Explosive Events in the Pre-planatary Nebula CRL 618

Chin-Fei Lee, Ragvendra Sahai, Carmen Sanchez-Contreras, Chun-Hui Yang & Po-Sheng Huang

ASIAA, Taiwan

CRL 618 is a C-rich multipolar PPN. A dusty dense core with a density enhancement is detected in the equatorial plane near the central source, collimating the PPN. The dense core is also detected in carbon chain molecules HC3N and HCN, and their isotopologues. The isotopic ratios of 12C/13C and 14N/15N are 9±4 and 150±50, respectively, both are too low to be produced by the cold CNO cycle inside the AGB star. These low isotopic ratios can be produced by a nova explosion, suggesting a nova-like activity at the center. In addition, a few coeval fast-moving bullets are detected ejecting from the center in different directions roughly perpendicular to the equatorial plane, suggesting a presence of a recent explosive event at the center. This explosive event and the low isotopic ratios both can be linked to a nova-like activity, suggesting a binary scenario for producing the multipolar PPN structure.

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