Circular No. 6425
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
Phone 617-495-7244/7440/7444 (for emergency use only)
 
 
CM DRACONIS
     E. L. Martin and H. Deeg, Instituto de Astrofisica de Canarias,
report:  "The TEP (Transits of Extrasolar Planets) international
collaboration (working group:  M. Chevreton, H. Deeg, L. Doyle, J.
Jenkins, W. Lee, E. L. Martin, E. Palaiologou, J. Schneider) has
been monitoring CM Dra since the first half of 1994 using CCD
cameras on eight telescopes, with the aim of detecting planetary
transits in this eclipsing-binary system.  So far, about 500 hr of
effective integration time have been analyzed in some 16 000 CCD
frames.  Night-to-night variations have been usually < 0.02 mag in
the R band.  In an 8.2-hr observation in photometric conditions
with the IAC80 telescope at Teide Observatory beginning 1994 May 27,
the R brightness of CM Dra started at 0.08 mag below the normal
zero level and gradually increased to normal in 4 hr; in the next
two hours it decreased again by 0.04 mag, and in the last two hours
it returned to its normal level (Deeg et al. 1996, A.Ap. Trans., in
press).  The first light drop is of amplitude similar to that
reported on IAUC 6423 and could be due to the same planet; the
period would be about 735 days or a submultiple of it.  However,
caution must be exercised because confirmation of a planetary
occultation requires repeated observations of transits in at least
two different filters and the determination of the total duration
and shape, which depend in a predictable way on the phase of the
binary orbit (Jenkins et al. 1996, Icarus 119, 244).  We also note
that timing of CM Dra eclipses made by the TEP group in 1994-1996
shows that there is a mean delay of about 130 s with respect to the
ephemerides of Lacy (1977, Ap.J. 218, 444), though no timing
periodicity is apparent in our data.  We encourage interested
observers to contact one of the TEP members for coordination of
observations."

                      (C) Copyright 1996 CBAT
1996 June 24                   (6425)            Daniel W. E. Green