J/AJ/152/164 I-band light curves of OGLE LMC Miras (He+, 2016) ================================================================================ Period estimation for sparsely-sampled quasi-periodic light curves applied to Miras. He S., Yuan W., Huang J.Z., Long J., Macri L.M. =2016AJ....152..164H (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: Magellanic Clouds ; Stars, variable ; Photometry, RI Keywords: methods: statistical - stars: variables: general Abstract: We develop a nonlinear semi-parametric Gaussian process model to estimate periods of Miras with sparsely sampled light curves. The model uses a sinusoidal basis for the periodic variation and a Gaussian process for the stochastic changes. We use maximum likelihood to estimate the period and the parameters of the Gaussian process, while integrating out the effects of other nuisance parameters in the model with respect to a suitable prior distribution obtained from earlier studies. Since the likelihood is highly multimodal for period, we implement a hybrid method that applies the quasi-Newton algorithm for Gaussian process parameters and search the period/frequency parameter space over a dense grid. A large-scale, high-fidelity simulation is conducted to mimic the sampling quality of Mira light curves obtained by the M33 Synoptic Stellar Survey. The simulated data set is publicly available and can serve as a testbed for future evaluation of different period estimation methods. The semi-parametric model outperforms an existing algorithm on this simulated test data set as measured by period recovery rate and quality of the resulting period-luminosity relations. Description: Most of the disk of M33 was observed by the DIRECT (Macri et al. 2001, Cat. J/AJ/121/861) and M33 Synoptic Stellar Survey (M33SSS; Pellerin & Macri 2011, Cat. J/ApJS/193/26) projects in the BVI bands, with a combined baseline of 7-9 years. We use the I-band observations to carry out the simulations, as this is the wavelength range where Miras are brightest (out of the three bands used by these projects). Detailed descriptions of the M33 observations can be found in the above referenced papers. We use the data products from a new reduction that will be presented in a companion paper (W. Yuan et al. 2016, in preparation). I-band light curves are available for ~2.5x10^5^ stars, with a median of 44 measurements and a maximum of 170. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table2.dat 41 884 *OGLE LMC Miras from Soszynski et al. 2009 (Cat. J/AcA/59/239) lc.dat 29 100000 Mapping between simulated light curve ID and the original OGLE object curves/* . 100000 Simulated light curves -------------------------------------------------------------------------------- Note on table2.dat: This table summarizes the relevant properties of Optical Gravitational Lensing Experiment Large Magellanic Cloud (OGLE LMC) Miras from Soszynski et al. 2009 (Cat. J/AcA/59/239) that were used to simulate the light curves. This table can be used to compare true versus derived periods and to generate Period-Luminosity Relations (PLRs). -------------------------------------------------------------------------------- See also: J/AJ/149/117 : LMC infrared survey. I. Photometry of Cepheids (Macri+, 2015) J/ApJS/193/26 : The M33 synoptic stellar survey. I. (Pellerin+, 2011) J/AcA/59/239 : Light curves of LMC long-period variables (Soszynski+, 2009) J/AJ/130/776 : Secular evolution in Mira pulsations (Templeton+, 2005) J/MNRAS/353/705 : OGLE Variables in Magellanic Clouds (Ita+, 2004) J/AJ/121/861 : BVI photometry of central part of M33 (Macri+, 2001) Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 5 I5 --- Star [82/91878] OGLE LMC Mira identification number (OGLE-LMC-LPV-NNNNN) from Soszynski et al. 2009 (Cat. J/AcA/59/239) 7- 17 A11 --- Type Spectral type Oxygen-rich or Carbon-rich 19- 24 F6.3 mag [12.178/15.25] Mean I-band magnitude 26- 31 F6.3 mag [15.101/21.472] Mean V-band magnitude 33- 39 F7.2 d Per [103.06/1265] Main period 41 A1 --- f_ [1] Extrapolated mean V magnitude for object with missing data (identified with a "1") -------------------------------------------------------------------------------- Byte-by-byte Description of file: lc.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 6 I06 --- LCNum [1/100000] Light curve identification number 8- 12 I5 --- Star [82/91878] OGLE LMC Mira identification number from Soszynski et al. 2009 (Cat. J/AcA/59/239) 14- 29 A16 --- Code Light curve internal code -------------------------------------------------------------------------------- Byte-by-byte Description of file: curves/* -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 10 F10.4 d JD Julian Date (JD-2450000) (1) 12- 17 F6.3 mag Imag I-band magnitude (1) 19- 23 F5.3 mag e_Imag Uncertainty in Imag (1) -------------------------------------------------------------------------------- Note (1): Simulated light curves generated following the procedure of Section 4 in the paper. Each light curve is stored in one file with three columns: MJD, I magnitude and uncertainty. The file name, e.g., lc006788.dat is generated sequentially and is only meant for bookkeeping purposes. A mapping between simulated light curve ID and the original OGLE object is given in the file lc.dat. -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 20-Jan-2017