Critical Differences and Clues in Eta Car's 2009 Event,

Mehner, A.; Davidson, Kris; Martin, John; Humphreys, R. M.; Ishibashi, Koji; Ferland, Gary J.

doi:10.1088/0004-637x/740/2/80

Cited by 37 publications

(114 citation statements)

References 61 publications

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“…The only caveat is that we do not account for any possible ionization of η A 's pre-shock wind to He iii by soft Xrays produced in the 420 km s −1 η A shock. However, any such He iii region near the WWIR zone at times around apastron is very likely to be negligible in extent, if it exists at all, as evidenced by the absence of any significant detectable He ii λ4686 emission in η Car during its spectroscopic high state (Mehner et al 2011;Teodoro et al 2012).…”

Section: Influence Of the Primary Star η Amentioning

confidence: 99%

3D radiative transfer in η Carinae: application of the SIMPLEX algorithm to 3D SPH simulations of binary colliding winds

Clementel

Madura

Kruip

et al. 2014

Monthly Notices of the Royal Astronomical Society

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Eta Carinae is an ideal astrophysical laboratory for studying massive binary interactions and evolution, and stellar wind-wind collisions. Recent three-dimensional (3D) simulations set the stage for understanding the highly complex 3D flows in η Car. Observations of different broad high-and low-ionization forbidden emission lines provide an excellent tool to constrain the orientation of the system, the primary's mass-loss rate, and the ionizing flux of the hot secondary. In this work we present the first steps towards generating synthetic observations to compare with available and future HST/STIS data. We present initial results from full 3D radiative transfer simulations of the interacting winds in η Car. We use the SimpleX algorithm to post-process the output from 3D SPH simulations and obtain the ionization fractions of hydrogen and helium assuming three different mass-loss rates for the primary star. The resultant ionization maps of both species constrain the regions where the observed forbidden emission lines can form. Including collisional ionization is necessary to achieve a better description of the ionization states, especially in the areas shielded from the secondary's radiation. We find that reducing the primary's mass-loss rate increases the volume of ionized gas, creating larger areas where the forbidden emission lines can form. We conclude that post processing 3D SPH data with SimpleX is a viable tool to create ionization maps for η Car.

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Section: Influence Of the Primary Star η Amentioning

confidence: 99%

3D radiative transfer in η Carinae: application of the SIMPLEX algorithm to 3D SPH simulations of binary colliding winds

Clementel

Madura

Kruip

et al. 2014

Monthly Notices of the Royal Astronomical Society

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“…Differences between the events provide valuable clues to their physics and the stellar system. We reported the differences between the 2003 and 2009 events and their implications in Mehner et al (2011b). Periastron passages may be triggering the long-term changes observed in η Car's light curves and spectra over the past two decades (Mehner et al 2014).…”

Section: Introductionmentioning

confidence: 96%

“…Strong He ii λ4686 emission appears and disappears at critical times of the X-ray light curve and may be related to a shock break-up (Davidson 2002;Soker 2003;Soker & Behar 2006;Martin et al 2006a;Mehner et al 2011b). The line profiles and line strengths of hydrogen and helium also show intricate (and not well understood) behavior.…”

Section: Introductionmentioning

confidence: 99%

Eta Carinae’s 2014.6 spectroscopic event: Clues to the long-term recovery from its Great Eruption

Mehner¹,

Davidson²,

Humphreys³

et al. 2015

A&A

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Aims. Every 5.5 years, η Car's light curve and spectrum change remarkably across all observed wavelength bands. These so-called spectroscopic events are most likely caused by the close approach of a companion. We compare the recent spectroscopic event in mid-2014 to the events in 2003 and 2009 and investigate long-term trends. Methods. Eta Car was observed with HST STIS, VLT UVES, and CTIO 1.5 m CHIRON for a period of more than two years in 2012−2015. Archival observations with these instruments cover three orbital cycles and the events of 2003.5, 2009.1, and 2014.6. The STIS spectra provide high spatial resolution and include epochs during the 2014 event when observations from most ground-based observatories were not feasible. The strategy for UVES observations allows for a multidimensional analysis, because each location in the reflection nebula is correlated with a different stellar latitude. Results. Important spectroscopic diagnostics during η Car's events show significant changes in 2014 compared to previous events.While the timing of the first He ii λ4686 flash was remarkably similar to previous events, the He ii equivalent widths were slightly larger, and the line flux increased by a factor of ∼7 Conclusions. The basic character of η Car's spectroscopic events has changed in the past two to three cycles. The ionizing UV radiation dramatically weakened during each pre-2014 event but not in 2014. The strengthening of He i and N ii emission and the weakening of the lower-excitation Hα and Fe ii wind features in our direct line of sight implies a substantial change in the physical parameters of the emitting regions. The polar spectrum at FOS4 shows fewer changes in the broad wind emission lines, which may be explained by the latitude-dependent wind structure of η Car. The quick and strong recovery of the He ii emission in 2014 supports a scenario, in which the wind-wind shock may not have completely collapsed as was proposed for previous events. As a result, the companion did not accrete as much material as in previous events. All this may be the consequence of just one elementary change, namely a strong decrease in the primary's mass-loss rate. This would mark the beginning of a new phase, in which the spectroscopic events can be described as an occultation by the primary's wind.

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“…Studies of the binary or binary wind-wind collision zone were reported by many authors (e.g., Damineli 1996;Damineli et al 1997Damineli et al , 1998Damineli et al , 2000Damineli et al , 2008bDavidson 1997;Davidson et al 2005Davidson et al , 2015Smith & Gehrz 2000;Smith et al 2004;Smith 2010;Pittard & Corcoran 2002;Corcoran et al 1997Corcoran et al , 2001Corcoran 2005;Ishibashi et al 1999;Soker 2003Soker , 2007Weis et al 2005;Gull et al 2006Gull et al , 2009Gull et al , 2011Gull et al , 2016Nielsen et al 2007;Weigelt et al 2007; Kashi & Soker 2007, 2009aParkin et al 2009;Groh et al 2010Groh et al , 2012bMadura & Owocki 2010;Madura et al 2012Madura et al , 2013Mehner et al 2010aMehner et al , 2011Mehner et al , 2012Mehner et al , 2015Richardson et al 2010;Teodoro et al 2013Teodoro et al , 2016Clementel et al 2015a,b;Hamaguchi et al 2016). The X-ray...…”

Section: Introductionmentioning

confidence: 99%

VLTI-AMBER velocity-resolved aperture-synthesis imaging ofηCarinae with a spectral resolution of 12 000

Weigelt

Hofmann

Schertl

et al. 2016

A&A

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Context. The mass loss from massive stars is not understood well. η Carinae is a unique object for studying the massive stellar wind during the luminous blue variable phase. It is also an eccentric binary with a period of 5.54 yr. The nature of both stars is uncertain, although we know from X-ray studies that there is a wind-wind collision whose properties change with orbital phase. Aims. We want to investigate the structure and kinematics of η Car's primary star wind and wind-wind collision zone with a high spatial resolution of ∼6 mas (∼14 au) and high spectral resolution of R = 12 000. Methods. Observations of η Car were carried out with the ESO Very Large Telescope Interferometer (VLTI) and the AMBER instrument between approximately five and seven months before the August 2014 periastron passage. Velocity-resolved aperture-synthesis images were reconstructed from the spectrally dispersed interferograms. Interferometric studies can provide information on the binary orbit, the primary wind, and the wind collision.Results. We present velocity-resolved aperture-synthesis images reconstructed in more than 100 different spectral channels distributed across the Brγ 2.166 µm emission line. The intensity distribution of the images strongly depends on wavelength. At wavelengths corresponding to radial velocities of approximately −140 to −376 km s −1 measured relative to line center, the intensity distribution has a fan-shaped structure. At the velocity of −277 km s −1 , the position angle of the symmetry axis of the fan is ∼126 • . The fan-shaped structure extends approximately 8.0 mas (∼18.8 au) to the southeast and 5.8 mas (∼13.6 au) to the northwest, measured along the symmetry axis at the 16% intensity contour. The shape of the intensity distributions suggests that the obtained images are the first direct images of the innermost wind-wind collision zone. Therefore, the observations provide velocity-dependent image structures that can be used to test three-dimensional hydrodynamical, radiative transfer models of the massive interacting winds of η Car.

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Critical Differences and Clues in Eta Car's 2009 Event,

Cited by 37 publications

References 61 publications

3D radiative transfer in η Carinae: application of the SIMPLEX algorithm to 3D SPH simulations of binary colliding winds

3D radiative transfer in η Carinae: application of the SIMPLEX algorithm to 3D SPH simulations of binary colliding winds

Eta Carinae’s 2014.6 spectroscopic event: Clues to the long-term recovery from its Great Eruption

VLTI-AMBER velocity-resolved aperture-synthesis imaging ofηCarinae with a spectral resolution of 12 000

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