COMMISSIONS 27 AND 42 OF THE IAU INFORMATION BULLETIN ON VARIABLE STARS Number 3942 Konkoly Observatory Budapest 15 October 1993 HU ISSN 0374 - 0676 RAPID CHANGE OF PERIOD OF AP AURIGAE (BAV Mitteilungen Nr. 67) The (Beta Lyr-type system AP Aur was discovered by A.S. Williams (Williams 1931). When constructing the database of minima of eclipsing binaries, D. Lichtenknecker first recognized the rapid change of the period of this system (Lichtenknecker 1983). His study of ?3 then available minimum timings led to the quadratic formula (Lichtenknecker 1986): Min I = HJD 2442443.620 + 0.5693473 * E + 8.08 10^-10 * E^2 The period variation of AP Aur was studied recently by Zhang et al. (Zhang et, al. 1993). Though 32 published minima timings were used together with new photoelectric ones, they could not match epoch numbers and observation properly. Jumps of half a period in their O-C-Diagram (Zhang et al., Fig 3a) are not, real but a consequence of the collision between their theory and reality. A rather complicated system of ephemeris formulae resulted. Stimulated by the note by Lichtenknecker, we put AP Aur on our observing program. Photoelectric observations were made at the private observatory of one of us (F.A.) with a 0.35 m automatic photoelectric telescope (Agerer 1988). The photometer was equipped with an uncooled EMI 9781A tube and Schott filters for B and V. One minimum (n. 86) was observed with a 20cm SC telescope, equipped with an uncoated CCD without filters. The minimum times are calculated using the Kwee - van Woerden method (Kwee, van Woerden 1956). 12 times of photoelectric minima were collected, which confirmed the ephemeris found. To expand our knowledge of period changes to the past, one of us (E.S.) investigated this star on 638 plates of the Sonneberg Sky Survey. 38 plates with weak images could be found. With this material at hand we were able to associate the epoch numbers and minimum timings without ambiguity (Table 1). There is one large gap remaining between the first two timings from the discovery plates and the visual observations by Williams. The normal minimum by Kukarkin (Kukarkin 1931 ) is not of great help. It is built up from 27 plate observations between 1919 and 1930. Moreover the author remarks, that `die Zerstreuung der Beobachtungen sind gross' (the scatter of the observations is large). Therefore minima Nr. 1- 3 were not used in calculating the new ephemeris. A least squares fit yields the following quadratic ephemeris: Min I = HJD 2448273.5736+ 0.56936859 * E + 9.063x10^-10 * E^2 +-7 +-29 +-7.5 (1) Table 1: observed times of minima for AP Aur, epochs and residuals computed with respect to the quadratic ephemeris derived in this paper. -------------------------------------------------------------------------------- N JD hel. W T^* Epoch (O-C) Lit| N JD hel. W T^* Epoch (O-C) 2400000+ | 2400000+ -------------------------------------------|------------------------------------ 1 15488.502 0 P:: -57586.5 -0.1328 (1) | 44 42464.401 5 V:-10203.0 0.0008 8 2 15846.517 0 P:: -56958.0 0.0993 (1) | 45 42528.443 10 V -10090.5 -0.0091 9 3 22842.95 0 F:: -44668.0 0.1243 (2) | 46 42716.539 2 P -9760.0 -0.0835 20 4 23080.520 10 V -44250.5 0.0166 (1) | 47 42756.490 2 P -9690.0 0.0129 20 5 23399.340 10 V -43690.5 0.0348 (1) | 48 42782.370 10 V -9644.5 -0.0125 10 6 23810.331 10 V -42968.5 -0.0016 (1) | 49 42831.332 2 P -9558.5 -0.0147 20 7 24139.943 10 V -42389.5 -0.0093 (1) | 50 43250.340 2 P -8822.5 -0.0498 20 8 26415.361 5 V: -38392.5 -0.0649 (1) | 51 43436.571 2 P -8495.5 0.0028 20 9 26419.387 10 V -38385.5 -0.0240 (1) | 52 43933.332 2 P -7823.0 0.0025 20 10 26771.233 10 V -37767.5 -0.0051 (3) | 53 44499.572 2 P -8828.5 0.0183 20 11 26771.533 5 V: -37767.0 0.0102 (3) | 54 44631.369 2 P -6397.0 0.0092 20 12 27760.679 20 F -36029.5 -0.0055 (4) | 55 45056.388 10 V -5650.5 0.0027 11 13 27815.338 20 F -35933.5 0.0004 (4) | 56 45056.391 10 V -5650.5 0.0057 11 14 28220.388 2 P -35222.0 -0.0095 (20)| 57 45254.425 2 P -5302.5 -0.0971 20 15 28238.342 2 P -35190.5 0.0114 (20)| 58 45388.311 10 V -5067.5 -0.0105 12 16 23425.617 2 P -34861.5 -0.0149 (20)| 59 45405.390 10 V -5037.5 -0.0123 12 17 28494.522 2 P -34740.5 0.0041 (20)| 60 45648.515 2 P -4610.5 -0.0040 20 18 28951.396 2 P -33938.0 0.0097 (20)| 61 45738.7672 40 E -4452.0 0.0046 13 19 30622.613 2 P -31002.5 0.0180 (20)| 62 48377.8729 40 E -3329.5 0.0020 13 20 31030.483 2 P -30286.0 -0.0248 (20)| 63 46436.8024 40 E -3228.0 0.0024 13 21 31873.428 2 P -28805.5 0.0493 (20)| 64 45461.2810 40 E -3183.0 -0.0016 14 22 35761.579 10 V -21976.0 0.0118 (5) | 65 46462.1380 40 E -3181.5 0.0014 14 23 35778.652 2 P -21946.0 0.0050 (20)| 66 46464.1331 40 E -3178.0 0.0037 14 24 35839.542 2 P -21839.0 -0.0232 (20)| 67 46716.637 2 P -2734.5 -0.0050 20 25 35875.436 2 P -21776.0 0.0031 (20)| 68 46776.1381 40 E -2630.0 -0.0024 14 26 36200.527 2 P -21205.0 0.0068 (20)| 69 47170.427 40 E -1937.5 0.0016 15 27 36466.411 10 V -20738.0 0.0135 (6) | 70 47207.435 40 E -1872.5 0.0009 15 28 36541.538 2 P -20606.0 -0.0113 (20)| 71 47469.623 20 F -1412.0 -0.0040 16 29 36898.524 2 P -19982.5 -0.0036 (20)| 72 47526.2762 40 E -1312.5 -0.0027 14 30 37018.361 2 P -19768.5 -0.0038 (20)| 73 47527.1318 40 E -1311.0 -0.0011 14 31 37400.386 2 P -19097.5 -0.0015 (20)| 74 47541.371 20 F -1286.0 0.0039 16 32 37562.601 2 P -18812.5 -0.0467 (20)| 75 47566.413 20 F -1242. -0.0062 16 33 37836.625 2 P -18682.5 -0.0362 (20)| 76 47579.518 20 F -1219.0 0.0014 16 34 37696.401 2 P -18577.5 -0.0404 (20)| 77 47586.3478 40 E -1207.0 0.0008 16 35 37733.361 2 P -18512.5 -0.0872 (20)| 78 47592.3254 40 E -1196.5 0.0000 16 36 38853.318 2 P -16545.5 -0.0157 (20)| 79 47803.5516 20 E: -825.5 -0.0088 17 37 39352.574 2 P -15688.5 -0.0703 (20)| 80 47861.3520 40 E -724.0 0.0008 17 38 39533.409 2 P -15351.0 -0.0009 (20)| 81 47861.6350 40 E -723.5 -0.0009 17 39 40648.422 2 P -13392.5 -0.0453 (20)| 82 47947.3263 40 E -573.0 0.0006 17 40 41217.576 2 P -12393.0 0.0481 (20)| 83 48273.5737 40 E 0.0 0.0001 18 41 41240.553 2 P -12352.5 -0.0334 (20)| 84 48308.3045 40 E 61.0 -0.0006 18 42 41717.371 2 P -11515.0 -0.0435 (20)| 85 48972.4712 40 E 1227.5 -0.0037 19 43 42443.609 10 V -10239.5 -0.0099 (7) | 86 49056.4591 40 E 1375.0 0.0020 19 -------------------------------------------------------------------------------- (1): A.Williams, (2): B.Kukarkin, (3): V.Tsesevich (1953), (4): V.Nikonov, (5): V.Tsesevich (1956), (6): V.Tsesevich (1960), (7): R.Diethelm (1975a),(8): R.Diethelm (1975b),(9): R.Diethelm (1975c), (10): R.Diethelm (1976), (11): Braune & Mundry (1982), (12): Braune et al. (1983), (13): D.Faulkner, (14): R.Zhang et al., (15): Hubscher & Lichtenknecker (1988), (16): Hubscher et al. (1989), (17): Hubscher et al. (1990), (18): Hubscher et al. (1992), (19): Hubscher et al. (1993), (20): this paper *) P denotes pg plate min., E photoel. min., F photographic series and V visual estimates. Those marked "::" were discarded. [FIGURE 1] Figure 1: O-C-Diagram for AP Aur computed with respect to the linear ephemeris Min I = 2448273.5736 + 0.56936859 x E. . represents photoelectric, o photographic series, + visual observations and squares photographic plate minima. [FIGURE 2] Figure 2: O-C-Diagram for AP Aur computed with respect to the new quadratic ephemeris (1). . represents photoelectric, o photographic series, + visual observations and squares photographic plate minima. F. AGERER E. SPLITTGERBER Bundesdeutsche Arbeitsgemeinschaft fur Veranderliche Sterne e.V. (BAV) Munsterdamm 90 D-12169 Berlin Germany References: Agerer, F.: 1988, BAV Rundbrief 37, 60. Braune, W., Mundry, E.: 1982 BAV Mitteilungen 34 Braune, W. et al.: 1983 BAV Mitteilungen 36 Diethelm, R.: 1975a BBSAG-Bulletin 20 Diethelm, R.: 1975b BBSAG-Bulletin 21 Diethelm, R.: 1975c BBSAG-Bulletin 22 Diethelm, R.: 1976 BBSAG-Bulletin 27 Faulkner, D.R.: 1986, Pub. astr. Soc. Pac. 88. 690 [BIBCODE 1986PASP...98..690F ] Hubscher, J., Lichtenknecker, D.: 1988 BAV Mitteilungen 50 Hubscher, J. et al.: 1989 BAV Mitteilungen 52 Hubscher, J. et al.: 1990 BAV Mitteilungen 56 Hubscher, J. et al.: 1992 BAV Mitteilungen 59 Hubscher, J. et al.: 1993 BAV Mitteilungen 62 Kukarkin, B.W.: 1931, Variable Stars, 3. 136 Kwee, K.K., van Woerden, H.: 1956, Bull. Astr. Inst. Netherlands, 12. 327 [BIBCODE 1956BAN....12..327K ] Lichtenknecker, D.:1983, BAV Rundbrief 32. 37. [BIBCODE 1983BAVRu..32...36L ] Lichtenknecker, D.:1986, BAV Rundbrief 35. 43. [BIBCODE 1986BAVRu..35...41L ] Nikonov, V.B.: 1937, Bull. Abastumani astr. Obs.1. 15 Tsesevich, V.P.: 1953, Izv. astr. Obs. Odessa 4. 1. 115 Tsesevich, V.P.: 1956, Astr. Circ. 174. 17 Tsesevich, V.P.: 1960, Ecl. Bin. Circ. Krakow 1-32 Williams, A.S.: 1931, Mon. Not. R. astr. Soc., 91. 698 [BIBCODE 1931MNRAS..91..698W ] Zhang, R.-X., et al.: 1993, ASP Conference Series, Vol. 38. 322. [BIBCODE 1993ASPC...38..322Z ]