Analysis of combined radial velocities and activity of BD+20 1790: evidence supporting the existence of a planetary companion

Context. In a previous paper we reported a planetary companion to the young and very active K5Ve star BD+20 1790. We found that this star has a high level of stellar activity (log R'_HK = -3.7) that manifests in a plethora of phenomena (starspots, prominences, plages, large flares). Based on a careful study of these activity features and a deep discussion and analysis of the effects of the stellar activity on the radial velocity measurements, we demonstrated that the presence of a planet provided the best explanation for the radial velocity variations and all the peculiarities of this star. The orbital solution resulted in a close-in massive planet with a period of 7.78 days. However, a paper by Figueira et al. (2010, A&A, 513, L8) questioned the evidence for the planetary companion. Aims. This paper aims to more rigorously assess the nature of the radial velocity measurements with an expanded data set and new methods of analysis. Methods. We have employed Bayesian methods to simultaneously analyse the radial velocity and activity measurements based on a combined data set that includes new and previously published observations. Results. We conclude that the Bayesian analysis and the new activity study support the presence of a planetary companion to BD+20 1790. A new orbital solution is presented, after removing the two main contributions of stellar jitter, one that varies with the photometric period (2.8 days) and another that varies with the synodic period of the star-planet system (4.36 days). We present a new method to determine these jitter components, considering them as second and third signals in the system. A discussion on possible star-planet interaction is included, based on the Bayesian analysis of the activity indices, which indicates that they modulate with the synodic period. We propose two different sources for flare events in this system: one related to the geometry of the system and the relative movement of the star and planet, and a second one purely stochastic source that is related to the evolution of stellar surface active regions. Also, we observe for the first time the magnetic field of the star, from spectropolarimetric data

Is it possible to detect planets around young active G and K dwarfs?

Theoretical predictions suggest that the distribution of planets in very young stars could be very different to that typically observed in Gyr old systems that are the current focus of radial velocity surveys. However, the detection of planets around young stars is hampered by the increased stellar activity associated with young stars, the signatures of which can bias the detection of planets. In this paper, we place realistic limitations on the possibilities for detecting planets around young active G and K dwarfs. The models of stellar activity based on tomographic imaging of the G dwarf HD 141943 and the K1 dwarf AB Dor also include contributions from plage and many small random starspots. Our results show that the increased stellar activity levels present on young solar-type stars strongly impacts the detection of Earth-mass and Jupiter-mass planets and that the degree of activity jitter is directly correlated with stellar v sin i. We also show that for G and K dwarfs, the distribution of activity in individual stars is more important than the differences in induced radial velocities as a function of spectral type. We conclude that Jupiter-mass planets can be detected close-in around fast-rotating young active stars, Neptune-mass planets around moderate rotators and that Super-Earths are only detectable around very slowly rotating stars. The effects of an increase in stellar activity jitter by observing younger stars can be compensated for by extending the observational base-line to at least 100 epochs.Peer reviewe

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

Detección de planetas en estrellas activas y estudio de la interacción estrella-planeta: el caso de BD+20 1790

Desde que en 1995 se descubriera el primer exoplaneta, la búsqueda de planetas alrededor de otras estrellas se ha convertido en uno de los campos con mayor productividad en Astrofísica, una auténtica cacería que ha dado como fruto cerca de 2000 nuevos mundos. La fauna planetaria descubierta presenta una diversidad nunca antes imaginada, tan amplia que ha llevado a replantear las teorías de formación de planetas, para poder explicar su existencia. La búsqueda de exoplanetas se ha centrado tradicionalmente en estrellas con niveles muy bajos de actividad. Los surveys de búsqueda de planetas descartaban de manera sistemática las estrellas activas y jóvenes, en favor de estrellas más viejas y menos activas. Esto introduce un importante sesgo observacional en los resultados, dejando sin explorar un importante régimen en el espacio de parámetros, imprescindible para ayudar a reconstruir los escenarios de formación y describir las etapas más tempranas de la evolución de los sistemas planetarios. Detectar planetas en estrellas jóvenes puede proporcionar una información muy valiosa de los mecanismos de formación y su escala temporal. Sin embargo, hay muy pocos planetas detectados en estrellas con edades menores de 100 millones de años. Esta Tesis doctoral se centra en el estudio de la estrella BD+ 20 1790, de tipo espectral K5Ve, excepcionalmente activa (log R′ HK=-3.7) y joven, con una edad estimada de 35-80 millones de años. En comparación con objetos del mismo tipo espectral, velocidad de rotación y rango de edad, BD+20 1790 presenta un nivel de actividad muy elevado, que se manifiesta en una plétora de fenómenos en todas las capas de la atmósfera. Mediante espectroscopía multilongitud de onda con alta resolución espectral y datos fotométricos de varias épocas, se ha podido determinar qué fenómenos ocurren en las distintas capas de la atmósfera de la estrella, su escala temporal y su intensidad. En la cromosfera se detectaron estructuras tipo protuberancia co-rotando con la estrella, localizadas en zonas de inestabilidad lejos del plano ecuatorial, y emisión debida a playas. A partir del análisis fotométrico se encontraron manchas fotosféricas con un factor de cobertura entre 9% y 15%, y que parecen regenerarse en un rango de latitudes. Son numerosas las fulguraciones muy intensas observadas, con una fase de decaimiento de varias horas. La tasa de ocurrencia de fulguraciones es altísima, del orden del 60%. La luminosidad en rayos X es mucho mayor que la promedio para una estrella K de similar edad. Observaciones espectropolarimétricas han permitidomedir por primera vez el campomagnético de la estrella. Las variaciones en la velocidad radial tienen una semiamplitud en torno a 1 km/s. Este hecho junto con el elevado nivel de actividad de la estrella, que no se justifica por su juventud, motivó el estudio de la naturaleza de la variación de las velocidades radiales..

La garantía de protección del derecho a la identidad de género de las personas trans en el ordenamiento jurídico Peruano

La tesis tuv0 c0m0 Problema general: “¿ Como se viene aplicando la garantía de protección del derecho a la identidad de género de las personas trans en el ordenamiento jurídico peruano?; siend0 el Objetivo general: Determinar cóm0 se viene aplicand0 la garantía de pr0tección del derech0 a la identidad de géner0 de las pers0nas trans en el 0rdenamient0 jurídic0 peruan0, y se tuv0 c0m0 Supuesto general: La garantía de pr0tección del derech0 a la identidad de géner0 se garantiza c0n el derech0 de acces0 a la justicia de las pers0nas trans En la investigación se aplicó el método de análisis y síntesis, el mét0d0 hermenéutic0 y el mét0d0 exegétic0, c0n un tip0 de Investigación Básica, en el Nivel de Investigación se utilizó el Descriptiv0 – Explicativ0, c0n un Diseño Descriptiv0. La Población estuv0 c0mpuesta p0r diez d0cument0s s0bre garantía de pr0tección del derech0 a la identidad de géner0 de las pers0nas trans y se t0mó c0m0 muestra la misma cantidad, el muestreo fue n0 pr0babilístic0: muestre0 p0r c0nveniencia. Las Técnicas e Instrumentos de Recolección de datos fueron el análisis d0cumental, c0n Instrumento de evaluación de una ficha estructurada; y las Técnicas de procesamiento de datos fue la utilización de la estadística descriptiva ap0yad0 a análisis de interpretación de dat0s, c0ntrastación de supuest0s estadístic0 de prueba dic0tómica; llegánd0se a la conclusión: A partir de l0s hallazg0s y del análisis de las fuentes se c0nfirma el supuest0 general que la garantía de pr0tección del derech0 a la identidad de géner0 se garantiza c0n el derech0 de acces0 a la justicia de las pers0nas trans

Teaching Astronomy in non-formal education: stars workshop

One of the fields in which teaching Astronomy is more demanded is non-formal education. The Stars Workshop we present in this contribution consisted on an introduction to Astronomy and observation methods. The main objectives were: to know the main components of the Universe, their characteristics and the scales of size and time existing between them; to understand the movement of the different celestial objects; to know the different observational techniques; to value the different historical explanations about the Earth and the position of Humanity in the Universe. This Stars Workshop was a collaboration with the Escuela de Tiempo Libre Jumavi, which is a school dedicated to the training and non-formal education in the leisure field

And the Oscar Goes to: BD+20 1790 for "The Mystery of the Unseen Companion"

BD+20 1790 is a young, rich metal and very active late–type K5Ve star. Our group has been developing a study of stellar activity and kinematics for this star over the past years. Previous results show a high level of stellar activity, with the presence of prominence-like structures, spots on surface and strong flare events. Radial velocity (RV) variations with a semi-amplitude of up to 1km s⁻¹ were detected. When the nature of these variations was investigated it was found that they are not due to stellar activity. Based upon the analysis of bisector velocity span, as well as Ca II H & K emission, we report that the best explanation for RV variations is the presence of a sub–stellar companion. The Keplerian fit of the RV data yields an orbital solution for a close-in massive planet with an orbital period of 7.783days. Also, the presence of this close–in massive planet could be an interpretation for the high level of stellar activity detected

FR Cnc revisited : photometry, polarimetry and spectroscopy

This paper is part of a multiwavelength study aimed at using complementary photometric, polarimetric and spectroscopic data to achieve an understanding of the activity process in late-type stars. Here, we present the study of FR Cnc, a young, active and spotted star. We performed analysis of All Sky Automated Survey 3 (ASAS-3) data for the years 2002-08 and amended the value of the rotational period to be 0.826518 d. The amplitude of photometric variations decreased abruptly in the year 2005, while the mean brightness remained the same, which was interpreted as a quick redistribution of spots. BVRC and I-C broad-band photometric calibration was performed for 166 stars in FR Cnc vicinity. The photometry at Terskol Observatory shows two brightening episodes, one of which occurred at the same phase as the flare of 2006 November 23. Polarimetric BVR observations indicate the probable presence of a supplementary source of polarization. We monitored FR Cnc spectroscopically during the years 2004-08. We concluded that the radial velocity changes cannot be explained by the binary nature of FR Cnc. We determined the spectral type of FR Cnc as K7V. Calculated galactic space-velocity components (U, V, W) indicate that FR Cnc belongs to the young disc population and might also belong to the IC 2391 moving group. Based on Li I lambda 6707.8 measurement, we estimated the age of FR Cnc to be between 10 and 120 Myr. Doppler tomography was applied to create a starspot image of FR Cnc. We optimized the goodness of fit to the deconvolved profiles for axial inclination, equivalent width and v sin i, finding v sin i = 46.2 kms(-1) and i = 55 degrees.. We also generated a synthetic V-band light curve based on Doppler imaging that makes simultaneous use of spectroscopic and photometric data. This synthetic light curve displays the same morphology and amplitude as the observed one. The starspot distribution of FR Cnc is also of interest since it is one of the latest spectral types to have been imaged. No polar spot was detected on FR Cnc.Peer reviewe

Astronomy and astrophysics communication in the UCM Observatory

We present a summary of the last activities of science communication that have taken place in the Observatorio de la Universidad Complutense de Madrid (UCM Observatory) on the occasion of the Third Science Week of the Comunidad Autónoma de Madrid (3–16 November 2003), including guided tours through the observatory facilities, solar observations, and several talks. Moreover the current telescopes, instruments and tools of the UCM Observatory have allowed us to organize other communicating activities such as the live observation, together with its internet broadcast, of total lunar eclipses and other exceptional astronomical events as the Venus transit that took place in 8 June 2004