Central Bureau for Astronomical Telegrams
IAUC 4803: Occn OF 28 Sgr BY TITAN; G29-38
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Circular No. 4803
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
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
MARSDEN or GREEN@CFA.BITNET MARSDEN or GREEN@CFAPS2.SPAN
OCCULTATION OF 28 SAGITTARII BY TITAN
The following additional reports have been received (cf. IAUC
4801; given as UT + July 3d22h; t1, t4 are beginning and end times
of the star's fading, and t2, t3 are beginning and end times of the
occultation):
Observer t1 t2 flash t3 t4
Elliott 39m10s 40m30s 42m00s 43m50s 44m50s
Kidger 38 40 39 33 41 25 42 33
A. Elliott (Reading, England). Long. = -0 56'39.7, Lat. =
+51 25'08.6. 0.25-m reflector + image intensifier. Central flash
lasted from 42m00s to 42m15s. Communicated by D. W. Dunham, IOTA.
M. Kidger, R. Casas, L. Sanchez, A. Gomez, and A. Jones (Tenerife).
0.50-m telescope + V filter. At t1, a shallow fading (0.33 mag) of
duration 7 s occurred; a similar event, of duration 3 s, occurred
51 s after t3. A complete obscuration of duration 12 s was seen
at 38m52s; a deep fading of duration 9 s was also seen at 42m02s.
Another complete obscuration, of duration 18 s, occurred at 39m11s.
For the final 4 s before occultation, the star was virtually
undimmed. After t3, a slow rise over 21 s to maximum brightness
was seen. A post-occultation decline to nearly complete
disappearance was seen at t4; no equivalent event was seen prior
to occultation.
G29-38
R. E. Nather, Department of Astronomy, University of Texas,
writes: "High-speed photometry of the white dwarf variable G29-38,
obtained by the Whole Earth Telescope sites at McDonald Observatory,
Mauna Kea, Anglo-Australian Observatory, Kavalur, South African
Astronomical Observatory, Haute Provence, LNA (Brazil), and European
Southern Observatory, shows that the pulse arrival times of the
615.15-s pulsation display systematic variations best explained
by light travel time effects produced by reflex motion about an unseen
orbital companion. Our best fitting model to the observations yield
an orbital eccentricity of 0.71, a minimum mass of 0.5 M solar mass,
a projected semi-major axis of 0.22 A.U., and a time of periastron
passage given by T(periastron) = JD 2447474 + 115 (+/- 16) E. The
pulsation data suggest a low inclination for the orbit, implying that
the unseen companion is either a neutron star or black hole. Velocity
variations of up to 40 km/s can be expected."
1989 July 6 (4803) Daniel W. E. Green
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