COMMISSIONS 27 AND 42 OF THE IAU 
               INFORMATION BULLETIN ON VARIABLE STARS 
                            Number 3703 
 
                                          Konkoly Observatory 
                                          Budapest 
                                          12 March 1992 
 
                                          HU ISSN 0374 - 0676 
 
 
      ON MAGNETIC FIELD OF Be STARS EM Cep AND LQ And 
 
 Some Be stars have a low-amplitude (not larger than 0.1m) 
photometric variability with periods within an interval of 0.5d-2d 
and a characteristic brightness curve which has two minima and maxima. 
EM Cep (BI IVe, P = 0.806187d (Breinhorst and Karimie, 1980)) and LQ 
And (B3-4, IV-Ve, P = 0.061904d (Harmanec et al., 1991)) are the most 
typical representatives of this group of objects. 
 
 Harmanec (1984) has suggested that these stars have the same nature 
of variability as sigma Ori E, a known Be star with a magnetic field 
(Landstreet and Borra, 1978), whose variability coincides with the 
photometric period 1.19080d. In May 1990 we obtained some estimates 
for the magnetic field of these stars in order to check this 
hypothesis. 
 
 Observations of EM Cep and LQ And were carried out at the primary 
focus of the 6-m telescope with a hydrogen magnetometer (Shtol' 1991). 
The measurements were made simultaneously in the wings of hydrogen 
lines H_gamma and H_beta with a mask width of 10 A (5 A from the 
line core). The hydrogen line profiles of these stars were 
investigated in a preliminary way from the high-dispersion 
spectrograms obtained on the same telescope. This allowed to select 
the width and location of the mask so that to exclude the contribution 
from the envelope component to the measurement of circular 
polarization as much as possible. So, in the case of EM Cep there is 
no envelope contribution and it is not significant in the region of H_beta 
line in the case of LQ And. Altogether we obtained 5 polarization 
estimates for EM Cep and 1 estimate for LQ And during 3 nights. 
 
  The results are presented in Table below: 
 
JD          Delta t(day)   Be(Gs)  +/- sigma 
2440000.+                         EM Cep 
8026.4800      0.0779    -429        297 
8027.4376      0.0577    + 96        342 
8027.4944      0.0536    -122        352 
8028.3995      0.0655    -435        354 
8028.4493      0.0309    +261        501 
                                  LQ And 
8026.4991      0.0576    +491        266 
 
 
 These results show that EM Cep probably has neither a magnetic field 
exceeding the observation error nor a variability with the photometric 
period of 0.806187d. 
 
 The only estimate of the magnetic field of LQ And does not allow to 
draw any conclusion on the presence of a magnetic field. A comparison 
of our data with the magnetic field strength for this star obtained 
earlier by Harmanec et al. (1991) points that it is either absent or 
small. 
 
 Thus, our observations of EM Cep and LQ And cast doubt on similar 
nature of variability of these stars and the magnetic Be star sigma 
Ori E. 
 
 
            A.E. TARASOV^1, V.D. BYCHKOV^2, V.G. SHTOL'^2 
 
        1 Crimean Astrophysical Observatory, Nauchny, Ukraine 
        2 Special Astrophysical Observatory of Russian AS, Nizhnij 
          Arkhyz 
 
 
References: 
 
Breinhorst, R.A., Karimie, M.T.: 1980, PASP, 92, 432.  [BIBCODE 1980PASP...92..432B ]
 
Harmanec, P.: 1984, Bull. Astron.  Inst.  Czechosl., 35, 193.  [BIBCODE 1984BAICz..35..193H ]
 
Harmanec, P., Matthews, J.M., Wehlau, W.H., Bohlender, D.A., Horn, J., 
  Koubsky, P., Walker, G.A.H., Yang, S.: 1991, Bull. Astron.  Inst. 
  Czechosl., 42, 1.  [BIBCODE 1991BAICz..42....1H ]
 
Landstreet, J.D., Borra, E.F.: 1978, Astrophys. J., 224, L5.  [BIBCODE 1978ApJ...224L...5L ]
 
Shtol', V.G.: 1991, Astrofiz. Issled.  (Izv.SAO) (in Russian), 33, 
  176. [BIBCODE 1991AISAO..33..176S ]