arXiv subjects

Felipe Murgas

Publications and source records attributed to Felipe Murgas.

130 records · Page 8Linked to original sources

arXiv2013

Two Super-Earths Orbiting the Solar Analogue HD41248 on the edge of a 7:5 Mean Motion Resonance

The number of multi-planet systems known to be orbiting their host stars with orbital periods that place them in mean motion resonances is growing. For the most part, these systems are in first-order resonances and dynamical studies have focused their efforts towards understanding the origin and evolution of such dynamically resonant commensurabilities. We report here the discovery of two super-Earths that are close to a second-order dynamical resonance, orbiting the metal-poor ([Fe/H]=-0.43 dex) and inactive G2V star HD41248. We analysed 62 HARPS archival radial velocities for this star, that until now, had exhibited no evidence for planetary companions. Using our new Bayesian Doppler signal detection algorithm, we find two significant signals in the data, with periods of 18.357 days and 25.648 days, indicating they could be part of a 7:5 second-order mean motion resonance. Both semi-amplitudes are below 3m/s and the minimum masses of the pair are 12.3 and 8.6Mearth, respectively. Our simulations found that apsidal alignment stabilizes the system, and even though libration of the resonant angles was not seen, the system is affected by the presence of the resonance and could yet occupy the 7:5 commensurability, which would be the first planetary configuration in such a dynamical resonance. Given the multitude of low-mass multiplanet systems that will be discovered in the coming years, we expect more of these second-order resonant configurations will emerge from the data, highlighting the need for a better understanding of the dynamical interactions between forming planetesimals.

astro-ph.EP↗

arXiv2013

Status of the Calan-Hertfordshire Extrasolar Planet Search

In these proceedings we give a status update of the Calan-Hertfordshire Extrasolar Planet Search, an international collaboration led from Chile that aims to discover more planets around super metal-rich and Sun-like stars, and then follow these up with precision photometry to hunt for new bright transit planets. We highlight some results from this program, including exoplanet and brown dwarf discoveries, and a possible correlation between metallicity and planetary minimum mass at the lowest planetary masses detectable. Finally we discuss the short-term and long-term future pathways this program can take.

astro-ph.EP↗

arXiv2012

A Hot Uranus Orbiting the Super Metal-rich Star HD77338 and the Metallicity - Mass Connection

We announce the discovery of a low-mass planet orbiting the super metal-rich K0V star HD77338 as part of our on-going Calan-Hertfordshire Extrasolar Planet Search. The best fit planet solution has an orbital period of 5.7361\pm0.0015 days and with a radial velocity semi-amplitude of only 5.96\pm1.74 m/s, we find a minimum mass of 15.9+4.7-5.3 Me. The best fit eccentricity from this solution is 0.09+0.25-0.09, and we find agreement for this data set using a Bayesian analysis and a periodogram analysis. We measure a metallicity for the star of +0.35\pm0.06 dex, whereas another recent work (Trevisan et al. 2011) finds +0.47\pm0.05 dex. Thus HD77338b is one of the most metal-rich planet host stars known and the most metal-rich star hosting a sub-Neptune mass planet. We searched for a transit signature of HD77338b but none was detected. We also highlight an emerging trend where metallicity and mass seem to correlate at very low masses, a discovery that would be in agreement with the core accretion model of planet formation. The trend appears to show that for Neptune-mass planets and below, higher masses are preferred when the host star is more metal-rich. Also a lower boundary is apparent in the super metal-rich regime where there are no very low-mass planets yet discovered in comparison to the sub-solar metallicity regime. A Monte Carlo analysis shows that this, low-mass planet desert, is statistically significant with the current sample of 36 planets at around the 4.5σ level. In addition, results from Kepler strengthen the claim for this paucity of the lowest-mass planets in super metal-rich systems. Finally, this discovery adds to the growing population of low-mass planets around low-mass and metal-rich stars and shows that very low-mass planets can now be discovered with a relatively small number of data points using stable instrumentation.

astro-ph.EP↗

arXiv2011

Detection of transit timing variations in excess of one hour in the Kepler multi-planet candidate system KOI 806 with the GTC

We report the detection of transit timing variations (TTVs) well in excess of one hour in the Kepler multi-planet candidate system KOI 806. This system exhibits transits consistent with three separate planets -- a Super-Earth, a Jupiter, and a Saturn -- lying very nearly in a 1:2:5 resonance, respectively. We used the Kepler public data archive and observations with the Gran Telescopio de Canarias to compile the necessary photometry. For the largest candidate planet (KOI 806.02) in this system, we detected a large transit timing variation of -103.5$\pm$6.9 minutes against previously published ephemeris. We did not obtain a strong detection of a transit color signature consistent with a planet-sized object; however, we did not detect a color difference in transit depth, either. The large TTV is consistent with theoretical predictions that exoplanets in resonance can produce large transit timing variations, particularly if the orbits are eccentric. The presence of large TTVs among the bodies in this systems indicates that KOI806 is very likely to be a planetary system. This is supported by the lack of a strong color dependence in the transit depth, which would suggest a blended eclipsing binary.

astro-ph.SR↗