The CHANDRA HETGS X-ray Grating Spectrum of Eta Car

Abstract

Eta Car may be the most massive and luminous star in the Galaxy and is suspected to be a massive, colliding wind binary system. The CHANDRA X-ray observatory has obtained a calibrated, high-resolution X-ray spectrum of the star uncontaminated by the nearby extended soft X-ray emisssion. Our 89 ksec CHANDRA observation with the High Energy Transmission Grating Spectrometer (HETGS) shows that the hot gas near the star is non-isothermal. The temperature distribution may represent the emission on either side of the colliding wind bow shock, effectively ``resolving'' the shock. If so, the pre-shock wind velocities are ~ 700 and ~ 1800 km/s in our analysis, and these velocities may be interpreted as the terminal velocities of the winds from Eta Car and from the hidden companion star. The forbidden-to-intercombination (f/i) line ratios for the He-like ions of S, Si and Fe are large, indicating that the line forming region lies far from the stellar photosphere. The iron fluorescent line at 1.93 Angstrom, first detected by ASCA, is clearly resolved from the thermal iron line in the CHANDRA grating spectrum. The Fe fluorescent line is weaker in our CHANDRA observation than in any of the ASCA spectra. The CHANDRA observation also provides an uninterrupted high-time resolution lightcurve of the stellar X-ray emission from Eta Car and suggests that there was no significant, coherent variability during the CHANDRA observation. The Eta Car CHANDRA grating spectrum is unlike recently published X-ray grating spectra of single massive stars in significant ways and is generally consistent with colliding wind emission in a massive binary.

revised after comments from referee and includes a new variability analysis, taking into account the effects of CCD pileup

References in corpus (5)

• High resolution X-Ray spectroscopy of Zeta Puppis with the XMM-Newton Reflection Grating Spectrometer
• Eta Carinae: Binarity Confirmed
• Chandra Discovers a Very High Density X-ray Plasma on the O-Star Zeta Orionis
• X-ray Line Emission from the Hot Stellar Wind of theta 1 Ori C
• Early Chandra X-ray Observations of Eta Carinae

Cited by in corpus (28)

• In Hot Pursuit of the Hidden Companion of Eta Carinae: An X-ray Determination of the Wind Parameters
• Carina OB Stars: X-ray Signatures of Wind Shocks and Magnetic Fields
• X-ray Spectral Variation of Eta Carinae through the 2003 X-ray Minimum
• The Conspicuous Absence of X-ray Emission from Carbon-Enriched Wolf-Rayet Stars
• On the He II Emission In Eta Carinae and the Origin of Its Spectroscopic Events
• Why a Single-Star Model Cannot Explain the Bipolar Nebula of Eta Carinae
• 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
• Wind-Wind Collision in the eta Carinae Binary System: a Shell-Like Event Near Periastron
• Waiting in the Wings: Reflected X-ray Emission from the Homunculus Nebula
• Millimeter-wave emission during the 2003 low excitation phase of eta Carinae
• Accretion onto the Companion of Eta Carinae During the Spectroscopic Event: II. X-Ray Emission Cycle
• Theoretical X-ray Line Profiles from Colliding Wind Binaries
• Colliding Stellar Winds Structure and X-ray Emission
• Hard X-ray identification of Eta Carinae and steadiness close to periastron
• Chandra Observations of Associates of $\eta$ Car: II. Spectra
• X-ray spectroscopy of Eta Carinae with XMM-Newton
• Accretion onto the Companion of Eta Carinae During the Spectroscopic Event: III. the He II 4686 Line
• A spectral and spatial analysis of eta Carinae's diffuse X-ray emission using CHANDRA
• The Binarity of Eta Carinae and its Similarity to Related Astrophysical Objects
• Accretion-Induced Collimated Fast Wind Model for Eta Carinae
• Eta Carinae's Thermal X-ray Tail Measured with XMM-Newton and NuSTAR
• Suzaku Monitoring of Hard X-ray Emission from Eta Carinae over a Single Binary Orbital Cycle
• A high-velocity transient outflow in Eta Carinae
• $\eta$ Carinae: high angular resolution continuum, H30$\alpha$ and He30$\alpha$ ALMA images
• LIFELINE: The program for the simulation of the X-ray line profiles in massive colliding wind binaries
• Variability in X-ray line ratios in helium-like ions of massive stars: the radiation-driven case
• Telluric absorption lines in the ALMA spectra of $\eta$ Car