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Jordan, Heinz; Weis, Michael

doi:10.1007/978-3-663-20211-0_9

Cited by 43 publications

(62 citation statements)

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“…The low velocities of these lines suggest that they arise from a near-stationary CSM distribution outside the supernova ejecta. Like SN 1988Z, SN 1997eg was characterized at early times by ''coronal lines'' of extremely highly ionized species, including [Fe iv] Although the last of these is only a marginal detection in our spectra, where it is possibly contaminated by [Ca v] k5309, it was also identified by Salamanca et al (2002) in spectra near day 200; its presence implies that part of the CSM had early-time electron temperatures of T e ¼ (0:2Y2) ; 10 5 K if photoionized (Schmidt et al 2006) and T e > 2 ; 10 6 K if collisionally heated (Jordan 1969). The high-excitation narrow lines weaken over time and then disappear from our spectra by day 231.…”

Section: Very Narrow Linesmentioning

confidence: 77%

The Dual‐Axis Circumstellar Environment of the Type IIn Supernova 1997eg

Hoffman

Leonard

Chornock

et al. 2008

Astrophysical Journal

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We present multi-epoch spectral and spectropolarimetric observations of the Type IIn supernova (SN ) 1997eg that indicate the presence of a flattened disklike concentration of circumstellar material surrounding aspherical ejecta, with which the disk is misaligned. The polarization across the broad H , H , and He i k5876 lines of SN 1997eg forms closed loops when viewed in the Stokes q-u plane. Such loops occur when the geometrical symmetry of one or both of the Stokes parameters across spectral lines is broken, in this case most likely by occultation of the ejecta by the equatorial circumstellar matter concentration. The polarization of the narrow Balmer lines possesses an intrinsic axis that differs by 12 from that of the elongated ejecta and probably indicates the orientation of the disklike circumstellar material. The existence of two different axes of symmetry in SN 1997eg suggests that neither rotation of the progenitor nor the influence of a companion star can be the sole mechanism creating a preferred axis within the supernova system. Our model supports the emerging hypothesis that the progenitors of some Type IIn supernovae are luminous blue variable stars, whose presupernova mass eruptions form the circumstellar shells that physically characterize the SN IIn subclass. These conclusions, which are independent of interstellar polarization effects, would have been unobservable with only a single epoch of spectropolarimetry.

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Section: Very Narrow Linesmentioning

confidence: 77%

The Dual‐Axis Circumstellar Environment of the Type IIn Supernova 1997eg

Hoffman

Leonard

Chornock

et al. 2008

Astrophysical Journal

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“…Most ion charge state distributions found in the literature are in the so-called lowdensity limit. Fractional ion abundances that take into account density effects were presented by Burgess & Summers (1969) and Jordan (1969). In particular, there are two main effects which become important at high densities, the suppression of the dielectronic recombination (DR), and the presence of metastable states.…”

Section: Density Effects On the Ion Abundancementioning

confidence: 99%

Density diagnostics derived from the O iv and S iv intercombination lines observed by IRIS

Polito

Zanna

Dudík

et al. 2016

A&A

100

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The intensity of the O iv 2s 2 2p 2 P-2s2p 2 4 P and S iv 3 s 2 3p 2 P-3s 3p 2 4 P intercombination lines around 1400 Å observed with the Interface Region Imaging Spectrograph (IRIS) provide a useful tool to diagnose the electron number density (N e ) in the solar transition region plasma. We measure the electron number density in a variety of solar features observed by IRIS, including an active region (AR) loop, plage and brightening, and the ribbon of the 22-June-2015 M 6.5 class flare. By using the emissivity ratios of O iv and S iv lines, we find that our observations are consistent with the emitting plasma being near isothermal (logT [K] ≈ 5) and iso-density (N e ≈ 10 10.6 cm −3 ) in the AR loop. Moreover, high electron number densities (N e ≈ 10 13 cm −3 ) are obtained during the impulsive phase of the flare by using the S iv line ratio. We note that the S iv lines provide a higher range of density sensitivity than the O iv lines. Finally, we investigate the effects of high densities (N e 10 11 cm −3 ) on the ionization balance. In particular, the fractional ion abundances are found to be shifted towards lower temperatures for high densities compared to the low density case. We also explored the effects of a non-Maxwellian electron distribution on our diagnostic method.

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“…It may be concluded that the ionization rate coefficients of Lötz 10 should be preferred at higher temperatures. The dielectronic coefficients for H, He, Ne, K -Ni sequences should be estimated by (2.4) only after proper reduction of f\_o • The dielectronic recombination broadens the peak for the maximum abundance in agreement with Jordan 4 .…”

Section: Resultsmentioning

confidence: 76%

“…The radiative recombination coefficients via bound levels are calculated using the formula (Wilson 21 ) «rad.b.i (X +:m ) = 1.2 • 10~6 (m + 1) 4 (2.7)…”

Section: Theoretical Detailsmentioning

confidence: 99%

“…A knowledge of the ionization equilibrium which provides information regarding Tmax(X + m ) is therefore of considerable interest. Extensive calculations of the ionization equilibrium for a large number of elements and for a wide range of temperatures have been carried out by House 1 , Tucker and Gould 2 , Allen and Dupree 3 , Jordan 4 , Ansari et al 5 and Landini and Monsignori Fossi 6 . Most of them, however, have used the collisional ionization rate coefficients of Seaton 7 in their investigations.…”

Section: Introductionmentioning

confidence: 99%

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