Sub-0.1′′ optical imaging of the Z CMa jets with SPHERE/ZIMPOL
1 INAF–Osservatorio Astronomico di Roma, via Frascati 33, 00078 Monte Porzio Catone, Italy
2 INAF–Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
3 Laboratoire Lagrange (UMR 7293), UNSA, CNRS, Observatoire de la Côte d’Azur, Bd de l’Observatoire, 06304 Nice Cedex 4, France
4 INAF–Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
5 Dipartimento di Fisica e Astronomia, Università degli Studi di Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
6 Dipartimento di Informatica, Bioingegneria, Robotica e Ingegneria dei Sistemi (DIBRIS), Università di Genova, via Dodecaneso 35, 16145 Genova, Italy
7 Institute for Astronomy, ETH Zürich, Wolfgang-Pauli-Strasse 27, 8093 Zürich, Switzerland
8 Université Grenoble Alpes, IPAG, 38000 Grenoble, France
9 CNRS, IPAG, 38000 Grenoble, France
10 Université Lyon, Université Lyon1, Ens de Lyon, CNRS, CRAL UMR 5574, 69230 Saint-Genis-Laval, France
11 Aix-Marseille Université, CNRS, LAM – Laboratoire d’Astrophysique de Marseille, UMR 7326, 13388 Marseille, France
Received: 19 May 2016
Accepted: 11 August 2016
Context. Crucial information on the mass accretion-ejection connection in young stars can be obtained from high spatial resolution images of jets in sources with known recurrent accretion outbursts.
Aims. Using the VLT/SPHERE ZIMPOL instrument, we observed the young binary Z CMa that is composed of a Herbig Be star and a FUor object, both driving a jet. We aim to analyse the structure of the two jets, their relation with the properties of the driving sources, and their connection with previous accretion events observed in this target.
Methods. We obtained optical images in the Hα and [O i] 6300 Å lines at the unprecedented angular resolution of ~0.03 arcsec, on which we have performed both continuum subtraction and deconvolution, thereby deriving results that are consistent with each other.
Results. Our images reveal extended emission from both sources: a fairly compact and poorly collimated emission SW of the Herbig component and an extended collimated and precessing jet from the FUor component. The compact emission from the Herbig star is compatible with a wide-angle wind and is possibly connected to the recent outburst events shown by this component. The FUor jet is traced down to 70 mas (80 AU) from the source and is highly collimated with a width of 26−48 AU at distances 100−200 AU, which is similar to the width of jets from T Tauri stars. This strongly suggests that the same magneto-centrifugal jet-launching mechanism also operates in FUors. The observed jet wiggle can be modelled as originating from an orbital motion with a period of 4.2 yr around an unseen companion with mass between 0.48 and 1 M⊙. The jet mass loss rate Ṁjet was derived from the [O i] luminosity and comprises of between 1 × 10-8 and 1 × 10-6M⊙ yr-1. This is the first direct Ṁjet measurement from a jet in a FUor. If we assume previous mass accretion rate estimates obtained through modelling of the accretion disk, the derived range of Ṁjet would imply a very low mass-ejection efficiency (Ṁjet/Ṁacc≲ 0.02), which is lower than that typical of T Tauri stars.
Key words: stars: pre-main sequence / stars: variables: T Tauri, Herbig Ae/Be / stars: winds, outflows / stars: individual: Z CMa / techniques: high angular resolution / circumstellar matter
© ESO, 2016