Central Bureau for Astronomical Telegrams
IAUC 3051: Occn OF SAO 158687 BY URANIAN Sat BELT; CSVS 6997
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Circular No. 3051
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Cable Address: SATELLITES, NEWYORK Telex: 921428
Telephone: (617) 864-5758
OCCULTATION OF SAO 158687 BY URANIAN SATELLITE BELT
J. L. Elliot, E. Dunham and D. Mink, Cornell University, report
that their observations from the Kuiper Airborne Observatory
show a group of five secondary occultations of SAO 158687 both before
and after the star was occulted by Uranus on Mar. 10 (cf. IAUC
3048). They note that the times of the individual secondary
occultations are remarkably symmetrical with respect to the occultation
by Uranus itself and suggest that the occulting material is therefore
confined to specific narrow rings in the 7000-km-wide belt.
The events, labeled with Greek letters in order of increasing
separation from Uranus, were recorded as follows, where the UT times
correspond to the middle of each occultation, and the subscripts 1
and 2 refer to the different (mean) locations of the Airborne
Observatory (the altitude of which was 12.5 km), namely, 1: Long. =
-82o11', Lat. = -50o20'; 2: Long. = -101o19', Lat. = -50o21'.
Event UT Duration Event UT Duration
alpha1 20h20m55s 1s alpha2 21h45m52s 1s
beta1 20 19 34 1 beta2 21 47 06 1
gamma1 20 16 58 1 gamma2 21 49 45 1
delta1 20 16 03 1 delta2 21 50 39 1
epsilon1 20 11 46 7 epsilon2 21 54 06 4
R. L. Millis, Lowell Observatory, reports that five occultation
events were also detected by P. Birch, D. Trout and himself
with the 61-cm reflector at the Perth Observatory (cf. IAUC 3048).
Mid-times of these events (denoted with subscript 3) are:
Event UT Duration Event UT Duration
alpha3 20h23m43s 1s delta3 20h15m59s 1s
beta3 20 23 19 1 epsilon3 20 10 33 8
gamma3 20 18 44 1-2
M. W. Feast, South African Astronomical Observatory, reports
that J. Churms monitored the occultation at Cape Town (subscript 4)
and (after learning of the times observed by Elliot et al.) provided
the following mid-times for some short-duration events:
Event UT Duration Event UT Duration
alpha4 21h55m20s - delta4 22h00m13s _
beta4 21 56 38 - epsilon4 22 03 44 6s
gamma4 21 59 18 - zeta4 22 07 11 8
These first four events were the only ones of significance (dips of
~ 1 mm on the photometer trace) observed between 21h45m and 22h02m
UT. Observations began at 20h40m, but the trace was less steady
during the early stages because of low altitude. The epsilon4 event was
a major one (amounting to ~ 1 cm on the trace, about as much as the
Uranus occultation itself), and the trace was noticeably ragged
(dips ~ 1 mm) between 22h02m and 22h05m. The zeta4 occultation had a
depth of 3 mm but occurred at the very end of the trace. Feast
remarks that the photometer was a conventional (not a high speed) one
and that the dips of short duration will not be faithfully reproduced
as to their shape.
A letter received from M. K. V. Bappu, Indian Institute of
Astrophysics, gives the time of the beginning of the occultation
observed at Kavalur as 20h19m51s UT (rather than 20h19m15s; cf. IAUC
3048), from which we can define for the middle of the event:
Event UT Duration
epsilon5 20h19m55s 9s
The values correlated below for the distances of the occulting
material from the center of Uranus (in km, and projected on the
plane of Uranus' equator) were derived by the undersigned. The
relative positions of Uranus and the star were adjusted so that the
distances for the first four events with subscripts 1 and 2 coincide
(the mutual agreement among them being +/- 40 km) and so that
the distance for epsilon5 is the mean of those for epsilon1 and 2 (i.e. 51 700
km). Coincidence of the distances for epsilon5 and 1 produces an
increase of ~ 600-700 km in the distances of the rings.
Event Distance Event Distance Event Distance
alpha3 42 200
beta3 42 500
alpha1,2 44 900 alpha4 45 000
beta1,2 45 900 gamma3 45 700 beta4 46 000
gamma1,2 47 900 delta3 47 800 gamma4 48 000
delta1,2 48 600 delta4 48 800
epsilon1 52 000 epsilon3 51 900
epsilon2 51 400 epsilon4 51 600
epsilon5 54 300
Dr. Elliot is planning to make a detailed study of these
occultations and would appreciate receiving observations (including
photometer tracings). His address is: Center for Radiophysics and
Space Research, Cornell University, Ithaca, NY 14853, U.S.A.
CSVS 6997
B. V. Kukarkin and N. E. Kurochkin, Sternberg Astronomical
Institute, propose CSVS 6997 (R.A. = 13h05m57s, Decl. = +32o52'.8, equinox
1900.0) as the counterpart for the radio source OP 313. Moscow
plates show an outburst to mpg ~ 16 in 1958; at minimum mpg ~ 19.
1977 March 21 (3051) Brian G. Marsden
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