Person:
Fernández Figueroa, María José

First Name

María José

Last Name

Fernández Figueroa

URI

https://hdl.handle.net/20.500.14352/83017

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Físicas

Area

Astronomía y Astrofísica

Identifiers

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Now showing 1 - 10 of 45

The behaviour of the excess Ca II H and K and H epsilon emissions in chromospherically active binaries
(Astronomy & Astrophysics, 1996) 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.
Late-type stars members of young stellar kinematic groups
(Stellar clusters and associations: convection, rotation, and dynamos, 2000) Montes Gutiérrez, David; Latorre, A.; Fernández Figueroa, María José; Pallavicini, R.; Micela, G.; Sciortino, S.
We have compiled a catalog of late-type stars (F5-M) members of representative, young disk, stellar kinematic groups: the Local Association (20-150 Myr), Ursa Mayor group (300 Myr), Hyades supercluster (600 Myr), IC 2391 supercluster (35 Myr), and Castor moving group (200 Myr). Stars have been selected from previously established members of stellar kinematic groups based in photometric and kinematic properties as well as from candidates based in other criteria as their level of chromospheric activity, rotation rate, lithium abundance. Precise measurements of proper motions and parallaxes taken from Hipparcos Catalogue, and published radial velocity measurements are used to calculate Galactic space motions (U, V, W) in order to determine the membership of the selected stars to the different stellar kinematic groups.
The Mg II emission in a sample of regular-period RS CVn systems
(Astronomy & Astrophysics, 1986) 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.
Analysis of Ca II emission lines in seven RSCVn systems
(Astronomy & Astrophysics, 1986) 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.
Chromospheric activity, lithium and radial velocities of single late-type stars possible members of young moving groups
(Astronomy and astrophysics, 2001) Montes Gutiérrez, David; López Santiago, Javier; Fernández Figueroa, María José; Galves, M. C.
We present here high resolution echelle spectra taken during three observing runs of 14 single late-type stars identified in our previous studies (Montes et al. 2001b, hereafter Paper I) as possible members of different young stellar kinematic groups (Local Association (20-150 Myr), Ursa Major group (300 Myr), Hyades supercluster (600 Myr), and IC 2391 supercluster (35 Myr)). Radial velocities have been determined by cross correlation with radial velocity standard stars and used together with precise measurements of proper motions and parallaxes taken from Hipparcos and Tycho-2 Catalogues, to calculate Galactic space motions (U, V, W) and to apply Eggen's kinematic criteria. The chromospheric activity level of these stars have been analysed using the information provided for several optical spectroscopic features (from the CaII H & K toCaII IRT lines) that are formed at different heights in the chromosphere. The Li I λ6707.8 Å line equivalent width (EW) has been determined and compared in the EW(Li I) versus spectral type diagram with the EW(Li I) of stars members of well-known young open clusters of different ages, in order to obtain an age estimation. All these data allow us to analyse in more detail the membership of these stars in the different young stellar kinematic groups. Using both, kinematic and spectroscopic criteria we have confirmed PW And, V368 Cep, V383 Lac, EP Eri, DX Leo, HD 77407, and EK Dra as members of the Local Association and V834 Tau, π^1 UMa, and GJ 503.2 as members of the Ursa Major group. A clear rotation-activity dependence has been found in these stars.
Hβ photometry for UVBY standard stars
(Astronomical journal, 1988) Reglero, V.; Giménez, A.; Fabregat, J.; de Catro, E.; Fernández Figueroa, María José; De Castro, A.
From 1984 to 1986 the authors made several observational campaigns at Calar Alto and La Palma Observatories using the uvby and β photometric systems to monitor a selected sample of late-type variable stars. In this paper they present the β values for 38 uvby standard stars to contribute to the uvby-β calibration works on late-type stars. In the final discussion, the β computed values are plotted against the Stroemgren b-y, m_(1), and c_(1) indices.
The transition region structure of κ ceti
(Astronomy and astrophysics, 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.
A uvbyß survey of northern-hemisphere active binaries .2. The m_1 deficiency
(Astronomy & Astrophysics, 1991) Giménez, A.; Reglero, V.; Castro Rubio, Elisa De; Fernández Figueroa, María José
New photometric observations, using the uvby and Hß systems of 72 northern-hemisphere active binaries are discussed in order to explain the main characteristics of their spectral light intensity distribution. Values of the parameter δm_1 range from 0.0 to 0.3 mag, which cannot be explained in terms of metal underabundance alone. The existence of some mechanism, responsible for such a colour-index anomaly, is thus suggested and is found to be in close relation with the involved degree of solar-type activity.
Evidence of the connection between internal magnetic fields and chromospheric activity in late-type stars
(Monthly notices of the Royal Astronomical Society, 1987) 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.
A uvbyβ survey of northern-hemisphere active binaries II: the m1 deficiency
(Astronomy & Astrophysics, 1991) Giménez, A.; Reglero, V.; De Castro, E.; Fernández Figueroa, María José
New photometric observations, using the uvby and Hβ systems of 72 northern-hemisphere active binaries are discussed in order to explain the main characteristics of their spectral light intensity distribution. Values of the parameter δm1 range from 0.0 to 0.3 mag, which cannot be explained in terms of metal underabundance alone. The existence of some mechanism, responsible for such a colour-index anomaly, is thus suggested and is found to be in close relation with the involved degree of solar-type activity.