Pierluigi Selvelli

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

Aims. A detailed study of the Oiii and Niii Bowen lines in the spectrum of RR Tel. Methods. Absolute intensities for the Heii ,O iii ,a nd Niii emission lines have been obtained from STIS, UVES, FEROS and IUE data, after re-calibration of UVES and FEROS on the STIS scale. Results. A new measure of reddening (E(B−V) ∼ 0.00) has been obtained from the comparison between the observed and the theoretical intensity decrement for 20 emission lines of the Heii Fowler (n → 3) series. This value has been confirmed by the STIS and IUE continuum distribution, and by the value of nH from the damped profile of the IS H Ly-α line. We have obtained very accurate measurements for about thirty Bowen lines of Oiii and a precise determination of the efficiency in the O1 and O3 excitation channels (18% and 0.7%, respectively). The relative Oiii 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 Oiii Bowen lines near λ 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 Niii λ 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 2 D5/2 and 3d 2 D3/2 levels of Niii. We point out the important role of multiple scattering in the resonance lines of Oiii and Niii near λ 374 and show that the observed Niii line ratios and intensities can be explained in terms of line fluorescence by the three resonance lines of Oiii at λλ 374.432, 374.162 and 374.073 under optically thick conditions.

XMM-Newton observations of RR Telescopii: evidence for wind signatures and shocked gas emission

Astronomy and Astrophysics 556 (2013): A85 reproduced with permission from Astronomy & Astrophysics

On the telescopes in the paintings of Jan Brueghel the Elder

We have investigated the nature and the origin of the telescopes depicted in three paintings of J. Brueghel the Elder completed between 1609 and 1618. The ”tube” that appears in the painting dated 1608-1612 represents a very early dutch spyglass, tentatively attributable to Sacharias Janssen or Lipperhey, prior to those made by Galileo, while the two instruments made of several drawtubes which appear in the two paintings of 1617 and 1618 are quite sophisticated and may represent early examples of Keplerian telescopes.

Bowen Fluorescence in the Symbiotic Nova RR Telescopii

We have identified and measured the accurate strengths of Bowen fluorescence lines of O III and N III in the spectra of the Symbiotic Nova RR Telescopii. Altogether 29 O III lines, some of them newly identified, have been measured. After re‐determining the inrestellar absorption, we show that the relative line strengths can be accounted for assuming that the ground state transitions as well as the pumping line of the Fowler He II Lyα have huge optical depths resulting in large broadening wings and significant overlap enhancing the fluorescent efficiency. This is also true for the N III lines where resonance scattering optical depths as large as 106 producing broad wings and pumping by more than one line can produce the observed line ratios. Other methods such as continuum fluorescence or recombination are shown not to be effective.

The active quiescence of the ex‐nova HR Del

We outline here some results of a recent study on HR Del that has included all of the IUE data taken from 1979 to 1992. This has allowed a detailed analysis of both the long‐time and the short‐time variations in its UV spectrum. Assuming d = 850 pc, after correction for reddening (EB−V = 0.16), we derive a mean UV luminosity LUV ∼ 56L⊙, the highest value among classical novae at “minimum”. Also the optical absolute magnitude (Mv = +1.35) indicates a very bright object. The mass accretion rate Ṁ is close to 1.4 × 10−7M⊙yr−1. The UV continuum has declined by a factor less than 1.2 over the 13 years of the IUE observations, while the UV emission lines have faded by larger factors. The wind components in the P Cyg profiles of the CIV and NV resonance lines are strong and variable on short timescales, with vedge up to −5000 kms−1, a remarkably high value. The modelling of the UV continuum shows that the quiescent optical magnitude at 12m has origin from a hot component that has a black body temperature close t...