COMMISSION 27 OF THE I. A. U.
            INFORMATION BULLETIN ON VARIABLE STARS
                         Number 3591

                                               Konkoly Observatory
                                               Budapest
                                               18 April 1991

                                               HU ISSN 0374 - 0676


              ON THE NEW ERUPTIVE OBJECT IN LIBRA


   Debehogne (1990) reported on the discovery of a new eruptive 
object in Libra at the position 15h07m31.10s, -1d44'01.7"
(1950.0), which appears bright on the sheets of the POSS, but
faint 14m ... 16m on other atlasses and on archival plates.
   Three plates of the Sonneberg Sky Patrol (Ernostar camera)
were taken by P. Ahnert at the European evenings just before
and after the Palomar plates were exposed. On these exposures
the object is invisible (n). Thus the following table for the
blue magnitudes of the star during the time of the eruption
can be made up:

    1955 Apr. 19   22:26 UT   (n) >14.0m   Ernostar 10502
              20   08:05           11.2    POSS O-1402
              20   23:58      (n) >12.5    Ernostar 10510
              21   23:45      (n) >14.0    Ernostar 10516

Our magnitude scale has been linked to the M5 sequence of Arp
(1955; 1962), stars A, B, D, and E. The brightness on POSS
O-1402 in confirmed by a comparison with BD -3d3746 on POSS
O-1431, made with the help of several stars in common on
both sheets: The variable is noticeably fainter than the BD
star, the U, B, V data of which were given by Corben et al.
(1972) and Roman (1955) and have been compiled by Mermilliod
and Nicolet (1977): V=9.85m, B = 10.99m
   Nova type and long-cycle dwarf nova variability can be 
excluded by the short duration of the eruption (<=1 day) and the
small amplitude. The fact, however, that the object is invisible 
on most of the 470 suitable Sonneberg Sky Patrol plates
taken mainly by P. Ahnert, H. Huth and B. Fuhrmann in the years
1929 to 1990 and barely detectable as a faint trace of 14m on
the rest, but never in strong further eruptions, speaks against
an SS Cygni type. It is not a minor planet, as can be seen by
blink comparison of the plates of 1955 Apr. 19 and 21.
   The red magnitude on POSS E-1402 is roughly 10.7m - linking
to the V sequence of Arp (l.c.) and taking into account the
conversion formula of Van den Bergh (1957).
   I thank Mrs. A. Wicklein for inspecting most of the plates.



                                                W. WENZEL

                                            Sternwarte Sonneberg
                                       Zentralinstitut für Astrophysik
                                                Deutschland



References:

Arp, H.C., 1955, Astron. J. 60, p.1 [BIBCODE 1955AJ.....60....1A ]
Arp, H.C., 1962, Astrophys. J. 135, p.311 [BIBCODE 1962ApJ...135..311A ]
Corben, P.M., et al., 1972, Mon. Notes Astron. Soc. South
   Africa 31, p.8 [BIBCODE 1972MNSSA..31....8C ]
Debehogne, H., 1990, IAU Circ. 5131 [BIBCODE 1990IAUC.5131....3D ]
Mermilliod, J.C., Nicolet, B., 1977, A General Catalogue of
          UBV Photoelectric Photometry, Centre de Donnees
          Stellaires, Strasbourg [BIBCODE 1977A&AS...29..259M ]
Roman, N.G., 1955, Astrophys. J. Suppl. Ser. 2, p.195 [BIBCODE 1955ApJS....2..195R ]
Van den Bergh, S., 1957, Astron. J. 62, p.100 [BIBCODE 1957AJ.....62..100V ]