# # Program information file # PROGRAM_ID 2023A056 PROGRAM_TITLE Investigating the history of accretion in the protostellar disks of Z CMa, a binary system of two eruptive young stars PROGRAM_INV1 Foteini Lykou PROGRAM_INV2 Peter Abraham PROGRAM_INV3 Agnes Kospal PROGRAM_INV4 Hermine Landt-Wilman PROGRAM_INV5 PROGRAM_SCICAT stellar PROGRAM_ABSTRACT_BEG The circumstellar disks of eruptive young stars are dynamical environments, continuously shaped by accretion processes. The residuals of such disks will eventually provide the building blocks of planet formation. The trigger mechanisms for such outbursts is not well understood, though recent discoveries suggest that flyby events may be the cause. One such very active system is Z CMa that is composed of not one but two eruptive young stars; an FU Ori-type one [whose last known outburst occurred last century] and a Herbig Ae/Be star that experienced multiple outbursts in the last 15 years but appears to have returned to quiescence. It is thought that the eruptions were triggered by a flyby event newly discovered by ALMA. Here we propose to study the effects of such an event in the accretion process in the protostellar disks. We will obtain 0.8-5 um spectra of the system with SpeX and compare these to archival data obtained during one of its recent outbursts, and thus study the accretion history of the circumstellar disks [temperature, mass accretion rate]. Furthermore, the new data will complement future high-angular resolution interferometic observations in the infrared - which will be able to resolve each of the protostellar disks but lack the spectral information - by helping us to associate spectral signatures to the individual components. The Z CMa system may be the Rosetta-stone of how external effects [companion, flyby object] could trigger an outburst, therefore to obtain a complete picture and in order to understand this system, it is necessary to combine detailed information in both space and wavelength. PROGRAM_ABSTRACT_END