Ágnes Kóspál, Péter Ábrahám, and Timo Prusti
OO SERPENTIS: AN INTERMEDIATE-TYPE OBJECT BETWEEN FUORS AND EXORS? (Poster)

OO SERPENTIS: AN INTERMEDIATE-TYPE OBJECT BETWEEN FUORS AND EXORS?

Ágnes Kóspál(1), Péter Ábrahám(1), and Timo Prusti(2)
(1) Konkoly Observatory of the Hungarian Academy of Sciences, P.O.Box 67, H-1525 Budapest, Hungary
(2) ESTEC/SCI-SAF, Postbus 299, 2200 AG Noordwijk, The Netherlands

OO Serpentis is a deeply embedded young star which brightened by 5 mag in the K band between 1994 and 1995, and gradually faded afterwards. In many respects the star and its outburst is very similar to the well-known young eruptive stars (FUors and EXors). These outbursts are closely connected to the circumstellar material, thus infrared observations are essential in understanding the physics of these objects. Since very few outbursts have ever been documented at infrared wavelengths, we monitored OO Ser for 20 months with the Infrared Space Observatory in the 3.6 $-$ 100 $\mu$m wavelength range. We complemented this dataset with new (ground-based and spaceborn) infrared observations from 2004 $-$ 2005, and constructed the light curve of the outburst at 10 different wavelengths as well as pre-outburst, outburst, and post-outburst spectral energy distributions. Our results show that by 2004 OO Ser had already returned to the pre-outburst state at 12 um and below, suggesing a significantly shorter outburst timescale than that of classical FUors, but longer than that of the EXors. This may indicate, that OO Ser - together with the recently erupted star V1647 Ori - is the first example of an intermediate object between FUors and EXors.