219 research outputs found
Probing Nearby Planetary Systems by Debris Disk Imaging
Many main-sequence stars possess tenuous circumstellar dust clouds believed to trace extrasolar analogs of the Sun's asteroid and Kuiper Belts. While most of these "debris disks" are known only from far-infrared photometry, a growing number of them are now spatially resolved. In this contribution, I review recent imaging results on debris disk structures from the Hubble, Spitzer, and Herschel Space Telescopes. Specific cases of disk interactions with imaged and radial velocity exoplanets will be discussed. I will show how combined modeling of the optical and infrared datasets can place strong constraints on dust particle properties in the disks. Future developments in debris disk imaging will be discussed
Herschel/PACS photometry of transiting-planet host stars with candidate warm debris disks
Dust in debris disks is produced by colliding or evaporating planetesimals,
remnants of the planet formation process. Warm dust disks, known by their
emission at < 24 micron, are rare (4% of FGK main sequence stars) and
especially interesting because they trace material in the region likely to host
terrestrial planets, where the dust has a very short dynamical lifetime.
Statistical analyses of the source counts of excesses as found with the mid-IR
Wide Field Infrared Survey Explorer (WISE) suggest that warm-dust candidates
found for the Kepler transiting-planet host-star candidates can be explained by
extragalactic or galactic background emission aligned by chance with the target
stars. These statistical analyses do not exclude the possibility that a given
WISE excess could be due to a transient dust population associated with the
target. Here we report Herschel/PACS 100 and 160 micron follow-up observations
of a sample of Kepler and non-Kepler transiting-planet candidates' host stars,
with candidate WISE warm debris disks, aimed at detecting a possible cold
debris disk in any of them. No clear detections were found in any one of the
objects at either wavelength. Our upper limits confirm that most objects in the
sample do not have a massive debris disk like that in beta Pic. We also show
that the planet-hosting star WASP-33 does not have a debris disk comparable to
the one around eta Crv. Although the data cannot be used to rule out rare warm
disks around the Kepler planet-hosting candidates, the lack of detections and
the characteristics of neighboring emission found at far-IR wavelengths support
an earlier result suggesting that most of the WISE-selected IR excesses around
Kepler candidate host stars are likely due to either chance alignment with
background IR-bright galaxies and/or to interstellar emission.Comment: 8 pages, 3 figures, accepted for publication at Astronomy &
Astrophysics on 4 August 201
Hubble Space Telescope Observations of the HD 202628 Debris Disk
A ring-shaped debris disk around the G2V star HD 202628 (d = 24.4 pc) was imaged in scattered light at visible wavelengths using the coronagraphic mode of the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. The ring is inclined by approx.64deg from face-on, based on the apparent major/minor axis ratio, with the major axis aligned along PA = 130deg. It has inner and outer radii (> 50% maximum surface brightness) of 139 AU and 193 AU in the northwest ansae and 161 AU and 223 AU in the southeast ((Delta)r/r approx. = 0.4). The maximum visible radial extent is approx. 254 AU. With a mean surface brightnesses of V approx. = 24 mag arcsec.(sup -2), this is the faintest debris disk observed to date in reflected light. The center of the ring appears offset from the star by approx.28 AU (deprojected). An ellipse fit to the inner edge has an eccentricity of 0.18 and a = 158 AU. This offset, along with the relatively sharp inner edge of the ring, suggests the influence of a planetary-mass companion. There is a strong similarity with the debris ring around Fomalhaut, though HD 202628 is a more mature star with an estimated age of about 2 Gyr. We also provide surface brightness limits for nine other stars in our study with strong Spitzer excesses around which no debris disks were detected in scattered light (HD 377, HD 7590, HD 38858, HD 45184, HD 73350, HD 135599, HD 145229, HD 187897, and HD 201219)
Lower Limits on Aperture Size for an ExoEarth-Detecting Coronagraphic Mission
The yield of Earth-like planets will likely be a primary science metric for
future space-based missions that will drive telescope aperture size. Maximizing
the exoEarth candidate yield is therefore critical to minimizing the required
aperture. Here we describe a method for exoEarth candidate yield maximization
that simultaneously optimizes, for the first time, the targets chosen for
observation, the number of visits to each target, the delay time between
visits, and the exposure time of every observation. This code calculates both
the detection time and multi-wavelength spectral characterization time required
for planets. We also refine the astrophysical assumptions used as inputs to
these calculations, relying on published estimates of planetary occurrence
rates as well as theoretical and observational constraints on terrestrial
planet sizes and classical habitable zones. Given these astrophysical
assumptions, optimistic telescope and instrument assumptions, and our new
completeness code that produces the highest yields to date, we suggest lower
limits on the aperture size required to detect and characterize a
statistically-motivated sample of exoEarths.Comment: Accepted for publication in ApJ; 38 pages, 16 Figures, 3 Table
High-Resolution Mid-Infrared Observations of Very Young Stellar Objects in NGC 1333
We observed 22 young stellar objects in the region of NGC 1333 by using the mid-infrared camera MIRLIN. NGC 1333 (in the Perseus OB2 molecular cloud complex) is a relatively well studied region, but not at high spatial resolution in the mid-infrared. MIRLIN's 05 spatial resolution allows us to look for source extension and multiplicity and to place new constraints on spectral energy distributions. We report here new detections of eight objects at mid-IR wavelengths. We find one object, SVS 12, that may be extended or multiple, and we confirm multiplicity in SVS 16. We find a new companion to ASR 107. We are able to classify six objects as Class I, flat spectrum, or II, place strong classification constraints on two objects, and more loosely restrict the classification of eight more objects. These observations will aid in interpretation of planned SIRTF observations of this cluster
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