Identification of BY Draconis Variable Stars Among ASAS Cepheid Candidates (Poster abstract)

Volume 42 number 1 (2014)

Jessica Johnson

Jessica Johnson Department of Physics and Earth Sciences, Central Connecticut State University, 1615 Stanley Street, New Britain, CT 06053; address email correspondence to Larsen@ccsu.edu

Kristine Larsen

Department of Physics and Earth Sciences, Central Connecticut State University, 1615 Stanley Street, New Britain, CT 06053; Larsen@ccsu.edu

Abstract

(Abstract only) Cepheid variables are well-known to be important to astronomers, as their period-luminosity relationship (the Leavitt relationship) is used to determine the distances to galaxies. The unambiguous identification of newly discovered Cepheid variables in large photometric data sets is therefore of significance. A data set of 3,548 candidate Cepheid variable stars in the ASAS data was provided by Patrick Wils (through Dr. Doug Welch). A computer program had originally identified these candidates, however, Wils investigated a small subset of the data by hand and discovered that the vast majority of these stars were misidentified. The most common misidentification was of BY Draconis stars (rotating spotted K and M dwarfs). In a companion piece, Swenton and Larsen [see above] sought out the most likely Cepheid candidates in the data; the work discussed here is instead focused on looking at stars that had properties that were clearly different from Cepheids, more specifically properties likely to be seen in BY Dra stars. We are sorting the spreadsheet stars by characteristics in order to find as many BY Dra variables as possible (since they seem to be the most commonly misidentified stars). Resources for these characteristics include newly available infrared photometry (2MASS), proper motion (PPMXL), and X-Ray emission (ROTSE) data (for which we received helpful guidance from Sebastian Otero), as well as VSX information. The first 103 stars to be studied are those with the smallest range in magnitude (less than or equal to 0.1). An analysis of their light curves and other available data is being undertaken in order to determine whether or not they are indeed BY Dra-type variables. In doing so the goal is to be able to submit and publish the correct identifications for these stars to the International Variable Star Index (VSX) and JAAVSO.