X-ray accretion signatures in the close CTTS binary V4046 Sagittarii

Günther, H. M.; Liefke, C.; Schmitt, J. H. M. M.; Robrade, J.; Ness, J. U.

doi:10.1051/0004-6361:20066306

Cited by 86 publications

(122 citation statements)

References 23 publications

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“…Strong X-ray emission from cool plasma of temperatures 3 − 4 MK and number densities 10 11 − 10 12 cm −3 was detected (as it was previously by [14]). This plasma, which is cooler and denser than is typical of coronal plasma, is associated with accretion shocks, where gas channelled along magnetic field lines slams into the stellar surface at supersonic speeds.…”

Section: A Near-simultaneous Multi-wavelength Observing Programsupporting

confidence: 80%

The magnetosphere of the close accreting PMS binary V4046 Sgr

Gregory

Holzwarth²,

Donati

et al. 2014

EPJ Web of Conferences

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Abstract. V4046 Sagittarii AB is a close short-period classical T Tauri binary. It is a circularised and synchronised system accreting from a circumbinary disk. In 2009 it was observed as part of a coordinated program involving near-simultaneous spectropolarimetric observations with ESPaDOnS at the Canada-France-Hawai'i Telescope and high-resolution X-ray observations with XMM-Newton. Magnetic maps of each star were derived from Zeeman-Doppler imaging. After briefly highlighting the most significant observational findings, we present a preliminary 3D model of the binary magnetosphere constructed from the magnetic maps using a newly developed binary magnetic field extrapolation code. The large-scale fields (the dipole components) of both stars are highly tilted with respect to their rotation axes, and their magnetic fields are linked.

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Section: A Near-simultaneous Multi-wavelength Observing Programsupporting

confidence: 80%

The magnetosphere of the close accreting PMS binary V4046 Sgr

Gregory

Holzwarth²,

Donati

et al. 2014

EPJ Web of Conferences

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“…This phenomenon has been detected in most CTTS observed so far (BP Tau: Schmitt et al 2005;A&A 519, A97 (2010) V4046 Sge: Günther et al 2006; RU Lup: MP Mus: Argiroffi et al 2007; Hen 3-600: Huenemoerder et al 2007). There are exceptions to this rule -in the more massive, eponymous T Tau itself, although known for its high accretion rate, the O vii triplet is consistent with the line ratio in the coronal limit .…”

Section: Introductionmentioning

confidence: 61%

The disk-bearing young star IM Lupi

Guenther¹,

Schmitt²,

Guêdel³

et al. 2010

A&A

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Context. Classical T Tauri stars (CTTS) differ in their X-ray signatures from older pre-main sequence stars, e.g., weak-lined TTS (WTTS). CTTS exhibit a soft excess and deviations from the low-density coronal limit in the He-like triplets. Aims. We test whether these features correlate with either accretion or the presence of a disk by observing IM Lup, a disk-bearing object apparently in transition between CTTS and WTTS without obvious accretion. Methods. We analyse a Chandra grating spectrum and additional XMM-Newton data of IM Lup and accompanying optical spectra, some of which where taken simultaneously with the X-ray observations. We fit the X-ray emission lines and decompose the Hα emission line into different components. Results. In X-rays, IM Lup has a bright and hot active corona, where elements with low first-ionisation potential are depleted. The He-like Ne ix triplet is in the low-density state, but because of the small number of counts in the data a high-density scenario cannot be excluded at the 90% confidence level. In terms of all its X-ray properties, IM Lup resembles a main-sequence star, but is also compatible with CTTS signatures at the 90% confidence level, thus we cannot decide whether the soft excess and deviations from the low-density coronal limit for the He-like triplets in CTTS are produced by accretion or only the presence of a disk. The star IM Lup is chromospherically active, which accounts for most of its emission in Hα. Despite its low equivalent width, the complexity of the Hα line profile is reminiscent of CTTS. We estimate the mass accretion rate to be 10 −11 M yr −1 .

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“…It has a spectral type of K7, and a mass of 0.8 M ⊙ (Kenyon & Hartmann 1995;Güdel et al 2007). The XMM-Newton spectra were previously discussed by Schmitt et al (2005) and Robrade & Schmitt (2006). They report the presence of high density soft X-ray emission from the O vii triplet, suggesting this could be due to accretion shocks.…”

Section: The Samplementioning

confidence: 80%

Multiwavelength diagnostics of accretion in an X-ray selected sample of CTTSs

Curran

Argiroffi

Sacco

et al. 2011

A&A

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Context. High resolution X-ray spectroscopy has revealed soft X-rays from high density plasma in Classical T-Tauri stars (CTTSs), probably arising from the accretion shock region. However, the mass accretion rates derived from the X-ray observations are consistently lower than those derived from UV/optical/NIR studies. Aims. We aim to test the hypothesis that the high density soft X-ray emission is from accretion by analysing optical accretion tracers from an X-ray selected sample of CTTSs in a homogeneous manner. Methods. We analyse optical spectra of the X-ray selected sample of CTTSs and calculate the accretion rates based on measuring Hα, Hβ, Hγ, He ii 4686Å , He i 5016Å , He i 5876Å , O i 6300Å and He i 6678Å equivalent widths. In addition, we also calculate the accretion rates based on the full width at 10% maximum of the Hα line. The different optical tracers of accretion are compared and discussed. The derived accretion rates are then compared to the accretion rates derived from the X-ray spectroscopy. Results. We find that, for each CTTS in our sample, the different optical tracers predict mass accretion rates that agree within the errors, albeit with a spread of ≈ 1 order of magnitude. Typically, mass accretion rates derived from Hα and He i 5876Å are larger than those derived from Hβ, Hγ and O i. In addition, the Hα full width at 10%, whilst a good indicator of accretion, may not accurately measure the mass accretion rate. When comparisons of the optical mass accretion rates are made to the X-ray derived mass accretion rates, we find that: a) the latter are always lower (but by varying amounts); b) the latter range within a factor of ≈ 2 around 2 × 10 −10 M ⊙ yr −1 , despite the fact that the former span a range of ≈ 3 orders of magnitude. We suggest that the systematic underestimation of the X-ray derived mass accretion rates could depend on the density distribution inside the accretion streams, where the densest part of the stream is not visible in the X-ray band because of the absorption by the stellar atmosphere. We also suggest that a non-negligible optical depth of X-ray emission lines produced by post-shock accreting plasma may explain the almost constant mass accretion rates derived in X-rays if the effect is larger in stars with larger optical mass accretion rates.

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X-ray accretion signatures in the close CTTS binary V4046 Sagittarii

Cited by 86 publications

References 23 publications

The magnetosphere of the close accreting PMS binary V4046 Sgr

The magnetosphere of the close accreting PMS binary V4046 Sgr

The disk-bearing young star IM Lupi

Multiwavelength diagnostics of accretion in an X-ray selected sample of CTTSs

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