Central Bureau for Astronomical Telegrams
IAUC 5253: N LMC 1991; EX Hya; 1991T
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Circular No. 5253
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)
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MARSDEN or GREEN@CFA.BITNET MARSDEN or GREEN@CFAPS2.SPAN
NOVA IN THE LARGE MAGELLANIC CLOUD 1991
R. Gonzalez-Riestra, J. Clavel, A. Cassatella, International
Ultraviolet Explorer (IUE) Observatory, European Space Agency,
Madrid; and J. Krautter, Heidelberg, on behalf of the European Target
of Opportunity Team for Novae, report: "This nova has been observed
by the IUE on Apr. 26.2 UT. The visual magnitude as measured
with the Fine Error Sensor onboard IUE was 9.5. Ultraviolet low-
resolution (0.5 nm) spectra in the range 115-330 nm show numerous
emission-absorption blends from singly ionized elements (e.g., Fe,
Mg, Si, Ni), very similar to the ones observed in N Cyg 1978 and the
N LMC 1988-1 shortly after visual maximum. The most prominent
emissions correspond to Fe II ultraviolet multiplets 1 and 191, and to
Mg II 280-nm. Fluxes at 130 and 260 nm are 2.7 x 10E-13 and 1.8 x
10E-12 erg cmE-2 sE-1 AE-1, respectively. Compared to N LMC 1988-1
near maximum light, N LMC 1991 is about a factor of 7.3 brighter
both in the visual range and in the ultraviolet."
A. C. Gilmore reports the following photometry (cf. IAUC 5250)
obtained with the 0.6-m Cassegrain reflector at Mount John University
Observatory: Apr. 26.47 UT (marginal conditions), V = 9.61 +/-
0.04, U-B = -0.75 +/- 0.02, B-V = +0.21 +/- 0.02, V-R = +0.40 +/-
0.01, V-I = +0.81 +/- 0.02; Apr. 28.35, 10.36 +/- 0.02, -0.83 +/-
0.02, +0.08 +/- 0.01, +0.59 +/- 0.01, +1.05 +/- 0.04.
EX HYDRAE
F. M. Bateson, Royal Astronomical Society of New Zealand,
reports that this dwarf nova (R.A. = 12h49m43s, Decl. = -28 58'.7,
equinox 1950.0) is having a rare outburst. Visual magnitude
estimates: Apr. 28.33 UT, 10.1 (A. F. A. L. Jones, Nelson, N.Z.);
28.34, 10.6 (Jones); 28.35, 10.4 (Jones); 28.40, 10.2 (S. Dreves,
Daisy Hill, Queensland); 28.43, 10.3 (Jones); 28.43, 10.5 (B.
Tregaskis, Mt. Eliza, Vic.); 28.43, 10.4 (P. Williams, Heathcote,
N.S.W.); 28.83, 10.7 (Dreves). The last outburst was reported in
1987 (IAUC 4383, 4385, 4387).
SUPERNOVA 1991T IN NGC 4527
Photometry by Gilmore (as above) on Apr. 28.51 UT: V = 11.52
+/- 0.02, U-B = -0.51 +/- 0.01, B-V = +0.14 +/- 0.01, V-R = +0.11
+/- 0.01.
1991 April 29 (5253) Daniel W. E. Green
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