We substantially update the capabilities of the open source software package Modules for Experiments in Stellar Astrophysics (MESA), and its one-dimensional stellar evolution module, MESA star. Improvements in MESA star's ability to model the evolution of giant planets now extends its applicability down to masses as low as one-tenth that of Jupiter. The dramatic improvement in asteroseismology enabled by the space-based Kepler and CoRoT missions motivates our full coupling of the ADIPLS adiabatic pulsation code with MESA star. This also motivates a numerical recasting of the Ledoux criterion that is more easily implemented when many nuclei are present at non-negligible abundances. This impacts the way in which MESA star calculates semi-convective and thermohaline mixing. We exhibit the evolution of 3-8 M ? stars through the end of core He burning, the onset of He thermal pulses, and arrival on the white dwarf cooling sequence. We implement diffusion of angular momentum and chemical abundances that enable calculations of rotating-star models, which we compare thoroughly with earlier work. We introduce a new treatment of radiation-dominated envelopes that allows the uninterrupted evolution of massive stars to core collapse. This enables the generation of new sets of supernovae, long gamma-ray burst, and pair-instability progenitor models. We substantially modify the way in which MESA star solves the fully coupled stellar structure and composition equations, and we show how this has improved the scaling of MESA's calculational speed on multi-core processors. Updates to the modules for equation of state, opacity, nuclear reaction rates, and atmospheric boundary conditions are also provided. We describe the MESA Software Development Kit that packages all the required components needed to form a unified, maintained, and well-validated build environment for MESA. We also highlight a few tools developed by the community for rapid visualization of MESA star results.

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Modules for Experiments in Stellar Astrophysics (MESA): Planets, Oscillations, Rotation, and Massive Stars

The presence of a nearby companion alters the evolution of massive stars in binary systems, leading to phenomena such as stellar mergers, x-ray binaries, and gamma-ray bursts. Unambiguous constraints on the fraction of massive stars affected by binary interaction were lacking. We simultaneously measured all relevant binary characteristics in a sample of Galactic massive O stars and quantified the frequency and nature of binary interactions. More than 70% of all massive stars will exchange mass with a companion, leading to a binary merger in one-third of the cases. These numbers greatly exceed previous estimates and imply that binary interaction dominates the evolution of massive stars, with implications for populations of massive stars and their supernovae.

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Binary Interaction Dominates the Evolution of Massive Stars

The temporal evolution of the optical spectra of various types of supernovae (SNe) is illustrated, in part to aid observers classifying supernova candidates. Type II SNe are defined by the presence of hydrogen, and they exhibit a very wide variety of photometric and spectroscopic properties. Among hydrogen-deficient SNe (Type I), three subclasses are now known: those whose early-time spectra show strong Si II (Ia), prominent He I (Ib), or neither Si II nor He I (Ic). The late-time spectra of SNe Ia consist of a multitude of blended emission lines of iron-group elements; in sharp contrast, those of SNe Ib and SNe Ic (which are similar to each other) are dominated by several relatively unblended lines of intermediatemass elements. Although SNe Ia, which result from the thermonuclear runaway of white dwarfs, constitute a rather homogeneous subclass, important variations in their photometric and spectroscopic properties are undeniably present. SNe Ib/Ic probably result from core collapse in massive stars largely stripped of their hydrogen (Ib) and helium (Ic) envelopes, and hence they are physically related to SNe II. Indeed, the progenitors of some SNe II seem to have only a low-mass skin of hydrogen; their spectra gradually evolve to resemble those of SNe Ib. In addition to the two well-known photometric subclasses (linear and plateau) of SNe II, which may exhibit minor spectroscopic differences, there is a new subclass (SNe IIn) distinguished by relatively narrow emission lines with little or no P Cygni absorption component and slowly declining light curves. These objects probably have unusually dense circumstellar gas with which the ejecta interact.

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Optical spectra of supernovae

We present analytic formulae that approximate the evolution of stars for a wide range of mass M and metallicity Z Stellar luminosity, radius and core mass are given as a function of age, M and Z, for all phases from the zero-age main sequence up to, and including, the remnant stages For the most part we find continuous formulae accurate to within 5 per cent of detailed models These formulae are useful for purposes such as population synthesis that require very rapid but accurate evaluation of stellar properties, and in particular for use in combination with N-body codes We describe a mass-loss prescription that can be used with these formulae, and investigate the resulting stellar remnant distribution

https://researchbank.swinburne.edu.au/file/9b350da3-a16d-47fc-927b-4cdb1a8aa58f/1/PDF (Accepted manuscript).pdf

Comprehensive analytic formulae for stellar evolution as a function of mass and metallicity

Galactic winds are the primary mechanism by which energy and metals are recycled in galaxies and are deposited into the intergalactic medium New observations are revealing the ubiquity of this process, particularly at high redshift We describe the physics behind these winds, discuss the observational evidence for them in nearby star-forming and active galaxies and in the high-redshift universe, and consider the implications of energetic winds for the formation and evolution of galaxies and the intergalactic medium To inspire future research, we conclude with a set of observational and theoretical challenges

Galactic Winds

Some of the most luminous stars have sporadic, violent mass-loss events whose cuases are not understood. These evolved hot stars are called Luminous Blue Variables (LBV's), and their instability may shape the appearance of the upper HR diagram. LBV eruptions are interestingly reminiscent of geysers, or even volcanos. They have received considerable observational attention since 1980, but theoretical work to explain the instability has been scarce. In a typical LBV eruption, the star's photosphere expands and the apparent temperature decreases to near 8000 K. During these normal eruptions the bolometric luminosity remains constant, as typified by S Dor, AG Car and R127. A few LBV's, specifically eta Car, P Cyg, V12 in NGC 2403 and SN1961V, have giant eruptions in which the total luminosity actually increases by more than one or two magnitudes. The star may expel as much as a solar mass or more with a total luminous output rivalling a supernova. The classical LBV's have luminosities greater than MBol approaching -9.6 mag, suggesting initial mass greater than 50 Solar Mass. These stars have very lkikely not been red supergiants as there are no evolved cool stars of comparable luminosity. Their instaibility may prevent their evolution to the red supergiant region. There is also a group of less luminous LBV's (MBol approaching -8 to -9 mag) with low temperatuers, smaller amplitudes and lower mass loss rates. These stars have probably been red supergiants and have shed a lot of mass prior to their current unstable state. Although the physical cuase of the LBV instability is not yet understood, the most likely mechanism involve radiation pressure (the opacity-modified Eddington limit) or dynamical instabilities in the outer layers as the star evolves off the main sequence. In this review, we summarize the physical characteristics and behavior of LBV's, and discuss their brief but critical role in massive star evolution, and possible mechanisms for their remarkable instability.

The Luminous Blue Variables: Astrophysical Geysers

▪ Abstract Eta Carinae (Eta) is one of the most remarkable of all well-studied stars and perhaps the most poorly understood. Observations with the Hubble Space Telescope and other modern instruments have solved a few of the mysteries concerning this object while opening a comparable number of new ones. In this review we first recount some essential background information concerning Eta, then we sketch most of the observational developments of the past few years, related to the star itself and to its ejecta. Throughout, we propose a series of specific unsolved observational and theoretical problems that seem especially interesting or important at this time.

http://www3.mpifr-bonn.mpg.de/staff/sbritzen/etacarinae

Eta carinae and its environment

Much of our information about quasars is derived from their emission-line spectra. The analysis of such spectra has become an intricate subject which differs considerably from traditional, low-density nebular astrophysics. This review is intended to explain our present understanding of the situation, including some aspects of galactic nuclei whose luminosities are more modest than quasars. Quasars' line-emitting regions are probably photoionized (even if supplementary heating processes also occur). So far, models have been constructed which include ionization and thermal equilibria, the transfer of resonance-line and related photons, and the likely effects of absorption and scattering by dust grains. From comparisons between emission-line intensities produced in these models and observed quasars' spectra, it appears that certain densities and pressures and size scales occur in or around quasars. The relative abundances of elements are not very far from solar values, although it is suspected that heavy elements---carbon, nitrogen, and oxygen in particular---are moderately "overabundant" in quasars. The emission-line intensities also provide indirect information about quasars' ultraviolet and soft-x-ray continua; there are hints that photons with energies between 20 and 300 eV---which are not directly observable---may even represent the peak of the luminous output of a typical quasar. Finally, some gas-dynamical questions, while extremely important, are very difficult to answer, because of a lack of observables.

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The emission lines of quasars and similar objects

Physics of luminous blue variables

Eta Carinae - From 1600 to the Present.- The Company Eta Carinae Keeps - Stellar and Interstellar Content of the Carina.- The Central Star - Instability and Recovery.- The Winds of Eta Carinae and Other Very Luminous Stars.- Physics of the Inner Ejecta.- High-resolution Studies of Eta Carinae's Ejecta and Stellar Wind.- All Things Homunculus.- The Outer Ejecta.- X-ray Variability and the Secondary Star.- Eta Carinae and the Luminous Blue Variables.- The Supernova Imposters.- Instability and Mass Loss Near the Eddington Limit.- The Final Struggles of Massive Star Evolution and Their Supernovae.

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Kris Davidson

Papers

The Luminous Blue Variables: Astrophysical Geysers

Eta carinae and its environment

The emission lines of quasars and similar objects

Physics of luminous blue variables

Eta Carinae and the supernova impostors