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
Identifiers
45 results
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Item Multiwavelength optical observations of chromospherically active binary systems III: high resolution echelle spectra from Ca II H& K to Ca III RT(Astronomy & astrophysics supplement series, 2000) Montes Gutiérrez, David; Fernández Figueroa, María José; Castro Rubio, Elisa de; Cornide Castro-Piñeiro, Manuel; Latorre, A.; Sanz Forcada, J.This is the third paper of a series aimed at studying the chromosphere of active binary systems using the information provided for several optical spectroscopic features. High resolution echelle spectra including all the optical chromospheric activity indicators from the Ca II H & K to Ca II IRT lines are analysed here for 16 systems. The chromospheric contribution in these lines has been determined using the spectral subtraction technique. Very broad wings have been found in the subtracted Hα profile of the very active star HU Vir. These profiles are well matched using a two-component Gaussian fit (narrow and broad) and the broad component can be interpreted as arising from microflaring. Red-shifted absorption features in the Hα line have been detected in several systems and excess emission in the blue wing of FG UMa was also detected. These features indicate that several dynamical processes, or a combination of them, may be involved. Using the E_(Hα) / E_(Hβ) ratio as a diagnostic we have detected prominence-like extended material viewed off the limb in many stars of the sample, and prominences viewed against the disk at some orbital phases in the dwarfs OU Gem and BF Lyn. The He I D3 line has been detected as an absorption feature in mainly all the giants of the sample. Total filling-in of the He I D3, probably due to microflaring activity, is observed in HU Vir. Self-absorption with red asymmetry is detected in the Ca II H & K lines of the giants 12 Cam, FG UMa and BM CVn. All the stars analysed show clear filled-in Ca II IRT lines or even notable emission reversal. The small values of the E_(8542) / E_(8498) ratio we have found indicate Ca II IRT emission arises from plage-like regions. Orbital phase modulation of the chromospheric emission has been detected in some systems, in the case of HU Vir evidence of an active longitude area has been found.Item Multiwavelength optical observations of chromospherically active binary systems III. High resolution echelle spectra from CaII H & K to CaII IRT(Astronomy & astrophysics supplement series, 2000) Montes Gutiérrez, David; Fernández Figueroa, María José; Castro Rubio, Elisa de; Cornide Castro-Piñeiro, Manuel; Latorre, A.; Sanz Forcada, J.This is the third paper of a series aimed at studying the chromosphere of active binary systems using the information provided for several optical spectroscopic features. High resolution echelle spectra including all the optical chromospheric activity indicators from the Ca II H & K to Ca II IRT lines are analysed here for 16 systems. The chromospheric contribution in these lines has been determined using the spectral subtraction technique. Very broad wings have been found in the subtracted H alpha profilp of the very active star HU Vir. These profiles are well matched using a two-component Gaussian fit; (narrow and broad) ard the broad component carl be interpreted as arising from microflaring. Red-shifted absorption features in the EHα line have been detected in several systems and excess emission in the blue wing of FG UMa was also detected. These features indicate that several dynamical processes, or a combination of them, may be involved. Using the EHα/EHβ ratio as a diagnostic we have detected prominence-like extended material viewed off the limb in many stars of the sample, and prominences viewed against the disk at some orbital phases in the dwarfs OU Gem and BF Lyn, The He I D_3 line has been detected as an absorption feature in mainly all the giants of the sample. Total filling-in of the He I D_3, probably due to microflaring activity, is observed in HU Vir. Self-absorption with red asymmetry is detected in the Ca II H & K lines of the giants 12 Cam: FG UMa and BM CVn. All the stars analysed show clear filled-in Ca II IRT lines or even notable emission reversal. The small values of the E_8542/E_8498 ratio we have found indicate Ca II IRT emission arises from plage-like regions. Orbital phase modulation of the chromospheric emission has been detected in some systems, in the case of HU Vir evidence of an active longitude area has been found.Item Uvbyβ photometry of active-chromosphere binaries .1. The system TZ Coronae Borealis(Astronomical journal, 1986) Giménez, A.; Ballester, J. L.; Reglero, V.; Fernández Figueroa, María José; Castro Rubio, Elisa deSimultaneous 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.Item General properties of RS CVn systems(Monthly notices of the Royal Astronomical Society, 1988) Montesinos, B.; Giménez, A.; Fernández Figueroa, María JoséIn this work we analyse the behaviour of 22 members of the RS CVn family whose absolute parameters are known by observation. We have carried out a study in comparison with detached and normal-evolution systems in order to obtain some general properties of this group of active binaries and test the evolutionary status. A comparison with evolutionary tracks of several metallicities and helium contents shows that there is a trend in these stars to have metal abundances equal to or larger than the solar one. The results are discussed in the light of the peculiar characteristics of this kind of binaries .Item Emissions from the transition regions and coronae of three cool dwarf stars(Astronomy & Astrophysics, 1983) Fernández Figueroa, María José; Castro Rubio, Elisa de; Rego Fernández, ManuelUltraviolet 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.Item Lithium abundance and activity in a sample of RS Canum Venaticorum and BY Draconis stars(Astronomy and astrophysics, 1993) Fernández Figueroa, María José; Barrado y Navascués, D.; Castro Rubio, Elisa de; Cornide Castro-Piñeiro, ManuelObservations 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.Item The relationship between soft X-rays and the 1640 Å feature fluxes in late-type stars(Astronomy and astrophysics, 1983) Rego Fernández, Manuel; González Riestra, R.; Fernández Figueroa, María JoséThe λ 1640 feature has been observed in a sample of late type stars of different luminosity classes. The intensity was measured from IUE low dispersion spectra, and it has been compared with the observed X-ray fluxes, finding a relationship between both quantities for "solar type" stars. The X-ray fluxes derived from this relationship for a reduced sample of stars are consistent with the observed ones in the case of "solar type" stars. "Non solar type" stars exhibit discrepancies that could be explained assuming that the λ 1640 feature is formed by contributers other than He II, which supply an important fraction of this emission in "solar type" stars. The obtained empirical relationship has been used to derive the X-ray flux for some stars that have not been observed in the X-ray range.Item Application of the spectral subtraction technique to the Ca II H & K and H_ε lines in a sample of chromospherically active binaries(Astronomy & astrophysics supplement series, 1995) Montes Gutiérrez, David; Castro Rubio, Elisa de; Fernández Figueroa, María José; Cornide Castro-Piñeiro, ManuelWe 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.Item A high-resolution spectroscopic survey of late-type stars: chromospheric activity, rotation, kinematics, and age(Astronomy and astrophysics, 2010) López Santiago, Javier; Montes Gutiérrez, David; Gálvez Ortiz, M. C.; Crespo Chacón, I.; Martínez Arnáiz, R. M.; Fernández Figueroa, María José; Castro Rubio, Elisa de; Cornide Castro-Piñeiro, ManuelAims. We present a compilation of spectroscopic data from a survey of 144 chromospherically active young stars in the solar neighborhood, which may be used to investigate different aspects of its formation and evolution in terms of kinematics and stellar formation history. The data have already been used by us in several studies. With this paper, we make all these data accessible to the scientific community for future studies on different topics. Methods. We performed spectroscopic observations with echelle spectrographs to cover the entirety of the optical spectral range simultaneously. Standard data reduction was performed with the IRAF echelle package. We applied the spectral subtraction technique to reveal chromospheric emission in the stars of the sample. The equivalent width of chromospheric emission lines was measured in the subtracted spectra and then converted to fluxes using equivalent width-flux relationships. Radial and rotational velocities were determined by the cross-correlation technique. Kinematics, equivalent widths of the lithium line lambda 6707.8 angstrom and spectral types were also determined. Results. A catalog of spectroscopic data is compiled: radial and rotational velocities, space motion, equivalent widths of optical chromospheric activity indicators from Ca II H & K to the calcium infrared triplet and the lithium line in lambda 6708 angstrom. Fluxes in the chromospheric emission lines and R(HK)' are also determined for each observation of a star in the sample. We used these data to investigate the emission levels of our stars. The study of the Ha emission line revealed two different populations of chromospheric emitters in the sample, clearly separated in the log F(H alpha)/F(bol) - (V - J) diagram. The dichotomy may be associated with the age of the stars.Item Optical long-slit spectroscopy and imaging of OH 231.8+4.2(Astronomy & Astrophysics, 2000) Sánchez Contreras, C.; Bujarrabal, V.; Miranda, L. F.; Fernández Figueroa, María JoséWe present optical long-slit spectra and complementary broad and narrow band images of the bipolar protoplanetary nebula OH231.8+4.2. Absolute J2000 coordinates have been calculated for our maps from the position of nearby stars. Our maps of the optical continuum show the spatial distribution of the starlight scattered by dust grains. This component is found to be highly elongated along the nebular axis, with a structure very similar to that of the molecular emission. Flux variations with time of the red continuum emission are detected. Our long-slit spectroscopy of H_α and other atomic lines reveals wide spectral profiles and, in general, a complex spatial and spectral emission distribution. The emission arises from two broad lobes and is shifted toward shorter (north lobe) and longer wavelengths (south lobe), indicating that the gas is flowing outwards at high velocity. The clumpiness of the emission nebula is remarkable. A simple model has been used to describe the complex structure and kinematics of this source. Our model suggests that, in addition to the two extended, hollow lobes identified in the H_α images, a smaller, bubble-like expanding structure should lie inside the south lobe. A comparison of the emission line spectrum with predictions of theoretical shock models confirms that the optical lines have been shock excited. We have estimated the electron density of the lobes and deduced the total ionized mass of the nebula, obtaining a low value of ∼5 x 10^-4 M_⨀. We interpret the shaping and evolution of OH231.8+4.2 in the wind interaction scenario for planetary nebulae formation. The peculiar structure and kinematics of the molecular outflow and the ionized envelope are explained in terms of a shock regime transition: the well collimated molecular outflow and the different components of the optical nebula would consist of circumstellar material swept-up by a unique shock in a radiative, and non-radiative regime, respectively. Finally, we briefly discuss the controversial evolutionary status of OH 231.8+4.2.