Chandra Reveals Variable Multi-Component X-ray Emission from FU Orionis

Abstract

FU Orionis is the prototype of a class of eruptive young stars (``FUors'') characterized by strong optical outbursts. We recently completed an exploratory survey of FUors using XMM-Newton to determine their X-ray properties, about which little was previously known. The prototype FU Ori and V1735 Cyg were detected. The X-ray spectrum of FU Ori was found to be unusual, consisting of a cool moderately-absorbed component plus a hotter component viewed through an absorption column density that is an order of magnitude higher. We present here a sensitive (99 ks) follow-up X-ray observation of FU Ori obtained at higher angular resolution with Chandra ACIS-S. The unusual multi-component spectrum is confirmed. The hot component is centered on FU Ori and dominates the emission above 2 keV. It is variable (a signature of magnetic activity) and is probably coronal emission originating close to FU Ori's surface viewed through cool gas in FU Ori's strong wind or accretion stream. In contrast, the X-ray centroid of the soft emission below 2 keV is offset 0.20 arcsec to the southeast of FU Ori, toward the near-IR companion (FU Ori S). This offset amounts to slightly less than half the separation between the two stars. The most likely explanation for the offset is that the companion contributes significantly to the softer X-ray emission below 2 keV (and weakly above 2 keV). The superimposed X-ray contributions from FU Ori and the companion resolve the paradox posed by XMM-Newton of an apparently single X-ray source viewed through two different absorption columns.

21 pages, 3 tables, 6 figures

References in corpus (10)

• The Hot Inner Disk of FU Ori
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• Discovery of a bipolar X-ray jet from the T Tauri star DG Tau
• Spitzer-IRS Observations of FU Orionis Objects
• X-rays from jet-driving protostars and T Tauri stars
• The nature of the soft X-ray source in DG Tau
• FU Orionis - The MIDI/VLTI Perspective
• The X-ray emission from Z CMa during an FUor-like outburst and the detection of its X-ray jet
• The Unusual X-ray Spectrum of FU Orionis
• X-ray Emission from the FU Orionis Star V1735 Cygni

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• Chemical Signatures of the FU Ori Outbursts
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• Constraining mass ratio and extinction in the FU Orionis binary system with infrared integral field spectroscopy
• Insights into the inner regions of the FU Orionis disc
• A Comparison of the X-ray Properties of FU Ori-type Stars to Generic Young Stellar Objects
• X-ray emission from an FU Ori star in early outburst: HBC 722
• RW Aur A : SpeX Spectral Evidence for Differentiated Planetesimal Formation, Migration and Destruction in an 3 Myr Old Excited CTTS System
• Discovery of a Long-Lived, High Amplitude Dusty Infrared Transient
• Chandra Resolves the Double FU Orionis System RNO 1B/1C in X-rays
• On the diversification and dissipation of protoplanetary disks