Chromospheric activity and rotation of FGK stars in the solar vicinity. An estimation of the radial velocity jitter

Context. Chromospheric activity produces both photometric and spectroscopic variations that can be mistaken as planets. Large spots crossing the stellar disc can produce planet-like periodic variations in the light curve of a star. These spots clearly affect the spectral line profiles, and their perturbations alter the line centroids creating a radial velocity jitter that might “contaminate” the variations induced by a planet. Precise chromospheric activity measurements are needed to estimate the activity-induced noise that should be expected for a given star. Aims. We obtain precise chromospheric activity measurements and projected rotational velocities for nearby (d ≤ 25 pc) cool (spectral types F to K) stars, to estimate their expected activity-related jitter. As a complementary objective, we attempt to obtain relationships between fluxes in different activity indicator lines, that permit a transformation of traditional activity indicators, i.e., Ca II H & K lines, to others that hold noteworthy advantages. Methods. We used high resolution (~50 000) echelle optical spectra. Standard data reduction was performed using the IRAF ECHELLE package. To determine the chromospheric emission of the stars in the sample, we used the spectral subtraction technique. We measured the equivalent widths of the chromospheric emission lines in the subtracted spectrum and transformed them into fluxes by applying empirical equivalent width and flux relationships. Rotational velocities were determined using the cross-correlation technique. To infer activity-related radial velocity (RV) jitter, we used empirical relationships between this jitter and the R’_HK index. Results. We measured chromospheric activity, as given by different indicators throughout the optical spectra, and projected rotational velocities for 371 nearby cool stars. We have built empirical relationships among the most important chromospheric emission lines. Finally, we used the measured chromospheric activity to estimate the expected RV jitter for the active stars in the sample.

Del síndrome al sinthome

Currently, the concept of symptom is based on the notion of singularity (from a base perspective, underlined by Freud, regarding the persistence of symptomatic residue). This indicates that the demise of the symptom will never be complete, since the demand drive will always persist and will not cease to search for satisfaction.Let us then, insist on this matter, on the existence of an incurable residue in the symptom (which entails a particular relationship between the subject and its own pleasure), resisting sense and interpretation. The following paper has been elaborated following a diachronic trajectory of psychoanalytic theory, which allows establishing pauses, outlining the most important shifts produced in Freudian and Lacanian elaborations, respectively. Starting from Freud‘s productions, as main fulcrum, the Lacanian approach of the symptom will be introduced to link to the proposal of the sinthome proposed by Lacan. Freud will explain symptoms through the theory of trauma; those will find themselves hinged on mnemic traces, which will make the analysis of the patient‘s produced associations a crucial activity, to comprehend the etiology of the symptoms and the development of the cure. The clinical practice of this period may be summarized as ―the unconscious is susceptible to become conscious‖, aiming to the discovery and/or decoding of the symptoms, as long as they carry meaning. All of this at the same time, will be the base of future elaborations...