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Beyond the dips of V807 Tau, a spectropolarimetric study of a dipper’s magnetosphere

Pouilly, K. and Bouvier, J. and Alecian, E. and Alencar, S. H. P. and Cody, A.-M. and Donati, J.-F. and Grankin, K. and Rebull, L. and Folsom, C. P. (2021) Beyond the dips of V807 Tau, a spectropolarimetric study of a dipper’s magnetosphere. Astronomy and Astrophysics, 656 . Art. No. A50. ISSN 0004-6361. doi:10.1051/0004-6361/202140850. https://resolver.caltech.edu/CaltechAUTHORS:20211208-559911000

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Abstract

Context. The so-called dippers are pre-main-sequence objects that accrete material from their circumstellar disks through the stellar magnetosphere. Their unique type of variability allows us to probe the magnetic star-disk interaction processes in young stellar objects. Aims. We aim to characterize the magnetospheric accretion process in the young stellar object V807 Tau, one of the most stable dippers revealed by K2 in the Taurus star forming region. Methods. We performed photometric and spectropolarimetric follow-up observations of this system with CFHT/ESPaDOnS in order to investigate the variability of the system over several rotational periods. Results. We derive a 4.38 day period from the K2 dipper light curve. This period is also seen in the radial velocity variations, which we ascribe to spot modulation. The slightly redshifted narrow component of the He I 5876 Å line as well as the high velocity red wing of the Hβ and Hγ emission line profiles also vary in intensity with the same periodicity. The former traces the accretion shock at the stellar surface, and the latter is a signature of an accretion funnel flow crossing the line of sight. We derive a surface brightness map and the topology of the surface magnetic field from the modeling of Stokes I and V profiles, respectively, for photospheric lines and for the He I emission line. The latter reveals a bright spot at the stellar surface, located at a latitude of 60°, and a maximum field strength of ∼2 kG at this location. The topology of the magnetic field at the stellar surface is dominated by a dipolar component inclined by about 40° onto the spin axis. Variable blueshifted absorption components seen in the Balmer line profiles suggest episodic outflows. Despite of its clear and stable dipper behavior, we derive a relatively low inclination of 40° to 50° for this system, which calls question the origin of the dips. The low inclination we infer is also consistent with the absence of deep inverse P Cygni components in the line profiles. Conclusions. We conclude that magnetospheric accretion is ongoing in V807 Tau, taking place through non-axisymmetric accretion funnel flows controlled by a strong, tilted, and mainly dipolar magnetic topology. Whether an inner disk warp resulting from this process can account for the dipper character of this source remains to be seen, given the low inclination of the system.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1051/0004-6361/202140850DOIArticle
ORCID:
AuthorORCID
Pouilly, K.0000-0002-9628-2959
Bouvier, J.0000-0002-7450-6712
Alecian, E.0000-0001-5260-7179
Alencar, S. H. P.0000-0002-5171-8376
Cody, A.-M.0000-0002-3656-6706
Donati, J.-F.0000-0001-5541-2887
Grankin, K.0000-0001-5707-8448
Rebull, L.0000-0001-6381-515X
Additional Information:© K. Pouilly et al. 2021. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Received 22 March 2021 / Accepted 13 September 2021. We thank an anonymous referee whose comments improved the content of this paper. This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 742095; SPIDI: Star-Planets-Inner Disk- Interactions; http://www.spidi-eu.org). This paper includes data collected by the Kepler mission. Funding for the Kepler mission is provided by the NASA Science Mission directorate. This work has made use of the VALD database, operated at Uppsala University, the Institute of Astronomy RAS in Moscow, and the University of Vienna. This project was funded in part by INSU/CNRS Programme National de Physique Stellaire and Observatoire de Grenoble Labex OSUG2020. S. H. P. Alencar acknowledges financial support from CNPq, CAPES and Fapemig. K. Grankin acknowledges the partial support from the Ministry of Science and Higher Education of the Russian Federation (grant 075-15-2020-780). Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council of Canada, the Institut National des Sciences de l’Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.
Group:Infrared Processing and Analysis Center (IPAC)
Funders:
Funding AgencyGrant Number
European Research Council (ERC)742095
NASAUNSPECIFIED
LabExOSUG2020
Institut national des sciences de l'Univers (INSU)UNSPECIFIED
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)UNSPECIFIED
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)UNSPECIFIED
Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG)UNSPECIFIED
Ministry of Science and Higher Education of the Russian Federation075-15-2020-780
Subject Keywords:stars: variables: T Tauri, Herbig Ae/Be / stars: pre-main sequence / accretion, accretion disks / stars: magnetic field / stars: individual: V807 Tau / starspots
DOI:10.1051/0004-6361/202140850
Record Number:CaltechAUTHORS:20211208-559911000
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20211208-559911000
Official Citation:Beyond the dips of V807 Tau, a spectropolarimetric study of a dipper’s magnetosphere K. Pouilly, J. Bouvier, E. Alecian, S. H. P. Alencar, A.-M. Cody, J.-F. Donati, K. Grankin, L. Rebull and C. P. Folsom A&A, 656 (2021) A50 DOI: https://doi.org/10.1051/0004-6361/202140850
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:112278
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:09 Dec 2021 17:47
Last Modified:01 Feb 2022 22:58

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