COMMISSION 27 OF THE I.A.U.
              INFORMATION BULLETIN ON VARIABLE STARS
                           Number 1408

                                                     Konkoly Observatory
                                                     Budapest
                                                     1978 April 3


             PHOTOELECTRIC MAXIMUM OF SZ LYNCIS

The variable star SZ Lyncis (BD +44d1718, HD 67390) was discovered by
Hoffmeister (1949). Broglia (1963) classified SZ Lyn as a dwarf cepheid
(AI Vel stars), having a period of near 0.12 day and a large amplitude
light variation of DeltaV=~0.5 magnitude. Van Genderen (1967) found that the
variation in the times of maximum might fit a sine curve with a period
of 1129 days. However, that data only covered about 1.6 cycles so the
believability of the sine curve was somewhat uncertain. Barnes and
Moffett (1975) reexamined all the published times of maximum and added
4 new timings. They found the times of maximum to vary with a period
of approximately 1146 days having an amplitude of approximately 1000 sec.
They felt that any doubt of the reality of the sinusoidal variation was
now removed since 3.8 cycles had been observed and interpreted it to be
a light-travel-time effect coming from the orbital motion of SZ Lyn about
an unseen companion.
   To see if the times of maximum would continue to follow the sinusoidal
curve we observed SZ Lyn with the 76-cm telescope at the McDonald Observatory 
using the high speed photometer described by Nather and Warner (1971).
The observations were obtained with an Amperex 56DVP photomultiplier and a
standard set of Johnson UBV filters. The integration time was 10 sec/filter,
yielding a cycle time of 40 seconds, a fourth filter position contained no
filter.


                 TABLE I.
             OBSERVED MAXIMA

JDmax o+
2440000.        CYCLE     (O-C)      psi

2531.7560       36565     +.0026     .846
2532.7210       36573     +.0034     .846
2533.6852       36581     +.0033     .846

   The times of maximum brightness in the B bandpass, see Table I, were
determined visually to an estimated accuracy of +-0.0007 day (1 min.). These
times of maximum were compared to the non-linear ephemeris of Barnes and
Moffett:

T(max)(JD0) = 2,438,124.39828+0.120534906(E)-0.00572cos2pi(1.0518Ex10^-4+0.010)
                     +-.00017+-.00000002    +-.00019        .0091x10^-4 +-.008

   We find that our average (O-C) value of 0.003 day is larger than the
standard deviation (+-0.002) for all the photoelectric data included in
the determination of the non-linear ephemeris. This may suggest that a
redetermination of the period be done with the new observations included.
Before this is done, we feel that many more times of maximum are needed
to achieve a greatly improved period. So it seems that the (O-C) diagram
of SZ Lyn has followed a sine curve for at least 4.5 cycles having a 
period near 1150 days.
   There is nothing in our observations to refute the idea that the 
variation in the times of maximum might be a light-travel-time effect.


                                      JOHN AFRICANO

                                McDonald Observatory
                                Box 1337 Ft. Davis, Texas 79734



References:

Barnes, T. G., and Moffett, T. J. 1975, A. J. 80, 48. [BIBCODE 1975AJ.....80...48B ]
Broglia, P. 1963, Mem. Soc. Astr. Ital. 34, 431. [BIBCODE 1963MmSAI..34..431B ]
Hoffmeister, C. 1949, Astr. Abhand. 12, 1.
Nather, R. E., and Warner, B. 1971, Mon. Not. R. Astr.
   Soc. 152, 209. [BIBCODE 1971MNRAS.152..209N ]
Van Genderen, A. M. 1967, Bull. Astr. Inst. Neth. 19, 74. [BIBCODE 1967BAN....19...74V ]