Anomalous X-ray line ratios in the cTTS TW Hya

Abstract

The cTTS TW Hya has been observed with high-resolution X-ray spectrometers. Previously found high densities inferred from He-like f/i triplets strongly suggested the detected X-ray emission to be dominated by an accretion shock. Because of their radiation field dependence He-like f/i ratios do not provide unambiguous density diagnostics. Here we present additional evidence for high densities from ratios of Fe XVII lines. Key Fe XVII line ratios in TW Hya deviate from theoretical expectations at low densities as well as from the same measurements in a large sample of stellar coronae. However, a quantitative assessment of densities is difficult because of atomic physics uncertainties. In addition, estimates of low optical depth in line ratios sensitive to resonance scattering effects also support a high-density emission scenario in the X-ray emitting regions of cTTS.

accepted for A&A Letters

References in corpus (5)

• X-ray emission from a metal depleted accretion shock onto the classical T Tauri star TW Hya
• On the sizes of stellar X-ray coronae
• X-rays from accretion shocks in T Tauri stars: The case of BP Tau
• Are stellar coronae optically thin in X-rays? - A systematic investigation of opacity effects
• Detection of X-ray Resonance Scattering in Active Stellar Coronae

Cited by in corpus (15)

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• X-rays from T Tau: A test case for accreting T Tauri stars
• X-ray accretion signatures in the close CTTS binary V4046 Sgr
• 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
• A multi-wavelength study of the young star V1118 Orionis in outburst
• The XMM-Newton Optical Monitor Survey of the Taurus Molecular Cloud
• Redshifted X-rays from the material accreting onto TW Hya: evidence of a low-latitude accretion spot
• On X-ray Optical Depth in the Coronae of Active Stars
• Electron density diagnostic for hot plasmas in coronal regime by using B-like ions
• X-raying the coronae of HD~155555
• Determinations of temperature and density for solar-like Stars using Si XI soft X-ray emission lines
• Fe XVII $2p$-$3s$ line ratio diagnostic of shock formation radius in O stars