carinae, in which the effects are most prominent, we are able to fit the model to 10 Balmer lines from H-alpha to H-kappa concurrently with a single set of orbital parameters: time of periastron $T_{0}=2454848$ (JD), eccentricity $e=0.91$, semi-amplitude $k=69$ km/s and longitude of periastron $\omega=241^\circ$. (2) for a more typical case, the Wolf-Rayet star in RMC 140, we demonstrate that for commonly used lines, such as He II and N III/IV/V, we expect deviations between the Keplerian orbit and the predicted radial velocities. Our study indicates that corrective modelling, such as presented here, is necessary in order to identify a consistent set of orbital parameters, independent of the emission line used, especially for future high accuracy work.

### SS433's Jet Trace from ALMA Imaging and Global Jet Watch Spectroscopy: Evidence for Post-launch Particle Acceleration

ASTROPHYSICAL JOURNAL LETTERS 867:2 (2018) ARTN L25

#### Authors:

Katherine M Blundell, Robert Laing, Steven Lee, Anita Richards