Multiwavelength optical observations of chromospherically active binary systems V. FF UMa (2RE J0933+624): a system with orbital period variation

This is the fifth paper in a series aimed at studying the chromospheres of active binary systems using several optical spectroscopic indicators to obtain or improve orbital solution and fundamental stellar parameters. We present here the study of FF UMa (2RE J0933+624), a recently discovered, X-ray/EUV selected, active binary with strong H_alpha emission. The objectives of this work are, to find orbital solutions and define stellar parameters from precise radial velocities and carry out an extensive study of the optical indicators of chromospheric activity. We obtained high resolution echelle spectroscopic observations during five observing runs from 1998 to 2004. We found radial velocities by cross correlation with radial velocity standard stars to achieve the best orbital solution. We also measured rotational velocity by cross-correlation techniques and have studied the kinematic by galactic space- velocity components (U, V, W) and Eggen criteria. Finally, we have determined the chromospheric contribution in optical spectroscopic indicators, from Ca II H & K to Ca II IRT lines, using the spectral subtraction technique. We have found that this system presents an orbital period variation, higher than previously detected in other RS CVn systems. We determined an improved orbital solution, finding a circular orbit with a period of 3.274 days. We derived the stellar parameters, confirming the subgiant nature of the primary component and obtained rotational velocities (vsini), of 33.57 km/s and 32.38 km/s for the primary and secondary components respectively. From our kinematic study, we can deduce its membership to the Castor moving group. Finally, the activity study has given us a better understanding of the possible mechanisms that produce the orbital period variation.Comment: Latex file with 16 pages, 18 figures. Available at http://www.ucm.es/info/Astrof/invest/actividad/actividad_pub.html Accepted for publication in: Astronomy & Astrophysics (A&A

Rotational modulation of the photospheric and chromospheric activity in the young, single K2-dwarf PW And

High resolution echelle spectra of PW And (HD~1405) have been taken during eight observing runs from 1999 to 2002. The detailed analysis of the spectra allow us to determine its spectral type (K2V), mean heliocentric radial velocity (V_hel = -11.15 km/s) rotational velocity (vsin{i} = 22.6 km/s), and equivalent width of the lithium line 6707.8 AA (EW(LiI) = 273 mAA). The kinematic (Galactic Velocity (U, V, W)) confirms its membership of the Local Association moving group, in agreement with the age (30 to 80 Myrs) inferred from the color magnitude diagram and the lithium equivalent width. Photospheric activity (presence of cool spots that disturb the profiles of the photospheric lines) has been detected as changes in the the bisectors of the cross correlation function (CCF) resulting of cross-correlate the spectra of PW And with the spectrum of a non active star of similar spectral type. These variations of the CCF bisectors are related to the variations in the measured radial velocities and are modulated with a period similar to the photometric period of the star. At the same time, chromospheric activity has been analyzed, using the spectral subtraction technique and simultaneous spectroscopic observations of the H_alpha, H_beta, NaI D_1 and D_2$, HeI D_3, MgI b triplet, CaII H&K, and CaII infrared triplet lines. A flare was observed during the last observing run of 2001, showing an enhancement in the observed chromospheric lines. A less powerful flare was observed on 2002 August 23. The variations of the chromospheric activity indicators seem to be related to the photospheric activity. A correlation between radial velocity, changes in the CCF bisectors and equivalent width of different chromospheric lines is observed with a different behaviour between epochs 1999, 2001 and 2002.Comment: Latex file with 20 pages, 21 figures tar'ed gzip'ed. Full postscript (text, figures and tables) available at http://www.ucm.es/info/Astrof/users/dmg/pub_dmg.html Accepted for publication in: Astronomy & Astrophysics (A&A

Estudio experimental de procesos de calentamiento y enfriamiento. Resultados e implicaciones didácticas

A detailed experimental study on different processes of heating and cooling allows to deduce that temperature variation, in these processes, in the course of time is not always the same, but it depends, to a great extent, on how the process is carried out. So to confuse the T-Q relations (always lineal) wirth T-t relations (dependent on the process) is a mistake that is necessary to avoid in our classes

The effect of magnetic activity saturation in chromospheric flux-flux relationships

We present a homogeneous study of chromospheric and coronal flux-flux relationships using a sample of 298 late-type dwarf active stars with spectral types F to M. The chromospheric lines were observed simultaneously in each star to avoid spread due to long term variability. Unlike other works, we subtract the basal chromospheric contribution in all the spectral lines studied. For the first time, we quantify the departure of dMe stars from the general relations. We show that dK and dKe stars also deviate from the general trend. Studying the flux-colour diagrams we demonstrate that the stars deviating from the general relations are those with saturated X-ray emission and that those stars also present saturation in the H$\alpha$ line. Using several age spectral indicators, we show that they are younger stars than those following the general relationships. The non-universality of flux-flux relationships found in this work should be taken into account when converting between fluxes in different chromospheric activity indicators.Comment: Accepted for publication in the Monthly Notices of the Royal Astronomical Societ

Insuficiencia cardíaca congestiva en la clínica de pequeños animales : terapéutica práctica moderna III. Diuréticos y bases xánticas en la clínica diaria

En el presente trabajo revisamos los medicamentos de efectos diuréticos más usados en la clínica de animales de compañía y aportamos nuestra experiencia personal en su uso y en la posible utilización de otros productos menos difundidos. Junto a ellos, y como una parte importante del tratamiento de muchos casos de insuficiencia cardíaca congestiva en el perro, una breve revisión de efectos, usos y problemas que pueden aportar las Xantinas de la clínica diaria.This paper reviews the diuretic drugs most often used in small animal practice and discloses the authors' personal experience in their application and the possible use of other less common products. A brief review of effects, uses and problems of Xantines in routine practice is also made, as an important element of the treatment of many cases of Congestivo Heart Failure in dogs

Theoretical prediction of the electronic and thermodynamic properties of YN-ZrN solid solutions

In this study, the results of structural parameters, electronic structure, and thermodynamic properties of the ZrxY1-xN solid solutions are presented. The effect of zirconium composition on lattice constant, and bulk modulus shows nonlinear dependence on concentration. Deviations of the lattice constant from Vegard's law and deviations of the bulk modulus from linear concentration dependence were found. Our findings indicate that the ZrxY1-xN solid solutions are metallic for x = 0.25, 0.5, 0.75. The calculated excess mixing enthalpy is positive over the entire zirconium composition range. The positive mixing enthalpies for ZrxY1-xN alloys indicate the existence of miscibility gaps and spinodal decompositions. The effect of temperature on the volume, bulk modulus, Debye temperature, and the heat capacity for ZrxY1-xN alloys were analyzed using the quasi-harmonic Debye model. Results show that the heat capacity is slightly sensitive to composition as temperature increases

Starspots on the fastest rotators in the Beta Pic moving group

Aims: We carried out high-resolution spectroscopy and BV(I)_C photometric monitoring of the two fastest late-type rotators in the nearby Beta Pictoris moving group, HD199143 (F7V) and CD-641208 (K7V). The motivation for this work is to investigate the rotation periods and photospheric spot patterns of these very young stars, with a longer term view to probing the evolution of rotation and magnetic activity during the early phases of main-sequence evolution. We also aim to derive information on key physical parameters, such as rotational velocity and rotation period. Methods: We applied maximum entropy (ME) and Tikhonov regularizing (TR) criteria to derive the surface spot map distributions of the optical modulation observed in HD199143 (F7 V) and CD-641208 (K7V). We also used cross-correlation techniques to determine stellar parameters such as radial velocities and rotational velocities. Lomb-Scargle periodograms were used to obtain the rotational periods from differential magnitude time series. Results: We find periods and inclinations of 0.356 days and 21.5deg for HD199143, and 0.355 days and 50.1deg for CD-641208. The spot maps of HD199143 obtained from the ME and TR methods are very similar, although the latter gives a smoother distribution of the filling factor. Maps obtained at two different epochs three weeks apart show a remarkable increase in spot coverage amounting to ~7% of the surface of the photosphere over a time period of only ~20 days. The spot maps of CD-641208 from the two methods show good longitudinal agreement, whereas the latitude range of the spots is extended to cover the whole visible hemisphere in the TR map. The distributions obtained from the first light curve of HD199143 show the presence of an extended and asymmetric active longitude with the maximum filling factor at longitude ~325degree.Comment: Accepted by A&A. 13 pages, 13 figures (4 online included), 5 Table

Chromospheric activity, lithium and radial velocities of single late-type stars possible members of young moving groups

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 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.Comment: Latex file with 19 pages, 7 figures tar'ed gzip'ed. Full postscript (text, figures and tables) available at http://www.ucm.es/info/Astrof/p_skg_stars_I_fv.ps.gz Accepted for publication in: Astronomy & Astrophysics (A&A