Central Bureau for Astronomical Telegrams
IAUC 5256: 1991T; N Her 1991
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Circular No. 5256
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 1991T IN NGC 4527
C. Wheeler, University of Texas at Austin, reports: "V. Smith
obtained a high-resolution spectrogram (range 589-595 nm, resolution
0.018 nm) of SN 1991T with a CCD detector at the coude focus on the
2.7-m telescope at McDonald Observatory on Apr. 25. The spectrum
shows the Na D lines in the host galaxy as having three distinct
absorption components. The weaker component is at 1805.0 and 1805.7
km/s, respectively, in the two lines, and the stronger components
are at 1784.7 and 1784.4 km/s, and at 1766.9 and 1765.6 km/s,
respectively. These observations indicate at least three components
to the interstellar medium along the line of sight with velocity
differences of about 20 km/s, and give a more accurate measure of
the true redshift of the supernova than reported on IAUC 5251 and
5255."
Photometry by A. C. Gilmore with the 0.6-m Cassegrain reflector
at Mount John University Observatory (cf. IAUC 5253) on Apr. 30.47
UT: V = 11.49 +/- 0.02, U-B = -0.44 +/- 0.03, B-V = +0.16 +/- 0.01,
V-R = +0.13 +/- 0.03, V-I = -0.20 +/- 0.03.
NOVA HERCULIS 1991
G. S. Rossano, R. J. Rudy, and R. C. Puetter, University of
California at San Diego; and D. K. Lynch and P. Erwin, Space and
Environment Technology Center, The Aerospace Corporation, report:
"Spectrophotometry from 0.75 to 1.65 microns was obtained with the
Lick Observatory 3-m telescope on Apr. 27.5 UT with spectral resolution
of 450, using a 9" beam. Broad emission features were observed
at Pa-beta, Pa-delta, and He I 1083-nm. No He II lines were detected.
He I 1083-nm was self-absorbed, with a line width of 4500 km/s.
The observed velocity centroid of He I 1083-nm agrees well with the
observations of Apr. 8.5 UT. The continuum is slightly redder than
observed on Apr. 8.5 UT. The continuum emission and He I 1083-nm
line strength have both decreased by a similar factor. A monochromatic
1.25-micron magnitude of 9.7 was observed. The Paschen lines
are peculiar, with Pa-delta too strong relative to Pa-beta. The red
components of the Paschen lines observed on Apr. 8.5 UT are no longer
present. Components have appeared shifted 5500 km/s to the blue
of the previously observed lines. Due to this velocity shift, Pa-
gamma is confused with He I 1083-nm, which was not observed to be
blue-shifted. Observations of the hydrogen lines are strongly
encouraged."
1991 May 1 (5256) Daniel W. E. Green
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