A new technique for performing two-dimensional spectroscopy of objects of large dynamic range: The binary system HD 167605 A+B

We present a new technique for performing two-dimensional (integral-field) spectroscopy of objects with a large range in intensity. It is based on the capability of optical fibers to discretize the intensity distribution at t he telescope focal plane. This allows not only reformatting but also the eq ualization of fiber output intensities, matching them to the dynamic range of the detector and reducing the optical cross talk inside the spectrograph . This technique, which we have called equalized integral field spectroscop y, permits spectral information to be obtained as well as accurate relative photometry and astrometry. Here we present the concept and a practical rea lization. Using this technique, we have observed the environment of the K2 V star HD 167605, for which recent Hubble Space Telescope/Near-Infrared Cam era and Multiobject Spectrometer observations in coronagraphic mode have re vealed the presence of a faint companion. We have also detected this star, whose spectral type was determined (M4 V), together with its relative dista nce (Delta alpha = +0." 80 and Delta delta = +0." 86) and photometry (Delta R = 3.8 +/- 0.1 and Delta I = 3.1 +/- 0.1 mag) with respect to the primary , confirming that these two stars form a binary system. For the companion w e have also found the presence of H alpha in emission, which indicates that this binary system is relatively young. The present technique may be of in terest for Next Generation Space Telescope instrumentation.