Exoplanetary oxygen fugacities from polluted white dwarf stars

AbstractThe intrinsic oxygen fugacity of a planet profoundly influences a variety of its geochemical and geophysical aspects. Most rocky bodies in our solar system formed with oxygen fugacities approximately five orders of magnitude higher than that corresponding to a hydrogen-rich gas of solar composition. Here we derive oxygen fugacities of extrasolar rocky bodies from the elemental abundances in 15 white dwarf (WD) stars polluted by accretion of rocks. We find that the intrinsic oxygen fugacities of rocks accreted by the WDs are similar to those of terrestrial planets and asteroids in our solar system. This result suggests that at least some rocky exoplanets are geophysically and geochemically similar to Earth.

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The search for planet and planetesimal transits of white dwarfs with the Zwicky Transient Facility

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320000204 ◽

2019 ◽

Vol 15 (S357) ◽

pp. 37-40

Author(s):

Keaton J. Bell

Keyword(s):

Solar System ◽

White Dwarf ◽

Metal Pollution ◽

White Dwarfs ◽

Dwarf Stars ◽

Orbital Inclination ◽

White Dwarf Stars ◽

Ultimate Fate ◽

Project Strategy ◽

Very High

AbstractPlanetary materials orbiting white dwarf stars reveal the ultimate fate of the planets of the Solar System and all known transiting exoplanets. Observed metal pollution and infrared excesses from debris disks support that planetary systems or their remnants are common around white dwarf stars; however, these planets are difficult to detect since a very high orbital inclination angle is required for a small white dwarf to be transited, and these transits have very short (minute) durations. The low odds of catching individual transits could be overcome by a sufficiently wide and fast photometric survey. I demonstrate that, by obtaining over 100 million images of white dwarf stars with 30-second exposures in its first three years, the Zwicky Transient Facility (ZTF) is likely to record the first exoplanetary transits of white dwarfs, as well as new systems of transiting, disintegrating planetesimals. In these proceedings, I describe my project strategy to discover these systems using the ZTF data.

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Oxygen fugacities of extrasolar rocks: Evidence for an Earth-like geochemistry of exoplanets

Science ◽

10.1126/science.aax3901 ◽

2019 ◽

Vol 366 (6463) ◽

pp. 356-359 ◽

Cited By ~ 31

Author(s):

Alexandra E. Doyle ◽

Edward D. Young ◽

Beth Klein ◽

Ben Zuckerman ◽

Hilke E. Schlichting

Keyword(s):

Solar System ◽

Oxygen Fugacity ◽

White Dwarfs ◽

Planetary Systems ◽

Elemental Abundances ◽

Oxidized Iron ◽

Solar Composition

Oxygen fugacity is a measure of rock oxidation that influences planetary structure and evolution. Most rocky bodies in the Solar System formed at oxygen fugacities approximately five orders of magnitude higher than a hydrogen-rich gas of solar composition. It is unclear whether this oxidation of rocks in the Solar System is typical among other planetary systems. We exploit the elemental abundances observed in six white dwarfs polluted by the accretion of rocky bodies to determine the fraction of oxidized iron in those extrasolar rocky bodies and therefore their oxygen fugacities. The results are consistent with the oxygen fugacities of Earth, Mars, and typical asteroids in the Solar System, suggesting that at least some rocky exoplanets are geophysically and geochemically similar to Earth.

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Spectra of White-Dwarf Stars at Wavelengths < 3000 A: A Theoretical Perspective

International Astronomical Union Colloquium ◽

10.1017/s025292110007576x ◽

1979 ◽

Vol 53 ◽

pp. 86-106 ◽

Cited By ~ 1

Author(s):

Harry L. Shipman

Keyword(s):

Solar System ◽

White Dwarf ◽

Extreme Ultraviolet ◽

Theoretical Perspective ◽

Electromagnetic Spectrum ◽

Dwarf Stars ◽

X Ray ◽

Satellite Technology ◽

White Dwarf Stars ◽

Current State

Astronomers studying objects outside the solar system first used the ultraviolet, extreme ultraviolet, and x-ray regions of the electromagnetic spectrum in the 1970s. The exploration of these wavelength regions has produced considerable improvements in our understanding of these objects. The achievements of x-ray astronomy are perhaps the best known. With the advance of satellite technology, other wavelength regions begin to play a role, and x-ray astronomy moves into the luminosity domain where quiescent as well as violent astrophysical processes can produce detectable amounts of radiation. This paper reviews the current state of our interpretation of white-dwarf stars at wavelengths less than 3000 A.

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Solar Elemental Abundances

Oxford Research Encyclopedia of Planetary Science ◽

10.1093/acrefore/9780190647926.013.145 ◽

2020 ◽

Author(s):

Katharina Lodders

Keyword(s):

Solar System ◽

Chemical Evolution ◽

Molecular Cloud ◽

The Sun ◽

Galactic Chemical Evolution ◽

Dwarf Star ◽

Dwarf Stars ◽

Elemental Abundances ◽

System Composition ◽

Solar Composition

Solar elemental abundances, or solar system elemental abundances, refer to the complement of chemical elements in the entire Solar System. The Sun contains more than 99% of the mass in the solar system and therefore the composition of the Sun is a good proxy for the composition of the overall solar system. The solar system composition can be taken as the overall composition of the molecular cloud within the interstellar medium from which the solar system formed 4.567 billion years ago. Active research areas in astronomy and cosmochemistry model collapse of a molecular cloud of solar composition into a star with a planetary system and the physical and chemical fractionation of the elements during planetary formation and differentiation. The solar system composition is the initial composition from which all solar system objects (the Sun, terrestrial planets, gas giant planets, planetary satellites and moons, asteroids, Kuiper-belt objects, and comets) were derived. Other dwarf stars (with hydrostatic hydrogen-burning in their cores) like the Sun (type G2V dwarf star) within the solar neighborhood have compositions similar to the Sun and the solar system composition. In general, differential comparisons of stellar compositions provide insights about stellar evolution as functions of stellar mass and age and ongoing nucleosynthesis but also about galactic chemical evolution when elemental compositions of stellar populations across the Milky Way Galaxy is considered. Comparisons to solar composition can reveal element destruction (e.g., Li) in the Sun and in other dwarf stars. The comparisons also show element production of, for example, C, N, O, and the heavy elements made by the s-process in low to intermediate mass stars (3–7 solar masses) after these evolved from their dwarf-star stage into red giant stars (where hydrogen and helium burning can occur in shells around their cores). The solar system abundances are and have been a critical test composition for nucleosynthesis models and models of galactic chemical evolution, which aim ultimately to track the production of the elements heavier than hydrogen and helium in the generation of stars that came forth after the Big Bang 13.4 billion years ago.

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Radio Emissions from Terrestrial Planets around White Dwarfs

Symposium - International Astronomical Union ◽

10.1017/s0074180900182373 ◽

2004 ◽

Vol 219 ◽

pp. 390-394

Author(s):

Andrew Willes ◽

Kinwah Wu

Keyword(s):

White Dwarf ◽

Terrestrial Planet ◽

Terrestrial Planets ◽

Dwarf Stars ◽

Radio Emissions ◽

White Dwarf Stars ◽

Cyclotron Maser ◽

Galilean Moons ◽

Electrodynamic Interaction ◽

Maser Sources

Terrestrial planets in close orbits around magnetic white dwarf stars can be electron-cyclotron maser sources, by analogy to planetary radio emissions generated from the electrodynamic interaction between Jupiter and the Galilean moons. We present predictions of the radio flux densities from white-dwarf/terrestrial-planet systems and discuss a scenario for the formation of these systems.

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The Time Dependence of the Phases of the Harmonics Relative to the 1490 sec Fundamental in PG1346+082

International Astronomical Union Colloquium ◽

10.1017/s0252921100099759 ◽

1989 ◽

Vol 114 ◽

pp. 296-299

Author(s):

J. L. Provencal ◽

J. C. Clemens ◽

G. Henry ◽

B. P. Hine ◽

R. E. Nather ◽

...

Keyword(s):

White Dwarf ◽

Compact Object ◽

Detailed Knowledge ◽

Line Profiles ◽

Pressure Broadening ◽

Dwarf Stars ◽

White Dwarf Stars ◽

Adequate Understanding ◽

Magnitude Variation ◽

Hydrogen Lines

White dwarf stars provide important boundary conditions for the understanding of stellar evolution. An adequate understanding of even these simple stars is impossible without detailed knowledge of their interiors. PG1346+082, an interacting binary white dwarf system, provides a unique opportunity to view the interior of one degenerate as it is brought to light in the accretion disk of the second star as the primary strips material from its less massive companion (see Wood et at. 1987).PG1346+082 is a photometric variable with a four magnitude variation over a four to five day quasi-period. A fast Fourier transform (FFT) of the light curve shows a complex, time-dependent structure of harmonics. PG1346+082 exhibits flickering – the signature of mass transfer. The optical spectra of the system contain weak emission features during minimum and broad absorption at all other times. This could be attributed to pressure broadening in the atmosphere of a compact object, or to a combination of pressure broadening and doppler broadening in a disk surrounding the compact accretor. No hydrogen lines are observed and the spectra are dominated by neutral helium. The spectra also display variable asymmetric line profiles.

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