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

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

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

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