A slitless spectrograph for observing transient events with small telescopes

Abstract

A slitless UBVR spectrograph was designed and built to be used on small telescopes. Tests and observations with this instrument attached to the 60-cm telescope have shown that it is an effective tool for the study of transient events. A number of features have been incorporated into the construction of the configuration to optimize its operations and data processing. It is capable of registering the continuous spectrum in the wavelength range 3500 – 9000 Å. The wavelength scale after calibration is accurate to about 30 Å. The grating spectrum has a resolution of R ≈ 100 around 4800 Å. The spectrograph provides a moderate signal-to-noise ratio for stars up to magnitude 16. Equivalent widths of non blended lines can be measured down to 0.7 Å. To identify intrinsic activity in spectra, a special software based on the theory of count statistics was developed; it is enabling us to detect the relative power of fluctuations down to (10^-5 – 10^-6). Observational data obtained with the aid of the spectrograph made it possible to discover new fine-scale features and flare-triggered phenomena in flaring red dwarfs, as well as a low-amplitude rapid variability in spectra of chromospherically active stars.