Central Bureau for Astronomical Telegrams
IAUC 3245: HEAO B; CARBYNE AND INTERSTELLAR GRAINS; JUPITER XIII (LEDA); GK Per
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Read IAUC 3246
Circular No. 3245
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM Telephone 617-864-5758
HEAO B
F. D. Seward writes: "The HEAO-B satellite, scheduled for
launch in November, will carry the first large x-ray telescope and
will perform astronomical observations In the energy range 0.2-4
keV. Either of two imaging instruments or two spectrometers can be
positioned at the focus. The spatial resolution is 2" for strong
sources. Twenty percent of the useful observing time during the
first year will be available for guest observations. There are
also opportunities to collaborate by participating in joint
radio/optical/x-ray observations or in the analysis of the x-ray data.
Proposals for guest observations are being evaluated by a NASA
selection committee (meeting four times per year). Details for
submission of proposals are given in a Space Science Notice dated June
7. Details concerning the instruments carried by HEAO B and the
planned observing program can be obtained from me at the address:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street,
Cambridge, NA 02138, U.S.A. (telephone 617-495-7282)."
CARBYNE AND INTERSTELLAR GRAINS
A. Webster, Cavendish Laboratory, communicates: "It is suggested
that carbyne is the major constituent of interstellar grains.
This white, refractory, acetylenic allotrope of carbon consists of
long, parallel, carbon chains, single-triple (etc.) bonded. The
best modern phase diagram (Whittaker 1978, Science 200, 763) shows
carbyne to be stable at higher temperatures than graphite is, and
thus that it forms first in stellar atmospheres. This is confirmed
by the theoretical virtual absence of a surface energy nucleation
barrier for 1-d crystals, witness the well-known existence of short
chain conjugated C2, C3 (etc.) molecules in hot carbon vapor. The
cyanopolyne molecules radio-detected in Heiles Cloud 2 have identical
carbon chains, and carbyne grains are suggested as the source
of this otherwise hopelessly carbon-rich, hydrogen-deficient family.
The fact that the crystals are white explains the non-ice-mantle
part of visible scattering extinction previously attributed to
silicon carbide despite cosmic abundance problems. From 1-d band
theory one expects band gaps of 2-3 eV for pi orbitals (explaining the
4400 A curvature of extinction and maximum of polarization) and 5 eV
for sigma orbitals (2200 A extinction peak). The grains are anisotropic,
birefringent cylinders perhaps 1000 A along the carbon chain axis
and 100 A in diameter; the latter explains the rising ultraviolet
scattering albedo. The known existence of closely-related allotropes
of carbyne, differing chiefly in the relative positions of
atoms in neighboring chains, accounts for Herbig's (1975, Astrophys.
J. 196, 129) observation of close pairs of diffuse interstellar
lines: different lines arise from different allotropes. Long
conjugated chains may have interesting magnetic properties for grain
alignment."
JUPITER XIII (LEDA)
The following continuation to the ephemeris (cf. IAUC 3102),
by K. Aksnes, Center for Astrophysics, is from a paper submitted
for publication in the Astron. J.:
1978/79 ET R. A. (1950) Decl. dR.A. dDecl. Delta r
Sept.29 8 26.33 +19 45.3 +1m82 + 8'8 5.566 0.087
Oct. 9 8 31.91 +19 31.4 +1.38 +14.3 5.422 0.087
19 8 36.49 +19 20.1 +0.85 +19.7 5.272 0.087
29 8 39.98 +19 11.7 +0.24 +24.7 5.119 0.086
Nov. 8 8 42.26 +19 06.8 -0.44 +29.1 4.969 0.085
18 8 43.25 +19 05.5 -l~l6 +32.4 4.824 0.083
28 8 42.94 +19 07.8 -1.89 +34.3 4.691 0.080
Dec. 8 8 41.33 +19 13.4 -2.57 +34.2 4.573 0.077
18 8 38.55 +19 21.5 -3.10 +31.6 4.475 0.074
28 8 34.79 +19 31.2 -3.41 +26.4 4.401 0.070
Jan. 7 8 30.36 +19 41.5 -3.40 +18.4 4.354 0.067
17 8 25.61 +19 51.4 -2.99 + 8.5 4.335 0.064
27 8 20.91 +20 00.6 -2.20 - 2.5 4.342 0.062
Feb. 6 8 16.58 +20 09.2 -1.12 -12.9 4.375 0.061
16 8 12.87 +20 17.2 +0.10 -21.3 4.431 0.062
26 8 09.92 +20 25.0 +1.26 -26.7 4.507 0.064
Mar. 8 8 07.87 +20 32.2 +2.21 -28.6 4.602 0.066
18 8 06.80 +20 38.3 +2.88 -27.6 4.713 0.069
28 8 06.76 +20 42.7 +3.26 -24.4 4.838 0.073
Apr. 7 8 07.81 +20 44.5 +3.38 -19.5 4.974 0.076
17 8 09.93 +20 43.4 +3.29 -13.9 5.116 0.079
27 8 13.06 +20 38.9 +3.04 - 7.9 5.262 0.082
May 7 8 17.14 +20 30.8 +2.69 - 1.9 5.409 0.084
17 8 22.08 +20 18.9 +2.27 + 3.8 5.552 0.086
GK PERSEI
Visual magnitude estimates: July 8.31 UT, 12.5 (D. W. E.
Green, Harvard College Observatory); 12.30, 13.0 (J. Bortle, Brooks
Observatory); 12.31, 12.7 (Green); 13.32, 13.1 (Bortle).
1978 July 18 (3245) Brian G. Marsden
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