Central Bureau for Astronomical Telegrams
IAUC 5847: 1993J
The following International Astronomical Union Circular may be linked-to from your own Web pages, but must not otherwise be redistributed (see these notes on the conditions under which circulars are made available on our WWW site).
Read IAUC 5848
.dvi or
.ps format.
Circular No. 5847
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
L. Wang, J. Y. Hu, A. G. Li, and H. B. Li, Beijing Astronomical
Observatory; and Z. W. Li, Beijing Normal University, report:
"Low-resolution spectrograms (about 0.53 nm/pixel; range 425-700
nm), taken on Aug. 8-9 with the 2.16-m telescope at the Xinglong
station of Beijing Observatory, show that SN 1993J has now entered
a nebular phase. The [O I] doublet at 630 and 636.4 nm is very
strong and now overtakes the neighboring H-alpha and He I 667.8-nm
complex in strength. [O I] at 557.7 nm is also a strong feature in
the spectra. The [O I] 557.7-nm line is clearly blueshifted, its
measured centroid velocity being about -1775 km/s (FWHM about 4300
km/s). The [O I] doublet (630.0, 636.4 nm) can be approximately
fitted by the profile of the [O I] 557.7-nm line, assuming the [O
I] 630.0- and 636.4-nm lines are of equal strength. The success of
this profile fit means that the [O I] doublet is optically thick.
The [O I] 630.0- and 636.4-nm lines are also clearly blueshifted,
by about the same amount as measured in the [O I] 557.7-nm line.
The double peak in H-alpha has now disappeared, while the overall
width of the line remains the same. Many fine structures appeared
in the H-alpha and [O I] lines. Typical FWHM of the feature is
about 750 km/s. The blueshift of the [O I] lines can be traced to
even earlier dates, to as early as Apr. 28, ever since the [O I]
line appeared. The fine structures clearly indicate that strong
instabilities have occurred in the ejecta. The blueshift may be
due to dust formation in the ejecta, as was observed by Danziger et
al. in SN 1987A (IAUC 4746). However, it should be recalled that
the blueshift in SN 1993J was observed at a much earlier date, and
the amount of blueshift is much larger. It is not clear whether
the ejecta can be cool enough for dust formation to occur."
A. Clocchiatti, J. C. Wheeler, and D. A. Swartz report: "A
fully reduced spectrogram (range 450-760 nm, dispersion 0.4 nm/
pixel) of SN 1993J, obtained on Aug. 14.16 UT at the 2.1-m telescope
of McDonald Observatory, shows that H-alpha and H-beta are still
present in blueshifted absorption (8650 and 8800 km/s, respectively),
superimposed on a very blue continuum. He I at 667.8 nm has
disappeared and H-alpha emission nearly so. [O I] at 557.7 nm
(centroid blueshifted by 1700 km/s) and [O I] at 630.0 and 636.5 nm
(centroid blueshifted by 500 km/s, with a weaker, narrow component
blueshifted by 2100 km/s) show fine structure in their profiles,
confirming the Beijing report above."
1993 August 18 (5847) Daniel W. E. Green
Read IAUC 5848
.dvi or
.ps format.
Our Web policy. Index to the CBAT/MPC/ICQ pages.
