Redshift of the Fermi Flaring Blazar PMN J2331-2148

Longo et al. (ATel #2101) reported a Fermi LAT detection of flaring from the flat-spectrum radio source PMN J2331-2148, of unknown redshift, on 2009 June 26. The optical counterpart of PMN J2331-2148 is visible on the Digitized Sky Survey with position from the USNO B1.0 catalog RA = 23h31m04.03s, Decl.=-21d48'15.3" (J2000.0). We obtained six 10 minute spectra using the Boller & Chivens CCD Spectrograph on the 2.4m Hiltner Telescope of the MDM Observatory on 2009 September 18, covering the wavelength range 3860-7530 Angstroms.