ATCA observations of the very young Planetary Nebula SAO 244567

Authors


E-mail: Grazia.Umana@oact.inaf.it

SAO predoc fellow, Harvard-Smithsonian Centre for Astrophysics, Cambridge, MA 02138, USA.

ABSTRACT

The radio emission from the youngest known Planetary Nebula, SAO 244567, has been mapped at 1384, 2368, 4800, 8640, 16832 and 18752 MHz by using the Australian Telescope Compact Array (ATCA). These observations constitute the first detailed radio study of this very interesting object, as they allow us to obtain the overall radio morphology of the source and to compute, for the first time, the radio spectrum up to the millimetre range. The radio emission is consistent with free–free from a wind-like shell, which is also the region where most of the [O iii] emission comes from as revealed by Hubble Space Telescope (HST) images. However, two other possible models, a uniform sphere and a uniform thin shell, can also reproduce the radio-observed quantities. Physical parameters of the radio nebula and of the central star were derived, for all the three proposed scenarios, all consistent with SAO 244567 being a very young Planetary Nebula still embedded in the dusty remnant of the asymptotic giant branch phase. The optically thin radio flux density appears to decrease when compared to data from the literature. The apparent variability of the radio emission, probably related to the evolution of the central object, needs further investigation.

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