arXiv subjects

Sebastian Pérez

Publications and source records attributed to Sebastian Pérez.

3 recordsLinked to original sources

arXiv2026

SaNDi-SHoP: Searching for Satellites'N'Disks with a Star-Hopping Program II. Spectrophotometric analysis and orbital monitoring of directly imaged companions

Over the past decade, advances in high-contrast imaging instrumentation, coupled with extreme adaptive optics systems, have enabled the discovery of tens of planets and brown dwarfs orbiting at wide separations from their host stars (a larger than 10 au). The existence of companions at these separations challenges current planet-formation paradigms, highlighting the importance of high-contrast imaging as the only technique capable of directly probing this region of planetary systems. In this paper, we present a survey of thirteen planets and brown dwarfs observed with VLT/SPHERE between June 2023 and July 2025. These data provide updated photometry in the 1.0-1.7 micron range and new high-precision astrometry, enabling tighter constraints on their orbital properties. We used the IRDIS subsystem to acquire dual-band H2H3 images (H2 = 1.593 microns, H3 = 1.667 microns) for all companions in our sample. For the three objects located within the IFS field of view (GQ Lup B, PZ Tel B, and HD 984 B), we additionally obtained low-resolution (R ~ 50) near-infrared (0.96-1.34 micron) spectra. We combined our new astrometric measurements with those available in the literature to derive updated orbital solutions. The orbital fitting was performed using the orbitize! Python package. For CT Cha b, HIP 78530 B, HIP 64892 B, and RX J1609.5-2105 b, this work provides the first orbital solutions to date. We derived new photometry for all objects, which, when compared with field dwarfs in color-magnitude diagrams, indicates spectral types ranging from mid-M to mid-L. For the companions observed with IFS, their spectra are best matched by those of M6-M8.5 field dwarfs. Our updated orbital fits provide tighter constraints for nearly all companions and are consistent with non-circular orbits in all cases, potentially disfavoring core-accretion formation within their circumstellar disks.

astro-ph.EP↗

arXiv2026

SaNDi-SHoP: Searching for Satellites'N'Disks with a Star-Hopping Program I. Analysis of the close surroundings of DI companions

We aim to search for satellites and circumplanetary or circumsubstellar disks around directly imaged substellar companions, exploring their immediate environment to constrain the conditions for satellites and disk formation. We conducted a dedicated survey of twelve planets and brown dwarfs with VLT/SPHERE using a novel application of the star hopping technique. By building libraries of contemporaneous point spread function (PSF) references from nearby stars, we applied a frame-by-frame subtraction of each companion's flux using the Negative Fake Companion method (NEGFC). This approach mitigates temporal PSF variability and enhances sensitivity to faint circumplanetary features. We derived contrast curves, translated them into mass detection limits using evolutionary models, and constrained the dynamically stable regions through estimates of Hill radii from orbital fits. Our analysis yields stringent limits on the presence of massive satellites, generally excluding companions more massive than a few Jupiter masses at separations beyond 1-5 au, depending on each system's Hill radius. In most cases, no convincing point-like or extended residuals were found. However, we identify promising signals for three systems: extended residuals consistent with a circumplanetary disk around CT Cha b, tentative repeated residuals near TYC 8047-232-1 B that may trace a bound satellite companion of 3-6 MJup, and marginal residual signals at the location of the previously reported candidate around DH Tau b, whose interpretation, however, remains uncertain due to possible contamination by instrumental effects. These results confirm the power of star hopping in reducing PSF-related artifacts and provide some of the most stringent constraints to date on the mass and location of potential satellites and disks around directly imaged substellar companions.

astro-ph.EP↗

arXiv2018

The Ophiuchus DIsc Survey Employing ALMA (ODISEA) - I : project description and continuum images at 28 au resolution

We introduce the Ophiuchus DIsc Survey Employing ALMA (ODISEA), a project aiming to study the entire population of Spitzer-selected protoplanetary discs in the Ophiuchus Molecular Cloud (~300 objects) from both millimeter continuum and CO isotopologues data. Here we present 1.3 mm/230 GHz continuum images of 147 targets at 0.2" (28 au) resolution and a typical rms of 0.15 mJy. We detect a total of 133 discs, including the individual components of 11 binary systems and 1 triple system. Fifty-three of these discs are spatially resolved. We find clear substructures (inner cavities, rings, gaps, and/or spiral arms) in 8 of the sources and hints of such structures in another 4 discs. We construct the disc luminosity function for our targets and perform comparisons to other regions. A simple conversion between flux and dust mass (adopting standard assumptions) indicates that all discs detected at 1.3 mm are massive enough to form one or more rocky planets. In contrast, only ~50 discs (~1/3 of the sample) have enough mass in the form of dust to form the canonical 10 M_Earth core needed to trigger runaway gas accretion and the formation of gas giant planets, although the total mass of solids already incorporated into bodies larger than cm scales is mostly unconstrained. The distribution in continuum disc sizes in our sample is heavily weighted towards compact discs: most detected discs have radii < 15 au, while only 23 discs (~15% of the targets) have radii > 30 au.

astro-ph.EP↗