Table 1: Strömgren photometry of AI Aurigae (MJD = JD-2400000)
MJD V b-y MJD V b-y MJD V b-y MJD V b-y

46351.000 9.182 1.348 46765.900 9.346 1.330 47529.783 9.451 1.357 48991.754 9.477 1.376

46352.996 9.192 1.353 46768.933 9.354 1.336 47535.796 9.384 1.348 49016.708 9.659 1.402

46353.996 9.205 1.348 46777.838 9.367 1.360 47541.771 9.261 1.347 49020.617 9.708 1.427

46357.987 9.259 1.352 46806.787 9.159 1.341 47542.725 9.261 1.350 49051.654 9.435 1.394

46362.975 9.357 1.368 46807.771 9.168 1.329 47544.725 9.248 1.345 49054.658 9.396 1.406

46375.958 9.609 1.413 46827.758 9.463 1.389 47578.683 9.389 1.382 49058.675 9.373 1.385

46376.954 9.615 1.401 46828.763 9.450 1.398 47579.679 9.407 1.379 49325.792 9.474 1.382

46385.942 9.693 1.421 46831.833 9.447 1.396 47585.704 9.455 1.389 49326.829 9.463 1.389

46388.917 9.714 1.422 46832.750 9.442 1.385 47586.658 9.471 1.392 49329.821 9.425 1.403

46389.921 9.717 1.440 46848.721 9.332 1.352 47592.658 9.536 1.414 49330.871 9.407 1.389

46403.917 9.457 1.387 46853.692 9.275 1.338 47599.671 9.522 1.391 49371.754 9.363 1.378

46420.813 9.236 1.361 46857.658 9.217 1.319 47606.671 9.423 1.385 49373.775 9.358 1.385

46421.817 9.240 1.359 46858.683 9.198 1.325 47618.633 9.232 1.356 49382.812 9.326 1.354

46431.875 9.297 1.373 46862.700 9.164 1.314 47623.633 9.195 1.342 49384.687 9.311 1.371

46449.850 9.547 1.399 46867.650 9.127 1.321 47624.625 9.196 1.334 49395.692 9.398 1.382

46450.742 9.561 1.420 46880.638 9.358 1.359 47626.625 9.194 1.347 49398.725 9.467 1.436

46457.783 9.563 1.373 46881.658 9.387 1.336 47640.638 9.430 1.392 49439.617 9.435 1.362

46463.767 9.483 1.396 46885.675 9.435 1.340 47826.929 9.181 1.321 49447.642 9.378 1.383

46483.675 9.200 1.356 46898.629 9.408 1.333 47843.900 9.357 1.324 49633.958 9.200 1.349

46484.662 9.535 1.380 46899.629 9.419 1.310 47880.813 9.375 1.328 49670.883 9.617 1.388

46486.700 9.206 1.364 47103.987 9.305 1.358 47896.683 9.328 1.343 49684.858 9.678 1.411

46487.679 9.205 1.359 47115.937 9.055 1.334 47915.692 9.445 1.353 49685.842 9.662 1.418

46490.700 9.239 1.357 47118.950 9.066 1.341 47919.754 9.519 1.373 49687.800 9.639 1.411

46496.667 9.355 1.373 47125.892 9.205 1.336 47921.779 9.539 1.369 49707.787 9.479 1.381

46510.671 9.509 1.391 47140.846 9.572 1.416 47925.683 9.530 1.379 49750.696 9.480 1.390

46511.671 9.529 1.373 47148.838 9.765 1.425 47932.683 9.481 1.366 49752.713 9.450 1.386

46512.662 9.535 1.380 47150.871 9.786 1.444 47969.667 9.090 1.323 49754.692 9.449 1.378

46516.650 9.557 1.382 47170.763 9.267 1.369 47972.650 9.195 1.336 49757.708 9.438 1.381

46530.650 9.430 1.360 47172.829 9.239 1.365 47974.671 9.266 1.366 49767.625 9.484 1.393

46534.638 9.345 1.362 47199.692 9.480 1.385 48218.854 9.249 1.374 49783.625 9.520 1.379

46539.629 9.220 1.363 47200.696 9.511 1.405 48294.700 9.495 1.396 49979.942 9.342 1.358

46544.650 9.133 1.335 47203.721 9.598 1.407 48296.646 9.501 1.394 50007.917 9.530 1.380

46547.654 9.108 1.341 47204.729 9.616 1.410 48322.608 9.677 1.400 50010.954 9.502 1.378

46550.638 9.113 1.325 47205.729 9.636 1.407 48597.858 9.440 1.368 50034.871 9.082 1.330

46678.979 9.280 1.370 47206.679 9.651 1.419 48631.787 9.555 1.405 50035.875 9.082 1.319

46679.979 9.287 1.375 47211.692 9.725 1.441 48635.787 9.566 1.392 50051.867 9.359 1.364

46703.992 9.351 1.373 47212.692 9.740 1.431 48636.708 9.562 1.394 50052.846 9.389 1.365

46704.979 9.351 1.377 47214.704 9.758 1.427 48638.812 9.555 1.391 50094.737 9.463 1.399

46716.963 9.421 1.392 47221.658 9.654 1.415 48645.787 9.478 1.381 50097.696 9.435 1.384

46720.954 9.403 1.389 47228.646 9.406 1.381 48646.779 9.459 1.375 50101.742 9.360 1.371

46723.963 9.364 1.386 47233.667 9.244 1.357 48649.767 9.411 1.389 50145.633 9.460 1.380

46724.950 9.343 1.402 47234.654 9.226 1.352 48652.754 9.375 1.378 50149.608 9.388 1.367

46728.958 9.238 1.367 47238.642 9.191 1.333 48693.642 9.398 1.389 50151.608 9.363 1.364

46731.950 9.149 1.354 47247.654 9.317 1.382 48697.633 9.420 1.373 50153.608 9.319 1.368

46739.921 9.061 1.337 47250.658 9.380 1.375 48866.975 9.259 1.358 50161.617 9.211 1.337

46740.971 9.057 1.357 47254.646 9.461 1.375 48874.967 9.088 1.355 50172.650 9.175 1.344

46741.946 9.074 1.338 47523.808 9.455 1.383 48888.925 9.408 1.382 50175.621 9.224 1.342

46742.954 9.062 1.360 47524.838 9.457 1.377 48891.904 9.466 1.366 50366.967 9.338 1.362

46747.933 9.104 1.335 47525.787 9.467 1.363 48927.879 9.396 1.340 50425.900 9.386 1.357

46759.933 9.326 1.328 47526.783 9.459 1.373 48976.812 9.384 1.355

**Table 1:** Strömgren photometry of AI Aurigae (MJD = JD-2400000)
MJD	V	b-y	MJD	V	b-y	MJD	V	b-y	MJD	V	b-y
46351.000	9.182	1.348	46765.900	9.346	1.330	47529.783	9.451	1.357	48991.754	9.477	1.376
46352.996	9.192	1.353	46768.933	9.354	1.336	47535.796	9.384	1.348	49016.708	9.659	1.402
46353.996	9.205	1.348	46777.838	9.367	1.360	47541.771	9.261	1.347	49020.617	9.708	1.427
46357.987	9.259	1.352	46806.787	9.159	1.341	47542.725	9.261	1.350	49051.654	9.435	1.394
46362.975	9.357	1.368	46807.771	9.168	1.329	47544.725	9.248	1.345	49054.658	9.396	1.406
46375.958	9.609	1.413	46827.758	9.463	1.389	47578.683	9.389	1.382	49058.675	9.373	1.385
46376.954	9.615	1.401	46828.763	9.450	1.398	47579.679	9.407	1.379	49325.792	9.474	1.382
46385.942	9.693	1.421	46831.833	9.447	1.396	47585.704	9.455	1.389	49326.829	9.463	1.389
46388.917	9.714	1.422	46832.750	9.442	1.385	47586.658	9.471	1.392	49329.821	9.425	1.403
46389.921	9.717	1.440	46848.721	9.332	1.352	47592.658	9.536	1.414	49330.871	9.407	1.389
46403.917	9.457	1.387	46853.692	9.275	1.338	47599.671	9.522	1.391	49371.754	9.363	1.378
46420.813	9.236	1.361	46857.658	9.217	1.319	47606.671	9.423	1.385	49373.775	9.358	1.385
46421.817	9.240	1.359	46858.683	9.198	1.325	47618.633	9.232	1.356	49382.812	9.326	1.354
46431.875	9.297	1.373	46862.700	9.164	1.314	47623.633	9.195	1.342	49384.687	9.311	1.371
46449.850	9.547	1.399	46867.650	9.127	1.321	47624.625	9.196	1.334	49395.692	9.398	1.382
46450.742	9.561	1.420	46880.638	9.358	1.359	47626.625	9.194	1.347	49398.725	9.467	1.436
46457.783	9.563	1.373	46881.658	9.387	1.336	47640.638	9.430	1.392	49439.617	9.435	1.362
46463.767	9.483	1.396	46885.675	9.435	1.340	47826.929	9.181	1.321	49447.642	9.378	1.383
46483.675	9.200	1.356	46898.629	9.408	1.333	47843.900	9.357	1.324	49633.958	9.200	1.349
46484.662	9.535	1.380	46899.629	9.419	1.310	47880.813	9.375	1.328	49670.883	9.617	1.388
46486.700	9.206	1.364	47103.987	9.305	1.358	47896.683	9.328	1.343	49684.858	9.678	1.411
46487.679	9.205	1.359	47115.937	9.055	1.334	47915.692	9.445	1.353	49685.842	9.662	1.418
46490.700	9.239	1.357	47118.950	9.066	1.341	47919.754	9.519	1.373	49687.800	9.639	1.411
46496.667	9.355	1.373	47125.892	9.205	1.336	47921.779	9.539	1.369	49707.787	9.479	1.381
46510.671	9.509	1.391	47140.846	9.572	1.416	47925.683	9.530	1.379	49750.696	9.480	1.390
46511.671	9.529	1.373	47148.838	9.765	1.425	47932.683	9.481	1.366	49752.713	9.450	1.386
46512.662	9.535	1.380	47150.871	9.786	1.444	47969.667	9.090	1.323	49754.692	9.449	1.378
46516.650	9.557	1.382	47170.763	9.267	1.369	47972.650	9.195	1.336	49757.708	9.438	1.381
46530.650	9.430	1.360	47172.829	9.239	1.365	47974.671	9.266	1.366	49767.625	9.484	1.393
46534.638	9.345	1.362	47199.692	9.480	1.385	48218.854	9.249	1.374	49783.625	9.520	1.379
46539.629	9.220	1.363	47200.696	9.511	1.405	48294.700	9.495	1.396	49979.942	9.342	1.358
46544.650	9.133	1.335	47203.721	9.598	1.407	48296.646	9.501	1.394	50007.917	9.530	1.380
46547.654	9.108	1.341	47204.729	9.616	1.410	48322.608	9.677	1.400	50010.954	9.502	1.378
46550.638	9.113	1.325	47205.729	9.636	1.407	48597.858	9.440	1.368	50034.871	9.082	1.330
46678.979	9.280	1.370	47206.679	9.651	1.419	48631.787	9.555	1.405	50035.875	9.082	1.319
46679.979	9.287	1.375	47211.692	9.725	1.441	48635.787	9.566	1.392	50051.867	9.359	1.364
46703.992	9.351	1.373	47212.692	9.740	1.431	48636.708	9.562	1.394	50052.846	9.389	1.365
46704.979	9.351	1.377	47214.704	9.758	1.427	48638.812	9.555	1.391	50094.737	9.463	1.399
46716.963	9.421	1.392	47221.658	9.654	1.415	48645.787	9.478	1.381	50097.696	9.435	1.384
46720.954	9.403	1.389	47228.646	9.406	1.381	48646.779	9.459	1.375	50101.742	9.360	1.371
46723.963	9.364	1.386	47233.667	9.244	1.357	48649.767	9.411	1.389	50145.633	9.460	1.380
46724.950	9.343	1.402	47234.654	9.226	1.352	48652.754	9.375	1.378	50149.608	9.388	1.367
46728.958	9.238	1.367	47238.642	9.191	1.333	48693.642	9.398	1.389	50151.608	9.363	1.364
46731.950	9.149	1.354	47247.654	9.317	1.382	48697.633	9.420	1.373	50153.608	9.319	1.368
46739.921	9.061	1.337	47250.658	9.380	1.375	48866.975	9.259	1.358	50161.617	9.211	1.337
46740.971	9.057	1.357	47254.646	9.461	1.375	48874.967	9.088	1.355	50172.650	9.175	1.344
46741.946	9.074	1.338	47523.808	9.455	1.383	48888.925	9.408	1.382	50175.621	9.224	1.342
46742.954	9.062	1.360	47524.838	9.457	1.377	48891.904	9.466	1.366	50366.967	9.338	1.362
46747.933	9.104	1.335	47525.787	9.467	1.363	48927.879	9.396	1.340	50425.900	9.386	1.357
46759.933	9.326	1.328	47526.783	9.459	1.373	48976.812	9.384	1.355

AI Aurigae was observed on 199 nights between 12 Oct. 1985 and 8 Dec. 1996. The observations were carried out at Lowell Observatory with the 0.53 m telescope. The detector was a single-channel photoelectric photometer (EMI 6256S tube) equipped with Strömgren b and y filters. The measurements were obtained almost always through a 29 $^{\prime\prime}$ diaphragm; some measurements in bad seeing were made through a 49 $^{\prime\prime}$ aperture, and in bright Moonlight a 19 $^{\prime\prime}$ aperture was occasionally used.

The differential magnitudes were aquired relative to HD 46159 (V=8 $.\!\!^{\rm m}$ 054, b-y=0 $.\!\!^{\rm m}$ 623, G8III), while the photometric stability was checked against HD 259662 (V=9 $.\!\!^{\rm m}$ 556, b-y=0 $.\!\!^{\rm m}$ 639, K0III). The data were corrected only for differential extinction using long-term monthly means for k_b and k_y (Lockwood & Thompson 1986). The standard transformations are represented with slight colour terms (roughly V=y+0.05(b-y)_i, b-y=1.08(b-y)_i). The internal consistency is of order of 0 $.\!\!^{\rm m}$ 005 as suggested by the rms errors of the means for the comparison stars in y and b(0 $.\!\!^{\rm m}$ 0046 and 0 $.\!\!^{\rm m}$ 0048). The quoted standard values for the comparison stars were determined on four nights from standard star observations (extending to several very red Landolt stars). Due to the red colour of the variable, there might be some remaining systematic shift of 0 $.\!\!^{\rm m}$ 020-0 $.\!\!^{\rm m}$ 025 in the Vbrightness. In any case, the scatter of the observations is essentially negligible compared to the range of the variations. The data (mean values of var-comp and var-check) are presented in Table 1 and plotted in Fig. 1.

2 Observations