COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                     NUMBER 243


                    ANNOUNCEMENT


An IAU Colloquium on Variable Stars, the fourth in the Bamberg-Budapest series,
will be held in Budapest on 5-9 September 1968, with the theme "Non-Periodic
Phenomena in Variable Stars". The meetings will be held at the Hungarian
Academy of Sciences, which will also act as hosts for the Colloquium.

This announcement is being sent to members of IAU Commissions 27 and 42, and to
a number of other individuals and institutions. However, the facilities are
limited in size, and so invitations can be extended only to those who can
contribute effectively to the scientific program. Those wishing to receive
invitations should write as soon as possible to Prof. L. Detre, Chairman of
the Local Organizing Committee, Konkoly Observatory, P.O. 114, Box 67,
Budapest XII. Hungary, giving information on their proposed contribution.
Prompt response is important, since the final list of those invited
participants who will require visas must be in the hands of the Hungarian
authorities by 15 April.

The purpose of the Colloquium is to focus attention, not primarily on the
irregular variable stars themselves, but on phenomena (in any kind of variable)
that do not repeat in a simple cyclic fashion. Contributions may present
either observational results, or theoretical studies. A provisional plan of
organization is as follows.

I. Theory

1. Statistical and astrophysical interpretation of irregularities.
2. Modern techniques of observation or analysis.

II. Intrinsic Irregular Variables

1. Very young stars: T Tauri, etc.
2. Be and shell stars.
3. Flare stars.
4. Irregular magnetic variables.
5. R CrB variables.
6. Irregular activity in novae or supernovae (at the outburst).

III. Irregular Activity in Periodic Variables

1. Beta CMa, Delta Sct variables.
2. RR Lyr, Delta Cep variables.
3. Late-type giants: long-period variables, Miras, irregulars.

IV. Non-Periodic Phenomena in Binary Systems

1. Hot, very short-period eruptive binaries: old novae, U Gem stars, Sco
   XR-1, etc.
2. Symbiotic stars.
3. Contact binaries and W UMa stars.
4. Conventional binaries:
   (a) The observed period variations - interpretation in terms of gas streams,
   mass exchange, etc.
   (b) Phenomena of atmospheric eclipses.

Certain of these topics will be introduced by invited speakers. The papers
presented at the Colloquium will be published in a Budapest Mitteilung.
Further details will be sent to participants later.

The Scientific Organizing Committee:

G.H. HERBIG (Chairman),
A. BOYARCHUK,
M.W. FEAST,
D. McNAMARA,
W. WENZEL (for Commission 27),
J.E. MERRILL,
D.J.K. O'CONNELL,
V. TSESEVITCH (for Commission 42)

December 26, 1967