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IAUC 6496: 1996bn; V2116 Oph

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                                                  Circular No. 6496
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 1996bn IN UGC 3430
     J. Mueller reports her discovery of a supernova (mag about 18)
on a IIIa-F plate taken on Oct. 17 UT with the 1.2-m Oschin Schmidt
telescope by K. M. Rykoski in the course of the second Palomar Sky
Survey.  SN 1996bn is located 2".7 west and 5".4 south of the
center of UGC 3430 (R.A. = 6h15m.8, Decl. = +64o26', equinox
2000.0).   M. H. van Kerkwijk (California Institute of Technology)
obtained a CCD spectrum of SN 1996bn in very poor seeing on Oct. 21
with the 5-m Hale reflector at Palomar.  Preliminary inspection of
the uncalibrated data by A. G. Riess, D. C. Leonard, and A. V.
Filippenko (University of California, Berkeley) confirms that the
object is a supernova, probably of type Ia, about 1 month past
maximum brightness.

     R. Sood, S. James, and W. Lawson, Australian Defence Force
Academy; and R. Manchanda, Tata Institute, report:  "Regular
monitoring of the H-alpha emission profile of V2116 Oph, the
optical counterpart of the symbiotic x-ray pulsar binary GX 1+4,
has been in progress in order to establish its orbital period.
Observations made with the 1.9-m telescope (+ coude spectrograph +
CCD) at Mount Stromlo Observatory on Oct. 16 failed to detect the
H-alpha line, the first such non-detection since observations were
started in 1991 Sept.  Previously the spectrum had been dominated
by the H-alpha emission, with an integrated line flux of about 2.5
x 10E-13 erg cmE-2 sE-1, about 100 times stronger than the
continuum.  Non-detection was confirmed by C. Heisler (Mount
Stromlo) with the 2.3-m telescope (+ DBS spectrograph + CCD) at
Siding Spring on Oct. 19, suggesting that the star was fainter than
V about 18.  The weakening of the H-alpha emission coincides with
the weakening of x-ray pulsations (IAUC 6478, 6488).  Our previous
observations made with the 1.9-m telescope on Aug. 9 detected the
H-alpha emission at a flaring level of about 10E-12 erg cmE-2 sE-1,
a factor of about 4 above the ambient H-alpha line flux, consistent
with the increase in the phase-averaged pulsed x-ray flux reported
on IAUC 6478.  Reports of optical pulsations from this symbiotic
binary at the x-ray pulse period (IAUC 6489), and the above
coincidence between the H-alpha line flux and x-ray pulse activity,
suggest a strong link between the H-alpha flux and the neutron star,
rather than with the accretion disk.  Further observations are
encouraged to monitor the current optical low state."

                      (C) Copyright 1996 CBAT
1996 October 22                (6496)            Daniel W. E. Green

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