Synthetic magnitudes of spectra. Time zero is 18 days before the estimated B maximum. The spectra are NOT corrected for extinction or heliocentric redshift and so these should be observed magnitudes. I also havn't corrected to make the early spectra agree with a fit to Bruno's template. The zdaya spectra have have the correction for extinction, redshift, and Bruno's template fit. The day 732 spectrum was obtained by scanning from Kirshner & Oke (1975) and so the value for day 732 are especially suspect which is too bad because they are vitally important. Note none of the U magnitudes are from good coverage of the U band. Thus these U's are probably pretty poor. I've tried extending the spectral flux to the blue to cover the whole U band. For the extrapolated flux, I just assumed a constant flux (flambda) equal to the first actual flux point. For the pre-100 day spectra this is probably an overestimate, but it tends to put an upper limit on the U band I think. For the post-100 day spectra there is some evidence (Ruiz-Lapuente et al. 1995 on SN 1992A) that the U flux is rather constant. So the U-extrapolated may be relatively rather good here; but absolutely still poor. Bessell's U band response function is below. For days 22--76 I'd take the U values with the guesstimated error. Except for the day 34 which is a wash-out. Days 98, 222, and 732 are wash-outs too. For days 253--365 I'd take the U-extra with the guesstimated error. No. t(days) U U-extra Delta U Estimated Error Guestimate Bluest Wavelength in blue end flux of U error estimated from (not by) Kirshner END: 22.0 8.904 1 8.883 .021 .08 .1 3247. 23.0 8.637 1 8.602 .037 .08 .1 3290. 24.0 8.499 1 8.464 .035 .08 .1 3283. 27.0 9.132 1 9.100 .032 .08 .1 3281. 29.0 9.561 1 9.444 .117 .08 .2 3402. 30.0 9.830 1 9.730 .100 .08 .2 3423. 34.0 .000 1 9.708 -9.708 .08 infinite 6071. 38.0 10.547 1 10.503 .044 .08 .1 3306. 41.0 10.395 1 10.273 .122 .08 .2 3401. 44.0 10.811 1 10.770 .041 .08 .1 3302. 53.0 11.626 1 11.441 .185 .08 .3 3389. 62.0 12.081 1 11.962 .119 .25 .3 3414. 73.0 11.707 1 11.576 .131 .15 .3 3414. 76.0 11.995 1 11.947 .048 .15 .2 3317. 98.0 13.489 1 12.662 .827 .25 1. 3636. 222.0 18.653 1 14.512 4.141 .25 4. 4008. 253.0 15.740 1 15.626 .114 .15 .25 3305. 365.0 17.677 1 17.292 .485 .25 .5 3408. 434.0 17.527 1 17.341 .186 .5 .7 3346. 732.0 23.653 1 21.277 2.376 1. infinite 3898. 0 means everything is OK. 1 means the spectrum did not cover the whole passband. The U band response function from Bessell 1990 band UX 25 3000. 0.000 3050. 0.016 3100. 0.068 3150. 0.167 3200. 0.287 3250. 0.423 3300. 0.560 3350. 0.673 3400. 0.772 3450. 0.841 3500. 0.905 3550. 0.943 3600. 0.981 3650. 0.993 3700. 1.000 3750. 0.989 3800. 0.916 3850. 0.804 3900. 0.625 3950. 0.423 4000. 0.238 4050. 0.114 4100. 0.051 4150. 0.019 4200. 0.000