Hubble and Spitzer Space Telescope Observations of the Debris Disk around the Nearby K Dwarf HD 92945

Abstract

[ABRIDGED] We present the first resolved images of the debris disk around the nearby K dwarf HD 92945. Our F606W (V) and F814W (I) HST/ACS coronagraphic images reveal an inclined, axisymmetric disk consisting of an inner ring 2".0-3".0 (43-65 AU) from the star and an extended outer disk whose surface brightness declines slowly with increasing radius 3".0-5".1 (65-110 AU) from the star. A precipitous drop in the surface brightness beyond 110 AU suggests that the outer disk is truncated at that distance. The radial surface-density profile is peaked at both the inner ring and the outer edge of the disk. The dust in the outer disk scatters neutrally but isotropically, and it has a low V-band albedo of 0.1. We also present new Spitzer MIPS photometry and IRS spectra of HD 92945. These data reveal no infrared excess from the disk shortward of 30 micron and constrain the width of the 70 micron source to < 180 AU. Assuming the dust comprises compact grains of astronomical silicate with a surface-density profile described by our scattered-light model of the disk, we successfully model the 24-350 micron emission with a minimum grain size of a_min = 4.5 micron and a size distribution proportional to a^-3.7 throughout the disk, but with a maximum grain size of 900 micron in the inner ring and 50 micron in the outer disk. Our observations indicate a total dust mass of ~0.001 M_earth. However, they provide contradictory evidence of the dust's physical characteristics: its neutral V-I color and lack of 24 micron emission imply grains larger than a few microns, but its isotropic scattering and low albedo suggest a large population of submicron-sized grains. The dynamical causes of the disk's morphology are unclear, but recent models of dust creation and transport in the presence of migrating planets indicate an advanced state of planet formation around HD 92945.

29 pages, 10 figures; to be published in The Astronomical Journal

References in corpus (14)

• Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics
• Planet formation around stars of various masses: The snow line and the frequency of giant planets
• The Complete Census of 70-um-Bright Debris Disks within the FEPS (Formation and Evolution of Planetary Systems) Spitzer Legacy Survey of Sun-like Stars
• HST/ACS Multiband Coronagraphic Imaging of the Debris Disk around Beta Pictoris
• The nearest young moving groups
• Collisional processes and size distribution in spatially extended debris discs
• Discovery of an 86 AU Radius Debris Ring Around HD 181327
• Outer edges of debris discs: how sharp is sharp?
• Discovery of extreme asymmetry in the debris disk surrounding HD 15115
• First scattered light images of debris disks around HD 53143 and HD 139664
• Collisional dust avalanches in debris discs
• The AU Microscopii Debris Disk: Multiwavelength Imaging and Modeling
• CARMA Millimeter-Wave Aperture Synthesis Imaging of the HD 32297 Debris Disk
• Discovery of an extended debris disk around the F2V star HD 15745

Cited by in corpus (45)

• Probing for Exoplanets Hiding in Dusty Debris Disks: Disk Imaging, Characterization, and Exploration with HST/STIS Multi-Roll Coronagraphy
• Herschel imaging of 61 Vir: implications for the prevalence of debris in low-mass planetary systems
• SONS: The JCMT legacy survey of debris discs in the submillimetre
• An icy Kuiper-Belt around the young solar-type star HD 181327
• Modeling Collisional Cascades In Debris Disks: Steep Dust-Size Distributions
• Why circumstellar disks are so faint in scattered light: The case of HD 100546
• Dynamical evolution of an eccentric planet and a less massive debris disc
• Binaries Among Debris Disk Stars
• The SEEDS Direct Imaging Survey for Planets and Scattered Dust Emission in Debris Disk Systems
• A DEBRIS Disk Around The Planet Hosting M-star GJ581 Spatially Resolved with Herschel
• A gap in the planetesimal disc around HD 107146 and asymmetric warm dust emission revealed by ALMA
• A Comprehensive Census of Nearby Infrared Excess Stars
• Direct imaging discovery of a super-Jovian around the young Sun-like star AF Leporis
• A Direct Imaging Survey of Spitzer detected debris disks: Occurrence of giant planets in dusty systems
• Hubble Space Telescope Observations of the HD 202628 Debris Disk
• Five Debris Disks Newly Revealed in Scattered Light from the HST NICMOS Archive
• A gap in HD 92945's broad planetesimal disc revealed by ALMA
• Saturn's G and D rings provide nearly complete measured scattering/phase functions of nearby debris disks
• Insights into the planetary dynamics of HD 206893 with ALMA
• Double-ringed debris discs could be the work of eccentric planets: explaining the strange morphology of HD 107146
• Formation of Gaps in Self-Gravitating Debris Disks by Secular Resonance in a Single-planet System I: A Simplified Model
• From scattered-light to millimeter emission: A comprehensive view of the Gyr-old system of HD 202628 and its eccentric debris ring
• Exo-zodi modelling for the Large Binocular Telescope Interferometer
• A HARPS RV search for planets around young nearby stars
• Results from The COPAINS Pilot Survey: four new brown dwarfs and a high companion detection rate for accelerating stars
• Multi-Epoch Observations of HD69830: High Resolution Spectroscopy and Limits to Variability
• Archival Legacy Investigations of Circumstellar Environments: Overview and First Results
• Investigating the presence of two belts in the HD 15115 system
• A Comprehensive Dust Model Applied to the Resolved Beta Pictoris Debris Disk from Optical to Radio Wavelengths
• HD 104860 and HD 192758: two debris disks newly imaged in scattered-light with HST
• Empty gaps? Depleting annular regions in debris discs by secular resonance with a two-planet system
• Density waves in debris discs and galactic nuclei
• Characterizing the morphology of the debris disk around the low-mass star GSC~07396-00759
• HD 117214 debris disk: scattered-light images and constraints on the presence of planets
• The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) II. The radial structure of debris discs
• Debris Disks: Probing Planet Formation
• Herschel Observations and Updated Spectral Energy Distributions of Five Sunlike Stars with Debris Disks
• Light Scattering and Thermal Emission by Primitive Dust Particles in Planetary Systems
• ALMA imaging of the M-dwarf Fomalhaut C's debris disc
• Hiding Dust Around $\epsilon$ Eridani
• The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) V: Comparison between scattered light and thermal emission
• Polarization measurements of the polluted white dwarf G29-38
• Limits on the presence of planets in systems with debris disks: HD 92945 and HD 107146
• Multi-wavelength aperture polarimetry of debris disc host stars
• On the stability of dust orbits in mean motion resonances with considered perturbation from an interstellar wind