Physical Conditions and Chemical Abundances of the Variable Planetary Nebula IC 4997

Abstract

The planetary nebula (PN) IC 4997 is one of a few rapidly evolving objects with variable brightness and nebular emission around a hydrogen-deficient star. In this study, we have determined the physical conditions and chemical abundances of this object using the collisionally excited lines (CELs) and optical recombination lines (ORLs) measured from the medium-resolution spectra taken in July 2014 with the FIbre-fed Échelle Spectrograph on the Nordic Optical Telescope at La Palma Observatory. We derived electron densities of $\gtrsim 3\times 10^4$ cm${}^{-3}$ and electron temperatures of $\gtrsim 14,000$ K from CELs, whereas cooler temperatures of $\sim 11,000$ and $\sim 7,000$ K were obtained from helium and heavy element ORLs, respectively. The elemental abundances deduced from CELs point to a metal-poor progenitor with [O/H]$\lesssim -0.75$, whereas the ORL abundances are slightly above the solar metallicity, [O/H]$\approx 0.15$. Our abundance analysis indicates that the abundance discrepancy factors (ADFs$\equiv$ORLs/CELs) of this PN are relatively large: ADF(O${}^{2+})\gtrsim 8$ and ADF(N${}^{2+})\gtrsim 7$. Further research is needed to find out how the ADFs and variable emissions are formed in this object and whether they are associated with a binary companion or a very late thermal pulse.

arXiv comment18 pages, 5 figures, 10 tables, accepted by MNRAS

References in corpus (74)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• The chemical composition of the Sun
• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• Estimating distances from parallaxes IV: Distances to 1.33 billion stars in Gaia Data Release 2
• Updated stellar yields from Asymptotic Giant Branch models
• Post-Asymptotic Giant Branch Evolution of Low- and Intermediate-Mass Stars. Preliminary Results
• New models for the evolution of Post-Asymptotic Giant Branch stars and Central Stars of Planetary Nebulae
• The Element Abundances in Bare Planetary Nebula Central Stars and the Shell Burning in AGB Stars
• Stellar Models and Yields of Asymptotic Giant Branch Stars
• Improving Predictions for Helium Emission Lines
• The formation and evolution of hydrogen-deficient post-AGB white dwarfs: the emerging chemical profile and the expectations for the PG1159-DB-DQ evolutionary connection
• The Hα surface brightness - radius relation: a robust statistical distance indicator for planetary nebulae
• Astrophysical supplements to the ASCC-2.5. Ia. Radial velocities of about 55000 stars and mean radial velocities of 516 Galactic open clusters and associations
• Heavy elements in Galactic and Magellanic Cloud HII regions: recombination-line versus forbidden-line abundances
• Ionization Correction Factors for Planetary Nebulae: I- Using optical spectra
• Evolution on the AGB and beyond: On the formation of H-deficient post-AGB stars
• X-ray enabled MOCASSIN: a 3D code for photoionized media
• Nucleosynthesis Predictions for Intermediate-Mass AGB Stars: Comparison to Observations of Type I Planetary Nebulae
• A deep survey of heavy element lines in planetary nebulae -- II. Recombination line abundances and evidence for ultra-cold plasma
• Internal mixing and surface abundance of [WC]-CSPN
• Binarity and the abundance discrepancy problem in planetary nebulae
• Corrigendum: Improved He~I Emissivities in the Case B Approximation
• The Nordic Optical Telescope
• Elemental abundances of Galactic bulge planetary nebulae from optical 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
• Electron temperatures and densities of planetary nebulae determined from the nebular hydrogen recombination spectrum and temperature and density variations
• [O II] line ratios
• NGC 6778: Strengthening the link between extreme abundance discrepancy factors and central star binarity in planetary nebulae
• The hydrogen-deficient knot of the `born again' planetary nebula Abell 58 (V605 Aql)
• Helium recombination spectra as temperature diagnostics for planetary nebulae
• Integral field spectroscopy of planetary nebulae: mapping the line diagnostics and hydrogen-poor zones with VLT FLAMES
• ALFA: an automated line fitting algorithm
• Analysis of chemical abundances in planetary nebulae with [WC] central stars. II. Chemical abundances and the abundance discrepancy factor
• The Curious Conundrum Regarding Sulfur Abundances In Planetary Nebulae
• First Stars XIV. Sulfur abundances in extremely metal-poor (EMP) stars
• The Origin and Evolution of the Halo PN BoBn 1: From a Viewpoint of Chemical Abundances Based on Multiwavelength Spectra
• Faint recombination lines in Galactic PNe with [WC] nucleus
• Three-dimensional photoionisation modelling of the hydrogen-deficient knots in the planetary nebula Abell 30
• New effective recombination coefficients for nebular N II lines
• An Evaluation of the Excitation Class Parameter for the Central Stars of Planetary Nebulae
• MUSE spectroscopy of planetary nebulae with high abundance discrepancies
• Three-dimensional chemically homogeneous and bi-abundance photoionization models of the "super-metal-rich" planetary nebula NGC 6153
• Plasma Diagnostics for Planetary Nebulae and H II Regions Using the N II and O II Optical Recombination Lines
• Recombination coefficients for O II lines in nebular conditions
• Planetary nebulae that cannot be explained by binary systems
• 3-D Photoionization Structure and Distances of Planetary Nebulae I. NGC6369
• The NII spectrum of the Orion Nebula
• IFU spectroscopy of Southern Planetary Nebulae IV: A Physical Model for IC 418
• Abell 30 -- A Binary Central Star Among the Born-Again Planetary Nebulae
• Exploring the differences of integrated and spatially resolved analysis using integral field unit data: The case of Abell 14
• Excitation of emission lines by fluorescence and recombination in IC418
• Electron Temperatures and Free-Electron Energy Distributions of Nebulae from C II Dielectronic Recombination Lines
• Classification of Planetary Nebulae by their Departure from Axisymmetry
• A search for hydrogenated fullerenes in fullerene-containing planetary nebulae
• The Discrepant Kinematics of ORLs and CELs in NGC 7009 as a Function of Ionization Structure
• Improved spectral descriptions of planetary nebulae central stars
• Bi-abundance photoionization models of planetary nebulae: determining the amount of Oxygen in the metal rich component
• IFU spectroscopy of Southern Planetary Nebulae V: Low-ionization structures
• Mapping Excitation in the Inner Regions of the Planetary Nebula NGC 5189 using HST WFC3 Imaging
• 3-D Photoionization Structure and Distances of Planetary Nebulae II. Menzel 1
• Proper Plasma Analysis Practice (PPAP), an Integrated Procedure of the Extinction Correction and Plasma Diagnostics: a Demo with an HST/WFC3 Image Set of NGC6720
• Dust Extinction in Compact Planetary Nebulae
• Morpho-kinematic properties of Wolf-Rayet planetary nebulae
• The Ultraviolet Spectra of the Weak Emission Line Central Stars of Planetary Nebulae
• An episodically variable stellar wind in the planetary nebula IC\,4997
• Seimei KOOLS-IFU Mapping of the Gas and Dust Distributions in Galactic Planetary Nebulae: the Case of IC2165
• Physical and chemical properties of Wolf-Rayet planetary nebulae
• Bi-abundance ionization structure of the Wolf-Rayet planetary nebula PB 8
• Surprising Variability of the Planetary Nebula IC 4997 = QV Sge
• proEQUIB: IDL Library for Plasma Diagnostics and Abundance Analysis
• Abundance Discrepancy Factors in high density planetary nebulae
• Resonant Temperature Fluctuations in Nebulae Ionized by Short-Period Binary Stars
• AtomNeb: IDL Library and Python Package for Atomic Data of Ionized Nebulae