High Resolution X-ray Spectroscopy of T Tauri Stars in the Taurus-Auriga Complex

Abstract

Differences have been reported between the X-ray emission of accreting and non-accreting stars. Some observations have suggested that accretion shocks could be responsible for part of the X-ray emission in Classical T Tauri stars (CTTS). We present high-resolution X-ray spectroscopy of nine pre-main sequence stars in order to test the proposed spectroscopic differences between accreting and non-accreting pre-main sequence stars. We use X-ray spectroscopy from the XMM-Newton Reflection Grating Spectrometers and the EPIC instruments. We interpret the spectra using optically thin thermal models with variable abundances, together with an absorption column density. For BP Tau and AB Aur we derive electron densities from the O VII triplets. Using the O VII/O VIII count ratios as a diagnostic for cool plasma, we find that CTTS display a soft excess (with equivalent electron temperatures of ~ 2.5-3 MK) when compared with WTTS or zero-age main-sequence stars. Although the O VII triplet in BP Tau is consistent with a high electron density (3.4 x 10^11 cm^-3), we find a low density for the accreting Herbig star AB Aur (n_e < 10^10 cm^-3). The element abundances of accreting and non-accreting stars are similar. The Ne abundance is found to be high (4-6 times the Fe abundance) in all K and M-type stars. In contrast, for the three G-type stars (SU Aur, HD 283572, and HP Tau/G2), we find an enhanced Fe abundance (0.4-0.8 times solar photospheric values) compared to later-type stars. Adding the results from our sample to former high-resolution studies of T Tauri stars, we find a soft excess in all accreting stars, but in none of the non-accretors. On the other hand, high electron density and high Ne/Fe abundance ratios do not seem to be present in all accreting pre-main sequence stars.

22 pages, 9 figures, to be published in A&A, to appear in a special section/issue dedicated to the XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST)

References in corpus (7)

• The XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST)
• X-ray Emission from T Tauri Stars and the Role of Accretion: Inferences from the XMM-Newton Extended Survey of the Taurus Molecular Cloud
• X-rays from T Tau: A test case for accreting T Tauri stars
• A statistical analysis of X-ray variability in pre-main sequence objects of the Taurus Molecular Cloud
• The first high-resolution X-ray spectrum of a Herbig Star: The case of AB Aurigae
• X-ray accretion signatures in the close CTTS binary V4046 Sgr
• Spectral properties of X-ray bright variable sources in the Taurus Molecular Cloud

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• The XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST)
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• Discovery of a bipolar X-ray jet from the T Tauri star DG Tau
• Exclusion of Cosmic Rays in Protoplanetary Disks. II. Chemical Gradients and Observational Signatures
• X-rays from T Tau: A test case for accreting T Tauri stars
• The X-ray soft excess in classical T Tauri stars
• X-rays from RU Lupi - Accretion and winds in CTTS
• X-ray emission from dense plasma in CTTSs: Hydrodynamic modeling of the accretion shock
• The first high-resolution X-ray spectrum of a Herbig Star: The case of AB Aurigae
• Evidence for Accretion in the High-resolution X-ray Spectrum of the T Tauri Star System Hen 3-600
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• X-ray Super-Flares From Pre-Main Sequence Stars: Flare Energetics And Frequency
• The stellar contents and star formation in the NGC 7538 region
• Laboratory disruption of scaled astrophysical outflows by a misaligned magnetic field
• Observation of enhanced X-ray emission from the CTTS AA Tau during a transit of an accretion funnel
• Coronal abundances of X-ray bright pre-main sequence stars in the Taurus Molecular Cloud
• No Transition Disk? Infrared Excess, PAH, H2, and X-rays from the Weak-Lined T Tauri Star DoAr 21
• Using Multiwavelength Variability to Explore the Connection between X-ray Emission, the Far-Ultraviolet H2 Bump, and Accretion in T Tauri Stars
• Bright hot impacts by erupted fragments falling back on the Sun: magnetic channelling
• The disk-bearing young star IM Lup
• Laboratory evidence for asymmetric accretion structure upon slanted matter impact in young stars
• A search for thermal gyro-synchrotron emission from hot stellar coronae
• X-rays from young stars - a summary of highlights from the XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST)
• Accretion, jets and winds: High-energy emission from young stellar objects
• X-ray and UV radiation in the planet-forming T-Tauri system PDS 70. Signs of accretion and coronal activity
• Spatially-resolved Chandra Imaging Spectroscopy of the classical/weak-lined T Tauri system V710 Tau