Near Infrared Photometry Of Long Period Variable Stars

Author : Andrew John Monson
Publisher :
ISBN 13 : 9781109532562
Total Pages : 144 pages
Book Rating : 4.5/5 (325 download)

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Download or read book Development of a Near Infrared Camera for Conducting a Survey of Northern Galactic Cepheid Variable Stars written by Andrew John Monson and published by . This book was released on 2009 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the past few decades there has been growing realization that the Cepheid Near-Infrared (NIR) Period-Luminosity (PL) relation is superior to the Optical PL relation, however, there has been little to no new NIR data gathered on Galactic Cepheids despite the growing popularity and availability of NIR detectors. Galactic Cepheids are, in general, too bright to be observed by telescopes with apertures larger than 1-meter and most NIR detector arrays are too costly to justify placing on sub-1m class telescopes. I describe the development of a near-infrared (NIR) camera for the University of Wyoming's 0.6m telescope at Red Buttes Observatory. The camera, known as BIRCAM (Buttes InfraRed CAMera), was conceived to be a temporary, inexpensive test-bed instrument designed to test the electronic and cryo-mechanical components of another large-scale NIR imaging camera. BIRCAM was designed to make use of a CMOS HgCdTe Hawaii-2 detector array sensitive from 0.9-2.5 microns and during its relatively short lifetime I used BIRCAM to synoptically survey 130 fields containing Galactic Cepheids. These data will help provide the means to calibrate the NIR Cepheid Period-Luminosity Relation. The Cepheid Period-Luminosity (PL) Relation is fundamental to determining distances to nearby galaxies and as such is essential to calibrating the distance scale of the Universe. The accuracy and precision of the distance scale is determined in part by the accuracy and precision of the Galactic PL relation. Observations of Galactic Cepheids in the NIR play an important role in reducing systematic errors inherent to optical observations. The future calibration and refinement of the distance scale relies on providing accurate NIR photometry of Galactic Cepheid Variable Stars. Current photometric studies of Galactic Cepheids in the NIR are limited in size and homo-geneity. The goal of this project is to provide a homogenous photometric study that triples the number of well-sampled Galactic Cepheid light-curves. In conjunction with future astrometric data from GAIA and/or SIM these data will enable the accurate and precise calibration of the Galactic NIR Cepheid Period-Luminosity Relation. I have obtained the NIR light-curves for 131 Northern Galactic Cepheids. With these light-curves I have determined the mean intensity weighted NIR magnitudes and using a subset of 19 Galactic Cepheids with currently known distances and extinctions I have created a Galactic NIR PL relation. The NIR PL relation determined shows a dispersion of 0.13 mag and a slope which is indistinguishable from that of Cepheids in the Large Magellanic Cloud (LMC). The scatter is as small as any survey to date and attests to the quality of the survey data and the potential of the full data set. I have used the Galactic NIR PL relation to determine a distance modulus of 18:49 ± 0:06 to the LMC, consistent with the generally accepted value. I also report on the serendipitous photometric discovery of 72 previously unclassified Galactic Variables. The individual data for each star are presented in the Supplemental Data document available upon request to the author.