Engineering topics

Hayashi, M

Publications and source records attributed to Hayashi, M.

5 records

DOE OSTI2012

THE STRUCTURE OF PRE-TRANSITIONAL PROTOPLANETARY DISKS. I. RADIATIVE TRANSFER MODELING OF THE DISK+CAVITY IN THE PDS 70 SYSTEM

Through detailed radiative transfer modeling, we present a disk+cavity model to simultaneously explain both the spectral energy distribution (SED) and Subaru H-band polarized light imaging for the pre-transitional protoplanetary disk PDS 70. In particular, we are able to match not only the radial dependence but also the absolute scale of the surface brightness of the scattered light. Our disk model has a cavity 65 AU in radius, which is heavily depleted of sub-micron-sized dust grains, and a small residual inner disk that produces a weak but still optically thick near-IR excess in the SED. To explain the contrast of the cavity's edge in the Subaru image, a factor of {approx}1000 depletion for the sub-micron-sized dust inside the cavity is required. The total dust mass of the disk may be on the order of 10{sup -4} M {sub Sun }, only weakly constrained due to the lack of long-wavelength observations and the uncertainties in the dust model. The scale height of the sub-micron-sized dust is {approx}6 AU at the cavity edge, and the cavity wall is optically thick in the vertical direction at H-band. PDS 70 is not a member of the class of (pre-)transitional disks identified by Dong et al., whose members only show evidence of the cavity in the millimeter-size dust but not the sub-micron-sized dust in resolved images. The two classes of (pre-)transitional disks may form through different mechanisms, or they may simply be at different evolution stages in the disk-clearing process.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2012

POLARIMETRIC IMAGING OF LARGE CAVITY STRUCTURES IN THE PRE-TRANSITIONAL PROTOPLANETARY DISK AROUND PDS 70: OBSERVATIONS OF THE DISK

We present high-resolution H-band polarized intensity (FWHM = 0.''1: 14 AU) and L'-band imaging data (FWHM = 0.''11: 15 AU) of the circumstellar disk around the weak-lined T Tauri star PDS 70 in Centaurus at a radial distance of 28 AU (0.''2) up to 210 AU (1.''5). In both images, a giant inner gap is clearly resolved for the first time, and the radius of the gap is {approx}70 AU. Our data show that the geometric center of the disk shifts by {approx}6 AU toward the minor axis. We confirm that the brown dwarf companion candidate to the north of PDS 70 is a background star based on its proper motion. As a result of spectral energy distribution fitting by Monte Carlo radiative transfer modeling, we infer the existence of an optically thick inner disk at a few AU. Combining our observations and modeling, we classify the disk of PDS 70 as a pre-transitional disk. Furthermore, based on the analysis of L'-band imaging data, we put an upper limit of {approx}30 to {approx}50 M{sub J} on the mass of companions within the gap. Taking into account the presence of the large and sharp gap, we suggest that the gap could be formed by dynamical interactions of sub-stellar companions or multiple unseen giant planets in the gap.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2011

Predicting and verifying transition strengths from weakly bound molecules

We investigated transition strengths from ultracold weakly bound {sup 41}K{sup 87}Rb molecules produced via the photoassociation of laser-cooled atoms. An accurate potential energy curve of the excited state (3){sup 1}{Sigma}{sup +} was constructed by carrying out direct potential fit analysis of rotational spectra obtained via depletion spectroscopy. Vibrational energies and rotational constants extracted from the depletion spectra of v{sup '}=41-50 levels were combined with the results of the previous spectroscopic study and they were used for modifying an ab initio potential. An accuracy of 0.14% in vibrational level spacing and 0.3% in rotational constants was sufficient to predict the large observed variation in transition strengths among the vibrational levels. Our results show that transition strengths from weakly bound molecules are a good measure of the accuracy of an excited state potential.

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2010

Coherent Transfer of Photoassociated Molecules into the Rovibrational Ground State

We report on the direct conversion of laser-cooled {sup 41}K and {sup 87}Rb atoms into ultracold {sup 41}K{sup 87}Rb molecules in the rovibrational ground state via photoassociation followed by stimulated Raman adiabatic passage. High-resolution spectroscopy based on the coherent transfer revealed the hyperfine structure of weakly bound molecules in an unexplored region. Our results show that a rovibrationally pure sample of ultracold ground-state molecules is achieved via the all-optical association of laser-cooled atoms, opening possibilities to coherently manipulate a wide variety of molecules.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2010

Unitary-process discrimination with error margin

We investigate a discrimination scheme between unitary processes. By introducing a margin for the probability of an erroneous guess, this scheme interpolates the two standard discrimination schemes: minimum-error and unambiguous discrimination. We present solutions for two cases. One is the case of two unitary processes with general prior probabilities. The other is the case with a group symmetry: The processes comprise a projective representation of a finite group. In the latter case, we found that unambiguous discrimination is a kind of 'all or nothing': The maximum success probability is either 0 or 1. We also thoroughly analyze how entanglement with an auxiliary system improves discrimination performance.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗