Central Bureau for Astronomical Telegrams
IAUC 2990: 1976e; 1975d; L19-2 AND LFT 1679
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Circular No. 2990
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
Western Union: RAPID SATELLITE CAMBMASS
PERIODIC COMET D'ARREST (1976e)
Further precise positions have been reported as follows:
1976 UT R. A. (1950) Decl. Observer
July 18.71528 19 36 02.29 +18 38 54.4 Candy
20.68750 19 41 57.82 +17 37 04.7 "
31.22309 20 23 43.36 + 8 26 56.7 Helin
Aug. 2.40729 20 34 46.84 + 5 38 17.0 "
3.93476 20 43 07.34 + 3 28 23.8 Waterfield
3.95556 20 43 14.02 + 3 26 35.9 "
7.08303 21 01 32.35 - 1 26 24.0 Codina
7.10560 21 01 40.27 - 1 28 36.6 "
17.68252 22 13 09.31 -19 47 59.6 Harwood
19.01084 22 22 28.25 -21 55 41.8 Rutter
19.22083 22 23 58.19 -22 14 53.3 Giclas
25.63542 23 06 44.04 -30 35 18.6 Candy
27.24062 23 16 31.90 -32 12 21.4 Giclas
28.42378 23 23 23.96 -33 16 08.3 Bus
30.69306 23 35 57.01 -35 01 50.6 C. Jekabsons
Sept. 8.69375 0 15 25.17 -39 16 59.5 Candy
10.70451 0 22 07.26 -39 46 32.2 P. Jekabsons
M. P. Candy, D. Harwood, C. Jekabsons and P. Jekabsons (Perth
Observatory, Bickley). 33-cm astrograph (not 25-cm, cf. IAUC 2968).
E. Helin and S. J. Bus (Palomar Mountain Observatory). Measurer:
Bus. 46-cm Schmidt telescope.
R. L. Waterfield, I. M. Purcell and G. H. Rutter (Woolston Observatory).
Measurer: Waterfield.
J. M. Codina (Fabra Observatory), Computer: N. Torras.
H. L. Giclas (Lowell Observatory). Measurer: N. L. Kantz.
G. K. G. Moore, Department of Physics, University of Wollongong,
writes that a sequence of 5-min 103a-F exposures with the 46-cm
f/5 reflector on Sept. 3.6-3.7 UT shows a small ejection moving
at 20"/hr in a direction opposite to that of the comet's motion.
Z. Sekanina, Center for Astrophysics, informs us that relatively
favorable projection conditions will prevail between Oct. 1976
and Jan.-Feb. 1977 for detecting emissions of submillimeter-sized
and larger debris from P/d'Arrest, extending essentially to the
west of the nucleus, Because of the anticipated very low surface
brightness of the feature, large Schmidt telescopes (or similar
instruments) will be necessary to record it. The ephemeris is on
IAUC 2900 and 2964. For best results calibrated panchromatic
plates and a red filter should be used. High-quality negative
observations should also be reported as they can provide an upper
limit to the production rate of the debris.
The following photoelectric observations were made by H.
Debehogne, J. Surdej and A. Surdej with the 50-cm photometric
reflector at the European Southern Observatory on Aug. 18.2 UT:
diaphragm 5", V = 11.46, B-V = +0.71, U-B = +0.14; 15", 10.86, +0.55,
+0.55; 20", 10.29, +0.68, +0.06; 30", 10.07, +0.63, +0.01.
Selected total visual magnitude estimates and coma diameters:
Aug. 22.24 UT) 6.0, 17' (K. Simmons, Switzerland, Florida, 14 x 100
binoculars); 25,24, 5.9, 20' (D. D. Meisel, Mees Observatory, 7 x
50 binoculars); 29.19, 5,7, 20' (Simmons); Sept. 12.31, 5.8, 10'
(P. Maley, Houston, Texas, 7 x 35 binoculars); 15.29, 6.0, 8'
(Maley); 22.30, 6.4, 10' (Maley; tail 0o.5 long in p.a. 355o).
COMET BRADFIELD (1975d)
The following precise positions were obtained by R. E.
McCrosky and C. Y. Shao with the 155-cm reflector at Harvard
Observatory's Agassiz Station. Measurers: J. H. Bulger and Shao.
1976 UT R. A. (1950) Decl.
Jan. 31.40968 12 22 52.24 +16 52 25.9
Feb. 5.28201 12 20 58.11 +17 50 38.2
L19-2 AND LFT 1679
J. E. Hesser, B. M. Lasker and H. E. Neupert, Cerro Tololo
Interamerican Observatory, write: "L19-2 and LFT 1679 (Wegner 1973,
Monthly Notices Roy. Astron. Soc. 163, 381; 1975, ibid. 171, 637),
DA white dwarfs, are low-amplitude variab1es of ZZ-Cet type. On
three of four nights in August, L19-2 showed relatively quiescent,
low-frequency time-domain behavior, while on a fourth night
low-frequency variations of ~ 0.05 magnitude were present. On all four
nights a period, 192s.7 +/- 0s.1, of average Fourier amplitude 0.005
magnitude was readily detected in the power spectra; a second,
lower-amplitude Fourier component, of period 113s.8 +/- 0s.1, was also
present on two nights. On three nights the luminosity variations
of LFT 1679 were dominated by low-frequency activity of time-domain
amplitude ~ 0.1 magnitude; a period, ~ 686s, with Fourier amplitude
0.005 magnitude was present on each night. As both stars are of
high southern declination, precise phasing of their variations
should ultimately be possible; extended observations this (waning)
season are urged as the first step in such analyses. Standard
differential photometry of LFT 1679 may also be useful, as aspects of
the available data might be accounted for by an eclipse phenomenon."
1976 September 30 (2990) Brian G. Marsden
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