Central Bureau for Astronomical Telegrams
IAUC 5787: 1993J; PSR 1823-13
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Circular No. 5787
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, communicate: "Spectra (range 300-1000 nm, resolution 0.5
nm) of SN 1993J obtained on May 11 UT with the Shane 3-m reflector
at Lick Observatory, in comparison with previous spectra, reveal
that SN 1993J is gradually transforming itself into a type-Ib
supernova. Prominent He I P-Cyg profiles have emerged, and the
strength of H-alpha emission is decreasing. The 'double peak'
appearance of H-alpha (cf. IAUC 5776, 5779), which has grown even
more striking, is produced by H-alpha blended with He I 667.8 nm.
Previously, the only other supernova known to have clearly experienced
a metamorphosis from type II to type Ib (or Ic) is SN 1987K
(Filippenko 1988, A.J. 96, 1941), although the possible development
of He I lines could not be monitored due to the object's proximity
to the sun. We predict that after a few months, the optical spectrum
of SN 1993J will be dominated by strong, broad [O I], [Ca II],
and Ca II emission lines, with H-alpha very weak or absent. Thus,
SN 1993J might be called a 'type IIb' supernova, following the
suggestion of Woosley et al. (1987, Ap.J. 318, 664) that such objects
could exist. The initial mass of the progenitor was probably 10-20
solar masses, but mass transfer onto a close companion led to the
removal of all but a small amount (few tenths of a solar mass) of
the hydrogen envelope prior to the explosion. This interpretation
is supported by preliminary theoretical studies of the bolometric
light curve being conducted by S. E. Woosley and his collaborators
(private communication)."
PSR 1823-13
J. P. Finley and H. Ogelman, University of Wisconsin at
Madison, report: "We have detected the 101-ms pulsar PSR 1823-13
(dynamic age about 22 000 yr) in the x-ray band 0.1-2.4 keV during
an 8700-s observation carried out between 1992 Oct. 12 and 14 with
the PSPC aboard ROSAT. The observed background-subtracted count
rate, including vignetting and deadtime corrections, is 0.006 +/-
0.001 count/s. The source counts reside above 0.7 keV, implying a
hard, absorbed x-ray spectrum. No pulsations were detected, and we
derive a 90-percent confidence level upper limit of 35 percent on
the pulsed fraction under the assumption of a sinusoidal modulation
at the radio period."
1993 May 11 (5787) Daniel W. E. Green
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