Central Bureau for Astronomical Telegrams
IAUC 5740: 1993J
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Circular No. 5740
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@CFA or GREEN@CFA (.SPAN, .BITNET or .HARVARD.EDU)
SUPERNOVA 1993J IN NGC 3031
A. V. Filippenko and T. Matheson, University of California at
Berkeley, report that careful examination of the fully reduced spectrum
obtained on Mar. 30.3 UT (cf. IAUC 5731) reveals many broad undulations
with peak-to-valley amplitudes of 2-8 percent. The peak of the most
prominent bump is near 536 nm; others are present at 450, 561, 645 nm
and elsewhere. Adjacent to the 645-nm emission, the amplitude of which
is only 3 percent, is a broad absorption trough of comparable strength
with a minimum near 627 nm; overall, this feature resembles a weak P-Cyg
profile. If this is identified with H alpha, the expansion velocity
derived from the minimum in the absorption trough is 13 000 km/s, and the
emission peak is blueshifted by 5000 km/s because we are viewing
predominantly the near side of optically-thick ejecta. Several weak,
unresolved (at 0.5-nm resolution) emission lines are also visible in
the spectrum. These include H alpha at an observed (heliocentric)
wavelength of 656.00 nm (equivalent width 0.014 nm), He II
at 468.36 nm (EW 0.035 nm; possibly resolved), and a line at 637.14 nm
(EW 0.034 nm) that might be [Fe X] 637.4 nm. High-excitation emission
lines could be produced by circumstellar gas photoionized by ultraviolet
radiation from the hot stellar surface after breakout of the supernova
shock wave. Unresolved interstellar absorption lines are visible at
373.45 nm (EW 0.028 nm; possibly Al II 373.46), 393.34 (EW 0.066 nm;
Ca II K) and 396.82 (EW 0.038 nm; Ca II H). The interstellar Na I D
lines are blended, perhaps due to the presence of multiple components
and have total EW 0.16 nm. There is also an unidentified, resolved
absorption line at 615.2 nm (EW 0.05 nm; FWHM 1.7 nm) and several
possibly resolved absorption lines blueward of the narrow H alpha
emission. Given the weakness of the broad features, it is possible that
at least some of them are produced by subtle calibration errors. On
the other hand, R. P. Kirshner and B. P. Schmidt, Center for
Astrophysics, confirm those at 450 and 540 nm, as well as the narrow
He II, H alpha and 637-nm emission lines, in partially calibrated
spectra (ranges 380-570 nm, 620-720 nm) obtained by N. Caldwell with
the Multiple-Mirror Telescope on Mar. 31.12 UT."
The object's outburst seems to have occurred between Mar. 27.91 UT,
when J.-C. Merlin, Le Creusot, France, failed to record the supernova
to mv = 16.0 on an Ektachrome 400 exposure, and Mar. 28.30 UT, when A.
Neely, Silver City, NM, found it at mag 13.8 on an unfiltered CCD image.
Visual magnitude estimates: Apr. 1.08 UT, 10.7 (P. Schmeer,
Bischmisheim, Germany); 1.81, 10.5 (T. Vanmunster, Landen, Belgium).
1993 April 2 (5740) Brian G. Marsden
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