A spectro-astrometric study of southern pre-main sequence stars

Takami, M.; Bailey, Jeremy; Chrysostomou, A.

doi:10.1051/0004-6361:20021544

Cited by 107 publications

(155 citation statements)

References 86 publications

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“…Reipurth et al (2002) report from their spectroscopy data, with the primary and secondary situated in the spectrograph entrance window, that the object is a spectroscopic binary candidate with a possible period of about 125 days. While the spectro-astrometric displacement found by Takami et al (2003) is small and might be caused by the binarity also recovered by us at ∼2 arcsec, Covino et al (1997), Melo (2003), Guenther et al (2007) and Joergens (2008) all found no evidence of a spectroscopic binarity.…”

Section: Sz 41supporting

confidence: 42%

Astrometric confirmation of young low-mass binaries and multiple systems in the Chamaeleon star-forming regions

Vogt

Schmidt

Neuhäuser

et al. 2012

A&A

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Context. The star-forming regions in Chamaeleon (Cha) are one of the nearest (distance ∼ 165 pc) and youngest (age ∼ 2 Myr) conglomerates of recently formed stars and the ideal target for population studies of star formation. Aims. We investigate a total of 16 Cha targets that have been suggested, but not confirmed, to be binaries or multiple systems in previous literature. Methods. We used the adaptive optics instrument Naos-Conica (NACO) at the Very Large Telescope Unit Telescope (UT) 4 / YEPUN of the Paranal Observatory, at 2-5 different epochs, in order to obtain relative and absolute astrometric measurements, as well as differential photometry in the J, H, and K band. On the basis of known proper motions and these observations, we analyse the astrometric results in our proper motion diagram (PMD: angular separation / position angle versus time), to eliminate possible (non-moving) background stars, establish co-moving binaries and multiples, and search for curvature as indications for orbital motion. Results. All previously suggested close components are co-moving and no background stars are found. The angular separations range between 0.07 and 9 arcsec, corresponding to projected distances between the components of 6-845 AU. Thirteen stars are at least binaries and the remaining three (RX J0919.4-7738, RX J0952.7-7933, VW Cha) are confirmed high-order multiple systems with up to four components. In 13 cases, we found significant slopes in the PMDs, which are compatible with orbital motion whose periods (estimated from the observed gradients in the position angles) range from 60 to 550 years. However, in only four cases there are indications of a curved orbit, the ultimate proof of a gravitational bond. Conclusions. A statistical study based on the 2MASS catalogue confirms the high probability of all 16 stellar systems being gravitationally bound. Most of the secondary components are well above the mass limit of hydrogen burning stars (0.08 M ), and have masses twice as high as this value or more. Massive primary components appear to avoid the simultaneous formation of equal-mass secondary components, while extremely low-mass secondary components are hard to find for both high and low mass primaries owing to the much higher dynamic range and the faintness of the secondaries.

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Section: Sz 41supporting

confidence: 42%

Astrometric confirmation of young low-mass binaries and multiple systems in the Chamaeleon star-forming regions

Vogt

Schmidt

Neuhäuser

et al. 2012

A&A

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“…For these simulations, we assume a point-symmetric extended component (for which we use the 2-GAUSS geometry discussed in Sect. 4.2) and add a compact companion at a separation of 60 mas, corresponding to the minimum separation of the proposed wide-separation companion star (Takami et al 2003). Then, we compute the residuals between the model with and without companion star and measure the amplitude of the wavelength-differential visibility and CP modulation for the K-band spectral window.…”

Section: Binary: Asymmetric Two-component Gaussian Modelmentioning

confidence: 99%

Revealing the sub-AU asymmetries of the inner dust rim in the disk around the Herbig Ae star R Coronae Austrinae

Kraus¹,

Hofmann²,

Malbet

et al. 2009

A&A

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Context. Unveiling the structure of the disks around intermediate-mass pre-main-sequence stars (Herbig Ae/Be stars) is essential for our understanding of the star and planet formation process. In particular, models predict that in the innermost AU around the star, the dust disk forms a "puffed-up" inner rim, which should result in a strongly asymmetric brightness distribution for disks seen under intermediate inclination.Aims. Our aim is to constrain the sub-AU geometry of the inner disk around the Herbig Ae star R CrA and search for the predicted asymmetries. Methods. Using the VLTI/AMBER long-baseline interferometer, we obtained 24 near-infrared (H-and K-band) spectrointerferometric observations on R CrA. Observing with three telescopes in a linear array configuration, each data set samples three equally spaced points in the visibility function, providing direct information about the radial intensity profile. In addition, the observations cover a wide position angle range (∼97 • ), also probing the position angle dependence of the source brightness distribution. Results. In the derived visibility function, we detect the signatures of an extended (Gaussian FWHM ∼ 25 mas) and a compact component (Gaussian FWHM ∼ 5.8 mas), with the compact component contributing about two-thirds of the total flux (both in H-and K-band). The brightness distribution is highly asymmetric, as indicated by the strong closure phases (up to ∼40 • ) and the detected position angle dependence of the visibilities and closure phases. To interpret these asymmetries, we employ various geometric as well as physical models, including a binary model, a skewed ring model, and a puffed-up inner rim model with a vertical or curved rim shape. For the binary and vertical rim model, no acceptable fits could be obtained. On the other hand, the skewed ring model and the curved puffed-up inner rim model allow us to simultaneously reproduce the measured visibilities and closure phases. From these models we derive the location of the dust sublimation radius (∼0.4 AU), the disk inclination angle (∼35 • ), and a north-south disk orientation (PA ∼ 180−190 • ). Our curved puffed-up rim model can reproduce reasonably well the interferometric observables and the SED and suggests a luminosity of ∼29 L and the presence of relatively large ( > ∼ 1.2 μm) Silicate dust grains. Our study also reveals discrepancies between the measured interferometric observables and the puffed-up inner rim models, providing important constraints for future refinements of these theoretical models. Perpendicular to the disk, two bow shock-like structures appear in the associated reflection nebula NGC 6729, suggesting that the detected sub-AU size disk is the driving engine of a large-scale outflow. Conclusions. Detecting, for the first time, strong non-localized asymmetries in the inner regions of a Herbig Ae disk, our study supports the existence of a puffed-up inner rim in YSO disks.

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“…by Takami et al (2003) line emission regions slightly off-set from the center of the continuum emission can in theory also be produced by unresolved, very close binary components. However, for our edge-on object a jet origin of the observed forbidden-line emission appears much more plausible.…”

Section: Wind and Jet Emission Linesmentioning

confidence: 99%

Edge-on T Tauri stars

Appenzeller¹,

Bertout

Stahl³

2005

A&A

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Abstract. Using the U echelle spectrograph at the ESO VLT we obtained two-dimensional high-resolution (R = 50 000) spectra of the edge-on disk objects HH30 * , HK Tau B, and HV Tau C. For comparison purposes we also observed with the same equipment both the classical T Tauri star HL Tau and the active late-type star LDN 1551-9. The spectra of all three observed edge-on disks consist of a T Tauri emission and absorption line spectrum with superimposed jet emission lines. Analysis of the spectra confirmed that the disks are completely opaque at visible wavelengths and that light from the central objects reaches us only via scattering layers above and below the disk planes. The central objects of our targets were found to be normal T Tauri stars showing moderate but different amounts of veiling of their photospheric spectra, indicating different accretion rates or evolutionary stages. We suggest that all classical T Tauri stars (CTTSs) show this observed morphology when viewed edge-on.Part of the jet emission from edge-on systems is directly visible to us in the forbidden lines as well as in Hα and He , a finding which contradicts the present paradigm of a pure magnetospheric accretion origin for the formation of hydrogen and helium emission lines in moderately active CTTSs. From a comparison with those Taurus-Auriga CTTSs for which the inclination is reliably known, we conclude that the view angle of CTTS systems is one of the key parameters governing apparent Hα emission strength in the T Tauri class. We discuss the various possible formation regions for the Na  D lines and show that profiles similar to observed ones can be formed at the base of the disk wind.

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A spectro-astrometric study of southern pre-main sequence stars

Cited by 107 publications

References 86 publications

Astrometric confirmation of young low-mass binaries and multiple systems in the Chamaeleon star-forming regions

Astrometric confirmation of young low-mass binaries and multiple systems in the Chamaeleon star-forming regions

Revealing the sub-AU asymmetries of the inner dust rim in the disk around the Herbig Ae star R Coronae Austrinae

Edge-on T Tauri stars

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