Surveying Planetary Nebulae Central Stars for Close Binaries: Constraining Evolution of Central Stars Based on Binary Parameters

The increase in discovered close binary central stars of planetary nebulae is leading to a sufficiently large sample to begin to make broader conclusions about the effect of close binary stars on common envelope evolution and planetary nebula formation. Herein I review some of the recent results and conclusions specifically relating close binary central stars to nebular shaping, common envelope evolution off the red giant branch, and the total binary fraction and double degenerate fraction of central stars. Finally, I use parameters of known binary central stars to explore the relationship between the proto-planetary nebula and planetary nebula stages, demonstrating that the known proto-planetary nebulae are not the precursors of planetary nebulae with close binary central~stars.Comment: 8 pages, 1 figur

Finding the Observability Fraction of Double Degenerate Binary Systems Using Monte Carlo Simulations

Double degenerate systems are binary systems consisting of two white dwarf stars. Many double degenerates are identified inside planetary nebulae where their physical conditions make them easier to detect and study. Planetary nebulae are made up of giant clouds of gas that glow due to the intense heat from a dying central star which ionizes the gas within the shell. We would like to determine what fraction of double degenerates are detectable using standard search methods, and how different physical parameters of the double degenerate system affect that fraction. Due to the small existing dataset for double degenerate systems, a Monte Carlo simulation code was used to create a statistically significant synthetic sample of double degenerate systems. In order to create accurate input for the Monte Carlo code, possible probability distributions for central star mass, companion star mass, age of the planetary nebulae, and orbital period had to be varied and compared to the available observational data. The resulting binary observability fraction is presented and discussed here. In addition, a brief discussion is included on how the results of this study also provide information on the occurrence of type Ia supernovae, an important class of events in our understanding the size and expansion of the Universe

Binary Central Stars of Planetary Nebulae Discovered Through Photometric Variability. III. The Central Star of Abell 65

A growing number of close binary stars are being discovered among central stars of planetary nebulae. Recent and ongoing surveys are finding new systems and contributing to our knowledge of the evolution of close binary systems. The push to find more systems was largely based on early discoveries which suggested that 10%–15% of all central stars are close binaries. One goal of this series of papers is confirmation and classification of these systems as close binaries and determination of binary system parameters. Here we provide time-resolved multi-wavelength photometry of the central star of Abell 65 as well as further analysis of the nebula and discussion of possible binary–nebula connections. Our results for Abell 65 confirm recent work showing that it has a close, cool binary companion, though several of our model parameters disagree with the recently published values. With our longer time baseline of photometric observations from 1989 to 2009 we also provide a more precise orbital period of 1.0037577 days

Post-red-giant-branch Planetary Nebulae

Common envelope events have been associated with the formation of a planetary nebulae since its proposition more than forty five years ago. However, until recently there have been doubts as to whether a common envelope while the donor is ascending the red giant branch, rather than the subsequent asymptotic red giant branch, would result in a planetary nebula. There is now strong theoretical and observational evidence to suggest that some planetary nebulae are, indeed, the products of common envelope phases which occurred while the nebular progenitor was on the red giant branch. The characterisation of these systems is challenging but has the potential to reveal much about the common envelope -- a critical evolutionary phase in the formation of a plethora of interesting astrophysical phenomena.Comment: 6 pages, to appear in Highlights of Spanish Astrophysics XI, Proceedings of the XV Scientific Meeting of the Spanish Astronomical Society held on September 4 0 9, 2022, in La Laguna, Spain. M. Manteiga, L. Bellot, P. Benavidez, A. de Lorenzo-Caceres, M. A. Fuente, M. J. Martinez, M. Vazquez- Acosta, C. Dafonte (eds.), 202

Variability in Protoplanetary Nebulae: X. Multi-year Periods as an Indicator of Potential Binaries

New observations are presented of four evolved objects that display long, multi-year variations in their light curves. These are interpreted as good evidence of their binary nature, with the modulation caused by the barycenter motion of the evolved star resulting in a periodic obscuration by a circumbinary disk. Although protoplanetary nebulae (PPNe) commonly possess bipolar nebulae, which are thought to be shaped by a binary companion, there are very few PPNe in which a binary companion has been found. Three of the objects in this study appear to be PPNe, IRAS 07253-2001, 08005-2356, and 17542-0603, with long periods of 5.2, 6.9, and 8.2 yrs, respectively. The binary nature of IRAS 08005-2356 has recently been confirmed by a radial velocity study. Two samples, one of PPNe and the other of post-AGB star candidates, are investigated for further evidence on how common is a long-period light curve variation. Both samples suggest such light variations are not common. The fourth object, IRAS 20056+1834 (QY Sge), is an obscured RV Tau variable of the RVb subclass, with a long period of 3.9 yrs and pulsation periods of 102.9 and 51.5 days. The period of this object is seen to vary by 2%. Evidence is presented for a recent mass ejection in IRAS 17542-0603.Comment: 22 pages, 6 figures, 1 machine-readable tabl

PHOTOMETRY OF TWO POORLY STUDIED PLANETARY NEBULAE WITH BINARY CENTRAL STARS

ABSTRACT We have observed the central stars of two planetary nebulae, Abell 65 and Hubble 12, both of which are claimed to be close binary systems. We looked at the differential photometry from these systems in hopes of confirming previous reports of variability caused by close binaries. Binary interaction in a planetary nebula is a possible source of the structure of bi-polar or butterfly PN. We determined that one of the two systems, Abell 65, most likely exhibits variability due to irradiation of a cool companion or deformation of one companion caused by it filing a significant fraction of its Roche Lobe. We cannot confirm the binary classification until a complete light curve is obtained. With Hubble 12, which was claimed to be an eclipsing binary system with an irradiation effect, we found no clear variability indicative of a binary system and recommend that it be removed from the list of known binary central stars

Binary Central Stars of Planetary Nebulae Discovered Through Photometric Variability III: The Central Star of Abell 65

A growing number of close binary stars are being discovered among central stars of planetary nebulae. Recent and ongoing surveys are finding new systems and contributing to our knowledge of the evolution of close binary systems. The push to find more systems was largely based on early discoveries which suggested that 10 to 15% of all central stars are close binaries. One goal of this series of papers is confirmation and classification of these systems as close binaries and determination of binary system parameters. Here we provide time-resolved multi-wavelength photometry of the central star of Abell 65 as well as further analysis of the nebula and discussion of possible binary--nebula connections. Our results for Abell 65 confirm recent work showing that it has a close, cool binary companion, though several of our model parameters disagree with the recently published values. With our longer time baseline of photometric observations from 1989--2009 we also provide a more precise orbital period of 1.0037577 days.Comment: Accepted for publication in the Astronomical Journa