COMMISSION 27 OF THE I.A.U.
        INFORMATION BULLETIN ON VARIABLE STARS
                     NUMBER 103




                                       Konkoly Observatory
                                       Budapest
                                       24 July 1965

                    ROSINO'S OBJECT


    On November 17, 1961 Rosino (1) discovered a variable
star of 14th magnitude at maximum near the galaxy NGC 4501 (M 88).
A second outburst of the star was observed by Zwicky (2) on March
26-27, 1965 at Palomar. Moreover, the writer (3) was able to find
an old maximum on April 26, 1892 inspecting the Isaac Roberts Plates.
In the following Table the Asiago observations during the recent
outburst are given. All the plates were obtained with the 50-40 cm
Schmidt telescope,  except that of May 2, taken with the 122 cm
reflector. The comparison stars are given in (3). The magnitudes
between brackets are derived from panchromatic emulsions and are
only indicative. A 103a-O plate + UG2 filter taken on April 29
shows that the variable has a strong ultraviolet emission.

  Plate No.      Date                     UT                  mpg


  5402         March 27, 1965           21h 25m                (12.9)

  5449         April  3                 22  31                 (13.6)

  5469               22                 21  26                  15.5

  5480               29                 23  15                  17.3

  7022         May    2                 23  41                  18.9

  5502                3                 23  21                  18.6:

  5507         June  17                 21  46                 [17

  5540               25                 22  18                 [17



These data show that the variable has fallen down of six
magnitudes in about one month. The rate this decline is comparable
with that of the 1961 outburst (3). The 1965 observations so far published
do not show has been the main peculiarity of the light
curve in 1961; namely the deep minimum on December 8. With this regard
it should be noted that the star has not been observed at Asiago on
December 5-6, 1961, contrarily to what is reported in (4). The 
observation at the Crimean Observatory on December 5-6, giving mpg = 15.8
allows then to establish that the decline of this secondary minimum
was less rapid than the rising, which took place in less than one day.

    Concerning the membership of the present variable star to the
class of recurrent novae or U Geminorum, it is very difficult to give
a definitive answer at the present time. However the 1961 observations 
at Asiago, i.e. continuous spectrum without emission lines
on November 22 and December 12, color B-V = 0.0 on December 16, 
indicate that the star might be assigned to the U Geminorum class. In
any case the object is a very peculiar one and should be constantly
followed in the future.


(1)   IAU Circular No. 1782, 1961
(2)   IAU Circular No. 1902, 1965
(3)   Ann. d'Ap. 27, 298, 1964  [BIBCODE 1964AnAp...27..298B ]
(4)   Astron. Cir. USSR No. 327, 1965


Asiago Astrophysical Observatory, July 1965


                                 F. BERTOLA