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INTRODUCING tlc_s05: A CODE TO FIT CEPHEID JHK BAND LIGHT CURVES USING A TEMPLATE APPROACH
NGEOW, CHOW-CHOONG,KANBUR, SHASHI M. The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2
We introduce a code called tlc_s05, to fit sparsely sampled JHK band Cepheid light curve data with template light curves to derive the mean magnitude. A brief description of the code is provided here. We tested the performance of the code in deriving the mean JHK band magnitudes using simulations, and we found that it is better to observe more than four evenly spaced data points per light curve, which permits tlc_s05 to derive accurate mean magnitudes for Cepheid JHK band light curves.
APPLICATION OF CEPHEIDS TO DISTANCE SCALE: EXTENDING TO ULTRA-LONG PERIOD CEPHEIDS
NGEOW, CHOW-CHOONG The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2
Classical Cepheids (hereafter Cepheids) belong to a class of important variable stars that can be used to determine distances to nearby galaxies via the famous period-luminosity (PL) relations, i.e. the Leavitt Law. In turn, these distances can then be used to calibrate a host of secondary distance indicators located well within the Hubble flow, and ultimately determine the Hubble constant in a manner independent of the Cosmic Microwave Background (CMB) measurements. Some recent progress in determining the Hubble constant to within ~ 3% level via the Cepheid-based distance scale ladder (the SH0ES and the Carnegie Hubble Program) were first summarized in this Proceeding, followed by a brief discussion on the prospect of using ultra-long period Cepheids (ULPC) in future distance scale work. ULPC are those Cepheids with periods longer than 80 days, which seem to follow a different PL relation than their shorter period Cepheids. It has been suggested that ULPC can be used to determine the Hubble constant in "one-step". However, based on the two ULPCs found in M31, it was found that the large dispersion in derived distance moduli leads to a less accurate distance modulus to M31 compared to the classical Cepheids. This finding might raise an alert regarding the use of ULPCs in future distance scale work.
Context-aware Workflow Management Engine for Networked Devices
Y.C. Ngeow,A. K. Mustapha,E. Goh,H. K. Low 보안공학연구지원센터 2007 International Journal of Multimedia and Ubiquitous Vol.2 No.3
In this paper, we present a novel Context-aware Workflow Management Engine (CWME) which offers seamless control and coordination of ubiquitous networked devices in a heterogeneous, autonomous, and distributed (HAD) environment. CWME adopts the concept from contemporary Business Process Management (BPM) systems where end users are allowed to design or customize activities and workflows involving network devices. A working CWME prototype has been developed as a proof of concept and tested using a device simulator. During the workflow design phase, a Feature Interaction Detection Engine (FIDE) is adopted in our system to detect all possible operation conflicts between the devices. During workflow execution phase, we propose Justified-Event-Condition -Action (JECA) rule and a Case-Based Reasoning (CBR) to enhance CWME's exception handling capability.
DISCOVERY OF AN X-RAY-EMITTING CONTACT BINARY SYSTEM 2MASS J11201034−2201340
Hu, Chin-Ping,Yang, Ting-Chang,Chou, Yi,Liu, L.,Qian, S.-B.,Hui, C. Y.,Kong, Albert K. H.,Lin, L. C. C.,Tam, P. H. T.,Li, K. L.,Ngeow, Chow-Choong,Chen, W. P.,Ip, Wing-Huen American Astronomical Society 2016 The Astronomical journal Vol.151 No.6
<P>We report the detection of orbital modulation, a model solution, and the X-ray properties of a newly discovered contact binary, Two Micron All Sky Survey (2MASS) J11201034-2201340. We serendipitously found this X-ray point source outside the error ellipse when searching for possible X-ray counterparts of 7-ray millisecond pulsars among the unidentified objects detected by the Fermi Gamma-ray Space Telescope. The optical counterpart of the X-ray source (unrelated to the 7-ray source) was then identified using archival databases. The long-term Catalina Real-Time Transient Survey detected a precise signal with a period of P = 0.28876208 (56) days. A follow-up observation made by the Super Light Telescope of Lulin Observatory revealed the binary nature of the object. Utilizing archived photometric data of multi-band surveys, we construct the spectral energy distribution (SED), which is well fit by a K2V spectral template. The fitting result of the orbital profile using the Wilson Devinney code suggests that 2MASS J11201034-2201340 is a short-period A-type contact binary and the more massive component has a cool spot. The X-ray emission was first noted in observations made by Swift, and then further confirmed and characterized by an XMM-Newton observation. The X-ray spectrum can be described by a power law or thermal Bremsstrahlung. Unfortunately, we could not observe significant X-ray orbital modulation. Finally, according to the SED, this system is estimated to be 690 pc from Earth with a calculated X-ray intensity of (0.7 - 1.5) x 10(30) erg s(-1), which is in the expected range of an X-ray emitting contact binary.</P>