Simulating the formation of η Carinae’s surrounding nebula through unstable triple evolution and stellar merger-induced eruption

Hirai, Ryosuke; Podsiadlowski, Philipp; Owocki, S. P.; Schneider, F. R. N.; Smith, Nathan

doi:10.1093/mnras/stab571

Cited by 42 publications

(35 citation statements)

References 164 publications

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“…In addition, there is also a large structure around the pinched "waist" of the bipolar lobes of HR Car's nebula at low velocities that could be interpreted as an equatorial "skirt"-like feature (Figure 5), similar to the one observed in η Car (Zethson et al 1999). Competing models for the eruptive mass loss that could lead to such nebula include super-Eddington winds (e.g., Owocki et al 2017), accretion onto a companion star (e.g., Kashi & Soker 2010), pulsational pair-instability events (e.g., Woosley 2017), and the merger of two massive stars (e.g., Portegies Zwart & van den Heuvel 2016, Hirai et al 2021). However, HR Car is a factor of at least five times less massive in terms of both stellar and nebular mass and the orbital parameters are substantially different.…”

Section: The Circumstellar Nebulasupporting

confidence: 52%

LBV phenomenon and binarity: The environment of HR Car

Mehner,

Janssens,

Agliozzo

et al. 2021

Preprint

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Luminous blue variable stars (LBVs) are of great interest in massive-star evolution as they experience very high mass-loss episodes within short periods of time. HR Car is a famous member of this class in the Galaxy. It has a large circumstellar nebula and has also been confirmed as being in a binary system. One means of gaining information about the evolutionary status and physical nature of LBVs is studying their environments. We investigated the stellar content within ∼ 100 pc of HR Car and also its circumstellar nebula. Very Large Telescope (VLT) Multi Unit Spectroscopic Explorer (MUSE) observations of a 2 × 2 region around the star highlight the incompleteness of stellar classification for stars with magnitudes of V > 13 mag. Eight B0 to B9 stars have been identified which may lie in close spatial vicinity to HR Car. For a region with a radius of r = 1.2 • (∼ 100 pc at a distance of 4.8 kpc) around HR Car, existing catalogs list several late O-type and early B-type stars, but only one early O-type star. Given the relatively low stellar and nebular masses in the HR Car system, no early O-type stars and only a few late O-type stars would be expected in association with HR Car. Instead, HR Car's location in a point vector diagram suggests that HR Car is not isolated, but is part of a moving group with a population of B-type stars in a spiral arm, and it has not received a strong kick from a supernova explosion of a companion star or a merger event. Potential binary evolution pathways for the HR Car system cannot be fully explored because of the unknown nature of the companion star. Furthermore, the MUSE observations reveal the presence of a fast outflow and "bullets" that have been ejected at intervals of about 400 years. These features may have been caused by recurrent mass transfer in the system.

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Section: The Circumstellar Nebulasupporting

confidence: 52%

LBV phenomenon and binarity: The environment of HR Car

Mehner,

Janssens,

Agliozzo

et al. 2021

Preprint

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“…The X-ray flux curve, followed over the past four orbital cycles has consistently reached minimum at the same orbital phase (Corcoran et al 2017;Espinoza Galeas et al 2021) to within a fraction of a day (Teodoro et al 2016). Hirai et al (2021) suggested that η Car was a three body system prior to the Great Eruption, an if so, we estimate a maximum residual apsidal motion of 3°per 5.54 yr orbit. 3.…”

Section: Changes In Fuv Flux In the Long Termmentioning

confidence: 55%

“…η Car is a unique massive binary system that underwent two major events, the very energetic Great Eruption in the 1840s and the Lesser Eruption in the 1890s, expelling massive amounts of ejecta (≈40 M e , Morris et al 2017) and yet has survived as a binary with a primary (≈100 M e ) and a hot secondary (≈40 M e ). Whether the events were due to a near-supernova event or a merger from triple to binary (Portegies Zwart & van den Heuvel 2016;Hirai et al 2021), we do not know, but gathering information about this dynamically changing system can only lead to new understanding of the evolution of massive stars in multiple stellar systems.…”

Section: Introductionmentioning

confidence: 99%

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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“…Since the GE ejected > 15 M following Morris et al (1999) and Smith et al (2003) or > 45 M following Morris et al (2017) -using a full radiative transfer model with a far more chemically realistic dust librarythe luminosity of the central star should have dropped by a large amount, unless it was compensated by some process. This favours the scenario of a merger in a triple system (Portegies Zwart & van den Heuvel 2016;Smith et al 2018;Hirai et al 2020) over a massive wind ejection as the mechanism for the GE, since the primary star would have been mixed internally in a merger, bringing fresh fuel to its central core.…”

Section: Consequences Of the Disappearance Of The Coronagraphmentioning

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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Simulating the formation of η Carinae’s surrounding nebula through unstable triple evolution and stellar merger-induced eruption

Cited by 42 publications

References 164 publications

LBV phenomenon and binarity: The environment of HR Car

LBV phenomenon and binarity: The environment of HR Car

Eta Carinae: A Tale of Two Periastron Passages

Spectroscopic signatures of the vanishing natural coronagraph of Eta Carinae

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