72 research outputs found
Analysis of B and Be Star Populations of the Double Cluster h and chi Persei
We present blue optical spectra of 92 members of h and chi Per obtained with
the WIYN telescope at Kitt Peak National Observatory. From these spectra,
several stellar parameters were measured for the B-type stars, including V sin
i, T_eff, log g_polar, M_star, and R_star. Stromgren photometry was used to
measure T_eff and log g_polar for the Be stars. We also analyze photometric
data of cluster members and discuss the near-to-mid IR excesses of Be stars.Comment: 4 pages, to appear in the proceedings of IAU Symposium 266: Star
Cluster
Investigation of mid-infrared AlInSb LEDs with an n-i-p structure
We report on the investigation on mid-infrared AlInSb LEDs with an n-i-p structure. Compared to the conventional AlInSb LEDs with a p-i-n structure, a better current spreading corresponding to a uniform current distribution in the active region is expected in the n-i-p structure because of a high electron mobility in the n-type AlInSb material. The output optical power of laterally injected LEDs were investigated as a function of the device geometry by COMSOL simulations and confirmed by experimental results
Liquid-filled hard gelatin capsules : excipient/capsule compatibility studies
Encapsulation of pharmaceutical formulations as liquids or semisolids, within hard gelatin capsules, presents an important oral dosage strategy for poorly water-soluble drugs, resulting in good bioavailability and reproducible drug absorption. In addition, this technology offers an inherently safer process than powder filled capsules and tablets for highly potent or cytotoxic drugs by avoiding dust generation. Here we present a compatibility study of hard gelatin capsules with common excipients in absence of active pharmaceutical
The Evolution of Protoplanetary Disks Around Millisecond Pulsars: The PSR 1257 +12 System
We model the evolution of protoplanetary disks surrounding millisecond
pulsars, using PSR 1257+12 as a test case. Initial conditions were chosen to
correspond to initial angular momenta expected for supernova-fallback disks and
disks formed from the tidal disruption of a companion star. Models were run
under two models for the viscous evolution of disks: fully viscous and layered
accretion disk models. Supernova-fallback disks result in a distribution of
solids confined to within 1-2 AU and produce the requisite material to form the
three known planets surrounding PSR 1257+12. Tidal disruption disks tend to
slightly underproduce solids interior to 1 AU, required for forming the pulsar
planets, while overproducing the amount of solids where no body, lunar mass or
greater, exists. Disks evolving under 'layered' accretion spread somewhat less
and deposit a higher column density of solids into the disk. In all cases,
circumpulsar gas dissipates on year timescales, making
formation of gas giant planets highly unlikely.Comment: 16 pages, 17 figures, Accepted for publication in The Astrophysical
Journal (September 20, 2007 issue
The Rise and Fall of Debris Disks: MIPS Observations of h and chi Persei and the Evolution of Mid-IR Emission from Planet Formation
We describe Spitzer/MIPS observations of the double cluster, h and
Persei, covering a 0.6 square-degree area surrounding the cores of both
clusters. The data are combined with IRAC and 2MASS data to investigate
616 sources from 1.25-24 . We use the long-baseline -[24] color
to identify two populations with IR excess indicative of circumstellar
material: Be stars with 24 excess from optically-thin free free
emission and 17 fainter sources (J 14-15) with [24] excess consistent
with a circumstellar disk. The frequency of IR excess for the fainter sources
increases from 4.5 through 24 . The IR excess is likely due to
debris from the planet formation process. The wavelength-dependent behavior is
consistent with an inside-out clearing of circumstellar disks. A comparison of
the 24 excess population in h and Per sources with results for
other clusters shows that 24 emission from debris disks 'rises' from 5
to 10 Myr, peaks at 10-15 Myr, and then 'falls' from 15/20 Myr to
1 Gyr.Comment: 48 pages, 15 figures, accepted for publication in The Astrophysical
Journa
Data Reduction Pipeline for the CHARIS Integral-Field Spectrograph I: Detector Readout Calibration and Data Cube Extraction
We present the data reduction pipeline for CHARIS, a high-contrast
integral-field spectrograph for the Subaru Telescope. The pipeline constructs a
ramp from the raw reads using the measured nonlinear pixel response, and
reconstructs the data cube using one of three extraction algorithms: aperture
photometry, optimal extraction, or fitting. We measure and apply both
a detector flatfield and a lenslet flatfield and reconstruct the wavelength-
and position-dependent lenslet point-spread function (PSF) from images taken
with a tunable laser. We use these measured PSFs to implement a -based
extraction of the data cube, with typical residuals of ~5% due to imperfect
models of the undersampled lenslet PSFs. The full two-dimensional residual of
the extraction allows us to model and remove correlated read noise,
dramatically improving CHARIS' performance. The extraction produces a
data cube that has been deconvolved with the line-spread function, and never
performs any interpolations of either the data or the individual lenslet
spectra. The extracted data cube also includes uncertainties for each spatial
and spectral measurement. CHARIS' software is parallelized, written in Python
and Cython, and freely available on github with a separate documentation page.
Astrometric and spectrophotometric calibrations of the data cubes and PSF
subtraction will be treated in a forthcoming paper.Comment: 18 pages, 15 figures, 3 tables, replaced with JATIS accepted version
(emulateapj formatted here). Software at
https://github.com/PrincetonUniversity/charis-dep and documentation at
http://princetonuniversity.github.io/charis-de
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