The close classical T Tauri binary V4046 Sgr: complex magnetic fields and distributed mass accretion

被引：67

作者：

Donati, J. -F. ^{[1
,2
]}

Gregory, S. G. ^{[3
]}

Montmerle, T. ^{[4
,5
,6
]}

Maggio, A. ^{[7
]}

Argiroffi, C. ^{[7
,8
]}

Sacco, G. ^{[9
]}

Hussain, G. ^{[10
]}

Kastner, J. ^{[9
]}

Alencar, S. H. P. ^{[11
]}

Audard, M. ^{[12
]}

Bouvier, J. ^{[5
,6
]}

Damiani, F. ^{[7
]}

Guedel, M. ^{[13
]}

Huenemoerder, D. ^{[14
]}

Wade, G. A. ^{[15
]}

机构：

[1] CNRS, IRAP, UMR 5277, F-31400 Toulouse, France

[2] Univ Toulouse, F-31400 Toulouse, France

[3] CALTECH, Pasadena, CA 91125 USA

[4] Inst Astrophys Paris, F-75014 Paris, France

[5] CNRS, IPAG, UMR 5274, F-38041 Grenoble, France

[6] Univ Grenoble 1, F-38041 Grenoble, France

[7] Osserv Astron Palermo, INAF, I-90134 Palermo, Italy

[8] Univ Palermo, Dip Fis, I-90134 Palermo, Italy

[9] Rochester Inst Technol, Ctr Imaging Sci, Rochester, NY 14623 USA

[10] ESO, D-85748 Garching, Germany

[11] Univ Fed Minas Gerais, Dept Fis, ICEx, BR-30270901 Belo Horizonte, MG, Brazil

[12] Univ Geneva, ISDC, Data Ctr Astrophys, CH-1290 Versoix, Switzerland

[13] Univ Vienna, Dept Astron, A-1180 Vienna, Austria

[14] MIT, Kavli Inst Astrophys & Space Res, Cambridge, MA 02139 USA

[15] Royal Mil Coll Canada, Dept Phys, Kingston, ON K7K 7B4, Canada

来源：

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY | 2011年 / 417卷 / 03期

关键词：

techniques: polarimetric; stars: formation; stars: imaging; stars: individual: V4046 Sgr; stars: magnetic fields; stars: rotation; MAGNETOSPHERIC ACCRETION; LITHIUM DEPLETION; TIDAL EVOLUTION; BROWN DWARFS; ACTIVE STARS; DYNAMO; SYSTEMS; CYCLES; FLOWS;

D O I：

10.1111/j.1365-2966.2011.19366.x

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

We report here the first results of a multi-wavelength campaign focusing on magnetospheric accretion processes within the close binary system V4046 Sgr, hosting two partly convective classical T Tauri stars of masses similar or equal to 0.9 M-circle dot and age similar or equal to 12 Myr. In this paper, we present time-resolved spectropolarimetric observations collected in 2009 September with ESPaDOnS at the Canada-France-Hawaii Telescope (CFHT) and covering a full span of 7 d or similar or equal to 2.5 orbital/rotational cycles of V4046 Sgr. Small circularly polarized Zeeman signatures are detected in the photospheric absorption lines but not in the accretion-powered emission lines of V4046 Sgr, thereby demonstrating that both system components host large-scale magnetic fields weaker and more complex than those of younger, fully convective classical T Tauri stars (cTTSs) of only a few Myr and similar masses. Applying our tomographic imaging tools to the collected data set, we reconstruct maps of the large-scale magnetic field, photospheric brightness and accretion-powered emission at the surfaces of both stars of V4046 Sgr. We find that these fields include significant toroidal components, and that their poloidal components are mostly non-axisymmetric with a dipolar component of 50-100G strongly tilted with respect to the rotation axis; given the similarity with fields of partly convective main-sequence stars of similar masses and rotation periods, we conclude that these fields are most likely generated by dynamo processes. We also find that both stars in the system show cool spots close to the pole and extended regions of low-contrast, accretion-powered emission; it suggests that mass accretion is likely distributed rather than confined in well-defined high-contrast accretion spots, in agreement with the derived magnetic field complexity.

引用

页码：1747 / 1759

页数：13

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