Performance of the SOAR Speckle Instrument

Abstract The High Resolution Camera (HRCam) speckle imager at the 4.1 m Southern Astrophysical Research telescope is a highly productive instrument that has accumulated about 40K observations to date. Its performance (detected flux, level of the speckle signal, signal-to-noise ratio, and limiting magnitude) is studied here using both the actual data and realistic simulations, including the detector noise. In the calculation of the speckle power spectrum, signal clipping is essential to reduce the noise impact and maximize the sensitivity. Increasing exposure time of individual frames beyond 30 ms does not improve the limiting magnitude, which ranges from 11.5 to 14 mag under a seeing from 1.″6 to 0.″6 in the wide-band I filter. A gain of at least one magnitude is expected if the current electron multiplication CCD is replaced by a high-end CMOS detector with a subelectron readout noise. This study will help in planning, executing, and automating future speckle observations with HRCam and other speckle imagers.