Measurement of the photoionization cross section of neutral iron

Lombardi, Gabriel G.; Smith, Peter L.; Parkinson, W. H.

doi:10.1103/physreva.18.2131

Cited by 16 publications

(5 citation statements)

References 17 publications

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“…Aside from possible dust, probably the only important current source of continuum opacity is Fe I. The photoionization cross-section of Fe I (Lombardi, Smith & Parkinson 1978;Hansen et al 1977) averages about 3 × 10 −18 cm 2 between threshold (1569 Å) and Lyman α (1216 Å), with a broad peak from many resonances between 1400 Å and 1250 Å. At an Fe I column density of 3×10 16 cm −2 through the center of the remnant, this implies an average continuum optical depth of about 0.1.…”

Section: Predicted Uv Spectrummentioning

confidence: 99%

Hubble Space Telescope Images and Spectra of the Remnant of SN 1885 in M31

Fesen

Gerardy

McLin

et al. 1999

ApJ

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Near UV HST images of the remnant of SN 1885 (S And) in M31 show a 0. ′′ 70 ± 0. ′′ 05 diameter absorption disk silhouetted against M31's central bulge, at SN 1885's historically reported position. The disk's size corresponds to a linear diameter of 2.5 ± 0.4 pc at a distance of 725 ±70 kpc, implying an average expansion velocity of 11000 ± 2000 km s −1 over 110 years. Low-dispersion FOS spectra over 3200-4800Å reveal that the absorption arises principally from Ca II H & K (equivalent width ≃ 215Å), with weaker absorption features of Ca I 4227Å and Fe I 3720Å. The flux at Ca II line center indicates a foreground starlight fraction of 0.21, which places SNR 1885 some 64 pc to the near side of the midpoint of the M31 bulge, comparable to its projected 55 pc distance from the nucleus. The absorption line profiles suggest an approximately spherically symmetric, bell-shaped density distribution of supernova ejecta freely expanding at up to 13100 ± 1500 km s −1 . We estimate Ca I, Ca II, and Fe I masses of 2.9 +2.4 −0.6 × 10 −4 M ⊙ , 0.005 +0.016 −0.002 M ⊙ , and 0.013 +0.010 −0.005 M ⊙ respectively. If the ionization state of iron is similar to the observed ionization state of calcium, M CaII /M CaI = 16 +42−5 , then the mass of Fe II is 0.21 +0.74 −0.08 M ⊙ , consistent with that expected for either normal or subluminous SN Ia.

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Section: Predicted Uv Spectrummentioning

confidence: 99%

Hubble Space Telescope Images and Spectra of the Remnant of SN 1885 in M31

Fesen

Gerardy

McLin

et al. 1999

ApJ

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“…These are neither easy to calculate or measure (H. P. Kelly 1980), and are not known for iron. These crossections are relatively well known for the ground states, however (Reilman and Manson 1978;Lombardi 1978;Hansen et al 1977;Kelly and Ron 1972). Given this situation, the recycling process has been evaluated in terms of the ground state crossections and an adjustable parameter 4> R , the equivalent ground state recom bination fraction, or "recycling fraction".…”

Section: '< • ^K Ta2)mentioning

confidence: 99%

Late time optical spectra from the /sup 56/Ni model for Type I supernovae

Axelrod¹

1980

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The hypothesis that the optical luminosity of Type I supernovae 56 results from the radioactive decay of Ni synthesized and ejected by the explosion has been investigated by numerical simulation of the optical spectrum resulting from a homologously expanding shell com-56 posed initially of pure Ni. This model, which neglects the cc effects of material external to the Ni core, is expected to pro vide a reasonable representation of the supernova at late times when the star is nearly transparent to optical photons. The numerical simulation determines the temperature, ionization state, and non-LTE level populations which result from energy deposition by the radio-56 56 active decay products of Ni and Co. The optical spectrum includes the effects of both allowed and forbidden lines. The optical spectra resulting from the simulation are found to be sensitive to the mass and ejection velocity of the Ni shell. A range of these parameters has been found which results in good agree ment with the observed spectra of SN1972e over a considerable range of time. In particular, evidence for the expected decaying abundance of Co 56 has been found in the spectra of SN1972e. These results are 56 used to assess the validity of the Ni model and set limits on the mass and explosion mechanism of the Type I progenitor. The possibili ties for improvement of the numerical model are discussed and future atomic data requirements defined. II. Numerical Modelling of the Nebular Phase of SNI 8 III. Energy Deposition by Decay Products 17 A. Thi Deposition Rate 17 B. Atomic Processes Induced by Decay Products 23 IV. The Ionization and Thermal Balances in Steady State 45 A. The Ionization Balance 45 B. The Thermal Balance 61 V. The Emergent Spectrum 89 VI. Application to Real SNI: The Optical Light Curve 123 VII. Application to Real SNI: The Optical Spectrum of SN1972e. . .148 A. Comparison of Calculated and Observed Spectra 151 B. Atmospheric Absorption Lines 155 C. Uncertainties in Atomic Data D. Evidence For Co 56 E. Limits on the Ni 56 Mass and Velocity VIII. Conclusion: Constraints on the Progenitors of SNI References 195 Appendix. Atomic Data 201

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“…The essential investigations of emission lines, which have been observed and used to establish the positions of many of the low-lying energy levels for most iron ions, were mentioned above; see Sugar and Corliss (1985) and references therein or NIST (2002). For neutral iron, photoionization cross section measurements have been performed for the threshold region (Lombardi et al 1978, Hansen et al 1977 as well as for the region of the 3p → 3d transitions (Feist et al 1996). However, the absolute photoionization cross section has only been measured at a single energy: Lombardi et al reported the cross section to be (5.0 +0.4 −0.7 ) × 10 −18 cm 2 at 8.05 eV.…”

Section: Introductionmentioning

confidence: 99%

Measurements of the absolute photoionization cross section of Feions from 15.8 to 180 eV

Kjeldsen¹,

Kristensen²,

Folkmann³

et al. 2002

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

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The absolute single-and double-photoionization cross sections of singly charged Fe ions have been measured from 15.8 to 180 eV using the merged-beam technique. The data yield information about the photoionization continua and the resonance structures resulting from excitation of the outer 3d and 4s electrons as well as the inner 3p and 3s electrons. The vast majority of the Fe+ target ions were present in the ground-state configuration, 3d64s, and term,6D. The experimental data have been compared with several calculations, for example R-matrix calculations from the Opacity Project and data obtained using the central-field approximations. The experimental data are available at http://www.ifa.au.dk/amo/atomphys/atomphys.htm.

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Measurement of the photoionization cross section of neutral iron

Cited by 16 publications

References 17 publications

Hubble Space Telescope Images and Spectra of the Remnant of SN 1885 in M31

Hubble Space Telescope Images and Spectra of the Remnant of SN 1885 in M31

Late time optical spectra from the /sup 56/Ni model for Type I supernovae

Measurements of the absolute photoionization cross section of Feions from 15.8 to 180 eV

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Measurement of the photoionization cross section of neutral iron

Cited by 16 publications

References 17 publications

Hubble Space Telescope Images and Spectra of the Remnant of SN 1885 in M31

Hubble Space Telescope Images and Spectra of the Remnant of SN 1885 in M31

Late time optical spectra from the /sup 56/Ni model for Type I supernovae

Measurements of the absolute photoionization cross section of Fe ions from 15.8 to 180 eV

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Product

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Measurements of the absolute photoionization cross section of Feions from 15.8 to 180 eV