Detection of He II 4686 in eta Carinae

Abstract

We report the detection of the emission line He II 4686 A in eta Carinae. The equivalent width of this line is ~100 mA along most of the 5.5-yr cycle and jumps to ~900 mA just before phase 1.0, followed by a brief disappearance. The similarity between the intensity variations of this line and of the X-ray light curve is remarkable, suggesting that they are physically connected. We show that the number of ionizing photons in the ultraviolet and soft X-rays, expected to be emitted in the shock wave from the colliding winds, is of the order of magnitude required to produce the He II emission via photoionization. The emission is clearly blueshifted when the line is strong. The radial velocity of the line is generally -100 Km/s, decreases steadily just before the event, and reaches -400 Km/s at ph = 1.001. At this point, the velocity gradient suddenly changes sign, at the same time that the emission intensity drops to nearly zero. Possible scenarios for explaining this emission are briefly discussed. The timing of the peak of He II intensity is likely to be associated to the periastron and may be a reliable fiduciary mark, important for constraining the orbital parameters.

arXiv commentaccepted in ApJLetters, 4 pages, 3 figures

References in corpus (5)

• In Hot Pursuit of the Hidden Companion of Eta Carinae: An X-ray Determination of the Wind Parameters
• Latitude-dependent effects in the stellar wind of Eta Carinae
• Direct measurement of the size and shape of the present-day stellar wind of Eta Carinae
• The 2003 Shell Event in eta Carinae
• The shape of $\eta$ Carinae and LBV Nebulae

Cited by in corpus (47)

• Dust Formation and He II 4686 emission in the Dense Shell of the Peculiar Type Ib Supernova 2006jc
• The periodicity of the eta Carinae events
• 3D modelling of the colliding winds in Eta Carinae - evidence for radiative inhibition
• Near-Infrared interferometry of Eta Carinae with high spatial and spectral resolution using the VLTI and the AMBER instrument
• The UV Scattering Halo of the Central Source Associated with Eta Carinae
• Constraints on decreases in Eta Carinae's mass loss from 3D hydrodynamic simulations of its binary colliding winds
• Eta Carinae across the 2003.5 minimum: Spectroscopic Evidence for Massive Binary Interactions
• X-ray Spectral Variation of Eta Carinae through the 2003 X-ray Minimum
• A multispectral view of the periodic events in eta Carinae
• On the influence of the companion star in Eta Carinae: 2D radiative transfer modeling of the ultraviolet and optical spectra
• On the He II Emission In Eta Carinae and the Origin of Its Spectroscopic Events
• The supergiant B[e] star LHA 115-S 18 - binary and/or luminous blue variable?
• He II $\lambda$4686 emission from the massive binary system in $\eta$ Car: constraints to the orbital elements and the nature of the periodic minima
• A spectroscopic event of eta Car viewed from different directions: The data and first results
• Accretion by the Secondary in Eta Carinae During the Spectroscopic Event: I. Flow Parameters
• Chandra X-ray Grating Spectrometry of Eta Carinae near X-ray Minimum: I. Variability of the Sulfur and Silicon Emission Lines
• Episodic Post-Shock Dust Formation in the Colliding Winds of Eta Carinae
• Spectral atlas of massive stars around He I 10830 A
• He II 4686 in eta Carinae: collapse of the wind-wind collision region during periastron passage
• Detection of high-velocity material from the wind-wind collision zone of Eta Carinae across the 2009.0 periastron passage
• Accretion onto the Companion of Eta Carinae During the Spectroscopic Event: II. X-Ray Emission Cycle
• X-ray Emission from Eta Carinae near Periastron in 2009 I: A Two State Solution
• Eta Carinae's 2014.6 Spectroscopic Event: Clues to the Long-term Recovery from its Great Eruption
• Critical Differences and Clues in Eta Car's 2009 Event
• The fossil wind structures of Eta Carinae: changes across on 5.54-year cycle
• 3D radiative transfer simulations of Eta Carinae's inner colliding winds - I. Ionization structure of helium at apastron
• Identification of the Infrared Counterpart to a Newly Discovered X-ray Source in the Galactic Center
• The Source of the Helium Visible Lines in Eta Carinae
• Accretion onto the Companion of Eta Carinae During the Spectroscopic Event: III. the He II 4686 Line
• To $v_{\infty }$ and beyond! The He I absorption variability across the 2014.6 periastron passage of $\eta$ Carinae
• The Binarity of Eta Carinae and its Similarity to Related Astrophysical Objects
• Eta Carinae's 2014.6 Spectroscopic Event: The Extraordinary He II and N II Features
• Wind-wind collision in the Carinae binary system II: Constrains to the binary orbital parameters from radio emission near periastron passage
• Accretion onto the Companion of Eta Carinae During the Spectroscopic Event. V. the Infrared Decline
• Uncovering the orbital dynamics of stars hidden inside their powerful winds: application to $\eta$ Carinae and RMC 140
• Accretion onto the Companion of Eta Carinae During the Spectroscopic Event. IV. the Disappearance of Highly Ionized Lines
• Time variations of the narrow FeII and HI spectral emission lines from the close vicinity of Eta Carinae during the spectral event of 2003
• 3D radiative transfer simulations of Eta Carinae's inner colliding winds - II: Ionization structure of helium at periastron
• Discovery of CH and OH in the -513 km s-1 Ejecta of Eta Carinae
• N II 5668-5712, a New Class of Spectral Features in Eta Carinae
• Variable Unidentified Emission Near 6307 AA in Eta Carinae
• Constraining the orbital orientation of Eta Carinae from H Paschen lines
• The orbital kinematics of eta Carinae over three periastra with a possible detection of the elusive secondary's motion
• Eta Carinae across the 2003.5 Minimum: Analysis in the visible and near infrared spectral region
• $\eta$ Carinae: high angular resolution continuum, H30$\alpha$ and He30$\alpha$ ALMA images
• The orientation of Eta Carinae and the powering mechanism of intermediate luminosity optical transients (ILOTs)
• Precession and Nutation in the eta Carinae binary system: Evidences from the X-ray light curve