Paschen α observations of be stars toward the SMC cluster NGC330

We made imaging observations of the young SMC cluster NGC330 in the near-infrared J , H, Ks as well as two narrow-band Paα and Paα-off filters. The observations were carried out at a high-altitude site, 5640 m, where the atmospheric extinction is small enough to make the spectral range around Paα transparent. We present the calibration of specially designed narrow-band filters, and the method used to identify Paα emission using photometric colors. We have successfully detected Paα emission from almost all Be stars within the detection limit of the small telescope and the narrow-band filters. The strength of Paα emission well correlates with that of Hα which also confirms the proper detection of Paα emission. This was the first systematic detection of the Paα emission line from Be stars. We also found new candidates of Paα emission-line objects. This work demonstrates that the photometric colors, including the Paα band, can be used to detect the Paα line when observed from high-altitude sites.