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IAUC 6508: 1996bv; GX 13+1; 91P

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                                                  Circular No. 6508
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
Phone 617-495-7244/7440/7444 (for emergency use only)

SUPERNOVA 1996bv IN UGC 3432
     Weidong Li, Yulei Qiu, Qiran Qiao, and Jingyao Hu, Beijing
Astronomical Observatory (BAO), on behalf of the BAO Supernova
Survey, report their discovery of a supernova on unfiltered CCD
images taken with the BAO 0.60-m reflector.  SN 1996bv is located
3".6 northwest of the center of UGC 3432 (R.A. = 6h16m.3, Decl. =
+57o03', equinox 2000.0), and was estimated at the following
magnitudes:  Nov. 3 UT, 16.6; 12, 15.7; 16, 15.6.  A V CCD image of
the same field taken on Oct. 18 shows no star at this position.  A
low-resolution spectrum (0.96 nm/pixel, range 300-900 nm) taken
with the BAO 2.16-m telescope by Li, Qiao, and J. Hao on Nov. 21.83
shows conspicuous Si II 635-nm absorption at 615 nm and typical
features of type-Ia supernovae at maximum light (Si II, S II, Ca
II, Mg II, etc.), with the overall spectrum resembling that of SN
1989B at maximum light.

GX 13+1
     R. Corbet, Goddard Space Flight Center (GSFC) and Universities
Space Research Association, reports on behalf of the RXTE ASM team
at GSFC and the Massachusetts Institute of Technology:  "Analysis
of the RXTE ASM lightcurve of the low-mass x-ray binary GX 13+1 (=
4U 1811-17) obtained between 1996 Feb. 23 and Nov. 14 suggests the
presence of a modulation with a period of 24.7 +/- 1 days.  The
folded lightcurve on this period shows a mean peak-to-peak
modulation of approximately 15 percent.  This periodicity is
apparently confirmed by the Ariel 5 ASM lightcurve of GX 13+1, as a
Fourier Transform of this shows that the largest peak, for periods
< 125 days, occurs at 25.2 +/- 0.15 days, consistent with the RXTE
result.  In the RXTE data, the modulation is most pronounced at low
energies (1.3-4.8 keV) and is reduced at higher energies (4.8-12.2
keV).  In addition, there is an anticorrelation between hardness
ratio and intensity in the RXTE data, which may suggest a
similarity with Cyg X-2 (Wijnands et al. 1996, Ap.J. 473, L45).  If
this periodicity is a persistent property of this source, it may
also be present in the variability of the infrared counterpart."

     CCD magnitude estimates by J. V. Scotti, University of Arizona,
with the Spacewatch 0.9-m telescope: Nov. 18.53 UT, 21.0; 19.54,
21.4.  The comet is of stellar appearance.

                      (C) Copyright 1996 CBAT
1996 November 20               (6508)            Daniel W. E. Green

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