Aims. In this work we present chromospheric activity indices, kinematics, radial-velocities, and rotational velocities for more than 850 FGK-type dwarfs and subgiant stars in the southern hemisphere and test how best to calibrate and measure S -indices from echelle spectra. Methods. We measured our parameters using the high-resolution and high-S /N FEROS echelle spectra acquired for this purpose. Results. We confirm the bimodal distribution of chromospheric activities for such stars and highlight the role that the more active K-dwarfs play in biasing the number of active stars. We show that the age-activity relationship does appear to continue to ages older than the Sun if we simply compare main sequence stars and subgiant stars with an offset of around 2.5 Gyr between the peaks of both distributions. Also we show evidence of an increased spin-down timescale for cool K dwarfs compared with earlier F and G type stars. We highlight that activities drawn from low-resolution spectra (R < 2500) significantly increase the rms scatter when calibrating onto common systems of measurements like the Mt. Wilson system. Also we show that older and widely used catalogues of activities in the south appear to be offset compared to more recent works at the ∼0.1 dex level in log R HK through calibrator drift. In addition, we show how kinematics can be used to preselect inactive stars for future planet search projects. We see the well known trend between projected rotational velocity and activity, however we also find a correlation between kinematic space velocity and chromospheric activity. It appears that after the Vaughan-Preston gap there is a quick step function in the kinematic space motion towards a significantly broader spread in velocities. We speculate on reasons for this correlation and provide some model scenarios to describe the bimodal activity distribution through magnetic saturation, residual low level gas accretion, or accretion by the star of planets or planetesimals. Finally, we provide a new empirical measurement for the disk-heating law, using the latest age-activity relationships to reconstruct the age-velocity distribution for local disk stars. We find a value of 0.337 ± 0.045 for the exponent of this power law (i.e. σ tot ∝ t 0.337 ), in excellent agreement with those found using isochrone fitting methods and with theoretical disk-heating models.

We use early-time photometry and spectroscopy of 12 Type II plateau supernovae (SNe IIP) to derive their distances using the expanding photosphere method (EPM). We perform this study using two sets of Type II supernova (SN II) atmosphere models, three filter subsets ({BV }, {BV I}, {V I}), and two methods for the host-galaxy extinction, which leads to 12 Hubble diagrams. We find that systematic differences in the atmosphere models lead to ∼ 50% differences in the EPM distances and to a value of H 0 between 52 and 101 km s −1 Mpc −1 . Using the {V I} filter subset we obtain the lowest dispersion in the Hubble diagram, σ µ = 0.32 mag. We also apply the EPM analysis to the well-observed SN IIP 1999em. With the {V I} filter subset we derive a distance ranging from 9.3 ± 0.5 Mpc to 13.9 ± 1.4 Mpc depending on the atmosphere model employed.-2on their light curves into Type IIP (plateau) and Type IIL (linear) (e.g., Patat et al. 1994). The former present a nearly constant optical luminosity during the photospheric phase (∼ 100 days after explosion), while the latter show a slow decline in luminosity during that phase. However, there are some SN II events, such as the SN 1987A, that show peculiar photometric properties. Also, studies of SN II spectra have revealed the existence of a subclass, characterized by the presence of narrow spectral lines, called SNe IIn (Schlegel 1990; Filippenko 1991a,b), which are most likely originated from the interaction of the SN ejecta with pre-existing circumstellar material; see Filippenko (1997) for a general review of SN spectra.Due to their high intrinsic luminosities, SNe II have great potential as extragalactic distance indicators. To date, several methods have been proposed to derive distances to SNe II, but two are the most commonly used: the expanding photosphere method (EPM) (Kirshner & Kwan 1974) and the standardized candle method (SCM) (Hamuy & Pinto 2002). The former is a geometrical technique that relates the photospheric radius and the angular radius of a SN in order to derive its distance, and has been applied to several SNe to derive the Hubble constant (e.g., Schmidt et al. 1992). The EPM is independent of the extragalactic distance ladder, and therefore does not need any external calibration. The SCM is based on the observed relation between expansion velocity and luminosity of SNe IIP. Recently, this method has been applied to a sample of high-redshift SNe (Nugent et al. 2006). Other methods have also been used to determine distances to SNe II, such as the spectral-fitting expanding atmosphere method (SEAM) ( Baron et al. 2004) and the plateau-tail relation proposed by Nadyozhin (2003).In this work we apply the EPM using early spectroscopy and photometry of 12 SNe IIP in order to derive their distances. We apply the method using two sets of SN II atmosphere models (Eastman et al. 1996;Dessart & Hillier 2005a), three filter subsets ({BV }, {BV I}, {V I}), and two methods for the host-galaxy extinction. The different combinations lead to 12 Hubble diagrams. Section 2 of...

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Context. More than 50 exoplanets have been found around giant stars, revealing different properties when compared to planets orbiting solar-type stars. In particular, they are super-Jupiters and are not found orbiting interior to ∼0.5 AU. Aims. We are conducting a radial velocity study of a sample of 166 giant stars aimed at studying the population of close-in planets orbiting giant stars and how their orbital and physical properties are influenced by the post-MS evolution of the host star. Methods. We have collected multiepoch spectra for all of the targets in our sample. We have computed precision radial velocities from FECH/CHIRON and FEROS spectra, using the I 2 cell technique and the simultaneous calibration method, respectively. Results. We present the discovery of a massive planet around the giant star HIP 105854. The best Keplerian fit to the data leads to an orbital distance of 0.81 ± 0.03 AU, an eccentricity of 0.02 ± 0.03 and a projected mass of 8.2 ± 0.2 M J . With the addition of this new planet discovery, we performed a detailed analysis of the orbital properties and mass distribution of the planets orbiting giant stars. We show that there is an overabundance of planets around giant stars with a ∼ 0.5−0.9 AU, which might be attributed to tidal decay. Additionally, these planets are significantly more massive than those around MS and subgiant stars, suggesting that they grow via accretion either from the stellar wind or by mass transfer from the host star. Finally, we show that planets around evolved stars have lower orbital eccentricities than those orbiting solar-type stars, which suggests that they are either formed in different conditions or that their orbits are efficiently circularized by interactions with the host star.

Context. To date, more than 30 planets have been discovered around giant stars, but only one of them has been found to be orbiting within 0.6 AU from the host star, in direct contrast to what is observed for FGK dwarfs. This result suggests that evolved stars destroy/engulf close-in planets during the red giant phase. Aims. We are conducting a radial velocity survey of 164 bright G and K giant stars in the southern hemisphere with the aim of studying the effect of the host star evolution on the inner structure of planetary systems. In this paper we present the spectroscopic atmospheric parameters (T eff , log g, ξ, [Fe/H]) and the physical properties (mass, radius, evolutionary status) of the program stars. In addition, rotational velocities for all of our targets were derived. Methods. We used high resolution and high S/N spectra to measure the equivalent widths of many Fe i and Fe ii lines, which were used to derive the atmospheric parameters by imposing local thermodynamic and ionization equilibrium. The effective temperatures and metallicities were used, along with stellar evolutionary tracks to determine the physical properties and evolutionary status of each star. Results. We found that our targets are on average metal rich and they have masses between ∼1.0 M and 3.5 M . In addition, we found that 122 of our targets are ascending the RGB, while 42 of them are on the HB phase.

Context. Exoplanet searches have revealed interesting correlations between the stellar properties and the occurrence rate of planets. In particular, different independent surveys have demonstrated that giant planets are preferentially found around metal-rich stars and that their fraction increases with the stellar mass. Aims. During the past six years we have conducted a radial velocity follow-up program of 166 giant stars to detect substellar companions and to characterize their orbital properties. Using this information, we aim to study the role of the stellar evolution in the orbital parameters of the companions and to unveil possible correlations between the stellar properties and the occurrence rate of giant planets. Methods. We took multi-epoch spectra using FEROS and CHIRON for all of our targets, from which we computed precision radial velocities and derived atmospheric and physical parameters. Additionally, velocities computed from UCLES spectra are presented here. By studying the periodic radial velocity signals, we detected the presence of several substellar companions. Results. We present four new planetary systems around the giant stars HIP 8541, HIP 74890, HIP 84056, and HIP 95124. Additionally, we study the correlation between the occurrence rate of giant planets with the stellar mass and metallicity of our targets. We find that giant planets are more frequent around metal-rich stars, reaching a peak in the detection of f = 16.7 +15.5 −5.9 % around stars with [Fe/H] ∼ 0.35 dex. Similarly, we observe a positive correlation of the planet occurrence rate with the stellar mass, between M ∼ 1.0 and 2.1 M , with a maximum of f = 13.0Conclusions. We conclude that giant planets are preferentially formed around metal-rich stars. In addition, we conclude that they are more efficiently formed around more massive stars, in the stellar mass range of ∼1.0-2.1 M . These observational results confirm previous findings for solar-type and post-MS hosting stars, and provide further support to the core-accretion formation model.

Radial velocity observations from three instruments reveal the presence of a 4 M Jup planet candidate orbiting the K giant HD 76920. HD 76920b has an orbital eccentricity of 0.856±0.009, making it the most eccentric planet known to orbit an evolved star. There is no indication that HD 76920 has an unseen binary companion, suggesting a scattering event rather than Kozai oscillations as a probable culprit for the observed eccentricity. The candidate planet currently approaches to about four stellar radii from its host star, and is predicted to be engulfed on a ∼100 Myr timescale due to the combined effects of stellar evolution and tidal interactions.

We report the discovery of a brown dwarf on an eccentric orbit and with a semimajor axis that places it in the brown dwarf desert region around the star HD 191760. The star has a spectral type of G3IV/V and a metallicity ([Fe/H]) of 0.29 dex. HD 191760 adds to the small number of metal‐rich stars with brown dwarf companions. The brown dwarf (HD 191760b) is found to have an orbital period of 505.57 ± 0.40 d and semimajor axis of 1.35 ± 0.01 au, placing it firmly in the brown dwarf desert. The eccentricity of HD 191760b is found to be 0.63 ± 0.01, meaning it reaches as close as 0.5 au from the host star. Dynamical simulations indicate that no inner planets could reside at separations beyond ∼0.17 au due to the disastrous gravity imposed by HD 191760b. In addition to these first results, we also refine the orbits found for the exoplanets around the stars HD 48265, HD 143361 and HD 154672. All one‐planet solutions are in agreement with those previously published by the Magellan Planet Search.