arXiv subjects

Enric Palle

Publications and source records attributed to Enric Palle.

171 records · Page 10Linked to original sources

arXiv2016

Ruling out the orbital decay of the WASP-43b

We present 15 new transit observations of the exoplanet WASP-43b in the $i'$,$g'$, and $R$ filters with the 1.0-m telescopes of Las Cumbres Observatory Global Telescope (LCOGT) Network and the IAC80 telescope. We combine our 15 new light curves with 52 others from literature, to analyze homogeneously all the available transit light curves of this exoplanet. By extending the time span of the monitoring of the transits to more than $5~yr$, and by analyzing the individual mid-times of 72 transits, we study the proposed shortening of the orbital period of WASP-43b. We estimate that the times of transit are well-matched by our updated ephemeris equation, using a constant orbital period. We estimate an orbital period change rate no larger than $\dot{P}=-0.02 \pm 6.6~ms~yr^{-1}$, which is fully consistent with a constant period. Based on the timing analysis, we discard stellar tidal dissipation factors $Q_{*}<10^{5}$. In addition, with the modelling of the transits we update the system parameters: $a/Rs=4.867(23)$, $i=82.11(10)^{\circ}$ and $R_p/R_s=0.15942(41)$, noticing a difference in the relative size of the planet between optical and NIR bands.

astro-ph.EP↗

arXiv2016

The K2-ESPRINT Project II: Spectroscopic follow-up of three exoplanet systems from Campaign 1 of K2

We report on Doppler observations of three transiting planet candidates that were detected during Campaign 1 of the K2 mission. The Doppler observations were conducted with FIES, HARPS-N and HARPS. We measure the mass of K2-27b (EPIC 201546283b), and provide constraints and upper limits for EPIC 201295312b and EPIC 201577035b. K2-27b is a warm Neptune orbiting its host star in 6.77 days and has a radius of $4.45^{+0.33}_{-0.33}~\mathrm{R_\oplus}$ and a mass of $29.1^{+7.5}_{-7.4}~\mathrm{M_\oplus}$, which leads to a mean density of $1.80^{+0.70}_{-0.55}~\mathrm{g~cm^{-3}}$. EPIC 201295312b is smaller than Neptune with an orbital period of 5.66 days, radius $2.75^{+0.24}_{-0.22}~\mathrm{R_\oplus}$ and we constrain the mass to be below $12~\mathrm{M_\oplus}$ at 95% confidence. We also find a long-term trend indicative of another body in the system. EPIC 201577035b, previously confirmed as the planet K2-10b, is smaller than Neptune orbiting its host star in 19.3 days, with radius $3.84^{+0.35}_{-0.34}~\mathrm{R_\oplus}$. We determine its mass to be $27^{+17}_{-16}~\mathrm{M_\oplus}$, with a 95% confidence uppler limit at $57~\mathrm{M_\oplus}$, and mean density $2.6^{+2.1}_{-1.6}~{\rm g~cm}^{-3}$. These measurements join the relatively small collection of planets smaller than Neptune with measurements or constraints of the mean density. Our code for performing K2 photometry and detecting planetary transits is now publicly available.

astro-ph.EP↗

arXiv2015

WASP-135b: a highly irradiated, inflated hot Jupiter orbiting a G5V star

We report the discovery of a new transiting planet from the WASP survey. WASP-135b is a hot Jupiter with a radius of 1.30 pm 0.09 Rjup, a mass of 1.90 pm 0.08 Mjup and an orbital period of 1.401 days. Its host is a Sun-like star, with a G5 spectral type and a mass and radius of 0.98 pm 0.06 Msun and 0.96 pm 0.05 Rsun respectively. The proximity of the planet to its host means that WASP-135b receives high levels of insolation, which may be the cause of its inflated radius. Additionally, we find weak evidence of a transfer of angular momentum from the planet to its star.

astro-ph.EP↗

arXiv2014

Kepler-432 b: a massive warm Jupiter in a 52-day eccentric orbit transiting a giant star

We study the Kepler object Kepler-432, an evolved star ascending the red giant branch. By deriving precise radial velocities from multi-epoch high-resolution spectra of Kepler-432 taken with the CAFE spectrograph at the 2.2m telescope of Calar Alto Observatory and the FIES spectrograph at the Nordic Optical Telescope of Roque de Los Muchachos Observatory, we confirm the planetary nature of the object Kepler-432 b, which has a transit period of 52 days. We find a planetary mass of Mp=5.84 +\- 0.05 Mjup and a high eccentricity of e=0.478 +\- 0.004. With a semi-major axis of a=0.303 +\- 0.007 AU, Kepler-432 b is the first bona fide warm Jupiter detected to transit a giant star. We also find a radial velocity linear trend of 0.44 +\- 0.04 m s$^{-1}$ d$^{-1}$, which suggests the presence of a third object in the system. Current models of planetary evolution in the post-main-sequence phase predict that Kepler-432 b will be most likely engulfed by its host star before the latter reaches the tip of the red giant branch.

astro-ph.EP↗

arXiv2014

The Transiting Exoplanet Survey Satellite

The Transiting Exoplanet Survey Satellite (TESS) will search for planets transiting bright and nearby stars. TESS has been selected by NASA for launch in 2017 as an Astrophysics Explorer mission. The spacecraft will be placed into a highly elliptical 13.7-day orbit around the Earth. During its two-year mission, TESS will employ four wide-field optical CCD cameras to monitor at least 200,000 main-sequence dwarf stars with I = 4-13 for temporary drops in brightness caused by planetary transits. Each star will be observed for an interval ranging from one month to one year, depending mainly on the star's ecliptic latitude. The longest observing intervals will be for stars near the ecliptic poles, which are the optimal locations for follow-up observations with the James Webb Space Telescope. Brightness measurements of preselected target stars will be recorded every 2 min, and full frame images will be recorded every 30 min. TESS stars will be 10-100 times brighter than those surveyed by the pioneering Kepler mission. This will make TESS planets easier to characterize with follow-up observations. TESS is expected to find more than a thousand planets smaller than Neptune, including dozens that are comparable in size to the Earth. Public data releases will occur every four months, inviting immediate community-wide efforts to study the new planets. The TESS legacy will be a catalog of the nearest and brightest stars hosting transiting planets, which will endure as highly favorable targets for detailed investigations.

astro-ph.EP↗

arXiv2012

A cosmic ray-climate link and cloud observations

Despite over 35 years of constant satellite-based measurements of cloud, reliable evidence of a long-hypothesized link between changes in solar activity and Earth's cloud cover remains elusive. This work examines evidence of a cosmic ray cloud link from a range of sources, including satellite-based cloud measurements and long-term ground-based climatological measurements. The satellite-based studies can be divided into two categories: 1) monthly to decadal timescale correlations, and 2) daily timescale epoch-superpositional (composite) analysis. The latter analyses frequently focus on high-magnitude reductions in the cosmic ray flux known as Forbush Decrease (FD) events. At present, two long-term independent global satellite cloud datasets are available (ISCCP and MODIS). Although the differences between them are considerable, neither shows evidence of a solar-cloud link at either long or short timescales. Furthermore, reports of observed correlations between solar activity and cloud over the 1983 to 1995 period are attributed to the chance agreement between solar changes and artificially induced cloud trends. It is possible that the satellite cloud datasets and analysis methods may simply be too insensitive to detect a small solar signal. Evidence from ground-based studies suggests that some weak but statistically significant CR-cloud relationships may exist at regional scales, involving mechanisms related to the global electric circuit. However, a poor understanding of these mechanisms and their effects on cloud make the net impacts of such links uncertain. Regardless of this, it is clear that there is no robust evidence of a widespread link between the cosmic ray flux and clouds.

physics.ao-ph↗

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↗

arXiv2009

The transmission spectrum of Earth through lunar eclipse observations

Of the 342 planets discovered so far orbiting other stars, 58 "transit" the stellar disk, meaning that they can be detected by a periodic decrease in the starlight flux. The light from the star passes through the atmosphere of the planet, and in a few cases the basic atmospheric composition of the planet can be estimated. As we get closer to finding analogues of Earth, an important consideration toward the characterization of exoplanetary atmospheres is what the transmission spectrum of our planet looks like. Here we report the optical and near-infrared transmission spectrum of the Earth, obtained during a lunar eclipse. Some biologically relevant atmospheric features that are weak in the reflected spectrum (such as ozone, molecular oxygen, water, carbon dioxide and methane) are much stronger in the transmission spectrum, and indeed stronger than predicted by modelling. We also find the fingerprints of the Earth's ionosphere and of the major atmospheric constituent, diatomic nitrogen (N2), which are missing in the reflected spectrum.

astro-ph.EP↗

arXiv2009

Earthshine observations of an inhabited planet

Earthshine is sunlight that has been reflected from the dayside Earth onto the dark side of the Moon and back again to Earth. In recent times, there has been renewed interest in ground-based visible and near-infrared measurements of earthshine as a proxy for exoplanet observations. Observations of earthshine allow us to explore and characterize the globally integrated photometric, spectral and polarimetric features of the Earth, and to extract precise information on the distinctive characteristics of our planet, and life in particular. They also allow us to quantify how this feature changes with time and orbital configuration. Here we present a brief review of the main earthshine observations and results.

astro-ph.EP↗