arXiv subjects

P. Cubillos

Publications and source records attributed to P. Cubillos.

3 recordsLinked to original sources

arXiv2023

A super-massive Neptune-sized planet

Neptune-sized planets exhibit a wide range of compositions and densities, depending onf cators related to their formation and evolution history, such as the distance from their host stars and atmospheric escape processes. They can vary from relatively low-density planets with thick hydrogen-helium atmospheres to higher-density planets with a substantial amount of water or a rocky interior with a thinner atmosphere, such as HD 95338 b, TOI-849 b and TOI-2196 b. The discovery of exoplanets in the hot-Neptune desert, a region close to the host stars with a deficit of Neptune-sized planets, provides insights into the formation and evolution of planetary systems, including the existence of this region itself. Here we show observations of the transiting planet TOI-1853 b, which has a radius of 3.46 +- 0.08 Earth radii and orbits a dwarf star every 1.24 days. This planet has a mass of 73.2 +- 2.7 Earth masses, almost twice that of any other Neptune-sized planet known so far, and a density of 9.7 +- 0.8 grams per cubic centimetre. These values place TOI-1853 b in the middle of the Neptunian desert and imply that heavy elements dominate its mass. The properties of TOI-1853 b present a puzzle for conventional theories of planetary formation and evolution, and could be the result of several proto-planet collisions or the final state of an initially high-eccentricity planet that migrated closer to its parent star.

astro-ph.EP↗

arXiv2020

Mitigating flicker noise in high-precision photometry. I -- Characterization of the noise structure, impact on the inferred transit parameters, and predictions for CHEOPS observations

In photometry, the short-timescale stellar variability ("flicker"), such as that caused by granulation and oscillations, can reach amplitudes comparable to the transit depth of Earth-sized planets and is correlated over the typical transit timescales. It can introduce systematic errors on the inferred planetary parameters when a small number of transits are observed. The objective of this paper is to characterize the statistical properties of this noise and quantify its impact on the inferred transit parameters. We used the extensive solar observations obtained with SoHO/VIRGO to characterize flicker noise. We simulated realistic transits across the solar disk using SDO/HMI data and used these to obtain transit light curves, which we used to estimate the errors made on the transit parameters. We make these light curves publicly available. To extend the study to a wider parameter range, we derived the properties of flicker noise using Kepler observations and studied their dependence on stellar parameters. Finally, we predicted the limiting stellar apparent magnitude for which the properties of the flicker noise can be extracted using high-precision CHEOPS and PLATO observations. Stellar granulation is a stochastic colored noise, and is stationary with respect to the stellar magnetic cycle. Both the flicker correlation timescales and amplitudes increase with the stellar mass and radius. If these correlations are not taken into account when fitting for the parameters of transiting exoplanets, this can bias the inferred parameters. In particular, we find errors of up to 10$\%$ on $R_p/R_s$ for an Earth-sized planet orbiting a Sun-like star. For F and G stars, flicker will significantly affect the inferred parameters of transits observed with CHEOPS and PLATO. Dedicated modeling strategies need to be developed to accurately characterize both the star and the transiting exoplanets.

astro-ph.EP↗

arXiv2011

Detection of a transit of the super-Earth 55 Cnc e with Warm Spitzer

We report on the detection of a transit of the super-Earth 55 Cnc e with warm Spitzer in IRAC's 4.5-micron band. Our MCMC analysis includes an extensive modeling of the systematic effects affecting warm Spitzer photometry, and yields a transit depth of 410 +- 63 ppm, which translates to a planetary radius of 2.08 +- 0.16 R_Earth as measured in IRAC 4.5-micron channel. A planetary mass of 7.81 +- 0.58 M_Earth is derived from an extensive set of radial-velocity data, yielding a mean planetary density of 4.8 +- 1.3 g cm-3. Thanks to the brightness of its host star (V = 6, K = 4), 55 Cnc e is a unique target for the thorough characterization of a super-Earth orbiting around a solar-type star.

astro-ph.EP↗