Person:
Fernández Figueroa, María José

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First Name
María José
Last Name
Fernández Figueroa
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Area
Astronomía y Astrofísica
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Now showing 1 - 10 of 18
  • Publication
    Application of the spectral subtraction technique to the Ca II H & K and H_ε lines in a sample of chromospherically active binaries
    (EDP Sciences, 1995-12) Montes Gutiérrez, David; Castro Rubio, Elisa de; Fernández Figueroa, María José; Cornide Castro-Piñeiro, Manuel
    We present new spectroscopic observations in the Ca II H & K line region for a sample of 28 chromospherically active binary systems (RS CVn and BY Dra classes), with different activity levels. By using the spectral subtraction technique (subtraction of a synthesized stellar spectrum constructed from reference stars of similar spectral type and luminosity class) we obtain the active-chromosphere contribution to the Ca II H & K lines and to the H_ε line when it is present. We have compared the emission equivalent widths obtained with this technique with those obtained by reconstruction of the absorption line profile below the emission peak(s). The emissions arising from each individual star were obtained when it was possible to deblend the contribution of both components. The Ca II line profiles corresponding to different seasons and orbital phases are analysed in order to determine the contribution of each component and to study the chromospheric activity variations.
  • Publication
    The behaviour of the excess Ca II H and K and H_ε emissions in chromospherically active binaries
    (EDP Sciencies, 1996-08) Montes Gutiérrez, David; Fernández Figueroa, María José; Cornide Castro-Piñeiro, Manuel; Castro Rubio, Elisa de
    In this work we analyze the behaviour of the excess Ca II H and K and H_ ε emissions in a sample of 73 chromospherically active binary systems (RS CVn and BY Dra classes), of different activity levels and luminosity classes. This sample includes the 53 stars analyzed by Fernandez-Figueroa et al. (1994) and the observations of 28 systems described by Montes et al. (1995c). By using the spectral subtraction technique (subtraction of a synthesized stellar spectrum constructed from reference stars of spectral type and luminosity class similar to those of the binary star components) we obtain the active-chromosphere contribution to the Ca II H and K lines in these 73 systems. We have determined the excess Ca II H and K emission equivalent widths and converted them into surface fluxes. The emissions arising from each component were obtained when it was possible to deblend both contributions. We have found that the components of active binaries are generally stronger emitters than single active stars for a given effective temperature and rotation rate. A slight decline of the excess Ca II H and K emissions towards longer rotation periods, P-rot, and larger Rossby numbers, R_0, is found. When we use R_0 instead of P_rot, the scatter is reduced and a saturation at R_0≈0.3 is observed. A good correlation between the excess Ca II K and H_ ε chromospheric emission fluxes has been found. The correlations obtained between the excess Ca II K emission and other activity indicators, (C IV in the transition region, and X-rays in the corona) indicate that the exponents of the power-law relations increase with the formation temperature of the spectral features.
  • Publication
    The age-mass relation for chromospherically active binaries. 1. The evolutionary status
    (EDP Sciencies, 1994-10) Barrado y Navascués, D.; Fernández Figueroa, María José; Montesinos, B.; Castro Rubio, Elisa de
    In this paper we present a study of the evolutionary status of a sample of chromospherically active binary systems for which accurate determinations of their stellar parameters are available. Stellar ages have been obtained by using evolutionary tracks. The agreement between the estimates of ages for the two components of a given system is very good, which proves the reliability of our method. It has been possible to separate the chromospherically active binaries in three groups, according to the mass of the primary component: evolved stars with masses in the range 2.5-5 M_⨀ , evolved stars (subgiants) with M≃1.4 M_⨀ and main-sequence stars with M≃1.1 M_⨀. We have found a relationship between stellar masses and ages of the form Log Age = 9.883(±0.022) - 2.965(±0.122) Log (Mass/M_⨀). This relationship is very close to that for stars on the TAMS. The relation can be understood, in the framework of the evolution of the components and orbital elements of binary systems, as an effect of the increase of the stellar radius as the components evolve off the main sequence, and the decrease of the rotation period due to tidal effects which leads to enhanced chromospheric emission levels, several times higher than that of the Sun. The relationship has a dependence on rotation, due to the fact that for a given range of masses, younger stars rotate faster. We have also found that the more evolved stars are the more active, for a given interval of rotation periods.
  • Publication
    The age-mass relation for chromospherically active binaries - III. Lithium depletion in giant components
    (EDP Sciencies, 1998-09-20) Barrado y Navascués, D.; Castro Rubio, Elisa de; Fernández Figueroa, María José; Cornide Castro-Piñeiro, Manuel; García López, R. J.
    We present a study of the lithium abundances of a sample of evolved components of Chromospherically Active Binary Systems. We show that a significant part of them have lithium excesses, independently of their mass and evolutionary stage. Therefore, it can be concluded that Li abundance does not depend on age for giant components of CABS. These overabundances appear to be closely related to the stellar rotation, and we interpret them as a consequence of the transfer of angular momentum from the orbit to the rotation as the stars evolve: in and off the Main Sequence, in a similar way as it happens in the dwarf components of the same systems and in the Tidally Locked Binaries belonging to the Hyades and M67.
  • Publication
    Ca II H and K and H_α emissions in chromospherically active binary-systems (RS Canum Venaticorum and BY Draconis)
    (University Chicago Press, 1994-01) Fernández Figueroa, María José; Montes Gutiérrez, David; Castro Rubio, Elisa de; Cornide Castro-Piñeiro, Manuel
    We report high-resolution observations of the Ca II H and K and Balmer H_α lines in 53 chromospherically active binary systems including the RS Canum Venaticorum binaries (RS CVn) and BY Draconis (BY Dra) classes. The rotational periods of the sample cover a range from 0.8 to 83.2 days. H and K emission-line surface fluxes have been calculated for all the stars in the sample. In spectra where the H_ε line appears in emission, absolute surface fluxes were also determined. The Ca II line profiles corresponding to different seasons and orbital phases are analyzed in order to determine the contribution of each component and to study the chromospheric activity variations. We have measured the H_α equivalent width of the program stars and the H_α core emission was determined by subtraction of the equivalent width of a presumably inactive star of the same spectral type and luminosity class. Three different types of H_α line profiles have been found: strong emission line, weak emission line with strong superposed absorption profile, and filled-in absorption line profile.
  • Publication
    Stellar activity in barium stars .1. Analysis of H-lines and K-lines CA-II-lines in 10 barium stars
    (IOP Publishing ltd, 1992-04) Cornide Castro-Piñeiro, Manuel; Fernández Figueroa, María José; Castro Rubio, Elisa de; Armentia, J. A.; Reglero, V.
    High dispersion spectra have been obtained in order to study the activity level of ten barium stars by means of the Ca II H and K emission flux, looking for a relation between barium intensity index and activity. Absolute magnitudes obtained from the Wilson-Bappu relationship disagree, in some cases, with the magnitudes computed from parallaxes, but this fact is not due to barium nature. Total emission fluxes, F(H + K) or R_HK index, plotted versus effective temperature show a distribution similar to that of cool giant stars. The asymmetry of K emission line, [F(K_2ν)/F(K_2r)], has been analyzed in relation with effective temperature, in this sense barium stars behave as expected of late-type giants with the only exception of two stars.
  • Publication
    Lithium abundance and activity in a sample of RS Canum Venaticorum and BY Draconis stars
    (EDP Sciencies, 1993-07) Fernández Figueroa, María José; Barrado y Navascués, D.; Castro Rubio, Elisa de; Cornide Castro-Piñeiro, Manuel
    Observations of the Li i doublet at 6707.8 angstrom for a sample of active binary systems RS CVn and By Dra have been carried out at the Calar Alto Observatory with the 2.2 m telescope. In addition, some single stars with different chromospheric activity levels have also been observed mainly for comparison purposes. Gaussian fits have been performed in order to separate the Fe I line at 6707.4 angstrom which is usually blended with the Li I doublet. Once the fit was achieved, the equivalent width was measured for each separated line. The contributions due to the continuum from both components have been taken into account to correct the equivalent width measurements. A curve-of-growth method has been used to derive lithium abundances. We have obtained a Li excess in the binary systems, in particular the K type stars. A correlation of the Li abundance with the activity levels is confirmed, as it was found by other authors, but RS CVn and BY Dra systems are 0.5 dex more active than single stars for the same Li abundance.
  • Publication
    The behaviour of the excess Ca II H and K and H epsilon emissions in chromospherically active binaries
    (EDP Sciencies, 1996-08) Montes Gutiérrez, David; Fernández Figueroa, María José; Cornide Castro-Piñeiro, Manuel; Castro Rubio, Elisa de
    In this work we analyze the behaviour of the excess Ca II H & K and H emissions in a sample of 73 chromospherically active binary systems (RS CVn and BY Dra classes), of diferent activity levels and luminosity classes. This sample includes the 53 stars analyzed by Fernández-Figueroa et al. (1994) and the observations of 28 systems described by Montes et al. (1995c). By using the spectral subtraction technique (subtraction of a synthesized stellar spectrum constructed from reference stars of spectral type and luminosity class similar to those of the binary star components) we obtain the active chromosphere contribution to the Ca II H & K lines in these 73 systems. We have determined the excess Ca ii H & K emission equivalent widths and converted them into surface fluxes. The emissions arising from each component were obtained when it was possible to deblend both contributions. We have found that the components of active binaries are generally stronger emitters than single active stars for a given effective temperature and rotation rate. A slight decline of the excess Ca II H & K emissions towards longer rotation periods_(1) P_(rot1) and larger Rossby numbers, R_(01) is found. When we use R_(0) instead of P_(rot) the scatter is reduced and a saturation at R_(0)≈ 0.3 is observed. A good correlation between the excess Ca II K and He chromospheric emission fluxes has been found. The correlations obtained between the excess Ca II K emission and other activity indicators, (C IV in the transition region, and X-rays in the corona) indicate that the exponents of the power-law relations increase with the formation temperature of the spectral features.
  • Publication
    Multiwavelength optical observations of the chromospherically active binary system MS Ser
    (Astronomical Society of the Pacific, 1999) Sanz Forcada, J.; Montes Gutiérrez, David; Fernández Figueroa, María José; Castro Rubio, Elisa de; Cornide Castro-Piñeiro, Manuel; Butler, C. J.; Doyle, J. G.
    We present here a continuation of our ongoing project of multiwavelength optical observations aimed at studying the chromosphere of active binary systems using the information provided for several optical spectroscopic features that are formed at different heights in the chromosphere. In this contribution we focus our study on the preliminary analysis of the active binary system MS Ser. We have taken Hα and Hβ spectra in 1995 and high resolution echelle spectra (covering Hα, Hβ, Na I D_1, D_2, He I D_3, Ca II H & K, and Ca II λ8662 lines) in 1998. Strong emission in the Ca II H & K and Ca III RT lines, coming from the primary component (recently classified as K2IV) is observed, and the secondary (G8V) also exhibits a small amount of emission. A near complete and variable filling-in of the Hα and Hβ is obtained after the application of the spectral subtraction technique. We detect also some seasonal variations between these two observing runs in comparison with our previous Ca II H & K observations taken in 1993.
  • Publication
    The Wilson-Bappu effect and other CA-II H-Line and K-line parameters relationships in chromospherically active binaries
    (EDP Sciencies, 1994-05) Montes Gutiérrez, David; Fernández Figueroa, María José; Castro Rubio, Elisa de; Cornide Castro-Piñeiro, Manuel
    We present measurements of the emission core width W_0 and the wavelength separation of the K_1 dips, W_1, of the Ca II H and K emission lines observed on high-dispersion spectra of 28 chromospherically active binary systems (RS CVn and BY Dra stars) and 18 single active stars. We test the width-luminosity correlations (the Wilson-Bappu (WB) effect, and (W_1, M_V) in these very active stars and analyse the influence of the activity level (I_K3) and the rotational broadening (Vsin i) in these correlations. We have found that for very active stars the emission widths, both W_0 and W_1, are larger than expected from previously accepted width-luminosity relations. The stars with strong emission intensities, I_K3 and large values of Vsin i seem to present larger values of W_0 than resulted from WB relation, the effect of the rotational velocity being the most remarkable. On the contrary, W_1 is strongly influenced by I_K3 but the effect of the rotational broadening is lesser. We also analyse the behaviour of the Ca II H and K line parameters in these very active stars in relation with less active stars and we found that the increase of W_1 and I_K1 With I_K3 presents a flattening for the most active stars which is different for each value of W_0. Finally we also find a Hepsilon width-luminosity correlation in the stars of the sample in which this emission line is present.