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IAUC 5047: 1990N; V3890 Sgr; 1990 MB

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                                                  Circular No. 5047
Central Bureau for Astronomical Telegrams
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

     G. Sonneborn, Goddard Space Flight Center; and R. Kirshner,
Center for Astrophysics, report: "Low-dispersion ultraviolet spectra
(range 200-335 nm, resolution 0.6 nm) of SN 1990N have been obtained
with the IUE satellite on June 26.8, 28.3, 30.6 and July 2.7 UT.  SN
1990N was detected longward of 250 nm on each date.  The mean flux in
the range 300 +/- 15 nm was 1.9**10-14 erg cm-2 s-1 A-1 on July 2.
The ultraviolet flux has approximately doubled every two days during
this period, while the shape of the spectrum has changed very little.
The spectrum resembles IUE spectra of other type Ia supernovae: it has
the pronounced flux maximum at 310 nm.  However, the secondary maximum
usually seen at 290 nm (e.g., in SN 1981B) is not present in SN 1990N.
The following visual magnitude estimates were obtained with the IUE
Fine Error Sensor (400-700 nm) on the dates given above: 14.4, 14.0,
13.4 and 13.2, indicating that the ultraviolet has been rising at about
twice the rate of the optical brightness.  Detection of a large
ultraviolet flux increase in a type Ia supernova is unprecedented.
Photometry and spectroscopy are needed in other wavelength regions, in
particular optical coverage extending shortward of 400 nm."

     K. Sekiguchi, South African Astronomical Observatory reports:
"The spectral evolution of V3890 Sgr has been monitored using the
1.9-m telescope at Sutherland since May 5.  The overall development of
the spectrum closely resembles that of the 1985 outburst of RS Oph.
The red-region spectrum (range 560-760 nm, resolution about 0.35 nm
FWHM) taken on June 22 shows the emerging TiO bands of an M4 III star.
Strong coronal Fe VII 608.6-nm emission, which was absent on May 14
(IAUC 5015), and the Fe X 637.4-nm line are present.  The star at the
Duerbeck and Williams positions (6" east and 10" north of V3890 Sgr)
was also observed.  No detectable emission line was seen in its
spectrum.  This suggests that the star observed by Williams (1983,
Ap.J. Suppl. 53, 523) was in fact V3890 Sgr = N Sgr 1962 in quiescent
state and that his finding chart was incorrect."

1990 MB
     Corrigendum.  E. Bowell informs us that this object (cf.
IAUC 5045) was actually discovered by David H. Levy.  Both Levy
and H. E. Holt were involved with the Palomar observations.

1990 July 5                    (5047)              Brian G. Marsden

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