Extinct Radioactivities and Protosolar Cosmic Rays: Self‐Shielding and Light Elements

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

doi:10.1086/319019

Cited by 205 publications

(338 citation statements)

References 64 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: 65%

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: 65%

Stellar energetic particle ionization in protoplanetary disks around T Tauri stars

Rab

Güdel

Padovani

et al. 2017

A&A

102

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“…The very short half-life of 7 Be (53 days vs. $megayears for other radionuclides) calls for a special treatment. Additional details on the irradiation model may be found in Gounelle et al (2001).…”

Section: Outline Of the Modelmentioning

confidence: 99%

“…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%

“…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%

See 1 more Smart Citation

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

Gounelle

Shu

Shang

et al. 2006

ApJ

Self Cite

124

140

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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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“…As regards the second feature that the flare activity may explain: both the anomalous abundances of elemental isotopes in chondrules and the inclusions of the most pristine carbonaceous chondrites, as well as the high abundances of daughter products of some short-lived nuclides, all point to high-energy processes that occurred during the early stages of our Solar System (see, e.g., Feigelson et al 2002;Gounelle et al 2001). Although external phenomena, like supernova explosions, have been used to explain these abundances, it has been suggested that they could also be due to spallation reactions from energetic (MeV) protons and ions originating in magnetic reconnection flares (see also Goswami et al 2001;Marhas et al 2002;Leya et al 2003).…”

Section: Effects Of Flares On Young Planetary Systemsmentioning

confidence: 99%

The weak-line T Tauri star V410 Tau

Fernández¹,

Stelzer

Henden

et al. 2004

A&A

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Abstract. We show that V410 Tau, a weak-line T Tauri star, is a flaring star. This result comes from an intensive, coordinated monitoring campaign carried out in November 2001 at visible and X-ray wavelength ranges. It is confirmed by previous, isolated observations found in the literature. Flares tend to occur mainly around the star's minimum brightness, when the most active regions face us. We report on the strongest flare detected up to now on this star, for which we have obtained simultaneous visible Strömgren photometry and intermediate resolution spectroscopy. We derive decay times from 3 to 0.7 h at several wavelengths for the continuum in the 3600−5600 Å range. We estimate the energy involved in this and the other flares for which we have good time sampling, and conclude that the strongest event, at least, could have important consequences for the matter in the surroundings of the star. If similar events took place on the young Sun and lasted for several Myr, they could explain the anomalous abundances of elemental isotopes found in some meteorites. They could have also contributed to eliminate part of the primary atmospheres of the planet embryos and would have provided enough energy for the melting of solid iron-magnesium silicates, a process that may explain the presence of chondrules in chondritic meteorites. High resolution spectroscopy of the H α emission line in the quiescent states of V410 Tau enables us to study the variability of the broad component. We suggest that this component is related to microflaring activity, such as the one observed on more evolved, magnetically-active stars. The large velocities and the energy associated with this component support this hypothesis.

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Extinct Radioactivities and Protosolar Cosmic Rays: Self‐Shielding and Light Elements

Cited by 205 publications

References 64 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

The weak-line T Tauri star V410 Tau

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