Search Publications
Spectral Energy Distribution in the symbiotic system BI Cru
Cidale, L. S.; Brandi, E.; Muratore, M. F. +1 more
BI Crucis is a symbiotic star classed as a D-type (dusty). It comprises a Mira variable; a hot compact object and a large bipolar nebula. We model the continuum spectral energy distribution of this star in a wide range of wavelengths. We derive its fundamental parameters using a theoretical model developed by zorec-1998 (Proceedings of the Paris w…
Multi-cycle chromospheric activity in II Peg and V711 Tau
Buccino, A. P.; Mauas, P. J. D.
In this work, we studied the Mount Wilson indexes we obtained indirectly from both IUE high and low-resolution spectra of the RS CVn-type systems II Peg (K2IV) and V711 Tau (K1IV+G5V). For both systems, we found a long-term chromospheric activity cycle related to the mean level of activity of the primary star and a shorter cycle associated to the …
Habitability around M stars: the action of flares
Buccino, A. P.; Mauas, P. J. D.; Lemarchand, G. A.
We analyzed the UV habitable zones (UV-HZ), defined in Buccino et al. (2006), around planetary dM stars observed by IUE: HIP 74995, HIP 109388, HIP 113020 and around two dMe stars: Ad Leo and EV Lac. We found that moderate flares could be an energy source in the biogenesis processes.
FULL TEXT IN SPANISHEspectros Multi-Onda de las Estrellas Mas Masivas
Walborn, N. R.
The systematic trends and relationships among normal OB spectra in the optical, ultraviolet, and X-ray domains are reviewed. The last of these are a recent surprise to many specialists, which establish important constraints on the physical origin of the X-ray emission. Some peculiar categories are also described, including CNO anomalies at the ear…
Analysis of chromospheric activity in late type stars from UV observations
Buccino, A. P.; Mauas, P. J. D.
The purpose of this work is to study the chromospheric activity of the latest main sequence stars, which are generally observed in low dispersion. In this work, we present a calibration between Mount Wilson index and the Mg II line-core flux, measured on simultaneous low resolution IUE spectra. FULL TEXT IN SPANISH
UV radiation as biologic limit in the origin and development of life in extrasolar planets
Buccino, A. P.; Mauas, P. J. D.; Lemarchand, G. A.
In this work, we displayed a new biological criterion that restricts the traditional habitable zone. We set the internal boundary of this new UV habitable zone from the maximum radiation that tolerates the DNA and its external boundary from the levels of UV radiation needed in the biogenesis processes. We also analyzed the evolution of the habitab…
Long-term variations of the Be star 88 Her
Granada, A.; Cidale, S. L.
Since its discovery as a variable star, 88 Her has undergone three photometric long-term variation cycles with transitions between Be-Shell and normal B phases. From the spectroscopic analysis of fifteen high resolution spectra obtained by the IUE satellite, we found that the radial velocities of Fe II lines follow the orbital cycle of the binary …
Young and Explosive BAL QSOs (at low and high redshifts)
Zheng, W.; Terlevich, R.; Mediavilla, E. +7 more
study of outflow (OF) and BAL systems in QSOs is presented. This study is based mainly on 1D and 3D spectroscopy (obtained at La Palma/WHT, HST, IUE, ESO/NTT, KPNO, APO and CASLEO observatories) plus HST images. In particular, for the nearest BAL QSO Mrk 231, we found clear evidence that the extreme nuclear OF process has at least 3 main and compo…
Analysis of stellar activity of F, G and K stars with IUE
Buccino, A. P.; Mauas, P. J. D.
In this work, we correct in colour (B-V) the calibration between the Mount Wilson (S_MW) and the Mg II index (X_hk) we have presented in previous works. With this calibration, we build a catalog of the Mg II and Ca II indexes for all the F, G and K main sequence stars with high resolution IUE spectra (i.e. 1640 observations of 269 stars). Finally,…
Nebular abundances in southern symbiotic stars
Luna, G. J. M.; Costa, R. D. D.
We have calculated relative elemental abundances for a sample of 43 symbiotic stars. Helium abundances and the relative elemental abundances N/O, Ne/O were derived from new spectra collected in the optical range through low dispersion spectroscopy and from IUE low resolution spectra (SWP camera). The He ionic abundances were derived taking into ac…