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تسجيل مستخدم جديدOrbits and Masses in the T Tauri System
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We investigate the binary star T Tauri South, presenting the orbital parameters of the two components and their individual masses. We combined astrometric positions from the literature with previously unpublished VLT observations. Model fits yield the orbital elements of T Tau Sa and Sb. We use T Tau N as an astrometric reference to derive an estimate for the mass ratio of Sa and Sb. Although most of the orbital parameters are not well constrained, it is unlikely that T Tau Sb is on a highly elliptical orbit or escaping from the system. The total mass of T Tau S is rather well constrained to 3.0 +0.15/-0.24 M_sun. The mass ratio Sb:Sa is about 0.4, corresponding to individual masses of M_Sa = 2.1+/-0.2 M_sun and M_Sb = 0.8+/-0.1 M_sun. This confirms that the infrared companion in the T Tauri system is a pair of young stars obscured by circumstellar material.
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We present new astrometric measurements of the components in the T Tauri system, and derive new orbits and masses. T Tauri was observed during the science verification time of the new extreme adaptive optics facility SPHERE at the VLT. We combine t
he new positions with recalibrated NACO-measurements and data from the literature. Model fits for the orbits of T Tau Sa and Sb around each other and around T Tau N yield orbital elements and individual masses of the stars Sa and Sb. Our new orbit for T Tau Sa/Sb is in good agreement with other recent results, which indicates that enough of the orbit has been observed for a reliable fit. The total mass of T Tau S is 2.65+/-0.11 Msun. The mass ratio M_Sb:M_Sa is 0.25+/-0.03, which yields individual masses of M_Sa = 2.12+/-0.10 Msun and M_Sb = 0.53+/-0.06 Msun. If our current knowledge of the orbital motions is used to compute the position of the southern radio source in the T Tauri system, then we find no evidence for the proposed dramatic change in its path.
We present results from adaptive optics imaging of the T Tauri triple system obtained at the Keck and Gemini Observatories in 2015-2019. We fit the orbital motion of T Tau Sb relative to Sa and model the astrometric motion of their center of mass rel
ative to T Tau N. Using the distance measured by Gaia, we derived dynamical masses of M_Sa = 2.05 +/- 0.14 Msun and M_Sb = 0.43 +/- 0.06 Msun. The precision in the masses is expected to improve with continued observations that map the motion through a complete orbital period; this is particularly important as the system approaches periastron passage in 2023. Based on published properties and recent evolutionary tracks, we estimate a mass of ~ 2 Msun for T Tau N, suggesting that T Tau N is similar in mass to T Tau Sa. Narrow-band infrared photometry shows that T Tau N remained relatively constant between late 2017 and early 2019 with an average value of K = 5.54 +/- 0.07 mag. Using T Tau N to calibrate relative flux measurements since 2015, we found that T Tau Sa varied dramatically between 7.0 to 8.8 mag in the K-band over timescales of a few months, while T Tau Sb faded steadily from 8.5 to 11.1 mag in the K-band. Over the 27 year orbital period of the T Tau S binary, both components have shown 3-4 magnitudes of variability in the K-band, relative to T Tau N.
We present a study of the orbits of the triple system LHS1070, with the aim to determine individual masses of its components. Sixteen new relative astrometric positions of the three components in the K band were obtained with NACO at the VLT, Omega
CASS at the 3.5m telescope on Calar Alto, and other high-spatial-resolution instruments. We combine them with data from the literature and fit orbit models to the dataset. We derive an improved fit for the orbit of LHS1070B and C around each other, and an estimate for the orbit of B and C around A. The orbits are nearly coplanar, with a misalignment angle of less than 10{deg}. The masses of the three components are M_A = 0.13 - 0.16 Msun, M_B = 0.077+/-0.005 Msun, and M_C = 0.071+/-0.004 Msun. Therefore, LHS1070C is certainly, and LHS1070B probably a brown dwarf. Comparison with theoretical isochrones shows that LHS1070A is either fainter or more massive than expected. One possible explanation would be that it is a binary. However, the close companion reported previously could not be confirmed.
The immediate vicinity of T Tauri was observed with the new high-contrast imaging instrument SPHERE at the VLT to resolve remaining mysteries of the system, such as the putative small edge-on disk around T Tauri Sa, and the assignment of the complex
outflow patterns to the individual stars. We used SPHERE IRDIS narrow-band classical imaging in Pa$beta$, Br$gamma$, and the $ u$ = 1-0 S(1) line of H$_2$, as well as in the nearby continua to obtain high spatial resolution and high contrast images over the NIR spectral range. Line maps were created by subtracting the nearby continuum. We also re--analyzed coronagraphic data taken with SPHEREs integral field spectrograph in $J$- and $H$-band with the goal to obtain a precise extinction estimate to T Tauri Sb, and to verify the recently reported claim of another stellar or substellar object in the system. A previously unknown coiling structure is observed southwest of the stars in reflected light, which points to the vicinity of T Tauri N. We map the circumbinary emission from T Tauri S in $J$- and $H$-band scattered light for the first time, showing a morphology which differs significantly from that observed in $K$-band. H$_2$ emission is found southwest of the stars, near the coiling structure. We also detect the H$_2$ emitting region T Tauri NW. The motion of T Tauri NW with respect to T Tauri N and S between previous images and our 2014 data, provides strong evidence that the Southeast-Northwest outflow triggering T Tauri NW is likely to be associated with T Tauri S. We further present accurate relative photometry of the stars, confirming that T Tauri Sa is brightening again. Our analysis rules out the presence of the recently proposed companion to T Tauri N with high confidence.
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 co
mponents, 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-{gamma} and H2 1-0 S(1) lines. Broadband imaging at 2.27 {mu}m 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 center 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 $144 pm 3$ mas, which shows the properties of a new companion.
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