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Papers by David Montes

Monthly Notices of The Royal Astronomical Society, 1999

We present high resolution optical echelle spectra and IUE observations during a strong flare on ... more We present high resolution optical echelle spectra and IUE observations during a strong flare on 1993 December 22 in the very active, young, rapidly rotating, single K2 dwarf LQ Hya. The initial impulsive phase of the flare, which started sometime between 2:42 UT and 4:07 UT, was characterized by strong optical continuum enhancement and blue-shifted emission lines with broad wings. The optical chromospheric lines reached their maximum intensity at ≈5:31 UT, by which time the blue-shift vanished and the optical continuum enhancement had sharply decreased. Thereafter, the line emission slowly decreased and the lines red-shift in a gradual phase that lasted at least two more hours. The Mg ii lines behaved similarly. Quiescent C iv flux levels were not recovered until 21 hours later, though a data gap and a possible second flare make the interpretation uncertain. In addition to the typically flare-enhanced emission lines (e.g., Hα and Hβ), we observe He i D 3 going into emission, plus excess emission (after subtraction of the quiescent spectrum) in other He i and several strong neutral metal lines (e.g., Mg i b). Flare enhancement of the far UV continuum generally agrees with a Si i recombination model. We estimate the total flare energy, and discuss the broad components, asymmetries, and Doppler shifts seen in some of the emission lines.

Hyades supercluster (600 Myr), and IC 2391 supercluster (35 Myr)). Radial velocities have been de... more 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 Ca II H & K to Ca II IRT lines) that are formed at different heights in the chromosphere. The Li I 6707.8 AA 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, pi^{1} UMa, and GJ 503.2 as members of the Ursa Major group. A clear rotation-activity dependence has been found in these stars.

Astrophysical Journal Supplement Series, 1999

We present a library of Penn State Fiber Optic Echelle (FOE) observations of a sample of field st... more We present a library of Penn State Fiber Optic Echelle (FOE) observations of a sample of field stars with spectral types F to M and luminosity classes V to I. The spectral coverage is from 3800Å to 10000Å with nominal a resolving power 12000. These spectra include many of the spectral lines most widely used as optical and near-infrared indicators of chromospheric activity such as the Balmer lines (Hα to Hǫ), Ca ii H & K, Mg i b triplet, Na i D 1 , D 2 , He i D 3 , and Ca ii IRT lines. There are also a large number of photospheric lines, which can also be affected by chromospheric activity, and temperature sensitive photospheric features such as TiO bands. The spectra have been compiled with the goal of providing a set of standards observed at medium resolution. We have extensively used such data for the study of active chromosphere stars by applying a spectral subtraction technique. However, the data set presented here can also be utilized in a wide variety of ways ranging from radial velocity templates to study of variable stars and stellar population synthesis. This library can also be used for spectral classification purposes and determination of atmospheric parameters (T eff , log g, [Fe/H]). A digital version of all the fully reduced spectra is available via ftp and the World Wide Web (WWW) in FITS format.

Astrophysics and Space Science, 1998

The star EZ Peg, long ago classified as cataclysmic variable, has been shown to be a chromospheri... more The star EZ Peg, long ago classified as cataclysmic variable, has been shown to be a chromospherically active binary system of the RS CVn-type. In this paper we have analysed, using the spectral subtraction technique, simultaneous spectroscopic observations of the Hα, Hβ, Na i D 1 and D 2 , He i D 3 , Mg i b triplet, Ca ii H & K, and Ca ii infrared triplet lines. We have found that the hot component is the active star of the system, showing strong emission in the Hα, Ca ii H & K, H , and Ca ii IRT lines, and a strong filling-in of the Hβ line, however the Na i D 1 and D 2 and Mg i b triplet lines do not present filled-in. The He i D 3 could present a total filling-in due to microflaring. The observed variations (in different epochs and with the orbital phase) of the different activity indicators, formed at different height in the chromosphere, are correlated. Very broad wings have been found in the subtracted profiles of Hα and Ca ii IRT λ8498 and λ8662 lines. These profiles are well matched using a two-component Gaussian fit (narrow and broad) and the broad component could be interpreted as arising from microflaring. The higher luminosity class of the hot component, that our spectra seem to indicate, could explain why the hot component is the active star of the system.

This is the first paper of a series aimed at studying the properties of late-type stars members o... more This is the first paper of a series aimed at studying the properties of late-type stars members of young stellar kinematic groups. We concentrate our study on classical young moving groups as: Local Association (Pleiades moving group, 20 - 150 Myr), IC 2391 supercluster (35 Myr), Ursa Major group (Sirius supercluster, 300 Myr), and Hyades supercluster (600 Myr); as well as on recently identified groups as: Castor moving group (200 Myr). In this paper we have compiled a preliminary list of single late-type stars possible members of some of these young stellar kinematic groups. Stars have been selected from previously established members of stellar kinematic groups based on photometric and kinematic properties as well as from candidates based on other criteria as their level of chromospheric activity, rotation rate, lithium abundance. Precise measurements of proper motions and parallaxes taken from Hipparcos Catalogue, as well as from Tycho-2 Catalogue, and published radial velocity measurements are used to calculate the Galactic space motions (U, V, W) and to apply the Eggen's kinematic criteria in order to determine the membership of the selected stars to the different groups. Additional criteria using age-dating methods for late-type stars will be applied in forthcoming papers of this series. A further study of the list of stars compiled here could lead to a better understanding of the chromospheric activity and their age evolution as well as of the star formation history in the solar neighbourhood. In addition, these stars are also potential search targets for direct imaging detection of sub-stellar companions.

Astrophysical Journal Supplement Series, 1994

Astronomy & Astrophysics Supplement Series, 1998

We present a library of Utrecht echelle spectrograph (UES) observations of a sample of F, G, K an... more We present a library of Utrecht echelle spectrograph (UES) observations of a sample of F, G, K and M field dwarf stars covering the spectral range from 4800 AA to 10600 AA with a resolution of 55000. These spectra include some of the spectral lines most widely used as optical and near-infrared indicators of chromospheric activity such as H_beta, Mg I b triplet, Na I D_1, D_2, He I D_3, H_alpha, and Ca II IRT lines, as well as a large number of photospheric lines which can also be affected by chromospheric activity. The spectra have been compiled with the aim of providing a set of standards observed at high-resolution to be used in the application of the spectral subtraction technique to obtain the active-chromosphere contribution to these lines in chromospherically active single and binary stars. This library can also be used for spectral classification purposes. A digital version with all the spectra is available via ftp and the World Wide Web (WWW) in both ASCII and FITS formats.

Monthly Notices of The Royal Astronomical Society, 1999

We present high resolution optical echelle spectra and IUE observations during a strong flare on ... more We present high resolution optical echelle spectra and IUE observations during a strong flare on 1993 December 22 in the very active, young, rapidly rotating, single K2 dwarf LQ Hya. The initial impulsive phase of the flare, which started sometime between 2:42 UT and 4:07 UT, was characterized by strong optical continuum enhancement and blue-shifted emission lines with broad wings. The optical chromospheric lines reached their maximum intensity at ≈5:31 UT, by which time the blue-shift vanished and the optical continuum enhancement had sharply decreased. Thereafter, the line emission slowly decreased and the lines red-shift in a gradual phase that lasted at least two more hours. The Mg ii lines behaved similarly. Quiescent C iv flux levels were not recovered until 21 hours later, though a data gap and a possible second flare make the interpretation uncertain. In addition to the typically flare-enhanced emission lines (e.g., Hα and Hβ), we observe He i D 3 going into emission, plus excess emission (after subtraction of the quiescent spectrum) in other He i and several strong neutral metal lines (e.g., Mg i b). Flare enhancement of the far UV continuum generally agrees with a Si i recombination model. We estimate the total flare energy, and discuss the broad components, asymmetries, and Doppler shifts seen in some of the emission lines.

Hyades supercluster (600 Myr), and IC 2391 supercluster (35 Myr)). Radial velocities have been de... more 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 Ca II H & K to Ca II IRT lines) that are formed at different heights in the chromosphere. The Li I 6707.8 AA 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, pi^{1} UMa, and GJ 503.2 as members of the Ursa Major group. A clear rotation-activity dependence has been found in these stars.

Astrophysical Journal Supplement Series, 1999

We present a library of Penn State Fiber Optic Echelle (FOE) observations of a sample of field st... more We present a library of Penn State Fiber Optic Echelle (FOE) observations of a sample of field stars with spectral types F to M and luminosity classes V to I. The spectral coverage is from 3800Å to 10000Å with nominal a resolving power 12000. These spectra include many of the spectral lines most widely used as optical and near-infrared indicators of chromospheric activity such as the Balmer lines (Hα to Hǫ), Ca ii H & K, Mg i b triplet, Na i D 1 , D 2 , He i D 3 , and Ca ii IRT lines. There are also a large number of photospheric lines, which can also be affected by chromospheric activity, and temperature sensitive photospheric features such as TiO bands. The spectra have been compiled with the goal of providing a set of standards observed at medium resolution. We have extensively used such data for the study of active chromosphere stars by applying a spectral subtraction technique. However, the data set presented here can also be utilized in a wide variety of ways ranging from radial velocity templates to study of variable stars and stellar population synthesis. This library can also be used for spectral classification purposes and determination of atmospheric parameters (T eff , log g, [Fe/H]). A digital version of all the fully reduced spectra is available via ftp and the World Wide Web (WWW) in FITS format.

Astrophysics and Space Science, 1998

The star EZ Peg, long ago classified as cataclysmic variable, has been shown to be a chromospheri... more The star EZ Peg, long ago classified as cataclysmic variable, has been shown to be a chromospherically active binary system of the RS CVn-type. In this paper we have analysed, using the spectral subtraction technique, simultaneous spectroscopic observations of the Hα, Hβ, Na i D 1 and D 2 , He i D 3 , Mg i b triplet, Ca ii H & K, and Ca ii infrared triplet lines. We have found that the hot component is the active star of the system, showing strong emission in the Hα, Ca ii H & K, H , and Ca ii IRT lines, and a strong filling-in of the Hβ line, however the Na i D 1 and D 2 and Mg i b triplet lines do not present filled-in. The He i D 3 could present a total filling-in due to microflaring. The observed variations (in different epochs and with the orbital phase) of the different activity indicators, formed at different height in the chromosphere, are correlated. Very broad wings have been found in the subtracted profiles of Hα and Ca ii IRT λ8498 and λ8662 lines. These profiles are well matched using a two-component Gaussian fit (narrow and broad) and the broad component could be interpreted as arising from microflaring. The higher luminosity class of the hot component, that our spectra seem to indicate, could explain why the hot component is the active star of the system.

This is the first paper of a series aimed at studying the properties of late-type stars members o... more This is the first paper of a series aimed at studying the properties of late-type stars members of young stellar kinematic groups. We concentrate our study on classical young moving groups as: Local Association (Pleiades moving group, 20 - 150 Myr), IC 2391 supercluster (35 Myr), Ursa Major group (Sirius supercluster, 300 Myr), and Hyades supercluster (600 Myr); as well as on recently identified groups as: Castor moving group (200 Myr). In this paper we have compiled a preliminary list of single late-type stars possible members of some of these young stellar kinematic groups. Stars have been selected from previously established members of stellar kinematic groups based on photometric and kinematic properties as well as from candidates based on other criteria as their level of chromospheric activity, rotation rate, lithium abundance. Precise measurements of proper motions and parallaxes taken from Hipparcos Catalogue, as well as from Tycho-2 Catalogue, and published radial velocity measurements are used to calculate the Galactic space motions (U, V, W) and to apply the Eggen's kinematic criteria in order to determine the membership of the selected stars to the different groups. Additional criteria using age-dating methods for late-type stars will be applied in forthcoming papers of this series. A further study of the list of stars compiled here could lead to a better understanding of the chromospheric activity and their age evolution as well as of the star formation history in the solar neighbourhood. In addition, these stars are also potential search targets for direct imaging detection of sub-stellar companions.

Astrophysical Journal Supplement Series, 1994

Astronomy & Astrophysics Supplement Series, 1998

We present a library of Utrecht echelle spectrograph (UES) observations of a sample of F, G, K an... more We present a library of Utrecht echelle spectrograph (UES) observations of a sample of F, G, K and M field dwarf stars covering the spectral range from 4800 AA to 10600 AA with a resolution of 55000. These spectra include some of the spectral lines most widely used as optical and near-infrared indicators of chromospheric activity such as H_beta, Mg I b triplet, Na I D_1, D_2, He I D_3, H_alpha, and Ca II IRT lines, as well as a large number of photospheric lines which can also be affected by chromospheric activity. The spectra have been compiled with the aim of providing a set of standards observed at high-resolution to be used in the application of the spectral subtraction technique to obtain the active-chromosphere contribution to these lines in chromospherically active single and binary stars. This library can also be used for spectral classification purposes. A digital version with all the spectra is available via ftp and the World Wide Web (WWW) in both ASCII and FITS formats.