Recent outburst of the young star V1180 Cassiopeiae^⋆

¹ INAF-Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monte Porzio Catone, Italy
e-mail: antoniucci@oa-roma.inaf.it
² Central Astronomical Observatory of Pulkovo, Pulkovskoe shosse 65, 196140 St. Petersburg, Russia
³ Fundación Galileo Galilei – INAF, Telescopio Nazionale Galileo, 38700 Santa Cruz de la Palma, Tenerife, Spain
⁴ Astronomical Institute of St. Petersburg University, St. Petersburg, Russia
⁵ INAF-Istituto di Astrofisica e Planetologia Spaziali, via Fosso del Cavaliere 100, 00133 Roma, Italy

Received: 8 April 2014
Accepted: 28 April 2014

Abstract

Aims. We report on the ongoing outburst of the young variable V1180 Cas, which is known to display characteristics in common with EXor eruptive variables. We present results that support the scenario of an accretion-driven nature of the brightness variations of the object and provide the first evidence of jet structures around the source.

Methods. We monitored the recent flux variations of the target in the R_C, J, H, and K bands. New optical and near-IR spectra taken during the current high state of V1180 Cas are presented, in conjunction with H₂ narrow-band imaging of the source.

Results. Observed near-IR colour variations are analogous to those observed in EXors and consistent with excess emission originating from an accretion event. The spectra show numerous emission lines, which indicates accretion, ejection of matter, and an active disc. Using optical and near-IR emission features we derive a mass accretion rate of ~ 3 × 10^-8M_⊙ yr^-1, which is an order of magnitude lower than previous estimates. In addition, a mass loss rate of ~ 4 × 10^-9 and ~ 4 × 10^-10M_⊙ yr^-1 are estimated from atomic forbidden lines and H₂, respectively. Our H₂ imaging reveals two bright knots of emission around the source and the nearby optically invisible star V1180 Cas B, clearly indicative of mass-loss phenomena. Higher resolution observations of the detected jet will help to clarify whether V1180 Cas is the driving source and to determine the relation between the observed knots.