2 Observations and data reduction

Data were obtained on 17 January 2001 using NICS, the near-IR imager and spectrograph on the 3.5 meter Telescopio Nazionale Galileo (TNG). We used the low-resolution IJ grism and a slit width of 0 $.\!\!^{\prime\prime}$75, yielding a dispersion of 5.7 Å/pix (resolution 16 Å) over the wavelength range 0.89-1.46 $\mu$m, and a scale of 0.25 $^{\prime\prime}$/pixel along the slit. The slit was centered on the near-IR peak and rotated to position angle 140$^\circ$ North of East. Total integration time on source was 20 min, consisting of four 5 min exposures in the standard "ABBA'' position raster. The observations were immediately followed by observations of the star HIP 69160 using the same instrument setup. The sky was not photometric and the seeing about 1 $^{\prime\prime}$.

Data were reduced using standard tasks within IRAF. The spectrum of HIP 69160 (stellar type G5V) was corrected for its intrinsic spectral shape and then used to correct the atmospheric absorption lines in the spectrum of NGC 5506. Absolute flux calibration was derived by previous observations of photometric standard stars and should be accurate to about 30%. Finally, the spectrum was Doppler corrected using a recessional velocity of 1815 km s^-1 as derived from H I observations (de Vaucouleurs et al. 1991). The final resolution was $\sim$16 Å over the full wavelength range.