Halpha Monitoring of Early-Type Emission Line Stars

We have begun a narrowband imaging program, using matched 5nm FWHM on-band (656nm) and off-band (645nm) filters, to monitor Hα emission in early-type (primarily Be) stars in young open clusters and associations. Such emission commonly varies over a range of timescales (Porter & Rivinus 2003). Some of the brightest, e.g. γ Cas, have been spectroscopically monitored, but there is little ongoing monitoring in samples including fainter stars (Peters 2009). Observing clusters, rather than individual targets, records multiple known and candidate program stars, and provides reference stars of similar spectral type. We hope to characterize Hα emission variations and search for periodicities that may constrain models of these stars. Observations began in the spring of 2010. Similar observations of other targets, using filters of unequal FWHM, are underway by V. Strelnitski at Maria Mitchell Observatory (e.g., Bedell et al. 2011).