Yasuhiro Hirahara

A survey of CCS, HC3N, HC5N, and NH3 toward dark cloud cores and their production chemistry

Survey observations of CCS (J N = 4 3 -3 2 , J N = 2 1 -1 0 ), HC 3 N (J = 5-4), HC 5 N (J = 9-8, J = 17-16), and NH 3 (J, K = 1, 1) were carried out toward 49 dark cloud cores to examine the existence of a systematic relation between the chemical evolution and the physical evolution of dark clouds. The J N = 3 3 -2 2 and J N = 3 4 -2 3 lines of CCS and the J = 4-3 line of C 3 S were also observed in several cores

Mapping observations of sulfur-containing carbon-chain molecules in Taurus Molecular Cloud 1 (TMC-1)

High-resolution mapping observations were carried out toward Taurus Molecular Cloud 1 (TMC-1) with sulfur-containing carbon-chain molecules, CCS and C 3 S, and other molecules, CS, C 34 S, HCS + , HC 3 N, HC 5 N, C 4 H, and NH 3 , to investigate detailed molecular distribution and physical structure of the cold dark cloud.

Laboratory detection of C5S by pulsed-discharge-nozzle Fourier transform microwave spectroscopy

The rotational spectrum of C 5 S in the X 1 Σ + (υ=0) ground state has been observed for the first time using a Fabry-Perot-type Fourier transform microwave spectrometer combined with a pulsed discharge nozzle. C 5 S was generated by a discharge in a mixture of CS 2 and C 2 H 2 diluted in Ar, and subsequently cooled down to a few kelvins in a supersonic jet. Eight rotational transitions of C 5 32 S have been observed in the 5-20 GHz region. Three lines for the less abundant 34 S species have also been detected to confirm the carrier of the observed lines to be C 5 S

Observations of molecular envelopes of late-type stars: CRL 618, CRL 2688, CRL 3068, and CIT 6

The HC3N, HC5N, HC7N, CCH, C4H, SiS, and HNC molecules were observed in the circumstellar envelopes of CRL 618, CRL 2688, CIT 6, and CRL 3068 with the Nobeyama 45 m radio telescope. The observed relative abundances of the cyanopolyynes, CCH, and C4H in these late-type stars are similar to those for IRC +10216. However, it was found that the abundance of HNC increased with the physical evolutionary stage of the stars. In CRL 2688, it is also found that HNC is more concentrated in the inner region than SiS. The production mechanism of HNC is discussed by considering ultraviolet radiation from the central stars. The HC3N J = 4-3 transition was observed to have a P Cygni line profile in CRL 618.

Laboratory detection of a new free radical C4S (3Sigma

A free radical C 4 S has been detected for the first time by using a Fabry-Perot-type Fourier-transform microwave spectrometer combined with a pulsed discharge nozzle. Rotationally cooled (∼1-2 K) C 4 S in its ground electronic state ( 3 Σ - ) has been produced by a discharge in a supersonic free jet of Ar-diluted samples of C 2 H 2 and CS 2 . The observed spectrum of C 4 S in the 5-24 GHz region was analyzed to determine the rotational constant and the spin-spin interaction constant. Toward the astronomical detection, transiton frequencies of C 4 S in the millimeter-wave region are tabulated

Development of a visible and near infrared spectrometer for Selenological and Engineering Explorer(SELENE)

Although the Moon has been investigated from the Earth, manned Apollo program, and numerous unmanned spacecraft including latest Clementine and Lunar Prospector, unresolved issues on the origin and evolution of the Moon still exist. To find clues or hopefully answers to these issues, Japan will send, to the Moon, an orbiting spacecraft called Selenological and Engineering Explore (SELENE) equipped with a suite of state-of-the-art mission instruments. Spectral Profiler (SP) is one of the instrument onboard SELENE, and will obtain 0.5-2.6 micrometers continuous reflectance spectra of the lunar surface just below SELENE with 500 m swath. As major minerals on the Moon, pyroxene, olivine, and feldspar, have diagnostic spectral features in this spectral region, SPs spectra will provide us information on mineral/rock distributions on the Moon surface globally. Such information from SP will, in combination with other instruments, clarify elemental/compositional characteristics of the lunar surface. This will contribute so much to depict a clear picture of the origin and the evolution of the Moon. To accomplish these scientific goals, engineering issues such as performance requirements and calibration procedures were discussed intensively and comprehensively among SP scientists and engineers. And based on such discussions, the basic instrument design of SP was determined and PM development was started in FY 1998. In FY 1999 and 2000, PM testings are being conducted. FM design will start in late- 2000. In the presentation, current status of SP development will be reported together with background information on SELENE, SP, and the science of the Moon.

Fourier transform infrared spectroscopy of the ν3 band of cyclopropenylidene, C3H2

The gas‐phase absorption spectrum of the ν3 band of cyclopropenylidene (cyclic C3H2 ) has been observed with a high‐resolution Fourier transform infrared spectrometer. The ring molecule was generated by a microwave discharge in an allene and Ar mixture. The spectrum observed between 1250 and 1305 cm−1 was analyzed by using Watson’s A‐reduced Hamiltonian to determine the band origin (ν0=1277.3711±0.0001 cm−1 ), rotational constants, and centrifugal distortion constants in the ν3 state.

Development of immersion grating for mid-infrared high dispersion spectrograph for the 8.2m Subaru Telescope

The mid-infrared high dispersion spectrograph (IRHS; tentative name) with a resolving power of 200,000 at 10 μm is a candidate of the second-generation instrument for the 8.2m Subaru Telescope. A germanium immersion grating will be employed as a dispersing element for this instrument. Germanium immersion gratings for the prototype IRHS were successfully fabricated by using a nano precision 3D profile grinding/turning machine and ELID grinding method on diamond machining. As a result, the fabricated gratings observed to have grooves with ideal saw-tooth shape, smooth surface and acceptable wave front error of a diffraction beam at 10μm. In the present paper, we characterized the performance of the developed immersion gratings.

Step-scan Fourier transform infrared absorption spectroscopy of acetylene monomer and solid in a supersonic free jet

Abstract The infrared spectra of acetylene monomer and solid generated in a pulsed supersonic jet have been obtained near 3300 cm −1 using step-scan Fourier transform infrared (FTIR) absorption spectroscopy. The rotational temperature of monomer was determined to be as low as 10 K. A broad band was also observed between 3220 and 3260 cm −1 with a dominant peak at 3234 cm −1 , which was assigned to the high-temperature cubic phase of solid acetylene.

SEQUENTIAL STAR FORMATION IN TAURUS MOLECULAR CLOUD 1

We discuss the fragmentation of a filamentary cloud on the basis of a 1-dimensional hydrodynamical simulation of a self-gravitating gas cloud. The simulation shows that dense cores are produced with a semi-regular interval in space and time from one edge to the other. At the initial stage the gas near one of the edges is attracted inwards by gravity and the accumulation of the gas makes a dense core near the edge. When the dense core grows in mass up to a certain amount, it gathers gas from the other direction. Accordingly the dense core becomes isolated from the main cloud and the parent filamentary cloud has a new edge. This cycle repeats and the fragmentation process propagates towards the other edge. The propagation speed is a few tens of percent larger than the sound speed. According to the theory, the age difference for the northwest-most and southeast-most cores in TMC-1 is estimated to be 0.68~pc/0.6~km~s