The emission/absorption FE 2 spectrum of HD 45677

The complex behavior of the emission/absorption spectrum of Fe II is analyzed. The far UV spectrum is characterized almost solely by absorption lines, while, in the near UV, strong emissions are predominant. Radiative excitation from the ground to the highest levels (chi is approximately 10 eV) with re-emission in the near UV, visible and I.R. seems to be the main mechanism capable of explaining the observed spectral features

The He II Fowler lines and the O III and N III Bowen fluorescence lines in the symbiotic nova RR Tel

A new measure of reddening (E$_{(B-V)}$$\sim$0.00) has been obtained from the comparison between the observed and the theoretical intensity decrement for 20 emission lines of the \ion{He}{ii} Fowler (n$\to$3) series. This value has been confirmed by the STIS and IUE continuum distribution, and by the value of n$_H$ from the damped profile of the IS H Ly-$\alpha$ line. We have obtained very accurate measurements for about thirty Bowen lines of \ion{O}{iii} and a precise determination of the efficiency in the O1 and O3 excitation channels (18 % and 0.7 %, respectively). The relative \ion{O}{iii} intensities are in good agreement with the predictions by Froese Fischer (1994). A detailed study of the decays from all levels involved in the Bowen mechanism has lead to the detection of two new \ion{O}{iii} Bowen lines near $\lambda$ 2190. High resolution IUE data have shown a nearly linear decline with time, from 1978 to 1995, in the efficiency of the O1 and O3 processes, with a steeper slope for the O3 channel. A detailed study of the \ion{N}{iii} $\lambda$ 4640 lines and of their excitation mechanism has shown that, recombination and continuum fluorescence being ruled out, line fluorescence remains the only viable mechanism to pump the 3d $^2D_{5/2}$ and 3d $^2D_{3/2}$ levels of \ion{N}{iii}. We point out the important role of multiple scattering in the resonance lines of \ion{O}{iii} and \ion{N}{iii} near $\lambda$ 374 and show that the observed \ion{N}{iii} line ratios and intensities can be explained in terms of line fluorescence by the three resonance lines of \ion{O}{iii} at $\lambda$$\lambda$ 374.432, 374.162 and 374.073 under optically thick conditions.Comment: Accepted version for Astronomy and Astrophysic

The Amazing Old Nova Q Cygni: A Far Ultraviolet Synthetic Spectral Analysis

Q Cygni (Nova Cygni 1876) is the third oldest old novae (after WY Sge and V841 Oph) with a long orbital period of 10.08 hours and spectroscopic peculiarities in the optical including the presence of variable wind outflow revealed by optical P Cygni profiles in the HeI lines and H alpha beta (Kafka et al. 2003). We have carried out a synthetic spectral analysis of a far ultraviolet IUE archival spectrum of Q Cygni using our optically thick, steady state, accretion disk models and model white dwarf photospheres. We find that the accretion light of a luminous accretion disk dominates the FUV flux of the hot component with a rate of accretion 2-3 1.E-9 Msun/yr. We find that Q Cygni lies at a distance of 741 \pm 110 pc . The implications of our results for theoretical predictions for old novae are presented.Comment: PASP, August 201

Absorption and emission features of 7Be II in the outburst spectra of V838 Her (Nova Her 1991)

High- and low-resolution International Ultraviolet Explorer (IUE) spectra of V838 Her in the early outburst stages exhibit a strong absorption feature shortward of λ3130. We discuss the nature of this spectral feature and provide convincing evidence that it corresponds to the blueshifted resonance doublet of singly ionized 7Be recently discovered in other novae. During the evolution of the outburst the appearance of an emission feature close to λ3130 Å is also identified as 7Be II λ3132 because the usual identification as the O III λ3133.7 Bowen fluorescence line is hardly compatible with both the known oxygen underabundance in the nova ejecta and the low optical depths in the nebula due to the high outflow velocity. The average 7Be abundance relative to hydrogen, estimated by four different methods, i.e. the 7Be II/Mg II absorption ratio, and the 7Be II/Mg II, 7Be II/He II1640, and 7Be II/Hβ emission ratios, is N(Be)/N(H) ≈2.5 × 10-5 (by number), i.e. ≈1.7 × 10-4 by mass. This corresponds to an overproduction of 7Be by about 1 dex in comparison with the theoretical models of massive CO and ONe novae. Since 7Be all converts into 7Li, the 7Be/H abundance implies a 7Li/H overabundance of about 4 dex over the 7Li/H meteoritic value and indicates a total ejected mass of 7Li of ≈9.5 × 10-10 M⊙. These data are in line with previous observations and indicate that large amounts of 7Li can be synthesized in a variety of novae, including very fast ONe novae

Fe VII lines in the spectrum of RR Telescopii

Thirteen transitions within the ground 3d^2 configuration of Fe VII are identified in ultraviolet and optical spectra of the symbiotic star RR Telescopii obtained with the STIS instrument of the Hubble Space Telescope. The line fluxes are compared with theoretical data computed with the recent atomic data of K.A. Berrington et al., and high resolution optical spectra from VLT/UVES are used to identify blends. Seven branching ratios are measured, with three in good agreement with theory and one affected by blending. The lambda5277/lambda4943 branching ratio is discrepant by > 3 sigma, indicating errors in the atomic data for the lambda5277 line. A least-squares minimization scheme is used to simultaneously derive the temperature, T, and density, N_e, of the RR Tel nebula, and the interstellar extinction, E(B-V), towards RR Tel from the complete set of emission lines. The derived values are: log T/K = 4.50 +/- 0.23, log N_e/cm^-3=7.25 +/- 0.05, and E(B-V)<0.27. The extinction is not well-constrained by the Fe VII lines, but is consistent with the more accurate value E(B-V)=0.109^{+0.052}_{-0.059} derived here from the Ne V lambda2974/lambda1574 ratio in the STIS spectrum. Large differences between the K.A. Berrington et al. electron excitation data and the earlier F.P. Keenan & P.H. Norrington data-set are demonstrated, and the latter is shown to give worse agreement with observations.Comment: To be published in Astronomy & Astrophysics; 7 pages, 4 figure