Protostellar Cosmic Rays and Extinct Radioactivities in Meteorites

Lee, Typhoon; Shu, Frank H.; Shang, Hsien; Glassgold, A. E.; Rehm, K.E.

doi:10.1086/306284

Cited by 239 publications

(294 citation statements)

References 86 publications

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“…One likely explanation for these abundance anomalies are spallation reactions of SPs with the dust in the protosolar nebula (e.g. Lee et al 1998b;McKeegan et al 2000;Gounelle et al 2001Gounelle et al , 2006. However, this would require a strongly enhanced SP flux of the young Sun by a factor 3 × 10 5 compared to the contemporary Sun (McKeegan et al 2000), consistent with the estimated SP flux of T Tauri stars derived by Feigelson et al (2002).…”

Section: Introductionsupporting

confidence: 66%

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Stellar energetic particle ionization in protoplanetary disks around T Tauri stars

Rab

Güdel

Padovani

et al. 2017

A&A

102

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Context. Anomalies in the abundance measurements of short lived radionuclides in meteorites indicate that the protosolar nebulae was irradiated by a high amount of energetic particles (E 10 MeV). The particle flux of the contemporary Sun cannot explain these anomalies. However, similar to T Tauri stars the young Sun was more active and probably produced enough high energy particles to explain those anomalies. Aims. We want to study the interaction of stellar energetic particles with the gas component of the disk (i.e. ionization of molecular hydrogen) and identify possible observational tracers of this interaction. Methods. We use a 2D radiation thermo-chemical protoplanetary disk code to model a disk representative for T Tauri stars. We use a particle energy distribution derived from solar flare observations and an enhanced stellar particle flux proposed for T Tauri stars. For this particle spectrum we calculate the stellar particle ionization rate throughout the disk with an accurate particle transport model. We study the impact of stellar particles for models with varying X-ray and cosmic-ray ionization rates. Results. We find that stellar particle ionization has a significant impact on the abundances of the common disk ionization tracers HCO + and N 2 H + , especially in models with low cosmic-ray ionization rates (e.g. 10 −19 s −1 for molecular hydrogen). In contrast to cosmic rays and X-rays, stellar particles cannot reach the midplane of the disk. Therefore molecular ions residing in the disk surface layers are more affected by stellar particle ionization than molecular ions tracing the cold layers/midplane of the disk. Conclusions. Spatially resolved observations of molecular ions tracing different vertical layers of the disk allow to disentangle the contribution of stellar particle ionization from other competing ionization sources. Modeling such observations with a model like the one presented here allows to constrain the stellar particle flux in disks around T Tauri stars.

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Section: Introductionsupporting

confidence: 66%

“…As already discussed the SP flux of young stars is actually derived from their stellar X-ray properties (Lee et al 1998b;Feigelson et al 2002). Also the CR ionization rate might be anti-correlated with the activity of the star .…”

Section: Model Seriesmentioning

confidence: 96%

Stellar energetic particle ionization in protoplanetary disks around T Tauri stars

Rab

Güdel

Padovani

et al. 2017

A&A

102

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“…These quantities can vary over many orders of magnitude, depending on the astrophysical environment, implying changes in the short-lived-radionuclide yields of many orders of magnitude. Other parameters, like the composite structure of the targets, the shielding, or the cosmicray properties, induce variations in the yields of the short-lived radionuclides that are no larger than a few orders of magnitude (Lee et al 1998;Goswami et al 2001;Gounelle et al 2001;Marhas et al 2002;Leya et al 2003). …”

Section: Outline Of the Modelmentioning

confidence: 99%

“…In our model, the number flux of protons is scaled to X-ray observations of young stellar objects (Lee et al 1998), with F p (E ! 10 MeV) $ 1:9 ; 10 10 cm 2 s À1 .…”

Section: Outline Of the Modelmentioning

confidence: 99%

“…More recently, an Orion-like environment has been suggested for the birth of the solar system (Hester et al 2004). The internal irradiation model conjectures that the radionuclides were created by the irradiation of the solar environment by energetic protons and 4 He and 3 He nuclei, accelerated by gradual or impulsive events near an active young Sun (Lee et al 1998;Goswami et al 2001;Gounelle et al 2001;Marhas et al 2002;Leya et al 2003). Thus, establishing the origin of the short-lived radionuclides can provide important constraints on the astrophysical setting of the Sun's birth, stellar nucleosynthesis models, irradiation processes around young stellar objects, and early solar system chronology (Gounelle & Russell 2005a, 2005bKita et al 2005).…”

Section: Introductionmentioning

confidence: 99%

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The Irradiation Origin of Beryllium Radioisotopes and Other Short‐lived Radionuclides

Gounelle

Shu

Shang

et al. 2006

ApJ

Self Cite

122

151

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Two explanations exist for the short-lived radionuclides (T 1/2 5 Myr) present in the solar system when the calcium-aluminum-rich inclusions (CAIs) first formed. They originated either from the ejecta of a supernova or by the in situ irradiation of nebular dust by energetic particles. With a half-life of only 53 days, 7 Be is then the key discriminant, since it can be made only by irradiation. Using the same irradiation model developed earlier by our group, we calculate the yield of 7 Be. Within model uncertainties associated mainly with nuclear cross sections, we obtain agreement with the experimental value. Moreover, if 7 Be and 10 Be have the same origin, the irradiation time must be short (a few to tens of years), and the proton flux must be of order F $ 2 ; 10 10 cm À2 s À1 . The X-wind model provides a natural astrophysical setting that gives the requisite conditions. In the same irradiation environment, 26 Al, 36 Cl, and 53 Mn are also generated at the measured levels within model uncertainties, provided that irradiation occurs under conditions reminiscent of solar impulsive events (steep energy spectra and high 3 He abundance). The decoupling of the 26 Al and 10 Be observed in some rare CAIs receives a quantitative explanation when rare gradual events (shallow energy spectra and low 3 He abundance) are considered. The yields of 41 Ca are compatible with an initial solar system value inferred from the measured initial 41 Ca / 40 Ca ratio and an estimate of the thermal metamorphism time (from Young et al.), alleviating the need for two-layer proto-CAIs. Finally, we show that the presence of supernova-produced 60 Fe in the solar accretion disk does not necessarily mean that other short-lived radionuclides have a stellar origin.

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Timing of Nebula Processes That Shaped the Precursors of the Terrestrial Planets

Chaussidon¹,

Liu²

2015

The Early Earth

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Protostellar Cosmic Rays and Extinct Radioactivities in Meteorites

Cited by 239 publications

References 86 publications

Stellar energetic particle ionization in protoplanetary disks around T Tauri stars

Stellar energetic particle ionization in protoplanetary disks around T Tauri stars

The Irradiation Origin of Beryllium Radioisotopes and Other Short‐lived Radionuclides

Timing of Nebula Processes That Shaped the Precursors of the Terrestrial Planets

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