X-ray Emission from T Tauri Stars and the Role of Accretion: Inferences from the XMM-Newton Extended Survey of the Taurus Molecular Cloud

Abstract

T Tau stars display different X-ray properties depending on whether they are accreting (classical T Tau stars; CTTS) or not (weak-line T Tau stars; WTTS). We use data from the XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST) to study differences in X-ray properties between CTTS and WTTS. We perform correlation and regression analysis between X-ray parameters and stellar properties. We confirm the existence of a X-ray luminosity (Lx) vs. mass (M) relation, Lx ~ M^(1.69 +/- 0.11), but this relation is a consequence of X-ray saturation and a mass vs. bolometric luminosity (L*) relation for the TTS with an average age of 2.4 Myr. X-ray saturation indicates Lx = const L*, although the constant is different for the two subsamples: const = 10^(-3.73 +/- 0.05) for CTTS and const = 10^(-3.39 +/- 0.06) for WTTS. Given a similar L* distribution of both samples, the X-ray luminosity function also reflects a real X-ray deficiency in CTTS, by a factor of ~ 2 compared to WTTS. The average electron temperatures Tav are correlated with Lx in WTTS but not in CTTS; CTTS sources are on average hotter than WTTS sources. The most fundamental properties are the two saturation laws, indicating suppressed Lx for CTTS. We speculate that some of the accreting material in CTTS is cooling active regions to temperatures that may not significantly emit in the X-ray band, and if they do, high-resolution spectroscopy may be required to identify lines formed in such plasma, while CCD cameras do not detect these components. The similarity of the Lx vs. Tav dependencies in WTTS and main-sequence stars as well as their similar X-ray saturation laws suggests similar physical processes for the hot plasma, i.e., heating and radiation of a magnetic corona.

accepted by A&A, to appear in a special section/issue dedicated to the XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST)

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• High Resolution X-ray Spectroscopy of T Tauri Stars in the Taurus-Auriga Complex
• X-ray emission from the young brown dwarfs of the Taurus Molecular Cloud
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• Coronal Emission Measures and Abundances for Moderately Active K Dwarfs Observed by Chandra
• The X-ray activity-rotation relation of T Tauri stars in Taurus-Auriga

Cited by in corpus (25)

• The XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST)
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• X-Ray Spectroscopy of Stars
• c2d Spitzer IRS Spectra of Disks around T Tauri Stars. III. [Ne II], [Fe I], and H_2 gas-phase lines
• A Chandra Study of the Rosette Star-Forming Complex. I. The Stellar Population and Structure of the Young Open Cluster NGC 2244
• Discovery of a bipolar X-ray jet from the T Tauri star DG Tau
• Turbulence-driven Polar Winds from T Tauri Stars Energized by Magnetospheric Accretion
• X-rays from T Tau: A test case for accreting T Tauri stars
• The X-ray soft excess in classical T Tauri stars
• High Resolution X-ray Spectroscopy of T Tauri Stars in the Taurus-Auriga Complex
• Evidence for Accretion in the High-resolution X-ray Spectrum of the T Tauri Star System Hen 3-600
• Atomic Diagnostics of X-ray Irradiated Protoplanetary Disks
• Emission Line Variability of the Accreting Young Brown Dwarf 2MASSW J1207334-393254: From Hours to Years
• Further X-ray detections of Herbig stars
• An outflow origin of the [NeII] emission in the T Tau triplet
• High-Resolution Chandra X-ray Imaging and Spectroscopy of the Sigma Orionis Cluster
• Protoplanetary Disk Evolution around the Triggered Star Forming Region Cepheus B
• Spectral properties of X-ray bright variable sources in the Taurus Molecular Cloud
• Multiwavelength studies of the gas and dust disc of IRAS 04158+2805
• The X-ray activity-rotation relation of T Tauri stars in Taurus-Auriga
• Chandra and Spitzer Imaging of the Infrared Cluster in NGC 2071
• The Stellar Population And Origin Of The Mysterious High-Latitude Star Forming Cloud CG 12
• X-rays from young stars - a summary of highlights from the XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST)
• Spatially-resolved Chandra Imaging Spectroscopy of the classical/weak-lined T Tauri system V710 Tau
• X-ray detection of the substellar twin 2MASS J11011926-7732383 AB