Protostars and Planets VI, Heidelberg, July 15-20, 2013

Poster 2B055

EXORCISM: EXOR optiCal Infrared Systematic Monitoring

Antoniucci, Simone (INAF - Osservatorio Astronomico di Roma)
Arkharov, Arkady A. (Central Astronomical Observatory of Pulkovo, St. Petersburg)
Di Paola, Andrea (INAF - Osservatorio Astronomico di Roma)
Giannini, Teresa (INAF - Osservatorio Astronomico di Roma)
Kishimoto, Makoto (Max Planck Institut fuer Radioastronomie, Bonn)
Kloppenborg, Brian (Max Planck Institut fuer Radioastronomie, Bonn)
Larionov, Valeri M. (Central Astronomical Observatory of Pulkovo, St. Petersburg; Astronomical Institute of St. Petersburg University)
Li Causi, Gianluca (INAF - Osservatorio Astronomico di Roma)
Lorenzetti, Dario (INAF - Osservatorio Astronomico di Roma)
Vitali, Fabrizio (INAF - Osservatorio Astronomico di Roma)

EXors are pre-main sequence eruptive stars showing intermittent outbursts (Dmag about 3-4) of short duration (months) superposed on longer (years) quiescence periods. While a general consensus exists about the origin of the outbursts (i.e. accretion events from the circumstellar disk), many important details (e.g. the trigger mechanism, the disk heating/cooling and its final fragmentation) are not clarified yet. To perform a comprehensive study of EXors, we have recently activated a regular optical/NIR photometric and spectroscopic monitoring program (EXORCISM - EXORs optiCal-Infrared Systematic Monitoring), which will carry on in a more systematic way an observational program that we started a few years ago. During this period we have already obtained interesting results that will be discussed here: (i) EXors become bluer (redder) when brightening (fading), but extinction cannot be uniquely responsible for that; (ii) (quasi-)simultaneous light-curves taken in different bands show a systematic lag with the wavelength; (iii) SEDs at outburst and quiescence differ by a single temperature black-body interpreted as the sudden heating of the inner disk wall by hot spots on the stellar surface; (iv) EXor near-IR spectra look like those of accreting T Tauri stars more than those of FUOr objects; (v) notably, near IR permitted line emission weakens when the continuum fades, but the continuum fluctuations appear faster than those of the lines. These results will help to clarify the scopes of our EXORCISM project and, more importantly, to framework new results on the mid-IR properties of EXors (mainly derived from WISE data), which are so far quite unexplored.

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