Kinematics and parameters of the gas in the vicinity of TW Hya

Ламзин, С. А.; Kravtsova, A. S.; Romanova, M. M.; Batalha, C.

doi:10.1134/1.1764888

Cited by 17 publications

(27 citation statements)

References 27 publications

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“…Focusing only on those objects for which the velocities are such that they could in principle be produced in an accretion shock (the wedge with 12 CTTSs in the upper right quadrant of Figure 9, below the dotted line, including MP Mus but excluding DR Tau), we conclude that the lack of observed double peaked profiles is due to the small difference between velocity components and to the fact that both components are very broad (perhaps as a result of turbulence in the flow). Notwithstanding the conclusions from Lamzin et al (2004) and Günther & Schmitt (2008), the ratio between the velocity components for the C iv profile from TW Hya is perfectly consistent with magnetospheric accretion.…”

Section: Kinematic Predictions Of the Accretion Shock Modelsupporting

confidence: 56%

Hot Gas Lines in T Tauri Stars

Ardila

Herczeg

Gregory

et al. 2013

ApJS

105

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For Classical T Tauri Stars (CTTSs), the resonance doublets of N v, Si iv, and C iv, as well as the He ii 1640Å line, trace hot gas flows and act as diagnostics of the accretion process. In this paper we assemble a large high-resolution, high-sensitivity dataset of these lines in CTTSs and Weak T Tauri Stars (WTTSs). The sample comprises 35 stars: one Herbig Ae star, 28 CTTSs, and 6 WTTSs. We find that the C iv, Si iv, and N v lines in CTTSs all have similar shapes. We decompose the C iv and He ii lines into broad and narrow Gaussian components (BC & NC). The most common (50 %) C iv line morphology in CTTSs is that of a low-velocity NC together with a redshifted BC. For CTTSs, a strong BC is the result of the accretion process. The contribution fraction of the NC to the C iv line flux in CTTSs increases with accretion rate, from ∼20% to up to ∼80%. The velocity centroids of the BCs and NCs are such that V BC 4 V N C , consistent with the predictions of the accretion shock model, in at most 12 out of 22 CTTSs. We do not find evidence of the post-shock becoming buried in the stellar photosphere due to the pressure of the accretion flow. The He ii CTTSs lines are generally symmetric and narrow, with FWHM and redshifts comparable to those of WTTSs. They are less redshifted than the CTTSs C iv lines, by ∼10 km s −1 . The amount of flux in the BC of the He ii line is small compared to that of the C iv line, and we show that this is consistent with models of the pre-shock column emission. Overall, the observations are consistent with the presence of multiple accretion columns with different densities or with accretion models that predict a slow-moving, lowdensity region in the periphery of the accretion column. For HN Tau A and RW Aur A, most of the C iv line is blueshifted suggesting that the C iv emission is produced by shocks within outflow jets. In our sample, the Herbig Ae star DX Cha is the only object for which we find a P-Cygni profile in the C iv line, which argues for the presence of a hot (10 5 K) wind. For the overall sample, the Si iv and N v line luminosities are correlated with the C iv line luminosities, although the relationship between Si iv and C iv shows large scatter about a linear relationship and suggests that TW Hya, V4046 Sgr, AA Tau, DF Tau, GM Aur, and V1190 Sco are silicon-poor, while CV Cha, DX Cha, RU Lup, and RW Aur may be silicon-rich.

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Section: Kinematic Predictions Of the Accretion Shock Modelsupporting

confidence: 56%

Hot Gas Lines in T Tauri Stars

Ardila

Herczeg

Gregory

et al. 2013

ApJS

105

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“…Winds, which could be of stellar origin or come from the disk, are observed over a wide wavelength range from radio to the UV (e.g. Alencar & Basri 2000;Beristain et al 2001;Dupree et al 2005a;Edwards et al 2006;Lamzin et al 2004). Some CTTS also have highly collimated jets, which are discussed in more detail in Sect.…”

Section: Windsmentioning

confidence: 99%

Accretion, jets and winds: High‐energy emission from young stellar objects – Doctoral Thesis Award Lecture 2010

Günther

2011

Astron Nachr

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This article summarizes the processes of high-energy emission in young stellar objects. Stars of spectral type A and B are called Herbig Ae/Be (HAeBe) stars in this stage, all later spectral types are termed classical T Tauri stars (CTTS). Both types are studied by high-resolution X-ray and UV spectroscopy and modeling. Three mechanisms contribute to the highenergy emission from CTTS: 1) CTTS have active coronae similar to main-sequence stars, 2) the accreted material passes through an accretion shock at the stellar surface, which heats it to a few MK, and 3) some CTTS drive powerful outflows. Shocks within these jets can heat the plasma to X-ray emitting temperatures. Coronae are already well characterized in the literature; for the latter two scenarios models are shown. The magnetic field suppresses motion perpendicular to the field lines in the accretion shock, thus justifying a 1D geometry. The radiative loss is calculated as optically thin emission. A mixture of shocked and coronal gas is fitted to X-ray observations of accreting CTTS. Specifically, the model explains the peculiar line-ratios in the He-like triplets of Ne IX and O VII. All stars require only small mass accretion rates to power the X-ray emission. In contrast, the HAeBe HD 163296 has line ratios similar to coronal sources, indicating that neither a high density nor a strong UV-field is present in the region of the X-ray emission. This could be caused by a shock in its jet. Similar emission is found in the deeply absorbed CTTS DG Tau. Shock velocities between 400 and 500 km −1 are required to explain the observed spectrum.

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“…We first rule out formation of the [Ne ii] emission in the accretion flow and shock. Lines commonly attributed to accretion, including He i k5876 and the C iv k1549, N v k1240, and O vi k1035 doublets (Alencar & Batalha 2002;Herczeg et al 2002;Lamzin et al 2004;Johns-Krull & Herczeg 2007;Yang et al 2007), have much broader line widths than the [Ne ii] emission from TW Hya and are redshifted from the stellocentric velocity. Second, we rule out fast outflows because the [Ne ii] line is centered at or near the stellocentric velocity and is limited to low velocities.…”

Section: Comparison To Other Emission Lines From Tw Hyamentioning

confidence: 99%

High‐Resolution Spectroscopy of [Neii] Emission from TW Hydrae

Herczeg

Najita

Hillenbrand

et al. 2007

ApJ

102

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We present high-resolution echelle spectra of [Ne ii] 12.81 m emission from the classical T Tauri star (CTTS) TW Hya, obtained with MICHELLE on Gemini North. The line is centered at the stellar radial velocity and has an intrinsic FWHM of 21 AE 4 km s À1. The line width is broader than other narrow emission lines typically associated with the disk around TW Hya. If formed in a disk, the line broadening could result from turbulence in a warm disk atmosphere, Keplerian rotation at an average distance of 0.1 AU from the star, or a photoevaporative flow from the optically thin region of the disk. We place upper limits on the [Ne ii] emission flux from the CTTSs DP Tau and BP Tau. Subject headingg s: infrared: stars -planetary systems: protoplanetary disks -stars: pre-main-sequence Online material: color figure

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Kinematics and parameters of the gas in the vicinity of TW Hya

Cited by 17 publications

References 27 publications

Hot Gas Lines in T Tauri Stars

Hot Gas Lines in T Tauri Stars

Accretion, jets and winds: High‐energy emission from young stellar objects – Doctoral Thesis Award Lecture 2010

High‐Resolution Spectroscopy of [Neii] Emission from TW Hydrae

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