Central Bureau for Astronomical Telegrams
IAUC 4613: 1988A
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Circular No. 4613
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
MARSDEN or GREEN@CFA.BITNET MARSDEN or GREEN@CFAPS2.SPAN
SUPERNOVA 1988A IN M58
M. Kidger, Instituto de Astrofisica de Canarias, telexes:
"Analysis of magnitude estimates published on the IAU Circulars and in
data supplied by G. M. Hurst, U.K. Nova and Supernova Patrol, reveals
that this object has shown an enduring plateau in its lightcurve.
After a possible initial spike, there is evidence of a decline of
0.011 mag/day until mid-February, followed by a standstill or slight
rise. A faster decline (0.015 mag/day) started in late March and has
continued. The standstill was accompanied by a considerable
reddening. B, V, R, I photometry by D. Jones, Observatorio del
Roque de los Muchachos, with the 1-m Jacobus Kapteyn Telescope on Apr.
23 gives B-V = +0.7 (in contrast to values close to zero shortly after
maximum), V = 15.1 +/- 0.1 (in close agreement with the UKNSNP
results), V-R = +0.6, V-I = +0.9. We note that the photometry of
Sadler and Simkin (IAUC 4563) shows evidence of a systematic
reddening over Jan. 23-25. This reddening is similar to but less than
that seen in SN 1987A. Near-infrared photometry by J. Jimenez
Fuensalida on Jan. 30 with the 1.5-m Carlos Sanchez Telescope
(Observatorio del Teide, Tenerife), reduced by A. Mampaso, IAC, gives
3-sigma-detection upper limits J = 12.2, H = 14.3; implied limits on
color indices are V-H = +0.4, V-J = +2.5, V-K = +2.0, this last value
being from a 2-sigma limit in K on Jan. 29. P. Hammersley, Imperial
College, and F. Garzon, IAC, obtained a positive detection with a
seven-element detector on the same telescope on June 11.85 UT at K =
13.2. A faint-object spectrograph CCD observation by P. Charles, ORM,
and P. Murdin, Royal Greenwich Observatory, with the 4.2-m William
Herschel Telescope on June 8 reveals that the spectrum (first order
486-970 nm, second order 340-486 nm) is exceptionally red, such that
there was no emission above sky noise in the second order. Comparison
by P. R. Lapuente, R. Canal and R. Lopez, University of Barcelona,
with a spectrum taken on Feb. 11 reveals that both H alpha and Ca II
857.9 nm still show prominent P-Cyg profiles. Both are now narrower,
as expected from the much diluted envelope. The expansion velocity
as estimated from the H alpha absorption minimum has fallen from 8120
km/s on Feb. 11 to 4560 km/s on June 9. In the latter spectrum the
[Ca II] doublet at 729.1 and 732.4 nm appears to be present, and lines
of neutral elements (e.g., Na I 589.0 nm, O I 777.3 and the S I 868.4,
888.0-nm doublet that gives a feature at 880.0 nm) appear stronger due
to the fall in temperature. The continuum is now considerably more
depressed. The two spectra are typical of an SN type IIp 'plateau',
as shown by comparison with SN 1986I."
1988 June 15 (4613) Brian G. Marsden
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