COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                      NUMBER 556

                                      Konkoly Observatory
                                      Budapest
                                      1971 May 26


    PHOTOMETRY OF DELTA SCUTI VARIABLES HR 2107 and HR 5005

In the course of a survey on Delta Scuti stars observations of HR 2107
and HR 5005 were made at the Pic-du-Midi Observatory in January and April
1970. 
      We used a refrigerated photomultiplier associated with the one-meter
telescope, the measurements were made with pulse counting technique. The
interference filters are

filter  I    Lambda eff = 4220 A   width = 50 A
filter II    Lambda eff = 4700 A   width = 30 A


HR 2107=1 Monocerotis (m_V = 6,28) 

	The comparison star was HR 2001 (m_V = 6,02), the root square
standard deviation of the observations was less than 0.004 m_V, each data point
was the mean of eight or nine  observations using an integration time of ten
seconds.

                    Table 1
  Photometric results Delta m = (HR 2001 - HR 2107)
             Night of 6 - 7 January 1970
--------------------------------------------------
J.D.hel.       Delta m_1 J.D. hel.    Delta m_2
--------------------------------------------------
2440593                 2440593
.449             0.558  .449           0.446
.457             0.565  .459           0.477
.497             0.327  .466           0.448
.511             0.189  .495           0.259
.525             0.165  .510           0.129
.536             0.200  .523           0.095
.544             0.259  .535           0.103
.555             0.350  .542           0.154
.566             0.399  .554           0.231
                        .565           0.276
--------------------------------------------------





      The results are in Table 1, the light curves in Figure I. The measured
period is p = 0.139 day which is nearly the same as that found by DANZIGER
and DICKENS (0.137 day). Amplitudes are 0.19 for filter I and 0.18 for filter II.

      max light filter I = J. D. hel. 2440593.525

and 0.002 days later for filter II observations.
      A second observation was made seven nights later and although it was
short, it is interesting, because it contains the minimum of the light curve. The
results are in Table 2.




                    Table 2
     Photometric results m = (HR 2001 - HR 2107)
            Night of 13-14 January 1970
------------------------------------------------
J.D. hel.   Delta m_1   J.D.hel.   Delta m_1
------------------------------------------------
2440600.375   0.397   2440600.412   0.551
.387          0.456   .429          0.443
.401          0.500
------------------------------------------------



      The time of minimum intensity for filter I was

              J.D.hel. 2440600.408

      The addition of 49,5 periods of 0.139 day onto the maximum observed
on the 6th January gives the minimum at 2440600.4055 J.D. hel which agrees
well with the observed minimum, the period of 0.137 days measured by DANZIGER 
and DICKENS would give a phase error of about pi/2.

HR 5005 (m_V = 6,49)
     
      The comparison star was HR 5014, the light curve is in Figure II.
The time covered by observations is four hours and forty minutes. No significant
variations in the light curve were found during this night, DANZIGER and DICKENS' 
observations on this star were too short to determine a period and our
observations are not conclusive.
      In conclusion, the similitude of the two measured periods of HR 2107
seems to be a good first approximation. In the case of HR 5005 it seems 
necessary to make more observations before we may conclude that it is really a 
Delta Scuti star.

Groupe "Etoiles Variables a Courtes
       Periodes"
PARIS, France
May 1, 1971                       J.-C. VALTIER
                                  Observatoire de Nice
                                  Le Mont-Gros
                                  06-NICE
                                  France

Reference:

DANZIGER, I.J., and DICKENS, R.J., 1967,  Astrophys. Journal, 149, 55 [BIBCODE 1967ApJ...149...55D ]


                       [FIGURE 1]
                       [FIGURE 2]