X-rays from T Tau: A test case for accreting T Tauri stars

Abstract

We test models for the generation of X-rays in accreting T Tauri stars (TTS), using X-ray data from the classical TTS T Tau. High-resolution spectroscopy from the Reflection Grating Spectrometers on XMM-Newton is used to infer electron densities, element abundances and the thermal structure of the X-ray source. We also discuss the ultraviolet light curve obtained by the Optical Monitor, and complementary ground-based photometry. A high-resolution image from Chandra constrains contributions from the two companions of T Tau N. The X-ray grating spectrum is rich in emission lines, but shows an unusual mixture of features from very hot (~30 MK) and very cool (1-3 MK) plasma, both emitted by similar amounts of emission measure. The cool plasma confirms the picture of a soft excess in the form of an enhanced OVII/OVIII Lya flux ratio, similar to that previously reported for other accreting TTS. Diagnostics from lines formed by this plasma indicate low electron densities (<~ 1E10 cm-3). The Ne/Fe abundance ratio is consistent with a trend in pre-main sequence stars in which this ratio depends on spectral type, but not on accretion. On the basis of line density diagnostics, we conclude that the density of the cool ``soft-excess'' plasma is orders of magnitude below that predicted for an accretion shock, assuming previously determined accretion rates of (3-6)E-8 M_sun/y. We argue that loading of magnetic field lines with infalling material suppresses the heating process in a part of the corona. We thus suggest that the X-ray production of T Tau is influenced by the accretion process although the X-rays may not form in the bulk of the accretion footpoints.

12 pages, 7 figures, A&A style. Accepted by A&A, to appear in a special section/issue dedicated to the XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST). See also http://www.issibern.ch/teams/Taurus/papers.html

References in corpus (8)

• 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 jet-driving protostars and T Tauri stars
• 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
• 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
• Accurate stellar masses in the multiple system T Tau

Cited by in corpus (26)

• The XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST)
• X-Ray Spectroscopy of Stars
• 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-ray properties of protostars in the Orion Nebula
• The X-ray soft excess in classical T Tauri stars
• X-rays from RU Lupi - Accretion and winds in CTTS
• High Resolution X-ray Spectroscopy of T Tauri Stars in the Taurus-Auriga Complex
• An outflow origin of the [NeII] emission in the T Tau triplet
• Where are the hot ion lines in classical T Tauri stars formed?
• Large gaps and high accretion rates in photoevaporative transition disks with a dead zone
• Spectral properties of X-ray bright variable sources in the Taurus Molecular Cloud
• X-ray radiative transfer in protoplanetary disks - The role of dust and X-ray background fields
• Observation of enhanced X-ray emission from the CTTS AA Tau during a transit of an accretion funnel
• Redshifted X-rays from the material accreting onto TW Hya: evidence of a low-latitude accretion spot
• Young cluster Berkeley 59 : Properties, evolution and star formation
• On beryllium-10 production in gaseous protoplanetary disks and implications on the astrophysical setting of refractory inclusions
• Using Multiwavelength Variability to Explore the Connection between X-ray Emission, the Far-Ultraviolet H2 Bump, and Accretion in T Tauri Stars
• The shared evaporation history of three sub-Neptunes spanning the radius-period valley of a Hyades star
• The disk-bearing young star IM Lup
• Spatially resolved H2 emission from the disk around T Tau N
• Signatures of Hot Molecular Hydrogen Absorption from Protoplanetary Disks: I. Non-thermal Populations
• Coronae of Stars with Super Solar Elemental Abundances
• 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
• On the diversification and dissipation of protoplanetary disks
• Pre main sequence: Accretion & Outflows