J. E. Steiner — Page 4

arXiv2000

Spatially-resolved spectra of the accretion disc of the novalike UU Aquarii

Time-resolved spectroscopy of the novalike variable UU Aquarii is analyzed with eclipse mapping techniques to produce spatially resolved spectra of its accretion disc and gas stream as a function of distance from disc centre in the range 3600-6900 Å. The spatially-resolved spectra show that the continuum emission becomes progressively fainter and redder for increasing disc radius -- reflecting the radial temperature gradient -- and reveal that the HI and HeI lines appear as deep, narrow absorption features in the inner disc regions transitioning to emission with P Cygni profiles for intermediate and large disc radii. The spectrum of the uneclipsed component has strong HI and HeI emission lines plus a Balmer jump in emission and is explained as optically thin emission from a vertically extended disc chromosphere + wind. Most of the line emission probably arises from the wind. The spatially-resolved spectra also suggest the existence of gas stream ``disk-skimming'' overflow in UU Aqr, which can be seen down to R \simeq 0.2 R_{L1}. The comparison of our eclipse maps with those of Baptista, Steiner & Horne (1996) suggests that the asymmetric structure in the outer disc previously identified as the bright spot may be the signature of an elliptical disc similar to those possibly present in SU UMa stars during superoutbursts.

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arXiv1999

Spectral mapping of the accretion flow of UU Aquarii

Time-resolved spectroscopy of the novalike variable UU Aquarii is analyzed with eclipse mapping techniques to produce spatially resolved spectra of its accretion disc and gas stream as a function of distance from disc centre in the range 3600-7000 Å. The spectrum of inner disc shows a blue continuum filled with deep, narrow absorption lines which transition to emission with clear P Cygni profiles at intermediate and large radii. The spectrum of the uneclipsed component has strong HI and HeI emission lines and Balmer jump in emission and is explained as optically thin emission from a vertically extended disc wind. Most of the line emission probably arises from the wind. The spatially-resolved spectra also suggest the existence of gas stream penetration in UU Aqr, which can be seen down to $R \simeq 0.2 R_{L1}$.

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arXiv1998

Polarimetry and spectroscopy of the polar RX J1141.3-6410

We present the first optical polarimetric measurements of RX J1141.3-6410 which confirm that star as a polar. The circular polarization varies between 0 and 13% with the orbital period. Halpha spectroscopy shows that this line is formed by, at least, two components: a broad and a narrow one. The phase of maximum redshift of the broad component is shifted by 0.5 with the phase of maximum circular polarization which is not usual for this class of stars. We suggest a geometrical configuration for the system which could explain the main features of the polarimetric and spectroscopic data.

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arXiv1995

Spectral classification and HR diagram for symbiotic stars in the galactic bulge

A sample of 45 symbiotic stars observed in the direction of the galactic bulge are classified in spectral type using TiO $λλ6180, 7100 Å$ and VO $λλ7865 Å$ absorption feature indices and visual comparison. The effective temperatures obtained are used together with K data from the literature to estimate the bolometric luminosity of the giant components if located at d=8.5 kpc. The ($T_{eff}$, $L/L_{\odot}$) pairs are plotted on the HR diagram together with evolutionary tracks for metal rich intermediate mass stars. The mass of the giant components seem to be scattered in the interval ($\sim 1.5 - \sim 4 M_{\odot}$). The giant components of D-type symbiotics appear as if they were more evolved objects than the corresponding giants in S-type systems. Nevertheless, it is unlikely that they form an evolutionary sequence. The results point also to the restriction of the symbiotic phenomenon to the thermally pulsating phase of the AGB, strengthening an accelerated mass loss scenario for the latest evolutionary stages of intermediate mass stars.

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