The Variable Radio Source T Tauri

Johnston, K. J.; Gaume, R. A.; Fey, A. L.; Vegt, C. de; Claussen, M. J.

doi:10.1086/345727

Cited by 32 publications

(81 citation statements)

References 24 publications

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“…3. There are also radio observations of this system, which list astrometric positions for presumably T Tau Sb, see Johnston et al (2003) and Smith et al (2003). However, even after correcting for the orbital motion of Sb around Sa, the radio observations do not align with the optical observations, and instead are grouped with the unresolved K-band observations.…”

Section: Astrometrymentioning

confidence: 99%

Examining the T Tauri system with SPHERE

Csépány

Ancker

Ábrahám

et al. 2015

A&A

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Context. The prototypical low-mass young stellar object, T Tauri, is a well-studied multiple system with at least three components. Aims. We aim to explore the T Tau system with the highest spatial resolution, study the time evolution of the known components, and re-determine the orbital parameters of the stars. Methods. Near-infrared classical imaging and integral field spectrograph observations were obtained during the Science Verification of SPHERE, the new high-contrast imaging facility at the VLT. The obtained FWHM of the primary star varies between 0.050 and 0.059 , making these the highest spatial resolution near-infrared images of the T Tauri system obtained to date. Results. Our near-infrared images confirm the presence of extended emission south of T Tau Sa, reported in the literature. New narrow-band images show, for the first time, that this feature shows strong emission in both the Br-γ and H 2 1−0 S(1) lines. Broadband imaging at 2.27 µm shows that T Tau Sa is 0.92 mag brighter than T Tau Sb, which is in contrast to observations from Jan. 2014 (when T Tau Sa was fainter than Sb), and demonstrates that T Tau Sa has entered a new period of high variability. The newly obtained astrometric positions of T Tau Sa and Sb agree with orbital fits from previous works. The orbit of T Tau S (the centre of gravity of Sa and Sb) around T Tau N is poorly constrained by the available observations and can be fit with a range of orbits ranging from a nearly circular orbit with a period of 475 years to highly eccentric orbits with periods up to 2.7 × 10 4 years. We also detected a feature south of T Tau N, at a distance of 144 ± 3 mas, which shows the properties of a new companion.

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Section: Astrometrymentioning

confidence: 99%

Examining the T Tauri system with SPHERE

Csépány

Ancker

Ábrahám

et al. 2015

A&A

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“…(c) Offset from T Tau Sa given by Köhler et al (2000). (d) Johnston et al (2003). We have used these offsets to calculate the positions for Sa and Sb which are given in Table 1.…”

Section: Source Positionsmentioning

confidence: 99%

“…Finally, in Table 1 we list the position of the southern 2 cm source observed by Johnston et al (2003) at epoch 2001.0531, which has been proper motion corrected to epoch 1999.958 using the proper motion reported for T Tau S by these authors.…”

Section: Source Positionsmentioning

confidence: 99%

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VLBI observations of T Tauri South

Smith¹,

Pestalozzi²,

Güdel³

et al. 2003

A&A

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Abstract. We report observations of the T Tauri system at 8.4 GHz with a VLBI array comprising the VLBA, VLA and Effelsberg 100 m telescopes. We detected a compact source offset approximately 40 mas from the best infrared position of the T Tau Sb component. This source was unresolved, and constrained to be less than 0.5 mas in size, corresponding to 0.07 AU or 15 R at a distance of 140 pc. The other system components (T Tau Sa, T Tau N) were not detected in the VLBI data. The separate VLA map contains extended flux not accounted for by the compact VLBI source, indicating the presence of extended emission on arcsecond scales. The compact source shows rapid variability, which together with circular polarization and its compact nature indicate that the observed flux arises from a magnetically-dominated region. Brightness temperatures in the MK range point to gyrosynchrotron as the emission mechanism for the steady component. The rapid variations are accompanied by dramatic changes in polarization, and we record an at times 100% polarized component during outbursts. This strongly suggests a coherent emission process, most probably an electron cyclotron maser. With this assumption it is possible to estimate the strength of the local magnetic field to be 1.5−3 kilogauss.

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“…While it has been suggested that this system may be on an unbound orbit (Loinard et al 2003), other studies have found possible closed orbits and derived a total mass of 2−6 M for T Tau S (Johnston et al 2003;Beck et al 2004). Using a refined method, Johnston et al (2004a,b) attempted for the first time to determine the individual masses of T Tau Sa and Sb.…”

Section: Introductionmentioning

confidence: 99%

Accurate stellar masses in the multiple system T Tauri

Duchêne¹,

Beust²,

Adjali³

et al. 2006

A&A

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Aims. We obtain accurate estimates for the individual masses of the components of the tight binary system T Tau S to settle the ongoing debate on the nature of T Tau Sa, a so-called infrared companion. Methods. We take advantage of the fact that T Tau S belongs to a triple system composed of two hierarchical orbits to simultaneously analyze the motion of T Tau Sb in the rest frames of T Tau Sa and T Tau N. With this method, it is possible to pinpoint the location of the center of mass of T Tau S and, thereby, to determine individual masses for T Tau Sa and T Tau Sb with no prior assumption about the mass/flux ratio of the system. This improvement over previous studies of the system results in much better constraints on orbital parameters. Results. We find individual masses of 2.73 ± 0.31 M for T Tau Sa and of 0.61 ± 0.17 M for T Tau Sb (in agreement with its early-M spectral type), including the uncertainty on the distance to the system. These are among the most precise estimates of the mass of any Pre-Main Sequence star, a remarkable result since this is the first system in which individual masses of T Tauri stars can be determined from astrometry only. This model-independent analysis confirms that T Tau Sa is an intermediate-mass star, presumably a very young Herbig Ae star, that may possess an almost edge-on disk.

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The Variable Radio Source T Tauri

Cited by 32 publications

References 24 publications

Examining the T Tauri system with SPHERE

Examining the T Tauri system with SPHERE

VLBI observations of T Tauri South

Accurate stellar masses in the multiple system T Tauri

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