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Stable accretion and episodic outflows in the young transition disk system GM Aurigae
A semester-long optical and near-infrared spectrophotometric monitoring campaign

J. Bouvier, A. Sousa, K. Pouilly, J. -M. Almenara, J.-F. Donati, S. Alencar, A. Frasca, K. N. Grankin, A. Carmona, G. Pantolmos, B. Zaire, X. Bonfils, A. Bayo, L. Rebull, J. Alonso-Santiago, J. F. Gameiro, N. J. Cook, E. Artigau


Context. Young stellar systems actively accrete from their circumstellar disk and simultaneously launch outflows. The physical link between accretion and ejection processes remains to be fully understood.
Aims. We investigate the structure and dynamics of magnetospheric accretion and associated outflows on a scale smaller than 0.1 au around the young transitional disk system GM Aur.
Methods. We devised a coordinated observing campaign to monitor the variability of the system on timescales ranging from days to months, including partly simultaneous high-resolution optical and near-infrared spectroscopy, multiwavelength photometry, and low-resolution near-infrared spectroscopy, over a total duration of six months, covering 30 rotational cycles. We analyzed the photometric and line profile variability to characterize the accretion and ejection processes.
Results. The optical and near-infrared light curves indicate that the luminosity of the system is modulated by surface spots at the stellar rotation period of 6.04 ± 0.15 days. Part of the Balmer, Paschen, and Brackett hydrogen line profiles as well as the HeI 5876 Å and HeI 10830 Å line profiles are modulated on the same period. The Paβ line flux correlates with the photometric excess in the u′ band, which suggests that most of the line emission originates from the accretion process. High-velocity redshifted absorptions reaching below the continuum periodically appear in the near-infrared line profiles at the rotational phase in which the veiling and line fluxes are the largest. These are signatures of a stable accretion funnel flow and associated accretion shock at the stellar surface. This large-scale magnetospheric accretion structure appears fairly stable over at least 15 and possibly up to 30 rotational periods. In contrast, outflow signatures randomly appear as blueshifted absorption components in the Balmer and HeI 10830 Å line profiles. They are not rotationally modulated and disappear on a timescale of a few days. The coexistence of a stable, large-scale accretion pattern and episodic outflows supports magnetospheric ejections as the main process occurring at the star-disk interface.
Conclusions. Long-term monitoring of the variability of the GM Aur transitional disk system provides clues to the accretion and ejection structure and dynamics close to the star. Stable magnetospheric accretion and episodic outflows appear to be physically linked on a scale of a few stellar radii in this system.

accretion, accretion disks / stars: magnetic field / stars: individual: GM Aur / stars: pre-main sequence / stars: variables: T Tauri, Herbig Ae/Be / stars: winds, outflows

- Tables containing the u′g′r′i′ LCOGT photometric measurements are only available at the CDS via anonymous ftp to ( or via
- Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT), at the Observatoire de Haute-Provence (OHP), at the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), and at the Las Cumbres Observatory global telescope network (LCOGT).

Astronomy & Astrophysics
Volume 672, Article Number A5, Number of pages 30
2023 April

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Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia