Atomic Astrophysics and Spectroscopy

Pradhan, Anil K.; Nahar, Sultana N.

doi:10.1017/cbo9780511975349

Cited by 135 publications

(194 citation statements)

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“…The transitions among these levels produce many lines that appear in the near-to mid-infrared bands (36,37). The lines to be analyzed in this work are the 1.25702, 1.64400, and 1.67734 µm lines.…”

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confidence: 99%

Phosphorus in the Young Supernova Remnant Cassiopeia A

Koo

Lee

Moon

et al. 2013

Science

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Phosphorus (31 P), which is essential for life, is thought to be synthesized in massive stars and dispersed into interstellar space when these stars explode as supernovae (SNe). Here we report on near-infrared spectroscopic observations of the young SN remnant Cassiopeia A, which show that the abundance ratio of phosphorus to the major nucleosynthetic product iron ( 56 Fe) in SN material is up to 100 times the average ratio of the Milky Way, confirming that phosphorus is produced in SNe. The observed range is compatible with predictions from SN nucleosynthetic models but not with the scenario in which the chemical elements in the inner SN layers are completely mixed by hydrodynamic instabilities during the explosion.1 Phosphorus (P) is an indispensable ingredient for life together with carbon, hydrogen, nitrogen, oxygen, and sulfur (S). In our solar system, its abundance relative to hydrogen is 2.8×10 −7by number, which is 50 to 1900 times less than those of the other life-keeping α elements (1).The abundance of P in the diffuse interstellar medium and stars in our galaxy's disk is comparable with that of the solar system or the cosmic abundance, with some dependence on metallicity (2, 3). P is believed to be mainly formed in massive [ > ∼ 8 M ⊙ ] stars by neutron capture on silicon (Si) in hydrostatic neon-burning shells in the pre-SN stage and also in explosive carbon and neon burning layers during SN explosion (4, 5).Freshly synthesized P should thus be found in young core-collapse SN remnants (SNRs)resulting from the explosion of massive stars. Cassiopeia A (Cas A) is the youngest confirmed core-collapse SNR in our galaxy; it has been extensively studied in all wavebands (Fig. 1).It is located at a distance of 3.4 kpc (6) and thought to be the remnant of a SN event in C.E.1681 ± 19 (7). The spectrum of the light echo from the SN event indicated a SN of Type IIb that had a small hydrogen envelope at the time of explosion (8). The total estimated mass of the SN ejecta is 2 to 4 M ⊙ , and the inferred initial mass of the progenitor star ranges from 15 to 25 M ⊙ (9, 10). Emission from P II was previously detected from Cas A (11), but no analysis of the emission line has been done.We conducted near-infrared (NIR) spectroscopic observations of the main SN ejecta shell using the TripleSpec spectrograph mounted on the Palomar 5-m Hale telescope in 2008 ( The knots show distinct spectroscopic and kinematic properties depending on their origins (Fig. 2) Their properties match those of "quasi-stationary flocculi", the material lost from the hydrogen envelope of the progenitor during its red-supergiant phase as slow wind (13,14). 3) imply that the P-to-Fe abundance ratio by number, X(P/Fe), of the SN ejecta knots is up to 100 times higher than the cosmic abundance X ⊙ (P/Fe) = 8.1 × 10 −3 (1), whereas the knots of the circumstellar medium have ratios close to the cosmic abundance. The enhanced P abundance over Fe in these SN ejecta knots is direct evidence for the in situ production of P in Cas A.The observed range of X...

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confidence: 99%

Phosphorus in the Young Supernova Remnant Cassiopeia A

Koo

Lee

Moon

et al. 2013

Science

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“…It is related to the inelastic scattering cross section σ mf of the 'intermediate' Auger electron from the middle level m to the final level f as (see, e.g., [29])…”

Section: Theory Of Dadmentioning

confidence: 99%

Collective relaxation processes in atoms, molecules and clusters

Kolorenč

Averbukh

Feifel

et al. 2016

J. Phys. B: At. Mol. Opt. Phys.

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Abstract. Electron correlation is an essential driver of a variety of relaxation processes in excited atomic and molecular systems. These are phenomena which often lead to autoionization typically involving two-electron transitions, such as the well-known Auger effect. However, electron correlation can give rise also to higherorder processes characterized by multi-electron transitions. Basic examples include simultaneous two-electron emission upon recombination of an inner-shell vacancy (double Auger decay) or collective decay of two holes with emission of a single electron. First reports of this class of processes date back to the 1960's, but their investigation intensified only recently with the advent of free-electron lasers. High fluxes of high-energy photons induce multiple excitation or ionization of a system on the femtosecond timescale and under such conditions the importance of multielectron processes increases significantly. We present an overview of experimental and theoretical works on selected multi-electron relaxation phenomena in systems of different complexity, going from double Auger decay in atoms and small molecules to collective interatomic autoionization processes in nanoscale samples.

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“…We have bound-free transitions, free-free transitions, Thomson scattering, and Rayleigh scattering. The most important source for the solar photosphere comes from bound-free transitions where the hydride H − absorb radiation to form hydrogen and a free electron (Marshall 2003;Pradhan & Nahar 2011). From Rutten (2003) we find that for bound-free transitions α ν = σn i 1 − exp − hν k B T , where σ is a constant that depends on the atom/ion involved in the bound-free transition, n i is the number density in the ionising level, h is the Planck constant, k B is the Boltzmann constant, T is the temperature of the plasma, and ν is the frequency.…”

Section: Appendix A: Surface With Constant Optical Depthmentioning

confidence: 99%

Cross-sectional area and intensity variations of sausage modes

Moreels

Goossens

Doorsselaere

2013

A&A

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Context. The observations obtained using the Rapid Oscillations in the Solar Atmosphere instrument (ROSA) show variations in both cross-sectional area and intensity for magnetic pores in the photosphere. Aims. We study the phase behaviour between cross-sectional area and intensity variations for sausage modes in a photospheric context. We aim to determine the wave mode by looking at the phase difference between the cross-sectional area and intensity variations. Methods. We used a straight cylinder as a model for the flux tube. The plasma is uniform both inside and outside the flux tube with a possible jump in the equilibrium values at the boundary, the magnetic field is directed along the flux tube. We derived analytic expressions for the cross-sectional area variation and the total intensity variation. Using these analytic expressions, we calculated the phase differences between the cross-sectional area and the intensity variations. These phase differences were then used to identify the wave mode. Results. We found that for slow sausage modes the cross-sectional area and intensity variations are always in phase, while for fast sausage modes the variations are in antiphase.

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Atomic Astrophysics and Spectroscopy

Cited by 135 publications

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Phosphorus in the Young Supernova Remnant Cassiopeia A

Phosphorus in the Young Supernova Remnant Cassiopeia A

Collective relaxation processes in atoms, molecules and clusters

Cross-sectional area and intensity variations of sausage modes

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