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The magnetic activity levels of planet host stars may differ from that of stars not known to host planets in several ways. Hot Jupiters may induce activity in their hosts through magnetic interactions, or through tidal interactions by…
Stellar activity may induce Doppler variability at the level of a few m/s which can then be confused by the Doppler signal of an exoplanet orbiting the star. To first order, linear correlations between radial velocity measurements and…
As is the case for all techniques involved in the research for exoplanets, direct imaging has to take into account the probability of so-called astrophysical false positives, which are phenomena that mimic the signature of objects we are…
Stellar magnetic activity is governed by the interplay between rotation, convection, and the evolution of surface magnetic structures, yet the role of planetary systems in shaping these processes remains uncertain. Here, we analyze…
The magnetic activity of planet-hosting stars is an important factor to estimate the atmospheric stability of close-in exoplanets and the age of their host stars. It has long been speculated that close-in exoplanets can influence the…
Empirical evidence suggests a tantalising but unproven link between various indicators of solar activity and the barycentric motion of the Sun. The latter is exemplified by transitions between regular and more disordered motion modulated by…
Stellar activity can be a source of radial velocity (RV) noise and can reproduce periodic RV variations similar to those produced by an exoplanet. We present the vigorous activity cycle in the primary of the visual binary HD200466, a system…
Exoplanets which are detected using the radial velocity technique have a well-known ambiguity of their true mass, caused by the unknown inclination of the planetary orbit with respect to the plane of the sky. Constraints on the inclination…
The stable oscillations of pulsating stars can serve as accurate timepieces, which may be monitored for the influence of exoplanets. An external companion gravitationally tugs the host star, causing periodic changes in pulsation arrival…
Robertson et al.(Reports, July 25 2014, p440-444)(1) claimed that activity-induced variability is responsible for the Doppler signal of the proposed planet candidate GJ 581d. We point out that their analysis using periodograms of residual…
Of the hundreds of exoplanets discovered using the radial velocity technique, many are orbiting close to their host stars with periods less than 10 days. One of these, HD 63454, is a young active K dwarf which hosts a Jovian planet in a…
Aims: Stellar activity may complicate the analysis of high-precision radial-velocity spectroscopic data when looking for exoplanets signatures. We aim at quantifying the impact of stellar spots on stars with various spectral types and…
The radial velocity method for detecting extra-solar planets relies on measuring the star's wobble around the system's center of mass. Since this is an indirect method, we may ask if there are other dynamical effects that can mimic such…
We present the results of radial velocity measurements of two samples of active stars. The first sample contains field G and K giants across the Red Giant Branch, whereas the second sample consists of nearby young stars (d < 150 pc) with…
Extra-solar planet search programs require high-precision velocity measurements. They need to study how to disentangle radial-velocity variations due to Doppler motion from the noise induced by stellar activity. We monitored the active K2V…
BD+20 1790 is a young active, metal-rich, late-type K5Ve star. We have undertaken a study of stellar activity and kinematics for this star over the past few years. Previous results show a high level of stellar activity, with the presence of…
A radial velocity (RV) survey to detect central stars in binary systems was carried out between 2002 and 2004. De Marco et al. (2004) reported that 10 out of 11 monitored stars exhibited strong RV variability, but periods were not detected.…
We have been using the Keck I High Resolution Spectrograph (HIRES) to search for planetary companions in the Hyades cluster. We selected four stars from this sample which showed significant radial velocity variability on short timescales to…
Upcoming space-based photometric satellites offer the possibility of detecting continuum flux variability at the micro-magnitude level. We show that the Doppler flux variability induced by the reflex motion of stars due to planetary…
This paper presents the simultaneous Bayesian analysis of the radial velocity and activity indices for the K5Ve active star BD+20 1790, that was proposed to host a close-in massive planet by Hern\'an-Obispo et al. (2010). The Bayesian…