Student's astronomical research in the Junior Session at the semi - annual meeting of the Astronomical Society of Japan 2008
I. A search for long-period variable stars in LMC.
Korrawe karunratanakul (6th), Kritee Chesdachai (6th),
Bangkok Christian College, Thailand.
Abstract .....download
We search for variable stars in the Large Magellanic Cloud (LMC) using data from the Robotic Optical Transient Search Experiment (ROTSE) telescope between September 2005 and May 2006. Our search process utilizes the blink comparison between images from each month and verify variable star candidate against the SIMBAD astronomical database. We have found five long period variable stars with periods on the order of few months. They are different from short period variable stars which take for only a few days. One of five variable stars which we discover is new one that nobody has found it before. Our search is sensitive to a minimum variability of 0.62 magnitude, limiting magnitude of 18.5, and the variability period of less than three years.
II. SMC distance estimation using Cepheid variables.
Kraiwit Norrarat (8th), Piliyalai School, Thailand.
Abstract .....download
We measure distance of the Small Magellanic Cloud (SMC) using period-luminosity relation of Cepheid variables. We analyzed a series of SMC images taken with the Robotic Optical Transient Search Experiment (ROTSE) telescope to produce light curve of three Cepheid variables from the Optical Gravitational Lensing Experiment (OGLE) catalog. The resulting distances fall between 210 kly - 240 kly, which agreed within 10% of the accepted value of 200 kly. We attribute the large dispersion of our result to a combination of uncertainties of the period-luminosity relation, geometrical distribution of Cepheid variables within the SMC, and uncertainties in our photometry.
III. Stellar initial mass function from population of open clusters.
Montika Ruangnaparat (11th), Kiratika Suksrithong(11th), Princess Chulabhorn’s College
Chiangrai, Raweewat Tawantaloengrit , (10th ) Wat Suttiwararam SchoolThailand.
Abstract .....download
We estimate the stellar initial mass function (IMF) by studying population of five open clusters, namely: M21, M25, M29, M34, M35, M36, M37, M38, M39, and M41.Open cluster is ideal for this study since we can assume that the distances to each member of the cluster are approximately identical. We obtain images of these open clusters using the Robotic Optical Transient Search Experiment (ROTSE) telescope and perform aperture photometry for the entire detectable population within each cluster. We then apply the mass-luminosity relation to estimate the stellar mass and create the initial mass function. We estimate the power-law indices of stellar IMF from our study to be within -3.3 between stellar mass of 1 - 10 solar masses, which agrees with the accepted Saltpeter IMF.
IV. A comparative study of Cataclysmic Variable luminosities in Milky Way and M31.
Lalitwadee Kawinwanithakij (12th), Suksanari School, Thailand.
Abstract .....download
We study luminosity of cataclysmic variables (CVs) in the M31 and Milky Way by analyzing photometric properties of eight known CVs discovered by the Robotic Optical Transient Search Experiment (ROTSE) sky survey. After we verified via lightcurve-shape analysis that optical transients are indeed novae, we calculated their apparent magnitudes from their relative intensities. We estimated the absolute magnitude of M31 CVs with the known distance of M31. We then made an assumption that the average absolute magnitude of galactic CVs is similar on the order of magnitude to those in the M31 to estimate distances of galactic CVs from the Earth. After we calculate the distance of CVs of the Milky Way galaxy, we have found that the distances are greater than the Milky Way galaxy's diameter. This method reveals that CVs in M31 and the Milky Way galaxy are difference types. And the luminosity of CVs in Milky Ways galaxy is more than CVs in M31. We also investigate the reddening effect of CVs due to the neutral-hydrogen column density in both the M31 and the Milky Way.
V. Observation of the 2007 Outburst of Comet 17/P Holmes.
Lertchon Tanasugarn, Pornbhud Sarredeelerd, Busara Songtanin
Demonstration School of Chulalongkorn University, Bangkok, Thailand.
Abstract .....download
The coma diameter and volume of Holmes Comet at different time points was measured from digital photographs that had been taken on the ROTSE telescope. From 30 October to 7 November 2007 the coma of Holmes Comet appeared to increase linearly from 3.51x105 km to 6.83x105 km in diameter.
