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Alert Notice 138: Nova Herculis 1991 AND Special request to monitor R Coronae Borealis stars

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THE AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS
    25 Birch Street, Cambridge, MA 02138 USA
    BITNET: aavso@cfaB SPAN: nssdca::cfa8::aavso
     Tel.617-354-0484 FAX 617-354-0665

    AAVSO ALERT NOTICE 138 (March 25, 1991)

NOVA HERCULIS 1991

We have just been informed by the Central Bureau of Astronomical Telegrams and
Guy Hurst, England, of the visual discovery of a bright nova in Hercules by
George Alcock, Yaxley, Peterborough, England, on March 25, 4.35 U.T. He observed
the object on March 25.19 U.T. at 5th magnitude with 10 X 50 binoculars from
inside his house through a plate glass window. Denis Buczynski, Conder Brow
Observatory, confirmed the discovery photographically at 4.45 U.T.

Matsuo Sugano independently discovered the nova photographically on March 24.78 U.T.
at magnitude 5.4 on Tri-X film.

Robert H. McNaught, Siding Spring, Australia, gives the following exact position
for this object:

   R. A. = 18h 44m 12.5s  Decl. = +12deg 10m 51" (1950)

Further magnitude estimates are: Mar. 25.67, 6.5 (R. McNaught); 25.68, 6.8 (M.
Sugano). Accompanying are a finder chart from the AAVSO Variable Star Atlas and
a "d" scale chart of VW Aql, which is relatively close by and has a well
established sequence. Please monitor this bright nova closely and inform us of
its brightness by calling the Headquarters answering machine (617-354-0484)
which is kept on nights and weekends.

SPECIAL REQUEST TO MONITOR R CORONAE BOREALIS STARS

Astronomers at the Center for Astrophysics and Space Astronomy at University of
Colorado and at the Harvard-Smithsonian Center for Astrophysics (see AAVSO
Alert Notice 123
) are continuing their observations of the following R Coronae
Borealis stars with the International Ultraviolet Explorer (IUE) satellite:

1544+28 R CrB

1834-23 V348 Sgr 1838-21 MY Sgr 1910-33 RY Sgr

RY Sgr, which is recovering from a recent minimum, and R CrB are of particular
interest. Please monitor the stars listed above closely in the months of April
and May, especially on April 14 and 15 and May 23, when the IUE satellite is
scheduled to observe them. Your observations during the previous IUE observing
runs have been vital and very much appreciated by the team of astronomers.

Many thanks for your valuable observations!

Clear Skies and Good Observing!

Janet A. Mattei
Director

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