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IAUC 6251: 51 Peg; C/1995 Q1

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                                                  Circular No. 6251
Central Bureau for Astronomical Telegrams
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)
Phone 617-495-7244/7440/7444 (for emergency use only)

     M. Mayor and D. Queloz, Geneva Observatory, have reported
the discovery of a Jupiter-mass object in orbit around the solar-type
star 51 Peg.  The announcement was made in Florence on Oct. 6 at the
Ninth "Cambridge" Workshop on "Cool Stars, Stellar Systems, and the Sun".
The claim is based on 18 months of precise Doppler measurements made with
the ELODIE spectrograph of the Observatoire de Haute-Provence.  The
parameters of the orbital motion are as follows: P = 4.2293 +/- 0.0011
days, e = 0 (assumed), K = 0.059 +/- 0.003 km/s, T0 = 2449797.773 +/- 0.036.
The minimum mass of the companion is 0.47 +/- 0.02 Jupiter mass.
Alternative explanations for the radial-velocity variation (pulsation
or spot rotation) seem to be ruled out by the absence of any
significant corresponding photometric variation.

     Following the Oct. 6 announcement, confirmation of the 4.2-day
radial-velocity variation was obtained in mid-October by G. Marcy
and P. Butler (San Francisco State University, University of California
atBerkeley) at the Lick Observatory, as well as by a joint team from
the Harvard-Smithsonian Center for Astrophysics (R. Noyes, S. Korzennik,
M. Krockenberger and P. Nisenson), the High Altitude Observatory (T. Brown,
T. Kennelly and C. Rowland) and Pennsylvania State University (S. Horner).

     G. Burki, M. Burnet and M. Kuenzli, Geneva Observatory and
Lausanne University, communicate: "Intensive photometric monitoring of
51 Peg has been carried out at the European Southern Observatory.  There
is no evidence for eclipses in the system.  The rms of the V magnitude
(on 17 nights) is 0.037, two comparison stars being used.  A 4.2-day
photometric variability larger than 0.002 mag can be ruled out."

     Total magnitude estimates, visual unless otherwise stated (B =
binoculars): Sept. 26.95 UT, 8 (Zhu Xinmin, Xinjiang Province, China;
independent discovery); 30.20, 8.1 (J. Carvajal, Madrid, Spain, 0.44-m
reflector); Oct. 1.15, 7.6, (R. Haver, Frasso Sabino, Italy, 15 x 80 B);
5.18, 8.3 (J. D. Shanklin, Cambridge, England, 14 x 100 B); 7.44, 8.2
(G. W. Kronk, Troy, IL, 20 x 80 B); 14.16, 9.2 (H. Mikuz, Ljubljana,
Slovenia, 0.19-m reflector + CCD + V filter); 19.24, 9.3: (A. Pereira,
Cabo da Roca, Portugal, 0.15-m reflector); 21.50, 8.3 (C. S. Morris,
Pine Mountain Club, CA, 20 x 80 B); 24.11, 9.2 (G. A.  Milani, Mt.
Tomba, Italy, 20 x 80 B).

1995 October 25                (6251)              Brian G. Marsden

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