arXiv subjects

Riccardo Papini

Publications and source records attributed to Riccardo Papini.

5 recordsLinked to original sources

arXiv2025

Confirmation of four hot Jupiters detected by TESS using follow-up spectroscopy from MaHPS at Wendelstein together with NEID and TRES

We report the confirmation and characterization of four hot Jupiter-type exoplanets initially detected by TESS: TOI-1295 b, TOI-2580 b, TOI-6016 b, and TOI-6130 b. Using observations with the high-resolution echelle spectrograph MaHPS on the 2.1m telescope at Wendelstein Observatory, together with NEID at Kitt Peak National Observatory and TRES at the Fred Lawrence Whipple Observatory, we confirmed the planetary nature of these four planet candidates. We also performed precise mass measurements. All four planets are found to be hot Jupiters with orbital periods between 2.4 and 4.0 days. The sizes of these planets range from 1.29 to 1.64 Jupiter radii, while their masses range from 0.6 to 1.5 Jupiter masses. Additionally, we investigated whether there are signs of other planets in the systems but have found none. Lastly, we compared the radii of our four objects to the results of an empirical study of radius inflation and see that all four demonstrate a good fit with the current models. These four planets belong to the first array of planets confirmed with MaHPS data, supporting the ability of the spectrograph to detect planets around fainter stars as faint as V=12.

astro-ph.EP↗

arXiv2024

OrCAS: Origins, Compositions, and Atmospheres of Sub-neptunes. I. Survey Definition

Sub-Neptunes - volatile-rich exoplanets smaller than Neptune - are intrinsically the most common type of planet known. However, the formation and nature of these objects, as well as the distinctions between sub-classes (if any), remain unclear. Two powerful tools to tease out the secrets of these worlds are measurements of (i) atmospheric composition and structure revealed by transit and/or eclipse spectroscopy, and (ii) mass, radius, and density revealed by transit photometry and Doppler spectroscopy. Here we present OrCAS, a survey to better elucidate the origins, compositions, and atmospheres of sub-Neptunes. This radial velocity survey uses a repeatable, quantifiable metric to select targets suitable for subsequent transmission spectroscopy and address key science themes about the atmospheric & internal compositions and architectures of these systems. Our survey targets 26 systems with transiting sub-Neptune planet candidates, with the overarching goal of increasing the sample of such planets suitable for subsequent atmospheric characterization. This paper lays out our survey's science goals, defines our target prioritization metric, and performs light-curve fits and statistical validation using existing TESS photometry and ground-based follow-up observations. Our survey serves to continue expanding the sample of small exoplanets with well-measured properties orbiting nearby bright stars, ensuring fruitful studies of these systems for many years to come.

astro-ph.EP↗

arXiv2022

TOI-2196 b: Rare planet in the hot Neptune desert transiting a G-type star

Highly irradiated planets in the hot Neptune desert are usually either small (R < 2 Rearth) and rocky or they are gas giants with radii of >1 Rjup. Here, we report on the intermediate-sized planet TOI-2196 on a 1.2 day orbit around a G-type star discovered by TESS in sector 27. We collected 42 radial velocity measurements with the HARPS spectrograph to determine the mass. The radius of TOI-2196 b is 3.51 +/- 0.15 Rearth, which, combined with the mass of 26.0 +/- 1.3 Mearth, results in a bulk density of 3.31+0.51-0.43 g/cm3. Hence, the radius implies that this planet is a sub-Neptune, although the density is twice than that of Neptune. A significant trend in the HARPS radial velocities points to the presence of a distant companion with a lower limit on the period and mass of 220 days and 0.65 Mjup, respectively, assuming zero eccentricity. The short period of planet b implies a high equilibrium temperature of 1860 +/- 20 K, for zero albedo and isotropic emission. This places the planet in the hot Neptune desert, joining a group of very few planets in this parameter space discovered in recent years. These planets suggest that the hot Neptune desert may be divided in two parts for planets with equilibrium temperatures of > 1800 K: a hot sub-Neptune desert devoid of planets with radii of 1.8-3 Rearth and a sub-Jovian desert for radii of 5-12 Rearth. More planets in this parameter space are needed to further investigate this finding. Planetary interior structure models of TOI-2196 b are consistent with a H/He atmosphere mass fraction between 0.4 % and 3 %, with a mean value of 0.7 % on top of a rocky interior. We estimated the amount of mass this planet might have lost at a young age, and we find that while the mass loss could have been significant, the planet had not changed in terms of character: it was born as a small volatile-rich planet, and it remains one at present.

astro-ph.EP↗

arXiv2021

TOI-1278 B: SPIRou unveils a rare Brown Dwarf Companion in Close-In Orbit around an M dwarf

We present the discovery of an $18.5\pm0.5$M$_{\rm Jup}$ brown dwarf (BD) companion to the M0V star TOI-1278. The system was first identified through a percent-deep transit in TESS photometry; further analysis showed it to be a grazing transit of a Jupiter-sized object. Radial velocity (RV) follow-up with the SPIRou near-infrared high-resolution velocimeter and spectropolarimeter in the framework of the 300-night SPIRou Legacy Survey (SLS) carried out at the Canada-France-Hawaii Telescope (CFHT) led to the detection of a Keplerian RV signal with a semi-amplitude of $2306\pm10$ m/s in phase with the 14.5-day transit period, having a slight but non-zero eccentricity. The intermediate-mass ratio ($M_\star/M_{\rm{comp}} \sim31$) is unique for having such a short separation ($0.095\pm0.001$ AU) among known M-dwarf systems. Interestingly, M dwarf-brown dwarf systems with similar mass ratios exist with separations of tens to thousands of AUs.

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arXiv2020

Discovery of a pre-cataclysmic binary with unusual chromaticity of the eclipsed white dwarf by the GPX Survey

We report the discovery of a relatively bright eclipsing binary system, which consists of a white dwarf and a main sequence K7 star with clear signs of chromospheric and spot activity. The light curve of this system shows $\sim0.2$mag ellipsoidal variability with a period of 0.297549d and a short total eclipse of the white dwarf. Based on our analysis of the spectral and photometric data, we estimated the parameters of the system. The K7V star is tidally deformed but does not fill its Roche lobe (the filling factor is about 0.86). The orbital inclination is $i=73^\circ.1\pm 0^\circ.2$, the mass ratio is $q=M_2/M_1\approx 0.88$. The parameters of the K7V star are $M_2\approx 0.64$M$_{\odot}$, $R_2=0.645\pm 0.012$R$_{\odot}$, $T_2\approx 4070$K. The parameters of the white dwarf are $M_1\approx 0.72$M$_{\odot}$, $R_1=0.013\pm 0.003$R$_{\odot}$, $T_1=8700\pm 1100$K. Photometric observations in different bands revealed that the maximum depth of the eclipse is in the \textit{SDSS r} filter, which is unusual for a system of a white dwarf and a late main sequence star. We suspect that this system is a product of the evolution of a common envelope binary star, and that the white dwarf accretes the stellar wind from the secondary star (the so-called low-accretion rate polar, LARP).

astro-ph.SR↗