The orbital kinematics of η Carinae over three periastra with a possible detection of the elusive secondary’s motion

Strawn, Emily; Richardson, Noel D.; Moffat, A. F. J.; Ibrahim, Nour; Lane, Alexis; Pickett, Connor S.; Chené, André-Nicolas; Corcoran, M. F.; Damineli, A.; Gull, Theodore R.; Hillier, D. J.; Morris, P.; Pablo, H.; Thomas, Joshua D.; Stevens, I. R.; Teodoro, Mairan; Weigelt, G.

doi:10.1093/mnras/stad018

Cited by 4 publications

(3 citation statements)

References 64 publications

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“…Using multiple ground-based spectrographs, we gathered spectra with a signal-to-noise ratio of 100-500 and spectral resolving power ranging from R ∼ 90,000 to 22,000 (see Table 1 for the origin of the spectra). Many of these spectra have been used in several recent papers by our group which detail the reductions of the data (see, e.g., Damineli et al 2008;Richardson et al 2010Richardson et al , 2015Richardson et al , 2016Teodoro et al 2016;Damineli et al 2019Damineli et al , 2021Pickett et al 2022;Damineli et al 2023;Strawn et al 2023). The spectra were normalized by using a linear fit through the pseudo-continuum in the range 4550-4750 Å.…”

Section: High-spectral Resolution Ground-based Spectroscopy From Cycl...mentioning

confidence: 99%

“…Archival analysis of spectra led to the discovery of the binary period based on the months-long low-ionization events (Damineli 1996). η Car was found to be an eccentric, massive binary system (Damineli et al 1997(Damineli et al , 2000Corcoran et al 2017;Grant et al 2020;Strawn et al 2023). The hot secondary provides the high-ionization photons leading to the doubly ionized narrow lines, which disappear while the secondary star plunges into the extended, dense wind of the primary across the periastron.…”

Section: Introductionmentioning

confidence: 99%

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Long-term Evolution in Ionization of Ejecta Illuminated by Eta Carinae

Damineli,

Richardson,

Navarete

et al. 2024

ApJ

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Changes in the flux and spectrum of Eta Carinae (η Car) since 1900 have been attributed to the evolution of the central binary by some. Others suggest evolution in the occulting ejecta. The brightness jump in the 1940s, which coincided with the appearance of narrow forbidden emission lines, may have been caused by the clearing and ionization of intervening circumstellar ejecta. The brightening changed at a slower pace up through 40 yr later. Here we continue earlier studies focused on the long-term, showing that the forbidden line emission increased in the early 1990s with no noticeable increase in the brightness of the Homunculus. We interpret that the increase in narrow-line emission is due to decreased extinction in the line of sight (LOS) from the central binary to the Weigelt clumps. In 2000, the central stellar core increased in brightness at a faster rate without associated changes in the Homunculus. By 2018, hundreds of narrow-line absorptions from singly ionized metals in our LOS from (η Car) disappeared, thought to be caused by increased ionization of metals. These three events (1990, 2000, and 2018) are explained by the dissipation of circumstellar material within the Homunculus close to the binary. Combining these changes with the steadiness of the Homunculus and the primary winds over the past four decades indicates that circumstellar ejecta in our direction have been cleared.

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Section: High-spectral Resolution Ground-based Spectroscopy From Cycl...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Long-term Evolution in Ionization of Ejecta Illuminated by Eta Carinae

Damineli,

Richardson,

Navarete

et al. 2024

ApJ

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“…The secondary properties remain inferred as direct measure of the secondary is yet to be accomplished because of the huge contrast in brightness between the companions. A possible exception may be the recent study by Strawn et al (2023) that tracked the weak He II λ4686 emission to measure the radial velocity orbit of the secondary directly, which moves in antiphase relative to the primary star; they find a minimum mass of 55 M e for η Car-B with a minimum mass for η Car-A of 102 M e .…”

Section: Introductionmentioning

confidence: 99%

Eta Carinae: The Dissipating Occulter Is an Extended Structure

Gull,

Hartman,

Teodoro

et al. 2023

ApJ

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Previous Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph (STIS) longslit observations of Eta Carinae (η Car) identified numerous absorption features in both the stellar spectrum, and in the adjacent nebular spectra, along our line of sight (LOS). The absorption features became temporarily stronger when the ionizing far-ultraviolet radiation field was reduced by the periastron passage of the secondary star. Subsequently, dissipation of a dusty structure in our LOS has led to a long-term increase in the apparent brightness of η Car, an increase in the ionizing ultraviolet (UV) radiation, and the disappearance of absorption from multiple velocity-separated shells extending across the foreground Homunculus lobe. We use HST/STIS spectro-images, coupled with published infrared and radio observations, to locate this intervening dusty structure. The velocity and spatial information indicate the occulter is ≈1000 au in front of η Car. The Homunculus is a transient structure composed of dusty, partially ionized ejecta that eventually will disappear due to the relentless rain of ionizing radiation and wind from the current binary system along with dissipation and mixing with the interstellar medium. This evolving complex continues to provide an astrophysical laboratory that changes on human timescales.

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Constraints on the multiplicity of the most massive stars known: R136 a1, a2, a3, and c

Shenar,

Sana,

Crowther

et al. 2023

A&A

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Context. The upper stellar mass limit is a fundamental parameter for simulations of star formation, galactic chemical evolution, and stellar feedback. An empirical bound on this parameter is therefore highly valuable. The most massive stars known to date are R 136 a1, a2, a3, and c, with reported masses in excess of 150–200 M⊙ and initial masses of up to ≈300 M⊙. They are located within the central cluster R 136a of the Tarantula nebula in the Large Magellanic Cloud (LMC), However, the mass estimation of these stars relies on the assumption that they are single. Aims. Via multi-epoch spectroscopy, we provide, for the first time, constraints on the presence of close stellar companions to the most massive stars known for orbital periods of up to ≈10 yr. Methods. We collected three epochs of spectroscopy for R 136 a1, a2, a3, and c with the Space Telescope Imaging Spectrograph (STIS) of the Hubble Space Telescope (HST) in the years 2020–2021 to probe potential radial-velocity (RV) variations. We combined these epochs with an additional HST/STIS observation taken in 2012. For R 136 c, we also used archival spectroscopy obtained with the Very Large Telescope (VLT). We used cross-correlation to quantify the RVs and establish constraints on possible companions to these stars up to periods of ≈10 yr. Objects are classified as binaries when the peak-to-peak RV shifts exceed 50 km s−1 and when the RV shift is significant with respect to errors. Results. R 136 a1, a2, and a3 do not satisfy the binary criteria and are thus classified as putatively single, although formal peak-to-peak RV variability on the level 40 km s−1 is noted for a3. Only R 136 c is classified as a binary, in agreement with the literature. We can generally rule out massive companions (M2 ≳ 50 M⊙) to R 136 a1, a2, and a3 out to orbital periods of ≲1 yr (separations ≲5 au) at 95% confidence, or out to tens of years (separations ≲100 au) at 50% confidence. Highly eccentric binaries (e ≳ 0.9) or twin companions with similar spectra could evade detection down to shorter periods (≳10 days), though their presence is not supported by the relative X-ray faintness of R 136 a1, a2, and a3. We derive a preliminary orbital solution with a 17.2 days period for the X-ray-bright binary R 136 c, though more data are needed to conclusively derive its orbit. Conclusions. Our study supports a lower bound of 150–200 M⊙ on the upper-mass limit at LMC metallicity.

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The orbital kinematics of η Carinae over three periastra with a possible detection of the elusive secondary’s motion

Cited by 4 publications

References 64 publications

Long-term Evolution in Ionization of Ejecta Illuminated by Eta Carinae

Long-term Evolution in Ionization of Ejecta Illuminated by Eta Carinae

Eta Carinae: The Dissipating Occulter Is an Extended Structure

Constraints on the multiplicity of the most massive stars known: R136 a1, a2, a3, and c

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