http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Kim, D.-W.,Protopapas, P.,Alcock, C.,Byun, Y.-I.,Kyeong, J.,Lee, B.-C.,Wright, N. J.,Axelrod, T.,Bianco, F. B.,Chen, W.-P.,Coehlo, N. K.,Cook, K. H.,Dave, R.,King, S.-K.,Lee, T.,Lehner, M. J.,Lin, H.- American Institute of Physics 2010 The Astronomical journal Vol.139 No.2
<P>We analyzed data accumulated during 2005 and 2006 by the Taiwan-American Occultation Survey (TAOS) in order to detect short-period variable stars (periods of <img entity='lsim' SRC='http://ej.iop.org/icons/Entities/lsim.gif' ALT='lsim' ALIGN='BASELINE' />1 hr) such as δ Scuti. TAOS is designed for the detection of stellar occultation by small-size Kuiper Belt Objects and is operating four 50 cm telescopes at an effective cadence of 5 Hz. The four telescopes simultaneously monitor the same patch of the sky in order to reduce false positives. To detect short-period variables, we used the fast Fourier transform algorithm (FFT) in as much as the data points in TAOS light curves are evenly spaced. Using FFT, we found 41 short-period variables with amplitudes smaller than a few hundredths of a magnitude and periods of about an hour, which suggest that they are low-amplitude δ Scuti stars. The light curves of TAOS δ Scuti stars are accessible online at the Time Series Center Web site (http://timemachine.iic.harvard.edu).</P>
Detrending time series for astronomical variability surveys
Kim, Dae-Won,Protopapas, Pavlos,Alcock, Charles,Byun, Yong-Ik,Bianco, Federica B. Blackwell Publishing Ltd 2009 Monthly notices of the Royal Astronomical Society Vol.397 No.1
<P>ABSTRACT</P><P>We present a detrending algorithm for the removal of trends in time series. Trends in time series could be caused by various systematic and random noise sources such as cloud passages, changes of airmass, telescope vibration, CCD noise or defects of photometry. Those trends undermine the intrinsic signals of stars and should be removed. We determine the trends from subsets of stars that are highly correlated among themselves. These subsets are selected based on a hierarchical tree clustering algorithm. A bottom-up merging algorithm based on the departure from normal distribution in the correlation is developed to identify subsets, which we call clusters. After identification of clusters, we determine a trend per cluster by weighted sum of normalized light curves. We then use quadratic programming to detrend all individual light curves based on these determined trends. Experimental results with synthetic light curves containing artificial trends and events are presented. Results from other detrending methods are also compared. The developed algorithm can be applied to time series for trend removal in both narrow and wide field astronomy.</P>
Ishioka, R.,Wang, S.-Y.,Zhang, Z.-W.,Lehner, M. J.,Alcock, C.,Axelrod, T.,Bianco, F. B.,Byun, Y.-I.,Chen, W. P.,Cook, K. H.,Kim, D.-W.,King, S.-K.,Lee, T.,Marshall, S. L.,Protopapas, P.,Rice, J. A.,Sc American Institute of Physics 2014 The Astronomical journal Vol.147 No.4
<P>The Taiwanese-American Occultation Survey project is designed for the detection of stellar occultations by small-size Kuiper Belt Objects, and it has monitored selected fields along the ecliptic plane by using four telescopes with a 3 deg<SUP>2</SUP> field of view on the sky since 2005. We have analyzed data accumulated during 2005-2012 to detect variable stars. Sixteen fields with observations of more than 100 epochs were examined. We recovered 85 variables among a total of 158 known variable stars in these 16 fields. Most of the unrecovered variables are located in the fields observed less frequently. We also detected 58 variable stars which are not listed in the International Variable Star Index of the American Association of Variable Star Observers. These variable stars are classified as 3 RR Lyrae, 4 Cepheid, 1 δ Scuti, 5 Mira, 15 semi-regular, and 27 eclipsing binaries based on the periodicity and the profile of the light curves.</P>
Kim, Dae-Won,Protopapas, Pavlos,Byun, Yong-Ik,Alcock, Charles,Khardon, Roni,Trichas, Markos IOP Publishing 2011 The Astrophysical journal Vol.735 No.2
<P>We present a new quasi-stellar object (QSO) selection algorithm using a Support Vector Machine, a supervised classification method, on a set of extracted time series features including period, amplitude, color, and autocorrelation value. We train a model that separates QSOs from variable stars, non-variable stars, and microlensing events using 58 known QSOs, 1629 variable stars, and 4288 non-variables in the MAssive Compact Halo Object (MACHO) database as a training set. To estimate the efficiency and the accuracy of the model, we perform a cross-validation test using the training set. The test shows that the model correctly identifies similar to 80% of known QSOs with a 25% false-positive rate. The majority of the false positives are Be stars. We applied the trained model to the MACHO Large Magellanic Cloud (LMC) data set, which consists of 40 million light curves, and found 1620 QSO candidates. During the selection none of the 33,242 known MACHO variables were misclassified as QSO candidates. In order to estimate the true false-positive rate, we crossmatched the candidates with astronomical catalogs including the Spitzer Surveying the Agents of a Galaxy's Evolution LMC catalog and a few X-ray catalogs. The results further suggest that the majority of the candidates, more than 70%, are QSOs.</P>
UPPER LIMITS ON THE NUMBER OF SMALL BODIES IN SEDNA-LIKE ORBITS BY THE TAOS PROJECT
Wang, J.-H.,Lehner, M. J.,Zhang, Z.-W.,Bianco, F. B.,Alcock, C.,Chen, W.-P.,Axelrod, T.,Byun, Y.-I.,Coehlo, N. ,K.,Cook, K. H.,Dave, R.,de Pater, I.,Porrata, R.,Kim, D.-W.,King, S.-K.,Lee, T.,Lin, American Institute of Physics 2009 The Astronomical journal Vol.138 No.6
<P>We present the results of a search for occultation events by objects at distances between 100 and 1000 AU in light curves from the Taiwanese-American Occultation Survey. We searched for consecutive, shallow flux reductions in the stellar light curves obtained by our survey between 2005 February 7 and 2006 December 31 with a total of ~4.5 × 10<SUP>9</SUP> three-telescope simultaneous photometric measurements. No events were detected, allowing us to set upper limits on the number density as a function of size and distance of objects in Sedna-like orbits, using simple models.</P>
Mondal, S.,Lin, C. C.,Chen, W. P.,Zhang, Z.-W.,Alcock, C.,Axelrod, T.,Bianco, F. B.,Byun, Y.-I.,Coehlo, N. K.,Cook, K. H.,Dave, R.,Kim, D.-W.,King, S.-K.,Lee, T.,Lehner, M. J.,Lin, H.-C.,Marshall, S. American Institute of Physics 2010 The Astronomical journal Vol.139 No.5
<P>The Taiwanese-American Occultation Survey (TAOS) project has collected more than a billion photometric measurements since 2005 January. These sky survey data—covering timescales from a fraction of a second to a few hundred days—are a useful source to study stellar variability. A total of 167 star fields, mostly along the ecliptic plane, have been selected for photometric monitoring with the TAOS telescopes. This paper presents our initial analysis of a search for periodic variable stars from the time-series TAOS data on one particular TAOS field, No. 151 (R.A. = 17<SUP>h</SUP>30<SUP>m</SUP>6<img entity='fs' SRC='http://ej.iop.org/icons/Entities/fs.gif' ALT='fs' ALIGN='BASELINE' />7, decl. = 27°17'30'', J2000), which had been observed over 47 epochs in 2005. A total of 81 candidate variables are identified in the 3 deg<SUP>2</SUP> field, with magnitudes in the range 8 < R < 16. On the basis of the periodicity and shape of the light curves, 29 variables, 15 of which were previously unknown, are classified as RR Lyrae, Cepheid, δ Scuti, SX Phonencis, semi-regular, and eclipsing binaries.</P>