COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                       Number 3131



                                     Konkoly Observatory
                                     Budapest
                                     19 January 1988

                                     HU ISSN 0374-0676



                     53 Psc REVISITED


 53 Psc (B2.5 IV, HR 155, HD 3379) is a variable star located on the red
side of the Beta CMa star instability strip. Williams (1954), Mathews (1956)
and Sareyan et al. (1979) observed short period variations in light and radial
velocity. Large profile variations were also claimed by Mathews (1956) and
Sareyan et al. (1979). The quoted periods range from 0.08 to 0.091 day and
the amplitudes are small : 0.01 mag in the UV domain, 0.002 to 0.01 in the
blue region, a few km/s to 25 km/s in radial velocity over a night. Percy (1971)and
Jerzykiewicz (1973, in Sareyan et al. 1979) found it to be constant in the
B and the y filter respectively.

  Recently, Wolf (1987) published a V light curve with an amplitude of 0.035
mag and a period of 0.096 d.
  We report here on series of observations that we performed on 53 Psc in
1982 and 1987 with the 62 cm telescope of the Nice observatory at Pico del
Veleta (Spain).
 Two comparison stars, viz. 34 Psc (HR 26) and 66 Psc (HR 254), were used.
The observations were made through our UV filter "4" and blue filter "5"
(Sareyan et al., 1976) in 1982. In 1987 we used Stromgren u and b filters.
Two nights of observation were obtained in October 1982, while in 1987, 2 and
4 nights were obtained in September and November respectively. The observational
runs lasted more than 4 hours. The air masses were less than 2 during
each observing sequence. Although the quality of the different nights were
not of first class, a variation with a total amplitude over 0.01 mag would
have been detected. This was not the case on any given night.
 In view of these results the behaviour of 53 Psc appears rather peculiar:
observed at different scattered moments this star exhibits variations with
amplitudes varying from 0.002 to 0.035 mag in visible light and from few to
25 km/s in radial velocity.
  Because a considerable amplitude in light variations is only observed on a
single night from among more than fifteen, it is statistically not probable
that the observed amplitude changes are related to a beat period between 
interfering modes.
 Although its period is very short, the pulsational constant of 53 Psc
derived from Shobbrook's (1985) new photometric calibration is equal to 0.017
which is a value similar to the pulsational constants of the Beta CMa variables
in NGC 6231 (Shobbrook, 1985).
 The observed amplitude variations could be related to the location of 53 Psc
at the low temperature border of the Beta CMa instability strip where the mechanism
responsible for the instability is perhaps not enough efficient to maintain a
stable pulsation. It would be interesting to look for such a phenomenon in iota
Her, another star of this region of the HR diagram in which short period 
variations have also been detected (Chapellier et al., 1987).
  Another possibility is that 53 Psc presents long term changes in amplitudes
similar to those pointed out in different Beta CMa stars (Chapellier, 1986).
  More simultaneous photometric and spectrographic observations are needed in
order to obtain a better understanding of the behaviour of 53 Psc which could
lead to new ideas on the mechanism responsible for this type of variability.


                  J.M. LE CONTEL 1, E. CHAPELLIER 1, J.C, VALTIER 1,
                  E. RODRIGUEZ 2, P. SEDANO 2,
                  P.J. MOREL 1, D. LE CONTEL 1

                  (1)L. A.128, Observatoire de Nice
                  B.P. 139 - 06003 NICE CEDEX, France
                  (2) I.A.A.
                  Apartado 2144, GRANADA, Spain


References:

Chapellier, E.: 1986, Astron, Astrophys. Suppl. Ser., 64, 275. [BIBCODE 1986A&AS...64..275C ]
Chapellier, E., Le Contel, J.M., Valtier, J.C., Gonzalez-Bedolla, S.F. Ducatel,
      D., Morel, P.J., Sareyan, J.P., Geiger, I., Antonelli, P. : 1987,
      Astron. Astrophys., 176, 255. [BIBCODE 1987A&A...176..255C ]
Mathews, R.T.: 1956, Publ, Astron. Soc. Pacific, 68,455. [BIBCODE 1956PASP...68..455M ]
Percy, J.R. : 1971, Astron. J., 76, 1105. [BIBCODE 1971AJ.....76.1105P ]
Sareyan J.P., Le Contel J.M., Valtier J.C.: 1976, Astron. Astrophys. Suppl. Ser.
      24, 129. [BIBCODE 1976A&AS...25..129S ]
Sareyan, J.P., Le Contel, J.M., Ducatel, D., Valtier, J.C.: 1979, Astron.
      Astrophys., 72, 313. [BIBCODE 1979A&A....72..313S ]
Shobbrook, R.R. : 1985, Monthly Not. Roy. Astron. Soc., 214, 33. [BIBCODE 1985MNRAS.214...33S ]
Williams, A.D. : 1954, Publ. Astron. Soc, Pacific, 66, 88. [BIBCODE 1954PASP...66...88W ]
Wolf, M. : 1987, IBVS, No. 3003.