Fernández Figueroa, María José

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First Name
María José
Last Name
Fernández Figueroa
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Astronomía y Astrofísica
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Now showing 1 - 8 of 8
  • Publication
    Emissions from the transition regions and coronae of three cool dwarf stars
    (EDP Sciencies, 1983) Fernández Figueroa, María José; Castro Rubio, Elisa de; Rego Fernández, Manuel
    Ultraviolet emissions of τCet, δPav, and 61 Cyg A have been analysed to determine the structure of their outer atmospheres. Emission line fluxes are used to find the emission measure distributions. Using two boundary values of the electron pressure, models of the transition region have been derived. In the two models of τCet the net conductive flux is less than the radiation losses at all temperatures. However, for δPav and 61 Cyg A the model with the upper boundary value of the electron pressure has a temperature range where the radiative losses are less than the net conductive fluxes. Measured X-ray fluxes are used to test the coronal temperature values derived from the ultraviolet observations.
  • Publication
    Hß photometry for uvby standard stars
    (IOP Publishing ltd, 1988-05) Reglero, V.; Giménez, A.; Fabregat, J.; Castro Rubio, Elisa de; Fernández Figueroa, María José; Castro, A. de
    From 1984 to 1986, we made several observational campaigns at Calar Alto and La Palma Observator­ies using the uvby and ß photometric systems to monitor a selected sample of late-type variable stars. In this paper we present the ß values for 38 uvby standard stars to contribute to the uvby-ß calibration works on late-type stars. In the final discussion, the ß computed values are plotted against the Ström­gren b - y, m_1, and c_1 indices.
  • Publication
    Analysis of the far ultraviolet emission lines in late type stars
    (EDP Sciencies, 1981) Castro Rubio, Elisa de; Fernández Figueroa, María José; Rego Fernández, Manuel; Ponz, D.
    Far ultraviolet emission lines in a sample of seven stars of spectral type later than F5 and different luminosity class have been analyzed to calculate the electron density and pressure in the formation region of the lines. Three different methods were used. We obtain electron pressures larger than solar for all dwarf stars of the sample. The low resolution observations were made with the IUE satellite.
  • Publication
    Analysis of Ca II emission lines in seven RSCVn systems
    (EDP Sciencies, 1986-11) Fernández Figueroa, María José; Montesinos, B.; Castro Rubio, Elisa de; Rego Fernández, Manuel; Giménez, A.; Reglero, V.
    We report here new Ca II H and K emission line fluxes and equivalent widths for seven RSCVn binary systems, observed at several orbital phases. All the stars show enhanced chromospheric activity. With information from available spectra, an in­ dividual study for each star has been done. Double emission has been found for some systems in which perhaps the hotter compo­nent could be the more active. We have tested spectroscopically the model of localized active regions for the prototype RSCVn.
  • Publication
    The Mg II emission in a sample of regular-period RS CVn systems
    (EDP Sciencies, 1986-11) Fernández Figueroa, María José; Sedano, J. L.; Castro Rubio, Elisa de
    We have studied a sample of ten RS CVn systems by means of IUE high resolution long wavelength spectra. A general trend toward decreasing chromospheric activity (R_hk) for slower rotating stars has been found. Considering the R_hk values and their relation with structural parameters (T_eff, logg, log P_rot) we suggest that there are two pos­sible different activity levels. The less active systems have Rhk chromospheric activity levels similar to the single cool stars showing the same general trend. A relation between R_hk and the inverse Rossby number has been obtained, in which the RS CVn stars fill the gap found by Rucinski between W UMa and the main-sequence stars.
  • Publication
    The transition region structure of κ ceti
    (EDP Sciencies, 1981) Fernández Figueroa, María José; Castro Rubio, Elisa de; Rego Fernández, Manuel
    Observations of κ Ceti (HD 20630), G5 V, obtained with the IUE satellite have been analysed to determine the structure of its outer atmosphere. This analysis is used to derive a model of transition region and to examine the terms of energy balance equation.
  • Publication
    Uvbyβ photometry of active-chromosphere binaries .1. The system TZ Coronae Borealis
    (IOP Publishing ltd, 1986-07) Giménez, A.; Ballester, J. L.; Reglero, V.; Fernández Figueroa, María José; Castro Rubio, Elisa de
    Simultaneous uvby and Hβ photometry of thee noneclipsing double-lined spectroscopic binary TZ CrB, an active binary system with almost unevolved components, is presented. A small amplitude distortion wave (0.012 mag in y) has been found with maximum light at phase ∽0.75. No variations in color or the βindex during the orbital cycle have been detected within the precision of the observations. The resulting color indices in the standard uvby system allow the estimation of some basic stellar parameters, such as the average effective temperature ∽6000 K and the stellar radii of the component stars ∽1.1 R_⨀. These results, together with available spectroscopic data, permit a consistent picture for this interesting binary to be obtained.
  • Publication
    Evidence of the connection between internal magnetic fields and chromospheric activity in late-type stars
    (Wiley, 1987-12-15) Montesinos, B.; Fernández Figueroa, María José; Castro Rubio, Elisa de
    In this work we try to establish a connection between the dynamo effect, which operates in the convection zone of late-type stars, and the chromospheric activity observed in these objects. We estímate in a theoretical way, for a sample of main-sequence active stars with spectral types G and K, the magnetic field generated in a region close to the base of the convection zone and the filling factor (fraction of stellar surface covered by strong magnetic fields). The analysis of the behaviour both of the filling factor and the activity indicator R(CaII + MgII) against several stellar parameters ( B-V and the Rossby number) supports the existence of a link between the interior processes and the surface activity.