X-ray Variability in the Young Massive Triple theta2 Ori A

Abstract

Massive stars rarely show intrinsic X-ray variability. The only O-stars credited to be intrinsically variable are theta1 Ori C due to effects from magnetic confinement of its wind, and theta2 Ori A suspected of similar activity. Early Chandra observations have shown that the most massive star system in the Orion Trapezium Cluster, theta2 Ori A, shows rapid variability on time scales of hours. We determine X-ray fluxes and find that the star shows very strong variability over the last 5 years. We observed a second large X-ray outburst in November 2004 with the high resolution transmission grating spectrometer on-board Chandra. In the low state X-ray emissivities indicate temperatures well above 25 MK. In the high state we find an extended emissivity distribution with high emissivities in the range from 3 MK to over 100 MK. The outburst event in stellar terms is one of the most powerful ever observed and the most energetic one in the ONC with a lower total energy limit of 1.5x10^37 ergs. The line diagnostics show that under the assumption that the line emitting regions in the low states are as close as within 1 -- 2 stellar radii from the O-star's photosphere, whereas the hard states suggest a distance of 3 -- 5 stellar radii. The two outbursts are very close to the periastron passage of the stars. We argue that the high X-ray states are possibly the result of reconnection events from magnetic interactions of the primary and secondary stars of the spectroscopic binary. Effects from wind collisions seem unlikely for this system. The low state emissivity and R-ratios strengthen the predicament that the X-ray emission is enhanced by magnetic confinement of the primary wind. We also detect Fe fluorescence indicative of the existence of substantial amounts of neutral Fe in the vicinity of the X-ray emission.

11 pages, 8 figures, accepted for publication in The Astrophysical Main Journal

References in corpus (34)

• Collisional Plasma Models with APEC/APED: Emission Line Diagnostics of Hydrogen-like and Helium-like Ions
• Ionization balance for optically thin plasmas: rate coefficients for all atoms and ions of the elements H to Ni
• The surprising magnetic topology of tauSco: fossil remnant or dynamo output?
• Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: I. Isothermal, Nonrotating, Radially Driven Flow
• Chandra Orion Ultradeep Project: Observations and Source Lists
• The Discordance of Mass-Loss Estimates for Galactic O-Type Stars
• The Chandra High Energy Transmission Grating: Design, Fabrication, Ground Calibration and Five Years in Flight
• X-ray emitting young stars in the Orion Nebula
• Bright X-ray flares in Orion young stars from COUP: evidence for star-disk magnetic fields?
• Line ratios for Helium-like ions: Applications to collision-dominated plasmas
• Ten Million Degree Gas in M 17 and the Rosette Nebula: X-ray Flows in Galactic H II Regions
• Chandra HETGS Multi-Phase Spectroscopy of the Young Magnetic O Star theta^1 Orionis C
• High resolution X-Ray spectroscopy of Zeta Puppis with the XMM-Newton Reflection Grating Spectrometer
• Discovery of a strong magnetic field on the O star HD 191612: new clues to the future of theta1 Orionis C?
• The Effect of Porosity on X-ray Emission Line Profiles from Hot-Star Winds
• X-ray emission from early-type stars in the Orion Nebula Cluster
• Chandra Discovers a Very High Density X-ray Plasma on the O-Star Zeta Orionis
• The X-Ray Spectrum and Global Structure of the Stellar Wind in Vela X-1
• The Density of Coronal Plasma in Active Stellar Coronae
• X-Ray Spectroscopy of II Pegasi: Coronal Temperature Structure, Abundances, and Variability
• Iron Fluorescent Line Emission from Young Stellar Objects in the Orion Nebula
• The Coronae of AR Lac
• Modeling the NeIX Triplet Spectral Region of Capella with the Chandra and XMM-Newton Gratings
• X-ray Modeling of Very Young Early Type Stars in the Orion Trapezium: Signatures of Magnetically Confined Plasmas and Evolutionary Implications
• The Ionized Stellar Wind in Vela X-1 During Eclipse
• X-ray Line Emission from the Hot Stellar Wind of theta 1 Ori C
• Chandra Observations of Variable Embedded X-ray sources in Orion. Paper I: Resolving Orion Trapezium
• A phase-resolved XMM-Newton Campaign on the Colliding Wind Binary HD 152248
• Chandra Grating Spectroscopy of the X-ray Binary 4U 1700-37 in a Flaring State
• An XMM-Newton observation of the massive binary HD159176
• Discovery of X-ray flaring on the magnetic Bp-star sigma Ori E
• X-ray Spectroscopy of the Contact Binary VW Cephei
• Differential Emission Measure Determination of Collisionally Ionized Plasma: II. Application to Hot Stars
• Coordinated Monitoring of the Eccentric O-star Binary Iota Orionis: The X-ray Analysis

Cited by in corpus (15)

• The young stellar population in M17 revealed by Chandra
• He-like ions as practical astrophysical plasma diagnostics: From stellar coronae to active galactic nuclei
• A Chandra Study of the Rosette Star-Forming Complex. I. The Stellar Population and Structure of the Young Open Cluster NGC 2244
• Carina OB Stars: X-ray Signatures of Wind Shocks and Magnetic Fields
• Expanding bubbles in Orion A: [CII] observations of M42, M43, and NGC 1977
• Hot stars observed by XMM-Newton II. A survey of Oe and Be stars
• An X-ray Imaging Study of the Stellar Population in RCW49
• Testing magnetically confined wind shock models for Beta Cep using XMM-Newton and Chandra phase-resolved X-ray observations
• A 33 year constancy of the X-ray coronae of AR Lac and eclipse diagnosis of scale height
• An X-ray survey of low-mass stars in Trumpler 16 with Chandra
• X-ray Emission and Corona of the Young Intermediate Mass Binary ${\theta }^1$ Ori E
• X-Ray Emission from Young Stars in the Massive Star Forming Region IRAS 20126+4104
• X-Atlas: An Online Archive of Chandra's Stellar High Energy Transmission Gratings Observations
• X-ray Properties of Low-Mass Pre-Main Sequence Stars in the Orion Trapezium Cluster
• Detailed X-Ray Line Properties of Theta2 Ori A in Quiescence