Observed Energy Distribution: Q1721+343 log nu0 log nu1 log nu2 log nuFnu Date Aper Filter Instrument Ref (Hz) (Hz) (Hz) (Jy Hz) (") or or Detector Telescope 8.78 8.78 8.78 < 8.48 1976 2640.0 - WSRT AAp105,279 9.15 9.15 9.15 8.93( + 0.02 - 0.02 ) 1976 1080.0 - WSRT AAp105,279 9.70 9.70 9.70 9.34( + 0.03 - 0.03 ) 1979 300.0 - WSRT AAp105,279 9.70 9.70 9.70 9.27( + 0.00 - 0.00 ) 1983 Apr 0.4 - VLA AJ89,1658 12.48 12.40 12.56 < 12.44 1983 300.0 IRAS4 IRAS Table11 12.70 12.57 12.87 11.84( + 0.08 - 0.10 ) 1983 300.0 IRAS3 IRAS Table11 13.08 13.00 13.20 12.16( + 0.07 - 0.08 ) 1983 300.0 IRAS2 IRAS Table11 13.40 13.30 13.55 12.30( + 0.10 - 0.12 ) 1983 300.0 IRAS1 IRAS Table11 13.47 13.36 13.56 11.92( + 0.06 - 0.07 ) 1985 Aug 29 6.0 N IRTF Table10 13.90 13.86 13.94 11.98( + 0.02 - 0.02 ) 1988 Apr 25 6.0 L' IRTF Table9 13.93 13.88 14.00 11.80( + 0.09 - 0.09 ) 1984 Sep 14 5.0 L MMT Table9 13.93 13.88 14.00 < 12.15 1985 May 31 9.0 L MMT Table9 13.93 13.88 14.00 11.91( + 0.07 - 0.07 ) 1985 Sep 25 5.0 L MMT Table9 14.13 14.11 14.19 11.88( + 0.02 - 0.02 ) 1984 Sep 14 5.0 K MMT Table9 14.13 14.11 14.19 11.93( + 0.03 - 0.03 ) 1985 May 31 9.0 K MMT Table9 14.13 14.11 14.19 11.86( + 0.05 - 0.05 ) 1985 Sep 25 5.0 K MMT Table9 14.13 14.11 14.19 11.89( + 0.02 - 0.02 ) 1988 Apr 25 6.0 K IRTF Table9 14.26 14.23 14.31 11.75( + 0.02 - 0.02 ) 1984 Sep 14 5.0 H MMT Table9 14.26 14.23 14.31 11.79( + 0.03 - 0.03 ) 1985 May 31 9.0 H MMT Table9 14.26 14.23 14.31 11.81( + 0.05 - 0.05 ) 1985 Sep 25 5.0 H MMT Table9 14.26 14.23 14.31 11.77( + 0.02 - 0.02 ) 1988 Apr 25 6.0 H IRTF Table9 14.38 14.35 14.45 11.85( + 0.02 - 0.02 ) 1984 Sep 14 5.0 J MMT Table9 14.38 14.35 14.45 11.91( + 0.03 - 0.03 ) 1985 May 31 9.0 J MMT Table9 14.38 14.35 14.45 11.91( + 0.05 - 0.05 ) 1985 Sep 25 5.0 J MMT Table9 14.38 14.35 14.45 11.84( + 0.02 - 0.02 ) 1988 Apr 25 6.0 J IRTF Table9 14.52 14.46 14.58 12.04( + 0.02 - 0.02 ) 1985 May 13 14.0 I MtHopk(24in) Table6 14.63 14.57 14.70 12.00( + 0.02 - 0.02 ) 1985 May 13 14.0 R MtHopk(24in) Table6 14.74 14.70 14.78 12.12( + 0.02 - 0.02 ) 1985 May 13 14.0 V MtHopk(24in) Table6 14.83 14.78 14.89 12.22( + 0.02 - 0.02 ) 1985 May 13 14.0 B MtHopk(24in) Table6 14.97 14.96 14.97 12.49( + 0.02 - 0.02 ) 1986 May 10 15.0 - LWP08171 RDAF 14.97 14.96 14.97 13.02( + 0.13 - 0.19 ) 1983 Aug 27 15.0 - LWR16678 RDAF 14.98 14.97 14.99 12.37( + 0.02 - 0.02 ) 1986 May 10 15.0 - LWP08171 RDAF 14.98 14.97 14.99 12.62( + 0.05 - 0.05 ) 1983 Aug 27 15.0 - LWR16678 RDAF 15.00 14.99 15.01 12.40( + 0.02 - 0.02 ) 1986 May 10 15.0 - LWP08171 RDAF 15.00 14.99 15.01 12.37( + 0.03 - 0.04 ) 1983 Aug 27 15.0 - LWR16678 RDAF 15.02 15.01 15.02 12.36( + 0.02 - 0.02 ) 1986 May 10 15.0 - LWP08171 RDAF 15.02 15.01 15.02 12.34( + 0.03 - 0.03 ) 1983 Aug 27 15.0 - LWR16678 RDAF 15.03 15.02 15.04 12.34( + 0.02 - 0.02 ) 1986 May 10 15.0 - LWP08171 RDAF 15.03 15.02 15.04 12.41( + 0.03 - 0.03 ) 1983 Aug 27 15.0 - LWR16678 RDAF 15.05 15.04 15.06 12.29( + 0.02 - 0.02 ) 1986 May 10 15.0 - LWP08171 RDAF 15.05 15.04 15.06 12.38( + 0.03 - 0.03 ) 1983 Aug 27 15.0 - LWR16678 RDAF 15.07 15.06 15.08 12.31( + 0.02 - 0.02 ) 1986 May 10 15.0 - LWP08171 RDAF 15.07 15.06 15.08 12.27( + 0.04 - 0.04 ) 1983 Aug 27 15.0 - LWR16678 RDAF 15.09 15.08 15.11 12.30( + 0.02 - 0.02 ) 1986 May 10 15.0 - LWP08171 RDAF 15.09 15.08 15.11 12.42( + 0.04 - 0.04 ) 1983 Aug 27 15.0 - LWR16678 RDAF 15.13 15.13 15.14 12.42( + 0.03 - 0.03 ) 1986 May 10 15.0 - LWP08171 RDAF 15.13 15.13 15.14 12.47( + 0.06 - 0.07 ) 1983 Aug 27 15.0 - LWR16678 RDAF 15.15 15.14 15.15 12.41( + 0.03 - 0.03 ) 1986 May 10 15.0 - LWP08171 RDAF 15.15 15.14 15.15 12.64( + 0.05 - 0.05 ) 1983 Aug 27 15.0 - LWR16678 RDAF 15.16 15.15 15.17 12.35( + 0.03 - 0.03 ) 1986 May 10 15.0 - LWP08171 RDAF 15.16 15.15 15.17 12.48( + 0.05 - 0.05 ) 1983 Aug 27 15.0 - LWR16678 RDAF 15.17 15.17 15.18 12.47( + 0.03 - 0.03 ) 1986 May 10 15.0 - LWP08171 RDAF 15.17 15.17 15.18 12.55( + 0.06 - 0.07 ) 1983 Aug 27 15.0 - LWR16678 RDAF 15.18 15.18 15.19 12.48( + 0.02 - 0.02 ) 1986 May 4 15.0 - SWP28261 RDAF 15.18 15.18 15.19 12.60( + 0.04 - 0.04 ) 1983 Aug 27 15.0 - SWP20817 RDAF 15.23 15.22 15.23 12.39( + 0.02 - 0.02 ) 1986 May 4 15.0 - SWP28261 RDAF 15.23 15.22 15.23 12.44( + 0.03 - 0.03 ) 1983 Aug 27 15.0 - SWP20817 RDAF 15.27 15.26 15.27 12.39( + 0.03 - 0.03 ) 1986 May 4 15.0 - SWP28261 RDAF 15.27 15.26 15.27 12.45( + 0.03 - 0.03 ) 1983 Aug 27 15.0 - SWP20817 RDAF 15.28 15.27 15.29 12.47( + 0.02 - 0.03 ) 1986 May 4 15.0 - SWP28261 RDAF 15.28 15.27 15.29 12.52( + 0.03 - 0.03 ) 1983 Aug 27 15.0 - SWP20817 RDAF 15.34 15.33 15.35 12.35( + 0.02 - 0.03 ) 1986 May 4 15.0 - SWP28261 RDAF 15.34 15.33 15.35 12.49( + 0.03 - 0.03 ) 1983 Aug 27 15.0 - SWP20817 RDAF 15.36 15.35 15.37 12.37( + 0.02 - 0.02 ) 1986 May 4 15.0 - SWP28261 RDAF 15.36 15.35 15.37 12.59( + 0.02 - 0.02 ) 1983 Aug 27 15.0 - SWP20817 RDAF 17.38 16.68 17.93 11.67( + 0.14 - 0.05 ) 1979 Aug 26 - IPC IPC ApJ323,343 17.99 17.68 18.38 11.84( + 0.00 - 0.00 ) 1989 May 5 3600.0 LAC GINGA-LAC ApJ398,087