The Near-infrared Period-luminosity Relations of Cepheids in the Large Magellanic Cloud

We present near-infrared (J & Ks) observations of Cepheids in the Large Magellanic Cloud. The goals of these observations are to better characterize the Cepheid Period-Luminosity relation at these wavelengths, especially for periods below 10 days, and to determine if the relation is linear or non-linear in these bandpasses. We observed approximately 1,200 fundamental and first-overtone Cepheids originally discovered by the OGLE-II survey. We used the CTIO 1.5-m telescope and the CPAPIR camera to image 49 separate fields within the LMC in the J & Ks filters. Observations were collected from November 2006 to December 2007 and each field was imaged approximately 10 times. The images were analyzed using standard astronomical software (IRAF and the DAOPHOT suite of photometry programs). We used the 2MASS Point Source Catalog to derive astrometric and photometric calibrations for our measurements. We present color-magnitude diagrams (CMDs) for all fields and period-luminosity relations for the Cepheid variables. Future work will ascertain the (non)-linearity of these P-L relations and make use of our CMDs for stellar population studies

Large Magellanic Cloud Near-Infrared Synoptic Survey. I. Cepheid variables and the calibration of the Leavitt Law

We present observational details and first results of a near-infrared (JHKs) synoptic survey of the central region of the Large Magellanic Cloud using the CPAPIR camera at the CTIO 1.5-m telescope. We covered 18 sq. deg. to a depth of Ks~16.5 mag and obtained an average of 16 epochs in each band at any given location. Our catalog contains more than 3.5x10^6 sources, including 1417 Cepheid variables previously studied at optical wavelengths by the OGLE survey. Our sample of fundamental-mode pulsators represents a 9-fold increase in the number of these variables with time-resolved, multi-band near-infrared photometry. We combine our large Cepheid sample and a recent precise determination of the distance to the LMC to derive a robust absolute calibration of the near-infrared Leavitt Law for fundamental-mode and first-overtone Cepheids with 10x better constraints on the slopes relative to previous work. We also obtain calibrations for the Tip of the Red Giant Branch and the Red Clump based on our ensemble photometry which are in good agreement with previous determinations.Comment: v3 contains small changes to the published results (~0.04, 0.025, 0.017 mag in JHKs, respectively) arising from a correction to the values of total-to-selective absorption. Erratum has been submitted to AJ. Data products available at http://faculty.physics.tamu.edu/lmacri/LMCNISS