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IAUC 6489: V2116 Oph; C/1996 R1

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                                                  Circular No. 6489
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
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)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
Phone 617-495-7244/7440/7444 (for emergency use only)


V2116 OPHIUCHI
     F. Jablonski, Laboratorio Nacional de Astrofisica (LNA),
Itajuba; M. Pereira and J. Braga, Instituto Nacional de Pesquisas
Espaciais, S.J. Campos, Brazil; and C. Gneiding, LNA, report on
optical observations of V2116 Oph, the counterpart of the accreting
x-ray pulsar GX 1+4, carried out during Apr.-Aug. with the LNA 1.6-
m and 0.6-m telescopes (+ CCD fast photometer):  "On April 26, from
3300 images (integration time 5 s each) at the 1.6-m telescope,
sinusoidal optical pulsations close to the about 2-min x-ray period
were clearly detected for the first time in V2116 Oph.  The
barycentric pulse period was 124.171 +/- 0.004 s and the
semiamplitude of the pulsations was 1.3 +/- 0.1 percent.  The
passband for the observations was defined by a CuSO4 filter.  The
power spectrum of the light curve shows a monochromatic signal with
peak power about 220 times the local continuum.  None of six
comparison stars (measured simultaneously) shows any feature with
significant spectral power.  Follow-up observations in different
conditions (with other filters and detectors) confirmed the
previous detections, showing relative semiamplitudes of the
pulsations of up to about 4 percent.  The pulse period is
consistent with BATSE and RXTE results (IAUC 6478, 6153) projected
to the epoch of the observations.  There is a definite correlation
between detectability of pulsations and the optical brightness of
V2116 Oph.  No pulsations were detected when the system was fainter
than R about 17.  Flickering similar to that observed in
cataclysmic variables is seen when V2116 Oph is bright.  Examples
of light curves obtained with LNA's fast photometer can be seen on
the Web at http://www.lna.br/instrum/novida_e.html."


COMET C/1996 R1 (HERGENROTHER-SPAHR)
     Ephemeris continuation to IAUC 6479 (elements MPC 27882):

1996 TT     R. A. (2000) Decl.   Delta     r    Elong. Phase    m1
Oct. 14    20 58.50   - 2 50.3   1.352   1.985  114.5   27.2   12.6
     24    20 42.24   - 9 31.3   1.608   2.024   99.4   29.0   13.1
Nov.  3    20 33.37   -14 06.2   1.882   2.069   86.2   28.6   13.5
     13    20 29.41   -17 19.6   2.159   2.120   74.5   26.7   13.9
     23    20 28.79   -19 40.2   2.426   2.176   63.7   24.0   14.3
Dec.  3    20 30.46   -21 26.1   2.678   2.237   53.5   20.8   14.6
     13    20 33.76   -22 48.7   2.908   2.302   43.9   17.2   14.9
     23    20 38.19   -23 55.6   3.113   2.371   34.6   13.6   15.2

                      (C) Copyright 1996 CBAT
1996 October 14                (6489)            Daniel W. E. Green

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