부산대학교 도서관

The planetary nebula (PN) NGC3132 is a striking example of the dramatic but poorly understood, mass-loss phenomena that (1-8) Msun stars undergo during their death throes as they evolve into white dwarfs (WDs). From an analysis of JWST multiwavelength (0.9-18 micron) imaging of NGC3132, we report the discovery of an asymmetrical dust cloud around the WD central star (CS) of NGC3132, seen most prominently in the 18 micron~image, with a surface-brightness limited radial extent of >~2 arcsec. We show that the A2V star located 1.7 arcsec to CS's North-East (and 0.75 kpc from Earth) is gravitationally-bound to the latter, by the detection of relative orbital angular motion of (0.24+/-0.045) deg between these stars over ~20 yr. Using aperture photometry of the CS extracted from the JWST images, together with published optical photometry and an archival UV spectrum, we have constructed the spectral-energy distribution (SED) of the CS and its extended emission over the UV to mid-IR (0.091-18 micron) range. We find that fitting the SED of the CS and the radial intensity distributions at 7.7, 12.8 and 18 micron with thermal emission from dust requires a cloud that extends to a radius of >~1785 au, with a dust mass of ~1.3 x 10^(-2) M(Earth) and grains that are 70% silicate and 30% amorphous carbon. We propose plausible origins of the dust cloud and an evolutionary scenario in which a system of three stars -- the CS, a close low-mass companion, and a more distant A2V star -- forms a stable hierarchical triple system on the main-sequence but becomes dynamically unstable later, resulting in the spectacular mass-ejections that form the current, multipolar PN.
Comment: 23 pages, 5 tables, 8 figures (ApJ, in press) references added, minor revision of Fig 5 caption, minor typos corrected