Research column

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2013

Lin, Chien-Cheng: By using the 2MASS data, we identified a star cluster G144.9+0.4 which is physically associated with the Cam OB1 association at a distance of about 1 kpc and with an age of 1-2 Myr. The cluster members including pre-main sequence stars are identified on the basis of photometric and proper motion data. A total of 91 additional OB star candidates was found in Cam OB 1A and 1B. The OB members show an age spread that indicates a sustained star formation for at least the last 10-15 Myr. The young cluster G144.9+0.4 represents the latest episode of sequential star formation in this cloud complex. (Lin, Chien-Cheng et al. 2013, ApJ, 775, 123)

Chen, Ying-Tung :We report the discovery of 2010 GB174, a likely new member of the Inner Oort Cloud (IOC). 2010 GB174 is 1 of 91 trans-Neptunian objects and Centaurs discovered in a 76 deg2 contiguous region imaged as part of the Next Generation Virgo Cluster Survey (NGVS)—a moderate ecliptic latitude survey reaching a manlimiting magnitude of g' ~= 25.5—using MegaPrime on the 3.6 m Canada-France-Hawaii Telescope. 2010 GB17 is found to have an orbit with a semi-major axis of a ~= 350.8 AU, an inclination of i ~=21.°6, and a percentr of q ~ 48.5 AU. This is the second larges tperihelion distance among known solar system objects. Based on the sky coverage and depth of the NGVS, we estimate the number of IOC members with sizes larger than 300 km (HV <= 6.2 mag) to be ~= 11,000. A comparison of the detection rate from the NGVS and the PDSSS (a characterized survey that "rediscovered" the IOC object Sedna) gives, for an assumed a power-law luminosity function for IOC objects, a slope of α ~ 0.7 ± 0.2 With only two detections in this region this slope estimate is highly uncerin. (Chen, Ying-Tung et al. 2013, ApJ, 755L, 8C)

Dr. Ngeow, Chow-Choong: We studied the structure of our own galaxy, the Milky Way, by fitting the Lin-Shu density wave theory with 233 Cepheids in Solar neighborhood. Our results suggest that one-arm spiral structure dominates the Solar neighborhood. (Griv et al. 2013, MNRAS, 433, 2511)

Hu, Chin-Ping:We used the Hilbert-Huang Trasform to defined the phase of superorbital modulation caused by the disk precession in SMC X-1. From the superorbital phase-resolved analysis of orbital profile, we found an X-ray dip appears in the superorbital transition state. (Hu, C.-P. et al. 2013, ApJ, 773, 58)

Dr. Yu, Po-Chieh: We compare the stellar age in the nuclear region of the non-HBLR and HBLR Seyfert 2 galaxies. Our results suggest that the non-HBLR Seyfert 2 galaxies have an older stellar population in nuclear regions than the HBLR galaxies. We propose a potential evolutionary scenario and a modified unification model for Seyfert galaxies to discuss the results. (Yu, Po-Chieh et al. 2013, ApJ, 768, 30)