COMMISSION 27 OF THE I. A. U.
	 INFORMATION BULLETIN ON VARIABLE STARS
		     Number 2652

			   	   Konkoly Observatory
				   Budapest
				   3 January 1985

				   HU ISSN 0374 - 0676


       PHOTOELECTRIC OBSERVATIONS OF V541 Cas AND ITS PERIOD


  The eclipsing system V541 Cas was observed photoelectrically from September
to December in 1982 with the 60 cm reflector at Beijing Astronomical 
Observatory. Some minimum times were obtained in December 1983 and September 1984.
  The photoelectric equipment is very close to the Johnson's standard system.
A total of 470 photoelectric BV observations were corrected for differential
extinction and transferred to UBV system.

  The coordinates of the comparison and check stars are given in Table I.

		     Table I
       ----------------------------------------
	Name	       R.A.(1982)    Dec.(1982)
       ----------------------------------------
       Comp.Star       2h33m05s      63d10'20"
       Check Star      2 32 44	     63 10 02
       ----------------------------------------

Using Kwee and Van Woerden's method, seven times of primary minimum and
five times of secondary minimum were determined. They are given in Table II.

		     Table II
----------------------------------------------------------------
JD Hel. 			  JD hel.
2445000+       filter m.e.   Min. 2445000+   filter  m.e.   Min.
----------------------------------------------------------------
231.2429       V      0.0006 II   231.2425	B    0.0008  II
232.1523       V      0.0005 II   232.1527	B    0.0001  II
236.2487       V      0.0007  I   236.2472	B    0.0004   I
258.0832       V      0.0009  I   258.0834	B    0.0003   I
266.2743       V      0.0007  I   266.2732	B    0.0006   I
267.1832       V      0.0011  I   267.1809	B    0.0010   I
293.1125       V      0.0006 II   293.1120	B    0.0002  II
298.1162       V      0.0020  I   298.1151	B    0.0008   I
329.0510       V      0.0005  I   329.0517	B    0.0007   I
675.2475       V      0.0001 II   675.2473	B    0.0001  II
962.3050       V      0.0004  I
967.3099       V      0.0006 II
---------------------------------------------------------------


  V541 Cas is a rather neglected system. In 1974 give its ephemeris
as follows:
   JD Hel. Min	I = 2439026.542 + 0.909026d*E

                       [FIGURE 1]

   O-C Diagram of the times of minimum light of V541 Cas. "triangle"
  represents photoelectric observations.

                      Table III

------------------------------------------------------------------------
 JD Hel.Min.	   E	     (O-C)   Min. Method   Observer
------------------------------------------------------------------------
2432477.4000   -7204.5	      0.2829d II   pg.	 Weber (see Busch,1974)
    503.3900   -7176.0	      0.3643   I   pg.	 Weber (see Busch,1974).
   8843.3300   - 201.5	     -0.0219  II   pg.	 Romano (see Busch,1974)
    950.2600	- 84.0	      0.0921   I   pg.	 Romano (see Busch,1974)
   9026.5370	   0.0	      0.0070   I   pg.	 Busch
     27.4510	   1.0	      0.0119   I   pg.	 "
     53.3640	  29.5	      0.0164  II   pg.	 "
     57.4570	  34.0	      0.0185   I   pg.	 "
     58.3540	  35.0	      0.0065   I   pg.	 "
     88.3640	  68.0	      0.0171   I   pg.	 "
 41.595.4580	2826.0	     -0.1109   I   pg.	 "
     96.3540	2827.0	     -0.1240   I   pg.
    602.2740	2833.5	     -0.1130  II   pg.	 "
  42036.3120	3311.0	     -0.1571   I   pg.	 "
  45231.2427	6825.5	     -0.1617  II   pe.	 this paper
     32.1525	6826.5	     -0.1610  II   pe.	 "
     36.2480	6831.0	     -0.1563   I   pe.	 "
     58.0833	6855.0	     -0.1387   I   pe.	 "
     66.2738	6864.0	     -0.1299   I   pe.	 "
     67.1821	6865.0	     -0.1307   I   pe.	 "
     93.1122	6893.5	     -0.1091  II   pe.	 "
     98.1156	6899.0	     -0.1056   I   pe.	 "
    329.0514	6933.0	     -0.0783   I   pe.	 "
    675.2474	7313.5	      0.2156  II   pe.	 "
    962.3050	7629.0	      0.4608   I   pe.	 "
    967.3099	7634.5	      0.4658  II   pe.	 "
-----------------------------------------------------------------

                           [FIGURE 2a]
                           [FIGURE 2b]

                BV light curves of V541 Cas in 1982.

 This ephemeris,  however, cannot be extended till the recent times of
minima (in Table II), and the period 0.909026 days also cannot be used to
combine our BV observations into smooth Light curves.

 Table III listed all the historic minima and their O-C based on ephemeris

(1). The O-C diagram (see Fig. 1) reveals that an abrupt change in the period
of V541 Cas happened between 1973-1982.

  If we simply use our much more accurate photoelectric minima, the following
new light elements could be proposed for current use after 1982

   JD Hel. Min I = 2445962.3049 + 0.90984695d*E
	        	+-.0003  +-.00000044*E

  The B, V light curves of V541 Cas are shown in Figure 2.

  It shows that: (1), there are obvious brightness variations outside the
eclipse; (2), the primary and secondary minima have almost the same depth;
(3), its light curve is very similar to those of detached system AT and AZ
Cam (Zhai et al, 1983 and Zhang et al., 1984).
  The light curve of the star and the change of its period should be analyzed
in more detail in a subsequent paper.





		     ZHANG JI-TONG, ZHANG RONG-XIAN,
		     LI CHI-SHENG, ZHAI DI-SHENG,
		     Beijing Astronomical Observatory, China





References:

Busch, H., 1974, I.B.V.S. No. 887
Zhai Di-sheng, Zhang Rong-xian and Zhang Ji-tong, 1983, I.B.V.S. No. 2274
Zhang Rong-xian, Zhang Ji-tong and Zhai Di-sheng, 1984, Acta Astronomica
                                                        Sinica, 25, 42 [BIBCODE 1984AcASn..25...42Z ]