Central Bureau for Astronomical Telegrams
IAUC 4746: 1987A; Occns BY SATURN'S MAGNETOSPHERE
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Circular No. 4746
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
SUPERNOVA 1987A IN THE LARGE MAGELLANIC CLOUD
I. J. Danziger, C. Gouiffes, P. Bouchet and L. B. Lucy,
European Southern Observatory, report: "During 1988 Aug.-Oct., the
emission line profiles of O I (630.0, 636.3 nm) and C I (982.4,
985.0 nm) became asymmetric with peak emission blueshifted by
500-600 km/s. Similar behavior is seen in the Na I and H-alpha
profiles. This effect is attributed to extinction by dust within
the metal-rich ejecta. Comparisons with theoretical line profiles
indicate that the dust is widely distributed in the ejecta and
extends out to the innermost part of the hydrogen envelope. At 650
days, the O I blueshift requires 1 mag of extinction to the center,
implying a condensation efficiency of only 10E-6 (Dwek 1988, Ap.J.
329, 814; Kozasa et al. 1988, preprint). Clumpiness allows higher
efficiencies, and obscuration by a dust clump might account for the
pulsar's non-recovery (IAUC 4735, 4743). This interpretation of the
blueshifts requires that the accelerated decline of optical light
after day 530 (Burki et al. 1989, preprint; Catchpole et al. 1988,
preprint) is due in part to dust extinction rather than entirely to
the increased escape of gamma- and x-ray photons. The re-emission
of this optical light by grains in equilibrium with the ambient
radiation field accounts for the observed infrared radiation longward
of 8 microns (ESO data). Roche et al. (1989, Nature 337, 533)
attribute the increasing 10-micron emission after day 450 to a
thermal echo from dust behind the supernova. But the corresponding
scattering echo is not evident in optical lightcurves."
OCCULTATIONS BY SATURN'S MAGNETOSPHERE
R. Vasundhara wishes to coordinate observations of possible
occultations by features in Saturn's magnetosphere between 12.5
and 19 radii from the planet. The star 28 Sgr = SAO 187255 (mag
5.8) should be occulted by a 19-radii feature around July 2d17h and
3d22h and by a 12.5-radii feature around July 2d22h and 3d17h UT (with
an occultation by Saturn itself from July 3d07h to 3d09h). The star
SAO 187036 (mag 9.6) should be occulted by a 19-radii feature around
Aug. 6d11h and 7d23h and by a 12.5-radii feature around Aug. 6d19h
and 7d14h UT. Prospective participants are requested to contact her
at Indian Institute of Astrophysics, Sarjapur Road, Bangalore 560034,
India (telex 8452763 IIAB IN).
1989 March 1 (4746) Daniel W. E. Green
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