Near-Infrared interferometry of Eta Carinae with high spatial and spectral resolution using the VLTI and the AMBER instrument

Abstract

We present the first NIR spectro-interferometry of the LBV Eta Carinae. The K band observations were performed with the AMBER instrument of the ESO Very Large Telescope Interferometer using three 8.2m Unit Telescopes with baselines from 42 to 89m. The aim of this work is to study the wavelength dependence of Eta Car's optically thick wind region with a high spatial resolution of 5 mas (11 AU) and high spectral resolution. The medium spectral resolution observations (R=1,500) were performed in the wavelength range around both the HeI 2.059 micron and the Br gamma 2.166 micron emission lines, the high spectral resolution observations (R=12,000) only in the Br gamma line region. In the K-band continuum, a diameter of 4.0 +/-0.2 mas (Gaussian FWHM, fit range 28-89m) was measured for Eta Car's optically thick wind region. If we fit Hillier et al. (2001) model visibilities to the observed AMBER visibilities, we obtain 50 % encircled-energy diameters of 4.2, 6.5 and 9.6mas in the 2.17 micron continuum, the HeI, and the Br gamma emission lines, respectively. In the continuum near the Br gamma line, an elongation along a position angle of 120+/-15 degrees was found, consistent with previous VLTI/VINCI measurements by van Boekel et al. (2003). We compare the measured visibilities with predictions of the radiative transfer model of Hillier et al. (2001), finding good agreement. Furthermore, we discuss the detectability of the hypothetical hot binary companion. For the interpretation of the non-zero differential and closure phases measured within the Br gamma line, we present a simple geometric model of an inclined, latitude-dependent wind zone. Our observations support theoretical models of anisotropic winds from fast-rotating, luminous hot stars with enhanced high-velocity mass loss near the polar regions.

22 pages, 14 figures, 2 tables; A&A in press

References in corpus (20)

• The Structure of the Homunculus: I. Shape and Latitude Dependence from H2 and [Fe II] Velocity Maps of Eta Carinae
• 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
• Eta Carinae: Binarity Confirmed
• Cepheid distances from infrared long-baseline interferometry - I. VINCI/VLTI observations of seven Galactic Cepheids
• Dissecting the Homunculus nebula around Eta Carinae with spatially resolved near-infrared spectroscopy
• Direct measurement of the size and shape of the present-day stellar wind of Eta Carinae
• Disk and wind interaction in the young stellar object MWC 297 spatially resolved with VLTI/AMBER
• The UV Scattering Halo of the Central Source Associated with Eta Carinae
• The Binarity of Eta Carinae Revealed from Photoionization Modeling of the Spectral Variability of the Weigelt Blobs B and D
• The 2003 Shell Event in eta Carinae
• On the He II Emission In Eta Carinae and the Origin of Its Spectroscopic Events
• A Change in the Physical State of $\eta$ Carinae?
• Detection of He II 4686 in eta Carinae
• The shape of $\eta$ Carinae and LBV Nebulae
• The sub-arcsecond dusty environment of Eta Carinae
• The Systemic Velocity of Eta Carinae
• Variability of eta Carinae III
• The angular size of the Cepheid L Car: a comparison of the interferometric and surface brightness techniques
• VLT-UVES observations of the Balmer line variations of eta Carinae during the 2003 spectroscopic event

Cited by in corpus (57)

• Mass loss from hot massive stars
• The origin of hydrogen line emission for five Herbig Ae/Be stars spatially resolved by VLTI/AMBER spectro-interferometry
• The periodicity of the eta Carinae events
• Optical Intensity Interferometry with the Cherenkov Telescope Array
• Constraining the Absolute Orientation of Eta Carinae's Binary Orbit: A 3-D Dynamical Model for the Broad [Fe III] Emission
• 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
• VLTI/AMBER spectro-interferometry of the Herbig Be star MWC 297 with spectral resolution 12 000
• On the influence of the companion star in Eta Carinae: 2D radiative transfer modeling of the ultraviolet and optical spectra
• Gas Distribution, Kinematics, and Excitation Structure in the Disks around the Classical Be Stars Beta Canis Minoris and Zeta Tauri
• Bona-fide, strong-variable galactic Luminous Blue Variable stars are fast rotators: detection of a high rotational velocity in HR Carinae
• AMBER/VLTI high spectral resolution observations of the Br$\gamma$ emitting region in HD 98922. A compact disc wind launched from the inner disc region
• Probing the accretion-ejection connection with VLTI/AMBER: High spectral resolution observations of the Herbig Ae star HD163296
• A measure of the size of the magnetospheric accretion region in TW Hydrae
• Multiplicity of Galactic Luminous Blue Variable stars
• Detection of high-velocity material from the wind-wind collision zone of Eta Carinae across the 2009.0 periastron passage
• Intensity interferometry of P Cygni in the H$\alpha$ emission line: towards distance calibration of LBV supergiant stars
• The 2008 outburst in the young stellar system ZCMa: I. Evidence of an enhanced bipolar wind on the AU-scale
• Eta Carinae's 2014.6 Spectroscopic Event: Clues to the Long-term Recovery from its Great Eruption
• HR 6819 is a binary system with no black hole -- revisiting the source with infrared interferometry and optical integral field spectroscopy
• Enhanced Halpha activity at periastron in the young and massive spectroscopic binary HD200775
• Is Eta Carinae a fast rotator, and how much does the companion influence the inner wind structure?
• The GRAVITY young stellar object survey. II. First spatially resolved observations of the CO bandhead emission in a high-mass YSO
• Tracing jet emission at the base of a high-mass YSO. First AMBER/VLTI observations of the Brγemission in IRAS 13481-6124
• Stellar Intensity Interferometry: Prospects for sub-milliarcsecond optical imaging
• Investigating the origin and spectroscopic variability of the near-infrared HI lines in the Herbig star VV Ser
• To $v_{\infty }$ and beyond! The He I absorption variability across the 2014.6 periastron passage of $\eta$ Carinae
• Pre-main-sequence binaries with tidally disrupted discs: the Br gamma in HD 104237
• A resolved, au-scale gas disk around the B[e] star HD 50138
• Probing local density inhomogeneities in the circumstellar disk of a Be star using the new spectro-astrometry mode at the Keck interferometer
• Gas dynamics in the inner few AU around the Herbig B[e] star MWC297: Indications of a disk wind from kinematic modeling and velocity-resolved interferometric imaging
• VLTI/AMBER observations of the binary B[e] supergiant HD 327083
• The GRAVITY young stellar object survey -- XI. Probing the inner disk and magnetospheric accretion region of CI Tau
• VLTI-AMBER velocity-resolved aperture-synthesis imaging of Eta Carinae with a spectral resolution of 12000. Studies of the primary star wind and innermost wind-wind collision
• Multiwavelength interferometric observations and modeling of circumstellar disks
• VLTI/AMBER unveils a possible dusty pinwheel nebula in WR118
• Mid-Cycle Changes in Eta Carinae
• The H-band Emitting Region of the Luminous Blue Variable P Cygni: Spectrophotometry and Interferometry of the Wind
• Near-Infrared Evidence for a Sudden Temperature Increase in Eta Carinae
• Resolving the asymmetric inner wind region of the yellow hypergiant IRC+10420 with VLTI/AMBER in low and high spectral resolution mode
• Post-processing the VLTI fringe-tracking data: First measurements of stars
• Spectroscopic Signatures of the Vanishing Natural Coronagraph of eta Carinae
• The orbital kinematics of eta Carinae over three periastra with a possible detection of the elusive secondary's motion
• A compact gaseous accretion disk in Keplerian rotation around MWC147
• Eta Carinae across the 2003.5 Minimum: Analysis in the visible and near infrared spectral region
• Interferometry concepts
• Interferometric observations of eta Carinae with VINCI/VLTI
• Explaining the transient fast blue absorption lines in the massive binary system Eta Carinae
• The wind and the magnetospheric accretion onto the T Tauri star S Coronae Australis at sub-au resolution
• The circumstellar environment of HD50138 revealed by VLTI/AMBER at high angular resolution
• First astrophysical results from AMBER/VLTI
• GRAVITY chromatic imaging of Eta Car's core
• AMBER on the VLTI: data processing and calibration issues
• A new concept for the combination of optical interferometers and high-resolution spectrographs
• The GRAVITY Young Stellar Object survey IV. The CO overtone emission in 51 Oph at sub-au scales
• Combining optical spectroscopy and interferometry
• Grown-up stars physics with MATISSE