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天文館

臺北天文館學報(出版品)

臺北天文館學報 第6期(English)

JTAM VOL. 6 (2008)


Cover & Back(pdf檔案)
Copyright & Contents(pdf檔案)


FieldAuthorTitleReceived DateAccepted Date
Solar System
Inferared
You-Hua ChuComets Prancing around Dying Stars?(pdf檔案)Invited Articles--
Star Cluster
Inferared
Kuan-Ju Fu,
W. P. Chen
Searching for Open Clusters in the Milky Way Disk(pdf檔案)2008.09.302008.12.04
Nebula
ISM
Inferared
Y. H. Shih, W. P. Chen, W. S. Hsiao, & M. TamuraNear Infrared Polarimetric Imaging of the Giant HII region NGC 3576(pdf檔案)2008.10.092008.12.12
Optical
Instrumen-tation
Hsiang-Fu Huang , Daisuke Kinoshita, Chia-You ShihThe Dark Current and Gain Measurements of CCD Camera PI1300B at Lulin Observatory(pdf檔案)2008.11.072008.12.12
----Abstracts of ASROC Symposium 2008(pdf檔案)----

Title: Comets Prancing around Dying Stars?

Author: You-Hua Chu

Keywords:--

Abstract:
   White dwrafs (WDs) are the final evolutionary product of stars similar to our Sun. Astronomers have been searching for planets and dust disks around WDs using excess infrared (IR) emission as diagnostics. Most searches have been using near-IR observations for WDs of temperatures a few 104 K. Recent Spitzer Space Telescope observations of the Helix Nebula revealed a bright mid-IR source at its central star, a 110,000 K hot WD. This mid-IR source has been analyzed and shown to originate from a dust disk at 50-100 AU from the star. This dust disk is most likely produced by collisions among Kuiper-Belt-like objects, or comets. To determine whether the Helix central star is unique, we have surveyed a large number of hot WDs and found several objects that show similar mid-IR excesses. Interestingly, they are all associated with planetary nebulae. Do they all have comets prancing around the central dying stars? At least one WD may have a companion accreting the mass loss from its progenitor. Follow-up observations will be made to solve this puzzle.

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Title: Searching for Open Clusters in the Milky Way Disk

Author: Kuan-Ju Fu, W. P. Chen

Keywords: star cluster ; infrared ; photometry

Abstract:
   We present the results of star counting of the 2MASS point sources to search for uncharted open clusters (OCs). As the first attempt, we identified regions with stellar density enhancements not associated with previously known star clusters along the Galactic disk, within the band l= 90 degto 270deg, and b = -3.5deg to +3.5deg. Visual inspection of the DSS and 2MASS images led to a final list of 103 regions as star cluster candidates, for each of which the central coordinates, angular size, projected stellar density profile, and total number of possible cluster members were derived. Four newly found OCs are presented here, including OC0234+6147, OC0251+6007, OC0456+4722, and OC0537+3159, each of which is associated with nebulosity, so is likely a young stellar group. We show how CCD photometric observations of OC0536+3112 were used to derive an estimated distance of 1.82 kpc and age of 0.2 Gyr.

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Title: Near Infrared Polarimetric Imaging of the Giant HII region NGC 3576

Author: Y. H. Shih, W. P. Chen, W. S. Hsiao, & M. Tamura

Keywords: star formation ; infrared ; polarimetry ; interstellar medium

Abstract:
   NGC 3576 is one of the brightest HII regions in infrared, harboring a group of massive stars with infrared excess indicative of their youth. We present the near-infrared JHKs polarization images taken by SIRPOL, an infrared polarimeter camera mounted on the IRSF (Infra-Red Survey Facility) telescope in Sutherland, South Africa. An overall scattering pattern is seen centrally symmetric around the luminous stellar group, indicating their dominant role in illuminating the nebulosity. Organized scattering patterns also reveal special dust distribution around embedded infrared sources, e.g., a dust ridge associated with IRS−1 #69 and perhaps also with #85. We find no systematic polarization of background stars, which may be the consequence of an entangled magnetic field structure in a turbulent environment of massive star formation.

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Title: The Dark Current and Gain Measurements of CCD Camera PI1300B at Lulin Observatory

Author: Hsiang-Fu Huang , Daisuke Kinoshita, Chia-You Shih

Keywords: instrumentation ; CCD: PI1300B ; Lulin Observatory ; dark current ; gain ; readout noise

Abstract:
   The condition of the instrument may vary through time, and influences the basic properties and performance of instruments. In order to ensure the stable science operation of observation, the characteristics and performance of CCD needs to be re-examined regularly. We have measured the dark current, gain, and readout noise of CCD camera PI1300B mounted on Lulin One-meter Telescope (LOT) at Lulin Observatory. We have obtained dark and flatfield frames to estimate the gain and readout noise. The dark current generation rates at different CCD cooling temperatures were measured. Results are compared with the previous study (Kinoshita et al. 2005), and it is found to be consistent. The instrument is found to be stably operated.

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Title: Abstracts of ASROC Symposium 2008

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