Resonant Temperature Fluctuations in Nebulae Ionized by Short-Period Binary Stars

Abstract

A prevailing open problem in planetary nebulae research, and photoionized gaseous nebulae research at large, is the systematic discrepancies in electron temperatures and ionic abundances as derived from recombination and collisionally excited lines. Peimbert (1967) proposed the presence of 'temperature fluctuations' in these nebulae, but the apparent amplitude of such fluctuations, as deduced from spectral diagnostics and/or abundance discrepancy factors, remain unexplained by standard photoionization modeling. While this and other alternative models to explain the temperature and abundance discrepancies remain inconclusive, recent observations seem to point at a connection between nebular abundance discrepancy factors and a binary nature of photoionizing stars. In this paper we show that large amplitude temperature fluctuations are expected to form in planetary nebulae photoionized by short-period binary stars. Resonant temperature fluctuations are first formed along the orbital disk around the binary stars, as the periodically varying ionizing radiation field induces periodic oscillations in the heating-minus-cooling function. Then, the temperatures fluctuations propagate vertically to the disk as thermal waves that later steepen into radiative shocks. The binary period of the ionizing stars is determinant in the formation and propagation of temperature fluctuations, as well as in associated density fluctuations. Fluctuations propagate efficiently only in systems with binary periods significantly shorter than the gas thermalization time, of the order of 10 days. Further, we propose temperature diagnostic line ratios that combine [O III] collisionally excited lines and O II recombination lines to determine the equilibrium temperature and the magnitude of resonant temperature fluctuations in nebulae.

arXiv comment7 figures, in press, The Astrophysical Journal 2018

References in corpus (21)

• On the abundance discrepancy problem in HII regions
• Binary planetary nebulae nuclei towards the Galactic bulge. II. A penchant for bipolarity and low-ionisation structures
• Do most planetary nebulae derive from binaries? I Population synthesis model of the galactic planetary nebula population produced by singlestars and binaries
• A deep survey of heavy element lines in planetary nebulae - I. Observations and forbidden-line densities, temperatures and abundances
• Properties of the ionized gas in HH202. II: Results from echelle spectrophotometry with UVES
• Binarity and the abundance discrepancy problem in planetary nebulae
• Chemical abundances for Hf 2-2, a planetary nebula with the strongest known heavy element recombination lines
• Physical conditions in the planetary nebula Abell 30
• Confirmation of the link between central star binarity and extreme abundance discrepancy factors in planetary nebulae
• Fine Scale Temperature Fluctuations in the the Orion Nebula and the t^2 Problem
• NGC 6778: Strengthening the link between extreme abundance discrepancy factors and central star binarity in planetary nebulae
• Spatially-Resolved O II Recombination Line Observations of the Ring Nebula, NGC 6720
• Temperature Variations from HST Spectroscopy of the Orion Nebula
• Temperature Variations from HST Imagery and Spectroscopy of NGC 7009
• Recombination coefficients for O II lines in nebular conditions
• Testing the existence of non-Maxwellian electron distributions in H II regions after assessing atomic data accuracy
• Very Large Telescope deep echelle spectroscopy of Galactic planetary nebulae NGC 6153, M 1-42 and Hf 2-2
• Time-dependent Photoionization of Gaseous Nebulae: the Pure Hydrogen Case
• Can solid body destruction explain abundance discrepancies in planetary nebulae?
• Studies of NGC 6720 with Calibrated HST WFC3 Emission-Line Filter Images--II:Physical Conditions
• The ionizing source of the bipolar HII region S106: a close massive binary

Cited by in corpus (5)

• Time Dependent Photoionization Modeling of Warm Absorbers in Active Galactic Nuclei
• NGC 6153: Reality is complicated
• Physical conditions and chemical abundances in PN M 2-36. Results from deep echelle observations
• Physical and chemical properties of Wolf-Rayet planetary nebulae
• Physical Conditions and Chemical Abundances of the Variable Planetary Nebula IC 4997