Central Bureau for Astronomical Telegrams
IAUC 4484: 1987A
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Circular No. 4484
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 617-495-7244/7440/7444
SUPERNOVA 1987A IN THE LARGE MAGELLANIC CLOUD
E. Oliva, A. F. M. Moorwood, and I. J. Danziger, European
Southern Observatory, communicate: "Spectral observations (range
1.03-5.12 microns, resolving power 1500) of SN 1987A obtained at the ESO
3.6-m telescope (+ array spectrometer 'IRSPEC') between Oct. 5 and
8 show that the infrared spectrum is dominated by broad (about 3000
km/s) emission lines including H, He, O, Na, Si, K, Mg, Fe+ and CO.
All of the lines are redshifted by 400-1500 km/s including the v =
2-0, v = 3-1, and v = 4-2 bands of CO at 2.294, 2.322, and 2.353
microns, which are clearly detected in our spectrum at 2.303, 2.330, and
2.361 microns. Neither the systematic redshift nor its spread can be
attributed to instrumental uncertainties (about 200 km/s). Only two
He I lines show a moderate P-Cyg absorption, whereas all other
lines have fairly symmetrical profiles. High-series Bracket and
Pfund transitions of H are redshifted by 800 km/s on average, the
same value observed for the brightest Paschen lines. Within 30
percent, the relative intensities of the 12 cleanest H lines are
consistent with a standard case-B recombination spectrum. The
observed emission of ionic lines and CO bands contributes at least
45, 40, 40, 40, and 80 percent of the total energy in the J, H, K,
L, and M photometric bands, respectively. A significant fraction
of the continuum underneath the lines can be accounted for by b-f
and f-f H emission. The shape and strength of the first overtone
band of CO suggest T(CO) about 2000 K and M(CO) about 0.0004 Mo. The
fundamental band of CO which dominates the emission in the M band
appears to be a factor of 3 weaker than expected relative to the
first overtone. If this is due to self-absorption in the Delta-v = 1
rotational-vibrational transitions of CO, one might expect the
different bands to vary by different amounts in the future. Faint
forbidden lines of Fe+ are detected at 1.26 and 1.64 microns. With T =
4000 K and n > 10E5 (high density limit), the luminosity of the
1.26-micron line corresponds to 0.04 Mo of Fe+. A prominent feature at
1.132 microns can be identified as a Lyman-beta pumped transition of O I at
1.129 microns. Its future variation relative to the H lines is of
interest in determining the O I/H I abundance ratio. Future studies
of the 1.0-1.35-micron spectrum can also be useful for decoding the
possible contribution of [S I] and [N I] transitions to the bright
features observed at 1.047, 1.086, and 1.132 microns."
1987 November 5 (4484) Daniel W. E. Green
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