COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                       NUMBER 687

                                          Konkoly Observatory
                                          Budapest
                                          1972 June 20


MULTIWAVELENGTH PROGRAM FOR THE ACTIVE SOURCES 3C 120, BL Lac AND OJ 287


Three variable radio sources which are quite active at both radio and optical
wavelengths are 3C 120, BL Lac, and OJ 287 (the approximate B magnitudes are
15, 16, and 13, respectively). Their long-term variations have been actively
studied at many observatories for a number of years. Very little is known,
however, about their variations on a time scale of less than a day except
in the case of BL Lac, which has been found by Rene Racine to have flickering
on a time scale of minutes. In an attempt to search for variations on a time
scale of hours or shorter, I have organized an international multiwavelength
cooperative program. BL Lac and 3C 120 were observed continuously during the
first and second halves, respectively, of each of five consecutive nights in
November 1971 and OJ 287 was observed all night long during five nights in
February 1972. Observations were made in the United States, France, England,
and Israel. Optical, infrared, and radio wavelengths were monitored.

R. and K. Hackney and R. Leacock at the University of Florida's Rosemary
Hill Observatory found definite evidence for intraday optical variability of
BL Lac, thereby verifying the earlier results of Racine. OJ 287 data obtained
by Epstein at 3.5 mm with the NRAO 36-ft antenna at Kitt Peak strongly
suggest intraday variability, a suggestion partially confirmed by 9-mm
results obtained by B. Gary with JPL's 18-ft antenna at Table Mountain. In
addition, the team of E. Becklin, C.G. Wynn-Williams, and G.
Neugebauer, working in the infrared at 2 microns with the 100-in telescope
at Mt. Wilson found definite intraday variability of OJ 287.

Two "campaigns" are being organized to observe these objects continuously
all night on several consecutive nights in late 1972 and in early 1973.
Redundancy of data is most desirable, so widespread participation is being
sought. Professional astronomers wishing to participate in these international
"campaigns" should write directly to me.

June 6, 1972

                                        EUGENE E. EPSTEIN
                                        The Aerospace Corporation
                                        Box 92957
                                        Los Angeles, California 90009
                                        U.S.A.





                  ERUPTIVE OBJECT IN URSA MAIOR


The eruptive object in Ursa Maior announced by B.V. Kukarkin and D.Ya. Martynov
in IAU Circular 2408 was estimated on Sonneberg patrol plates (Tessar 71/250
mm):

1972 May 13.892 UT    mpg = 11.1


June 7, 1972

H. HUTH
Deutsche Akademie der Wissenschaften
Zentralinstitut fur Astrophysik
Sternwarte Sonneberg