skip to main content

Title: Testing the Interaction between a Substellar Companion and a Debris Disk in the HR 2562 System

The HR 2562 system is a rare case where a brown dwarf companion resides in a cleared inner hole of a debris disk, offering invaluable opportunities to study the dynamical interaction between a substellar companion and a dusty disk. We present the first ALMA observation of the system as well as the continued Gemini Planet Imager monitoring of the companion’s orbit with six new epochs from 2016 to 2018. We update the orbital fit, and in combination with absolute astrometry from GAIA, place a 3σupper limit of 18.5MJon the companion’s mass. To interpret the ALMA observations, we used radiative transfer modeling to determine the disk properties. We find that the disk is well resolved and nearly edge-on. While the misalignment angle between the disk and the orbit is weakly constrained, due to the short orbital arc available, the data strongly support a (near) coplanar geometry for the system. Furthermore, we find that the models that describe the ALMA data best have inner radii that are close to the companion’s semimajor axis. Including a posteriori knowledge of the system’s SED further narrows the constraints on the disk’s inner radius and places it at a location that is in reasonable agreement with more » (possibly interior to) predictions from existing dynamical models of disk truncation by an interior substellar companion. HR 2562 has the potential over the next few years to become a new test bed for dynamical interaction between a debris disk and a substellar companion.

« less
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more » ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; « less
Publication Date:
Journal Name:
The Astronomical Journal
Page Range or eLocation-ID:
Article No. 219
DOI PREFIX: 10.3847
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    We present the results ofN-body simulations meant to reproduce the long-term effects of mutually inclined exoplanets on debris disks, using the HD 202628 system as a proxy. HD 202628 is a Gyr-old solar-type star that possesses a directly observable, narrow debris ring with a clearly defined inner edge and nonzero eccentricity, hinting at the existence of a sculpting exoplanet. The eccentric nature of the disk leads us to examine the effect on it over Gyr timescales from an eccentric and inclined planet, placed on its orbit through scattering processes. We find that, in systems with dynamical timescales akin to that of HD 202628, a planetary companion is capable of completely tilting the debris disk. This tilt is preserved over the Gyr age of the system. Simulated observations of our models show that an exoplanet around HD 202628 with an inclination misalignment ≳10° would cause the disk to be observably diffuse and broad, which is inconsistent with Atacama Large Millimeter Array (ALMA) observations. With these observations, we conclude that, if there is an exoplanet shaping this disk, it likely had a mutual inclination of less than 5° with the primordial disk. The conclusions of this work can be applied eithermore »to debris disks appearing as narrow rings (e.g., Fomalhaut and HR 4796) or to disks that are vertically thick at ALMA wavelengths (e.g., HD 110058).

    « less

    Brown dwarfs with well-measured masses, ages, and luminosities provide direct benchmark tests of substellar formation and evolutionary models. We report the first results from a direct imaging survey aiming to find and characterize substellar companions to nearby accelerating stars with the assistance of the Hipparcos–Gaia Catalog of Accelerations (HGCA). In this paper, we present a joint high-contrast imaging and astrometric discovery of a substellar companion to HD 176535 A, a K3.5V main-sequence star aged approximately $3.59_{-1.15}^{+0.87}$ Gyr at a distance of 36.99 ± 0.03 pc. In advance of our high-contrast imaging observations, we combined precision High Accuracy Radial velocity Planet Searcher (HARPS) Radial Velocities (RVs) and HGCA astrometry to predict the potential companion’s location and mass. We thereafter acquired two nights of KeckAO/NIRC2 direct imaging observations in the L′ band, which revealed a companion with a contrast of $\Delta L^{\prime }_p = 9.20\pm 0.06$ mag at a projected separation of ≈0.35 arcsec (≈13 au) from the host star. We revise our orbital fit by incorporating our dual-epoch relative astrometry using the open-source Markov chain Monte Carlo orbit fitting code orvara. We obtain a dynamical mass of $65.9_{-1.7}^{+2.0} M_{\rm Jup}$ that places HD 176535 B firmly in the brown dwarf regime. HD 176535 Bmore »is a new benchmark dwarf useful for constraining the evolutionary and atmospheric models of high-mass brown dwarfs. We found a luminosity of $\rm log(\mathit{ L}_{bol}/L_{\odot }) = -5.26\pm 0.07$ and a model-dependent effective temperature of 980 ± 35 K for HD 176535 B. We infer HD 176535 B to be a T dwarf from its mass, age, and luminosity. Our dynamical mass suggests that some substellar evolutionary models may be underestimating luminosity for high-mass T dwarfs. Given its angular separation and luminosity, HD 176535 B would make a promising candidate for Aperture Masking Interferometry with JWST and GRAVITY/Keck Planet Imager and Characterizer, and further spectroscopic characterization with instruments like the CHARIS/SCExAO/Subaru integral field spectrograph.

    « less
  3. Abstract

    Dynamical masses of giant planets and brown dwarfs are critical tools for empirically validating substellar evolutionary models and their underlying assumptions. We present a measurement of the dynamical mass and an updated orbit of PZ Tel B, a young brown dwarf companion orbiting a late-G member of theβPic moving group. PZ Tel A exhibits an astrometric acceleration between Hipparcos and Gaia EDR3, which enables the direct determination of the companion’s mass. We have also acquired new Keck/NIRC2 adaptive optics imaging of the system, which increases the total baseline of relative astrometry to 15 yr. Our joint orbit fit yields a dynamical mass of279+25MJup, semimajor axis of274+14au, eccentricity of0.520.10+0.08, and inclination of91.730.32+0.36°. The companion’s mass is consistent within 1.1σof predictions from four grids of hot-start evolutionary models. The joint orbit fit also indicates a more modest eccentricity of PZ Tel B than previous results. PZ Tel joins a small number of young (<200 Myr) systems with benchmark substellar companions that have dynamical masses and precise ages from moving group membership.

  4. Abstract

    We present the direct-imaging discovery of a giant planet orbiting the young star AF Lep, a 1.2Mmember of the 24 ± 3 MyrβPic moving group. AF Lep was observed as part of our ongoing high-contrast imaging program targeting stars with astrometric accelerations between Hipparcos and Gaia that indicate the presence of substellar companions. Keck/NIRC2 observations inLwith the vector vortex coronagraph reveal a point source, AF Lep b, at ≈340 mas, which exhibits orbital motion at the 6σlevel over the course of 13 months. A joint orbit fit yields precise constraints on the planet’s dynamical mass of3.20.6+0.7MJup, semimajor axis of8.41.3+1.1au, and eccentricity of0.240.15+0.27. AF Lep hosts a debris disk located at ∼50 au, but it is unlikely to be sculpted by AF Lep b, implying there may be additional planets in the system at wider separations. The stellar inclination (i*=549+11°) and orbital inclination (io=5012+9°) are in good agreement, which is consistent with the system having spin–orbit alignment. AF Lep b is the lowest-mass imaged planet with a dynamical mass measurement and highlights the promise of using astrometric accelerations as a toolmore »to find and characterize long-period planets.

    « less
  5. Abstract

    Benchmark brown dwarf companions with well-determined ages and model-independent masses are powerful tools to test substellar evolutionary models and probe the formation of giant planets and brown dwarfs. Here, we report the independent discovery of HIP 21152 B, the first imaged brown dwarf companion in the Hyades, and conduct a comprehensive orbital and atmospheric characterization of the system. HIP 21152 was targeted in an ongoing high-contrast imaging campaign of stars exhibiting proper-motion changes between Hipparcos and Gaia, and was also recently identified by Bonavita et al. (2022) and Kuzuhara et al. (2022). Our Keck/NIRC2 and SCExAO/CHARIS imaging of HIP 21152 revealed a comoving companion at a separation of 0.″37 (16 au). We perform a joint orbit fit of all available relative astrometry and radial velocities together with the Hipparcos-Gaia proper motions, yielding a dynamical mass of244+6MJup, which is 1–2σlower than evolutionary model predictions. Hybrid grids that include the evolution of cloud properties best reproduce the dynamical mass. We also identify a comoving wide-separation (1837″ or 7.9 × 104au) early-L dwarf with an inferred mass near the hydrogen-burning limit. Finally, we analyze the spectra and photometry of HIP 21152 B using the Saumon & Marley (2008)more »atmospheric models and a suite of retrievals. The best-fit grid-based models havefsed= 2, indicating the presence of clouds,Teff= 1400 K, andlogg=4.5dex. These results are consistent with the object’s spectral type of T0 ± 1. As the first benchmark brown dwarf companion in the Hyades, HIP 21152 B joins the small but growing number of substellar companions with well-determined ages and dynamical masses.

    « less