COMMISSION 27 OF THE I. A. U.
            INFORMATION BULLETIN ON VARIABLE STARS
                         Number 3364

                                              Konkoly Observatory
                                              Budapest
                                              8 August 1989

                                              HU ISSN 0374-0676


     CALL FOR A CAMPAIGN OF LONG-TERM PHOTOMETRY OF SYMBIOTIC STARS


We suggest to launching an observing campaign for photometry of the 
selected 28 symbiotic stars (SS).

Long-term (weeks to decades) variations of the brightness (amplitudes 2 to 7
mag) related to the outbursts of SS and sometimes also to orbital motion of the
components are commonly observed in many SS, In some cases short-term (minutes
to hours) variations (amplitudes 0.01 to 1 mag) are seen, very probably caused
by the physical effects in the accreted material around the compact component,
The changes of brightness are sudden and unexpected, being the outcome of
strong interaction among the components, although their very cause could be
different for particular systems. Detailed information on SS one may find
besides the quoted references also in the volume: "The Symbiotic Phenomenon",
Proc. of the 103rd Colloquium of the IAU, Torun, Poland, August 18 - 20, 1987,
Edited by Mikolajewska, J., Friedjung, M., Kenyon, S. J. and Viotti, R.,
Dordrecht, Holland.

The proposed programme is aimed at long-term photometry mainly in the standard
Johnson UBV system. Its purpose is (i) Compilation and publication of the
original photometric data.

                   Table I.

     List of the- chosen symbiotic stars

Star       alpha 1950.0   delta 1950.0        V      Sp
             h  m  s         d '  "           m
EG And      00 41 52.7      40 24 22.6        7.5     M2
AX Per      01 33 05.7      54 00 07         12       M
V741 Per    01 55 32.9      52 39 15                  G2
UV Aur      05 18 33.3      32 27 50          7.9     C
BX Mon      07 22 52.7     -03 29 51         12       M4
TX CVn      12 42 17.9      37 02 14          9.3     M0
RW Hya      13 31 31.9     -25 07 29         10       M2
T CrB       15 57 24.5      26 03 39         10.0     M3
AG Dra      16 01 23.2      66 56 25         11.2     K3
Draco C-1   17 19 08.5      57 53 01         17.0     C1,2
RS Oph      17 47 31.6     -06 41 40         11.5     M2
AS 289      18 09 34.7     -11 40 55         10.5     M3
YY Her      18 12 25.9      20 58 20         12       M2
AS 296      18 12 33.0     -00 19 53         10.5     M5
V443 Her    18 20 02.9      23 25 47         11.5     M3
AS 338      19 01 32.0      16 21 47         11.5     M5
BF Cyg      19 21 55.2      29 34 34         12       M4
CH Cyg      19 23 14.2      50 08 31          7       M6
HM Sge      19 39 41.4      16 37 33         16       M
AS 360      19 43 35.7      18 29 23         11.0     M6
CI Cyg      19 48 20.6      35 33 23         11.1     M4
V1016 Cyg   19 55 19.8      39 41 30         16       M6
PU Vul      20 19 01.1      21 24 43          9       M4-5
V1329 Cyg   20 49 02.6      35 23 37         14       M5
V407 Cyg    21 00 24.1      45 34 41         15       M
AG Peg      21 48 36.2      12 23 27          9.4     M2
Z And       23 31 15.3      48 32 31         10.5     M2
R Aqr       32 41 14.3     -15 33 43          5.8     M7

(ii)Making sense to the observations of long-term variations of brightness for
    various SS and also for a single observer.

The aims of the programme could be well fulfilled by rather short (an hour)
observations and therefore it is quite suitable for filling in the gaps between
other planned observations. Thus the participation in the campaign could
enhance the efficiency of using Your instrument without disturbing Your main
research programme.

Everybody who wish to participate could select an arbitrary SS (not only those
that are proposed by the undersigned) that could be most easily attached to
his/her own programme.

All contributions will be gathered by the undersigned and subsequently
published in Contr. Astron. Obs. Skalnate Pleso annually (September
dead-line). All astronomers who submit good quality data will become the
coauthor of the paper and will receive its reprint.

The proposed list contains SS accessible from the northern hemisphere and
bright enough for photometry with a small telescope. The data in our list were
taken from the book by Kenyon (1986), The values of V magnitudes and spectral
types serve for orientation only and describe predominantly the cold components
of SS.

Moreover we prepared the finding charts for every programme SS after Becvar
(1962, 1964), POSS (1953), Dixon et al, (1985) and Allen (1984), We selected
the comparison stars following the Catalogue by Blanco et el. (1968) and the
SAO Star Catalog (1966), In all cases the comparison star S_1 was measured in
all colours of the UBV system. We recommend to derive secondary comparison
stars in cases when the angular distance between SS and S_1 is rather large.
The observations should be reduced to the international colour system.

We are ready to submit complete campaign instructions to the participants upon
request. Of course, all additions and suggestions from the participants are
most welcome.


LADISLAV HRIC, AUGUSTIN SKOPAL
Astronomical Institute of the Slovak Academy of Sciences,
059 60 Tatranska
Lomnica, Czechoslovakia

References:

Allen, D. A.: 1984, Proc. ASA 5, 369. [BIBCODE 1984PASAu...5..369A ]
Becvar, A.: 1962, Atlas Borealis, Praha [BIBCODE 1962atbo.book.....B ]
Becvar, A.: 1964, Atlas Eclipticalis, Praha [BIBCODE 1964atec.book.....B ]
Blanco, D. M., Demers, S., Douglas, G. G., Fitzgerald, M. P.: 1968, Publ. U. S.
   Naval Obs. 2nd ser. 21. [BIBCODE 1968PUSNO..21....1B ]
Dixon, R. S., Gearhart, M. R., Schmidtke, P. C.: 1985, Atlas of the Sky Overlay
   Maps (for the POSS) 2nd Edition, Ohio State University Radio Observatory. 
Kenyon, S. J.: 1986, The Symbiotic Stars, University Press, Cambridge. [BIBCODE 1986syst.book.....K ]
Star Catalogue 1966: Smithsonian Astrophysical Observatory, Part 1, 2, 3.