Do All Low-Mass Stars Undergo Extra Mixing Processes?

Abstract

Standard stellar evolution models that only consider convection as a physical process to mix material inside of stars predict the production of significant amounts of 3He in low-mass stars (M < 2 Msun), with peak abundances of 3He/H ~ few x 10-3 by number. Over the life-time of the Galaxy, this ought to produce 3He/H abundances that diminish with increasing Galactocentric radius. Observations of 3He+ in HII regions throughout the Galactic disk, however, reveal very little variation in the 3He abundance with values of 3He/H similar to the primoridal abundance, (3He/H)p ~ 10-5 . This discrepancy, known as the "3He Problem", can be resolved by invoking in stellar evolution models an extra-mixing mechanism due to the thermohaline instability. Here, we observe 3He+ in the planetary nebula J320 (PN G190.3-17.7) with the Jansky Very Large Array (JVLA) to confirm a previous 3He+ detection made with the VLA that supports standard stellar yields. This measurement alone indicates that not all stars undergo extra mixing. Our more sensitive observations do not detect 3He+ emission from J320 with an RMS noise of 58.8 microJy/beam after smoothing the data to a velocity resolution of 11.4 km/s . We estimate an abundance limit of 3He/H <= 2.75 x 10-3 by number using the numerical radiative transfer code NEBULA. This result nullifies the last significant detection of 3He+ in a PN and allows for the possibility that all stars undergo extra mixing processes.

arXiv commentAccepted for publication in the ApJ

References in corpus (46)

• The NumPy array: a structure for efficient numerical computation
• The Dawes Review 2: Nucleosynthesis and stellar yields of low and intermediate-mass single stars
• A Bitter Pill: The Primordial Lithium Problem Worsens
• Thermohaline mixing: A physical mechanism governing the photospheric composition of low-mass giants
• The White Dwarf Initial-Final Mass Relation for Progenitor Stars From 0.85 to 7.5 M${}_{\odot }$
• A consistent explanation for ${}^{12}$C/${}^{13}$C, ${}^7$Li, and ${}^3$He anomalies in red giant stars
• Thermohaline instability and rotation-induced mixing. I - Low- and intermediate-mass solar metallicity stars up to the end of the AGB
• Deep Mixing of He-3: Reconciling Big Bang and Stellar Nucleosynthesis
• First astrophysical detection of the helium hydride ion (HeH${}^{+}$)
• Rotational mixing in low-mass stars II. Self-consistent models of Pop II RGB stars
• CNONa and 12C/13C in giants of 10 open clusters
• Carbon star formation as seen through the non-monotonic initial-final mass relation
• Thermohaline mixing in evolved low-mass stars
• Thermohaline Mixing: Does It Really Govern the Atmospheric Chemical Composition of Low-Mass Red Giants?
• Light element evolution resulting from WMAP data
• 3He in Planetary Nebulae: A Challenge to Stellar Evolution Models
• Giant Branch Mixing and the Ultimate Fate of Primordial Deuterium in the Galaxy
• Metallicity Structure in the Milky Way Disk Revealed by Galactic HII Regions
• Chemical abundances of planetary nebulae towards the direction of the galactic anticenter
• The thermohaline, Richardson, Rayleigh-Taylor, Solberg-Hoiland, and GSF criteria in rotating stars
• Inhibition of thermohaline mixing by a magnetic field in Ap star descendants: Implications for the Galactic evolution of 3He
• What's The Problem With ^3He?
• A self-consistent stellar and 3D nebular model for Planetary Nebula IC418
• Thermohaline instability and rotation-induced mixing II- Yields of 3He for low- and intermediate-mass stars
• Sulfur, Chlorine, & Argon Abundances in Planetary Nebulae. IIB: Abundances in a Southern Sample
• 3He-Driven Mixing in Low-Mass Red Giants: Convective Instability in Radiative and Adiabatic Limits
• CO Isotopes in Planetary Nebulae
• Effects of thermohaline instability and rotation-induced mixing on the evolution of light elements in the Galaxy : D, 3He and 4He
• Interstellar 12C/13C from CH+ absorption lines: Results from an extended survey
• The Detection of 3He+ in a Planetary Nebula Using the VLA
• The effect of rotation on fingering convection in stellar interiors
• Searching for central stars of planetary nebulae in Gaia DR2
• The population of Galactic planetary nebulae: a study of distance scales and central stars based on the second GAIA release
• ${}^{12}$C/${}^{13}$C ratio in planetary nebulae from the IUE archives
• The Southern HII Region Discovery Survey I: The Bright Catalog
• The symmetric dust shell and the central star of the bipolar planetary nebula NGC 6537
• The 12C/13C ratio in the Planetary Nebula NGC3242 from Hubble Space Telescope STIS observations
• The White Dwarfs of the Old, Solar Metallicity Open Star Cluster Messier 67: Properties and Progenitors
• Kinematical Investigation of Possible Fast Collimated Outflows in Twelve Planetary Nebulae
• Co-spatial UV-optical HST/STIS Spectra of Six Planetary Nebulae: Nebular and Stellar Properties
• First Detection of ${}^3$He${}^{+}$ in the Planetary Nebula IC418
• 3-He in the Milky Way Interstellar Medium: Ionization Structure
• Neon, sulphur and argon abundances of planetary nebulae in the sub-solar metallicity Galactic anti-centre
• Green Bank Telescope Observations of ${}^3\mathbf{H}{\mathbf{e}}^{+}$: Planetary Nebulae
• CO and HCN isotopologue ratios in the outflows of AGB stars
• 3He: Does the problem persists?