Chih-Hao Hsia

Maser Observations of Westerlund 1 and Comprehensive Considerations on Maser Properties of Red Supergiants Associated with Massive Clusters

We report the results of Australia Telescope Compact Array observations of the Westerlund 1 (Wd1) region in the SiO v = 1, J = 1-0, and H2O 616-523 maser lines, and we also report the analysis of maser properties of red supergiants (RSGs) associated with six massive clusters including Wd1. The primary purpose of this research is to explore possibilities of using maser emission for investigating the nature of massive clusters and associated RSGs. The SiO v = 1, J = 1-0, and H2O 616-523 maser lines are detected toward two of four known RSGs in Wd1. The large velocity ranges of maser emission are consistent with the RSG status. RSGs with maser emission tend to exhibit redder log (F 21/F 12) and [K-12.13] colors compared to RSGs with no maser emission. The mass-loss rates derived from dust radiative transfer modeling suggest that RSGs with maser emission tend to exhibit larger mass-loss rates compared to RSGs with no maser emission. In an extended sample of 57 RSGs in six massive clusters, detections in the SiO line tend to homogeneously distribute in absolute luminosity L, whereas those in the H2O line tend to distribute in a region with large L values.

HUBBLE SPACE TELESCOPE OBSERVATIONS AND GEOMETRIC MODELS OF COMPACT MULTIPOLAR PLANETARY NEBULAE

We report high angular resolution Hubble Space Telescope observations of 10 compact planetary nebulae (PNs). Many interesting internal structures, including multipolar lobes, arcs, two-dimensional rings, tori, and halos, are revealed for the first time. These results suggest that multipolar structures are common among PNs, and these structures develop early in their evolution. From three-dimensional geometric models, we have determined the intrinsic dimensions of the lobes. Assuming the lobes are the result of interactions between later-developed fast winds and previously ejected asymptotic giant branch winds, the geometric structures of these PNs suggest that there are multiple phases of fast winds separated by temporal variations and/or directional changes. A scenario of evolution from lobe-dominated to cavity-dominated stages is presented. The results reported here will provide serious constraints on any dynamical models of PNs.

DISCOVERY OF A MULTIPOLAR STRUCTURE WITH AN EQUATORIAL DISK IN NGC 6072

From near-infrared and molecular hydrogen imaging observations, we have discovered that the planetary nebula NGC 6072 has a multipolar structure with a prominent equatorial ring. We have modeled the object by a double bipolar system, each with an equatorial ring and a pair of bipolar lobes. The bipolar axes of the two systems are estimated to be separated by 47°. The existence of such a double bipolar system suggests that the object has undergone separate fast outflow episodes separated by several thousand years.

[Fe III] EMISSION LINES IN THE PLANETARY NEBULA NGC 2392

NGC 2392 is a young double-shell planetary nebula (PN). Its intrinsic structure and shaping mechanism are still not fully understood. In this paper we present new spectroscopic observations of NGC 2392. The slits were placed at two different locations to obtain the spectra of the inner and outer regions. Several [Fe III] lines are clearly detected in the inner region. We infer that NGC 2392 might have an intrinsic structure similar to the bipolar nebula Mz 3, which also exhibits a number of [Fe III] lines arising from the central regions. In this scenario, the inner and outer regions of NGC 2392 correspond to the inner lobes and the outer outflows of Mz 3, respectively. We construct a three-dimensional morpho-kinematic model to examine our hypothesis. We also compare the physical conditions and chemical composition of the inner and outer regions, and discuss the implications on the formation of this type of PN.

Search for Hydrogenated C60 (Fulleranes) in Circumstellar Envelopes

The recent detection of fullerene (C

THE 6 μm FEATURE AS A TRACER OF ALIPHATIC COMPONENTS OF INTERSTELLAR CARBONACEOUS GRAINS

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Coaxial rings and H2 knots in Hubble 12

) in space and the positive assignment of five diffuse interstellar bands to C

DISCOVERY OF A HALO AROUND THE HELIX NEBULA NGC 7293 IN THE WISE ALL-SKY SURVEY

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Wide Field CO Mapping in the Region of IRAS 19312+1950

reinforce the notion that fullerene-related compounds can be efficiently formed in circumstellar envelopes and be present in significant quantities in the interstellar medium. Experimental studies have shown that C

Extremely Strong 13CO J = 3→2 Line in the "Water Fountain" IRAS 16342-3814: Evidence for the Hot-Bottom Burning

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