412 research outputs found
Debris Disks in the Scorpius-Centaurus OB Association Resolved by ALMA
We present a CO(2-1) and 1240 um continuum survey of 23 debris disks with
spectral types B9-G1, observed at an angular resolution of 0.5-1 arcsec with
the Atacama Large Millimeter/Submillimeter Array (ALMA). The sample was
selected for large infrared excess and age ~10 Myr, to characterize the
prevalence of molecular gas emission in young debris disks. We identify three
CO-rich debris disks, plus two additional tentative (3-sigma) CO detections.
Twenty disks were detected in the continuum at the >3-sigma level. For the 12
disks in the sample that are spatially resolved by our observations, we perform
an independent analysis of the interferometric continuum visibilities to
constrain the basic dust disk geometry, as well as a simultaneous analysis of
the visibilities and broad-band spectral energy distribution to constrain the
characteristic grain size and disk mass. The gas-rich debris disks exhibit
preferentially larger outer radii in their dust disks, and a higher prevalence
of characteristic grain sizes smaller than the blowout size. The gas-rich disks
do not exhibit preferentially larger dust masses, contrary to expectations for
a scenario in which a higher cometary destruction rate would be expected to
result in a larger mass of both CO and dust. The three debris disks in our
sample with strong CO detections are all around A stars: the conditions in
disks around intermediate-mass stars appear to be the most conducive to the
survival or formation of CO.Comment: 16 pages, 6 figures, accepted for publication in Ap
MESAS: Measuring the Emission of Stellar Atmospheres at Submm/mm wavelengths
In the early stages of planet formation, small dust grains grow to become mm
sized particles in debris disks around stars. These disks can in principle be
characterized by their emission at submillimeter and millimeter wavelengths.
Determining both the occurrence and abundance of debris in unresolved
circumstellar disks of A-type main-sequence stars requires that the stellar
photospheric emission be accurately modeled. To better constrain the
photospheric emission for such systems, we present observations of Sirius A, an
A-type star with no known debris, from the JCMT, SMA, and VLA at 0.45, 0.85,
0.88, 1.3, 6.7, and 9.0 mm. We use these observations to inform a PHOENIX model
of Sirius A's atmosphere. We find the model provides a good match to these data
and can be used as a template for the submm/mm emission of other early A-type
stars where unresolved debris may be present. The observations are part of an
ongoing observational campaign entitled Measuring the Emission of Stellar
Atmospheres at Submm/mm wavelengths (MESAS)Comment: 17 pages, 1 figure, Accepted to AJ on April 25th 201
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