8,642 research outputs found
Modeling Self-Subtraction in Angular Differential Imaging: Application to the HD 32297 Debris Disk
We present a new technique for forward-modeling self-subtraction of spatially
extended emission in observations processed with angular differential imaging
(ADI) algorithms. High-contrast direct imaging of circumstellar disks is
limited by quasi-static speckle noise and ADI is commonly used to suppress
those speckles. However, the application of ADI can result in self-subtraction
of the disk signal due to the disk's finite spatial extent. This signal
attenuation varies with radial separation and biases measurements of the disk's
surface brightness, thereby compromising inferences regarding the physical
processes responsible for the dust distribution. To compensate for this
attenuation, we forward-model the disk structure and compute the form of the
self-subtraction function at each separation. As a proof of concept, we apply
our method to 1.6 and 2.2 micron Keck AO NIRC2 scattered-light observations of
the HD 32297 debris disk reduced using a variant of the "locally optimized
combination of images" (LOCI) algorithm. We are able to recover disk surface
brightness that was otherwise lost to self-subtraction and produce simplified
models of the brightness distribution as it appears with and without
self-subtraction. From the latter models, we extract radial profiles for the
disk's brightness, width, midplane position, and color that are unbiased by
self-subtraction. Our analysis of these measurements indicates a break in the
brightness profile power law at r~110 AU and a disk width that increases with
separation from the star. We also verify disk curvature that displaces the
midplane by up to 30 AU towards the northwest relative to a straight fiducial
midplane.Comment: Accepted for publication in ApJ, 20 pages, 10 figures, 1 tabl
Genome sequence of canine herpesvirus
Canine herpesvirus is a widespread alphaherpesvirus that causes a fatal haemorrhagic disease of neonatal puppies. We have used high-throughput methods to determine the genome sequences of three viral strains (0194, V777 and V1154) isolated in the United Kingdom between 1985 and 2000. The sequences are very closely related to each other. The canine herpesvirus genome is estimated to be 125 kbp in size and consists of a unique long sequence (97.5 kbp) and a unique short sequence (7.7 kbp) that are each flanked by terminal and internal inverted repeats (38 bp and 10.0 kbp, respectively). The overall nucleotide composition is 31.6% G+C, which is the lowest among the completely sequenced alphaherpesviruses. The genome contains 76 open reading frames predicted to encode functional proteins, all of which have counterparts in other alphaherpesviruses. The availability of the sequences will facilitate future research on the diagnosis and treatment of canine herpesvirus-associated disease
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