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IAUC 4974: Poss. N IN Sgr; Millisec PULSAR IN TERZAN 5; 1990a

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                                                  Circular No. 4974
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM     EASYLINK 62794505

     W. Liller, Vina del Mar, Chile, reports his discovery with
Problicom of an apparent nova at R.A. = 17h56m07s, Decl. =
-29 09'.7 (equinox 1950.0).  V2449 Sgr is 105" due east of this
object.  Magnitude estimates from 2415 film:  Feb. 20.36 UT,
[11 (orange filter); 23.38, 8.0 (orange filter); 24.33, 8.9;
Mar. 2.39, 9.8.

     A. G. Lyne and S. Johnston, University of Manchester, Jodrell
Bank; R. N. Manchester and L. Staveley-Smith, Australia Telescope
National Facility; N. D'Amico, University of Palermo; J. Lim,
Macquarie University; A. S. Fruchter, Carnegie Institution of
Washington; and W. M. Goss, Very Large Array, National Radio
Astronomy Observatory, write:  "We report the discovery of an
eclipsing millisecond binary pulsar in the globular cluster Terzan
5 (Terzan 1971, A.Ap. 12, 477).  The pulsar, which has a period
of 11.563 ms and dispersion measure of 240 cm-3 pc, was detected
in observations made at the Parkes radiotelescope in the 20-cm
band in 1989 November and 1990 January.  Variations in the
apparent pulsar period show that the pulsar is a member of a
binary system.  The orbit is of low eccentricity and has a period
of 1.8 hr.  Only the ascending portion of the pulse period
curve is seen, suggesting that the pulsar is in eclipse for
nearly half of the orbital period.  The minimum companion mass
is 0.1 solar mass.  The 20-cm mean flux density of the (uneclipsed)
pulsar is 2 mJy.  This is equal within errors to the flux density
of a steep-spectrum continuum source, located within 20" of the
cluster center, which was detected by the Very Large Array in
1989 June and September."

     Total visual magnitude estimates (cf. IAUC 4963):  Feb. 17.27,
12.4 (A. Hale, Las Cruces, NM, 0.41-m reflector); 20.97, 12.7 (S.
Korth, Dusseldorf, W. Germany, 0.36-m reflector); 21.97, 12.0 (O.
Midtskogen, Tranby, Norway, 0.32-m reflector); 25.06, 12.1 (G. Kronk,
Troy, IL, 0.33-m reflector); 28.01, 12.3 (B. H. Granslo, Blindern,
Oslo, Norway, 0.20-m reflector); Mar. 1.89, 12.0 (Midtskogen); 3.04,
12.5 (H. Dahle, Oslo, Norway, 0.20-m reflector); 3.33, 12.5 (Hale).

1990 March 7                   (4974)             Daniel W. E. Green

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