SiO and H2O Maser Observations of Red Supergiants in Star Clusters Embedded in the Galactic Disk

We present the result of radio observations of red supergiants in the star cluster, Stephenson's #2, and candidates for red supergiants in the star clusters, Mercer et al. (2005)'s #4, #8, and #13, in the SiO and H$_2$O maser lines.The Stephenson's #2 cluster and nearby aggregation at the South-West contain more than 15 red supergiants. We detected one at the center of Stephenson's #2 and three in the south-west aggregation in the SiO maser line, and three of these 4 were also detected in the H2O maser line. The average radial velocity of the 4 detected objects is 96 km s^{-1}, giving a kinematic distance of 5.5 kpc, which locates this cluster near the base of the Scutum-Crux spiral arm. We also detected 6 SiO emitting objects associated with the other star clusters. In addition, mapping observations in the CO J=1--0 line toward these clusters revealed that an appreciable amount of molecular gas still remains around Stephenson's #2 cluster in contrast to the prototypical red-supergiant cluster, Bica et al.'s #122. It indicates that a time scale of gas expulsion differs considerably in individual clusters.Comment: high res. figures available at http://www.nro.nao.ac.jp/~lib_pub/report/data/no674.pdf. PASJ 62, No.2 (2010, April 25 issue) in pres

The Radon Monitoring System in Daya Bay Reactor Neutrino Experiment

We developed a highly sensitive, reliable and portable automatic system (H$^{3}$) to monitor the radon concentration of the underground experimental halls of the Daya Bay Reactor Neutrino Experiment. H$^{3}$ is able to measure radon concentration with a statistical error less than 10\% in a 1-hour measurement of dehumidified air (R.H. 5\% at 25$^{\circ}$C) with radon concentration as low as 50 Bq/m$^{3}$. This is achieved by using a large radon progeny collection chamber, semiconductor $\alpha$-particle detector with high energy resolution, improved electronics and software. The integrated radon monitoring system is highly customizable to operate in different run modes at scheduled times and can be controlled remotely to sample radon in ambient air or in water from the water pools where the antineutrino detectors are being housed. The radon monitoring system has been running in the three experimental halls of the Daya Bay Reactor Neutrino Experiment since November 2013

High-Resolution Near-Infrared Imaging and Polarimetry of Four Proto-Planetary Nebulae

High-resolution near-infrared HST NICMOS (F160W, F222M) images and polarization (2 um) observations were made of four bipolar proto-planetary nebulae (PPNs): IRAS 17150-3224, IRAS 17441-2411, IRAS 17245-3951, and IRAS 16594-4656. The first three of these are viewed nearly edge-on, and for the first time the central stars in them are seen. Color maps reveal a reddened torus between the bipolar lobes in the edge-on cases, with bluer lobes. The polarization values are high, with maximum values ranging from 40 to 80%. The polarization patterns are basically centrosymmetric, with some deviations in the low polarization equatorial regions. For IRAS 17150-3224, circumstellar arcs are seen at 1.6 um, along with a newly-discovered loop in the equatorial region. Bright caps are seen at the end of the lobes, indicating that they are not open-ended. A distinct point-symmetric pattern is seen in the strengths of the polarization vectors, especially in IRAS 17150-3224. HST NICMOS observations provide a valuable complement to the WFPC2 visible images in deriving the basic structure of bipolar PPNs.Comment: 20 pages, 12 figures, accepted for publication in Astronomical Journal higher resolution figures are available on http://katherine.as.arizona.edu/~ksu/cv/su_nicmos7840.ps.g

A molecular line survey of CRL 2688 at 1 mm and 3 mm wavelengths

Author: Dinh-V-Trung (Dinh, VT) = Dinh Van TrungIt is well established that circumstellar envelopes (CSEs) around evolved stars are active sites of molecular synthesis, and CSEs are one of the major sources of chemical enrichment in the interstellar space. The investigation of molecular compositions in CSEs is essential to understand the chemical evolution of the Galaxy. In order to study circumstellar chemistry in different environments, we have been systematically performing molecular line surveys of a sample of evolved stars from asymptotic giant branch (AGB) stars, proto-planetary nebulae (PPNs), to planetary nebulae (PNs). The dynamical time scales in different evolutionary stages can impose a time limit on the reaction time scales. Here we report our results for CRL 2688. © 2013 International Astronomical Union.published_or_final_versio

Molecular Line Observations of the Carbon-rich Circumstellar Envelope CIT 6 at 7 mm Wavelengths

published_or_final_versio

Planetary nebulae detected in the Spitzer Space Telescope GLIMPSE 3D Legacy Survey

Due to interstellar extinction, optical census of Galactic planetary nebulae (PNs) is highly incomplete, and some compact H ii regions might have been mis-classified as PNs. The problem is particularly severe in the Galactic plane where the extinction in the optical is significant and hampers the detections of PNs. Unlike optical observations, infrared (IR) observations are hardly affected by interstellar extinction, and provide a good opportunity to study highly obscured PNs. In this study, we use the data from the Spitzer Legacy Infrared Mid-Plane Survey Extraordinaire 3D (GLIMPSE 3D) to investigate the mid-infrared (MIR) properties of PNs and PN candidates. © 2012 International Astronomical Union.published_or_final_versionThe IAU Symposium No. 283: 'Planetary Nebulae: an Eye to the Future', Puerto de la Cruz, Tenerife, Spain, 25-29 July 2011. In International Astronomical Union Proceedings, 2011, v. 7 n. S283, p. 528-52

Fabrication and Characterization of Topological Insulator Bi2_2Se3_3 Nanocrystals

In the recently discovered class of materials known as topological insulators, the presence of strong spin-orbit coupling causes certain topological invariants in the bulk to differ from their values in vacuum. The sudden change of invariants at the interface results in metallic, time reversal invariant surface states whose properties are useful for applications in spintronics and quantum computation. However, a key challenge is to fabricate these materials on the nanoscale appropriate for devices and probing the surface. To this end we have produced 2 nm thick nanocrystals of the topological insulator Bi$_2$Se$_3$ via mechanical exfoliation. For crystals thinner than 10 nm we observe the emergence of an additional mode in the Raman spectrum. The emergent mode intensity together with the other results presented here provide a recipe for production and thickness characterization of Bi$_2$Se$_3$ nanocrystals.Comment: 4 pages, 3 figures (accepted for publication in Applied Physics Letters

Identification of Very Red Counterparts of SiO Maser and OH/IR Objects in the GLIMPSE Survey

Using the 3.6/4.5/5.8/8.0 micron images with 1.2 arcsec pixel resolution from the Spitzer/GLIMPSE survey, we investigated 23 masing and 18 very red objects that were not identified in the 2MASS survey. Counterparts for all selected objects were found in the GLIMPSE images. Color indices in these IR bands suggest the presence of a high-extinction layer of more than a few tenths of a solar mass in front of the central star. Furthermore, radio observations in the SiO and H2O maser lines found characteristic maser-line spectra of the embedded objects, e.g., the SiO J=1-0 line intensity in the v=2 state stronger than that of the v=1 state, or very widespread H2O maser emission spectra. This indicates that these objects are actually enshrouded by very thick circumstellar matter, some of which cannot be ascribed to the AGB wind of the central star. Individually interesting objects are discussed, including two newly found water fountains and an SiO source with nebulosity.Comment: High resolution figures available at ftp://ftp.nro.nao.ac.jp/nroreport/no653.pdf.gz. ApJ No. 655 no.1 issue in pres

Morphokinematic properties of the 21 micron source IRAS 22272+5435

We obtained a high-resolution CO map of IRAS 22272+5435 in the CO J=2-1 line using CARMA. The target exhibits a second biggest angular size of the circumstellar molecular envelope among known 21 μm sources. In the preliminary results, we found that the CO properties of IRAS 22272+5435 is clearly different from those of IRAS 07134+1005, which is another well-investigated 21 μm source. For example, elongations seen in the mid-infrared and CO images are extended in mutually perpendicular directions, although in case of IRAS 07134+1005 the CO feature coincides well with the mid-infrared structure. © 2012 International Astronomical Union.published_or_final_versio