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

Grant, David; Blundell, Katherine M.; Matthews, James H.

doi:10.1093/mnras/staa669

Cited by 21 publications

(41 citation statements)

References 82 publications

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“…The continuum islands are where there are fewer, weaker absorptions. However, portions of some continuum islands are modulated by broad absorptions that appear to shift with orbital phase in a manner much like the velocity shifts seen in the higher Balmer lines studied by Grant et al (2020). The continuum islands are consistent with flux originating from deeper within the primary stellar wind and possibly with contributions from both the wind-wind interaction region and the secondary star.…”

Section: Discussionsupporting

confidence: 53%

Eta Carinae: A Tale of Two Periastron Passages

Gull

Navarete

Corcoran

et al. 2021

ApJ

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Since 2002, the far-ultraviolet (FUV) flux (1150–1680 Å) of Eta Carinae, monitored by the Hubble Space Telescope/Space Telescope Imaging Spectrograph, has increased by an order of magnitude. This increase is attributed to partial dissipation of a line-of-sight (LOS) occulter that blocks the central core of the system. Across the 2020 February periastron passage, changes in the FUV emission show a stronger wavelength dependence than occurred across the 2003 July periastron passage. Across both periastron passages, most of the FUV spectrum dropped in flux then recovered a few months later. The 2020 periastron passage included enhancements of FUV flux in narrow spectral intervals near periastron followed by a transient absorption and recovery to pre-periastron flux levels. The drop in flux is due to increased absorption by singly ionized species as the secondary star plunges deep into the wind of the primary star, which blocks the companion’s ionizing radiation. The enhanced FUV emission is caused by the companion’s wind-blown cavity briefly opening a window to deeper layers of the primary star. This is the first time transient brightening has been seen in the FUV comparable to transients previously seen at longer wavelengths. Changes in resonance line-velocity profiles hint that the dissipating occulter is associated with material in LOS moving at −100 to −300 km s−1, similar in velocity of structures previously associated with the 1890s lesser eruption.

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Section: Discussionsupporting

confidence: 53%

Eta Carinae: A Tale of Two Periastron Passages

Gull

Navarete

Corcoran

et al. 2021

ApJ

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“…Through this paper we use the binary ephemerides reported by Teodoro et al (2016): period = 2022.7 d, phase zero = HJD 2456874.4. Following Grant, Blundell & Matthews (2020) the actual periastron passage occurs 4 d earlier than this definition of phase zero. The numbering of the orbital cycles was defined by Groh & Damineli (2004).…”

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confidence: 95%

Spectroscopic signatures of the vanishing natural coronagraph of Eta Carinae

Damineli

Navarete

Hillier

et al. 2021

Monthly Notices of the Royal Astronomical Society

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Eta Carinae is a massive interacting binary system shrouded in a complex circumstellar environment whose evolution is the source of the long-term brightening observed during the last 80 years. An occulter, acting as a natural coronagraph, impacts observations from our perspective, but not from most other directions. Other sight-lines are visible to us through studies of the Homunculus reflection nebula. The coronagraph appears to be vanishing, decreasing the extinction towards the central star, and causing the star’s secular brightening. In contrast, the Homunculus remains at an almost constant brightness. The coronagraph primarily suppresses the stellar continuum, to a lesser extent the wind lines, and not the circumstellar emission lines. This explains why the absolute values of equivalent widths (EWs) of the emission lines in our direct view are larger than those seen in reflected by the Homunculus, why the direct view absolute EWs are decreasing with time, and why lower-excitation spectral wind lines formed at larger radii (e.g Fe ii 4585Å) decrease in intensity at a faster pace than higher excitation lines that form closer to the star (e.g. Hδ). Our main result is that the star, despite its 10-fold brightening over two decades, is relatively stable. A vanishing coronagraph that can explain both the large flux evolution and the much weaker spectral evolution. This is contrary to suggestions that the long-term variability is intrinsic to the primary star that is still recovering from the Great Eruption with a decreasing mass-loss rate and a polar wind that is evolving at a slower pace than at the equator.

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“…Paper A has shown that Gaussian fitting is a robust method to extract emission lines centers, amongst other studies (e.g. Blundell et al 2007;Grant et al 2020). The 1.583-day periodicity is detected in the RVs of the He I emission lines, and in some Si II and Fe II emission lines.…”

Section: Spectroscopic Variabilitymentioning

confidence: 83%

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

Porter

Blundell

Podsiadlowski

et al. 2021

Monthly Notices of the Royal Astronomical Society

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GG Carinae is a binary whose primary component is a B[e] supergiant. Using photometric data from TESS, ASAS, OMC, and ASAS-SN, and spectroscopic data from the Global Jet Watch to study visible He i, Fe ii and Si ii emission lines, we investigate the short-period variations which are exhibited in GG Car. We find a hitherto neglected periodicity of 1.583156 ± 0.0002 days that is present in both its photometry and the radial velocities of its emission lines, alongside variability at the well-established ∼31-day orbital period. We find that the amplitudes of the shorter-period variations in both photometry and some of the emission lines are modulated by the orbital phase of the binary, such that the short-period variations have largest amplitudes when the binary is at periastron. There are no significant changes in the phases of the short-period variations over the orbital period. We investigate potential causes of the 1.583-day variability, and find that the observed period agrees well with the expected period of the l = 2 f-mode of the primary given its mass and radius. We propose that the primary is periodically pulled out of hydrostatic equilibrium by the quadrupolar tidal forces when the components are near periastron in the binary’s eccentric orbit (e = 0.5) and the primary almost fills its Roche lobe. This causes an oscillation at the l = 2 f-mode frequency which is damped as the distance between the components increases.

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

Cited by 21 publications

References 82 publications

Eta Carinae: A Tale of Two Periastron Passages

Eta Carinae: A Tale of Two Periastron Passages

Spectroscopic signatures of the vanishing natural coronagraph of Eta Carinae

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

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