An occultation event in the nucleus of the planetary nebula M 2-29

• Published in: Astronomy and astrophysics (Berlin) 2008-11, Vol.490 (2), p.L7-L10
• Main Authors: Hajduk, M., Zijlstra, A. A., Gesicki, K.
• Format: Article
• Language: English
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; ISM: planetary nebulae: individual: PN G004.0-03.0; planetary nebulae: general; stars: AGB and post-AGB
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361:200810492

Aims. Eclipses and occultations of post-AGB stars provide a powerful method of exploring the near-stellar environment, including close companions and circumstellar debris disks. Only six eclipsing systems and one dust-occultation system are currently known. New cases are important for our understanding of binary evolution during the AGB mass-loss phase. Methods. We study the post-AGB central star of the (bipolar) Galactic bulge planetary nebula M 2-29. We have obtained additional HST imaging and SAAO spectroscopy of the object. Results. The star showed a pronounced, long-lasting occultation with subsequent recovery. The event lasted almost 3 years, with a secondary minimum 9 years later. The photometric behavior of M 2-29 resembles the dust-occultation events seen in NGC 2346, and is modeled as an occultation by a circumbinary disk, where the binary period is 18 yr. Modulation during the decline shows evidence of another companion with a period of 23 days. Conclusions. M 2-29 is the first eclipsing disk system among post-AGB stars. Close binaries with periods of around 1 month, as found in M 2-29, have been proposed to supply the energy needed to create the tori of bipolar planetary nebulae.