The GRAVITY young stellar object survey V. The orbit of the T Tauri binary star WWCha

被引：4

作者：

Eupen, F. ^{[1
]}

Labadie, L. ^{[1
]}

Grellmann, R. ^{[1
]}

Perraut, K. ^{[2
]}

Brandner, W. ^{[3
]}

Duchene, G. ^{[2
,4
]}

Kohler, R. ^{[5
]}

Sanchez-Bermudez, J. ^{[3
,6
]}

Lopez, R. Garcia ^{[3
,7
,8
]}

Garatti, A. Caratti O. ^{[3
,7
,8
]}

Benisty, M. ^{[2
,9
]}

Dougados, C. ^{[2
]}

Garcia, P. ^{[10
,11
]}

Klarmann, L. ^{[3
]}

Amorim, A. ^{[10
,16
]}

Baubock, M. ^{[13
]}

Berger, J. P. ^{[2
]}

Caselli, P. ^{[13
]}

Clenet, Y. ^{[12
]}

Foresto, V. Coude du ^{[12
]}

Zeeuw, P. T. de ^{[13
,17
]}

Drescher, A. ^{[13
]}

Duvert, G. ^{[2
]}

Eckart, A. ^{[1
,15
]}

Eisenhauer, F. ^{[13
]}

Filho, M. ^{[10
,11
]}

Ganci, V ^{[1
]}

Gao, F. ^{[13
]}

Gendron, E. ^{[12
]}

Genzel, R. ^{[13
]}

Gillessen, S. ^{[13
]}

Heissel, G. ^{[12
]}

Henning, Th ^{[3
]}

Hippler, S. ^{[3
]}

Horrobin, M. ^{[1
]}

Hubert, Z. ^{[2
]}

Jimenez-Rosales, A. ^{[13
]}

Jocou, L. ^{[2
]}

Kervella, P. ^{[12
]}

Lacour, S. ^{[12
]}

Lapeyrere, V ^{[12
]}

Bouquin, J. B. Le ^{[2
]}

Lena, P. ^{[12
]}

Ott, T. ^{[13
]}

Paumard, T. ^{[12
]}

Perrin, G. ^{[12
]}

Pfuhl, O. ^{[14
]}

Rodriguez-Coira, G. ^{[12
]}

Rousset, G. ^{[12
]}

Scheithauer, S. ^{[3
]}

机构：

[1] Univ Cologne, Phys Inst 1, Zulpicher Str 77, D-50937 Cologne, Germany

[2] Univ Grenoble Alpes, IPAG, CNRS, F-38000 Grenoble, France

[3] Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany

[4] Univ Calif Berkeley, Dept Astron, 601 Campbell Hall, Berkeley, CA 94720 USA

[5] Univ Vienna, Dept Astrophys, Turkenschanzstr 17, A-1180 Vienna, Austria

[6] Univ Nacl Autonoma Mexico, Inst Astron, Apdo Postal 70264, Ciudad De Mexico 04510, Mexico

[7] Dublin Inst Adv Studies, 31 Fitzwilliam Pl, Dublin D02 XF86, Ireland

[8] Univ Coll Dublin, Sch Phys, Dublin 4, Ireland

[9] Univ Chile, Dept Astron, CNRS, Unidad Mixta Int Franco Chilena Astron,UMI 3386, Camino Observatorio 1515, Santiago, Chile

[10] Inst Super Tecn, Ctr Astrofis & Gravitacao, CENTRA, Ave Rovisco Pais 1, P-1049 Lisbon, Portugal

[11] Univ Porto, Fac Engn, Rua Dr Roberto Frias, P-4200465 Porto, Portugal

[12] PSL Res Univ, Sorbonne Univ, Univ Paris Diderot, Observ Paris,LESIA,CNRS,UPMC Univ Paris 06,Sorbon, Paris, France

[13] Max Planck Inst Extraterr Phys, Giessenbachstr, D-85741 Garching, Germany

[14] European Southern Observ, Karl Schwarzschild Str 2, D-85748 Garching, Germany

[15] Max Planck Inst Radio Astron, Hugel 69, D-53121 Bonn, Germany

[16] Univ Lisbon, Fac Ciencias, P-1749016 Lisbon, Portugal

[17] Leiden Univ, Sterrewacht Leiden, Postbus 9513, NL-2300 RA Leiden, Netherlands

来源：

ASTRONOMY & ASTROPHYSICS | 2021年 / 648卷

基金：

爱尔兰科学基金会; 欧盟地平线“2020”; 欧洲研究理事会;

关键词：

binaries: close; stars: pre-main sequence; stars: variables: T Tauri; Herbig Ae /Be; stars: individual: WW Cha; techniques: high angular resolution; techniques: interferometric; PRE-MAIN-SEQUENCE; LOW-MASS STARS; CHAMELEON-I; OPTICAL INTERFEROMETRY; CIRCUMSTELLAR DISKS; CIRCUMBINARY DISCS; PULSED ACCRETION; DATA REDUCTION; MULTIPLICITY; POPULATION;

D O I：

10.1051/0004-6361/202039599

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

Context. Close young binary stars are unique laboratories for the direct measurement of pre-main-sequence (PMS) stellar masses and their comparison to evolutionary theoretical models. At the same time, a precise knowledge of their orbital parameters when still in the PMS phase offers an excellent opportunity for understanding the influence of dynamical effects on the morphology and lifetime of the circumstellar as well as circumbinary material. Aims. The young T Tauri star WW Cha was recently proposed to be a close binary object with strong infrared and submillimeter excess associated with circum-system emission, which makes it dynamically a very interesting source in the above context. The goal of this work is to determine the astrometric orbit and the stellar properties of WW Cha using multi-epoch interferometric observations. Methods. We derive the relative astrometric positions and flux ratios of the stellar companion in WW Cha from the interferometric model fitting of observations made with the VLTI instruments AMBER, PIONIER, and GRAVITY in the near-infrared from 2011 to 2020. For two epochs, the resulting uv-coverage in spatial frequencies permits us to perform the first image reconstruction of the system in the K band. The positions of nine epochs are used to determine the orbital elements and the total mass of the system. Combining the orbital solution with distance measurements from Gaia DR2 and the analysis of evolutionary tracks, we constrain the mass ratio. Results. We find the secondary star orbiting the primary with a period of T = 206.55 days, a semimajor axis of a = 1.01 au, and a relatively high eccentricity of e = 0.45. The dynamical mass of M-tot = 3.20 M-circle dot can be explained by a mass ratio between similar to 0.5 and 1, indicating an intermediate-mass T Tauri classification for both components. The orbital angular momentum vector is in close alignment with the angular momentum vector of the outer disk as measured by ALMA and SPHERE, resulting in a small mutual disk inclination. The analysis of the relative photometry suggests the presence of infrared excess surviving in the system and likely originating from truncated circumstellar disks. The flux ratio between the two components appears variable, in particular in the K band, and may hint at periods of triggered higher and lower accretion or changes in the disks' structures. Conclusions. The knowledge of the orbital parameters, combined with a relatively short period, makes WW Cha an ideal target for studying the interaction of a close young T Tauri binary with its surrounding material, such as time-dependent accretion phenomena. Finding WW Cha to be composed of two (probably similar) stars led us to reevaluate the mass of WW Cha, which had been previously derived under the assumption of a single star. This work illustrates the potential of long baseline interferometry to precisely characterize close young binary stars separated by a few astronomical units. Finally, when combined with radial velocity measurements, individual stellar masses can be derived and used to calibrate theoretical PMS models.

引用

页数：18

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