Central Bureau for Astronomical Telegrams
IAUC 4933: 1987A; 1989f1
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Circular No. 4933
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
P. Bouchet, I. J. Danziger, and L. B. Lucy, European
Southern Observatory, report: "Continuing infrared photometry in
the J, H, K, L, M, N1, N2, N3, Q bands at La Silla, combined with
UBVRI photometry reported from Cerro Tololo (cf. IAUC 4881, 4910)
shows that the bolometric light curve on 1989 Nov. 10 (day 991)
lies 1 x 10E38 erg sE-1 above a linear extrapolation from earlier
epochs (Suntzeff and Bouchet 1989, A.J., in press). This levelling
off was already apparent from the previous observation (Aug. 14;
day 903), though at a lower level of significance, and is confirmed
by observations in less-than-ideal conditions on Dec. 20 (day 1030),
when blackbody fitting gives T = 160 K and log L = 38.30 +/- 0.05.
Because more than 80 percent of the flux is now emitted redward of
the M band, the levelling-off is almost completely due to the near
constancy of the flux integrated over the M, N, Q bands for days
903, 991, and 1030. This implies that a hitherto-undetected energy
source is now contributing significantly to the total energy output.
If it were due to 57Co, the original amount would have to be 20-25
times the anticipated 0.0017 solar mass (Woosley and Pinto 1988,
Workshop on Gamma-ray Spectroscopy), but this is contradicted by
the observed [Co II] 10.52-micron line strength on day 526 (Danziger
et al. 1989, Proceedings of Santa Cruz Workshop). A thermal echo
from external dust seems unlikely since it would coincidentally
need to have a color temperature (150-180 K) similar to that of the
supernova's emission. Moreover, the corresponding scattering echo
(cf. IAUC 4746) is not evident in the smooth UBVR light curves (IAUC
4881, 4910). Nevertheless, CCD frames should be inspected for new
echoes within 5" of the SN. (Uncertainties in luminosities derived
by fitting blackbody curves to the far-infrared data have been
checked using emission curves for isothermal dust clouds of astronomical
silicate. With a dust mass of 0.05 solar mass, inefficient
dust emission at wavelengths greater than 30 microns lowers the
luminosity by only 10E0.1.) Pulsar emission, absorbed and
reradiated by dust in the ejecta (IAUC 4746) seems the most likely
explanation of our observations. Other signatures of such input
should be sought."
COMET McKENZIE-RUSSELL (1989f1)
Total visual magnitude estimates: Dec. 25.55 UT, 13.0 (A.
Pearce, Scarborough, W. Australia, 0.41-m reflector); 27.80, 12.8 (A.
Boattini, Piazzano, Italy, 0.40-m reflector); 28.63, 13.3 (Pearce).
1989 December 29 (4933) Daniel W. E. Green
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