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IAUC 3628: V801 Ara = 4U 1636-53 = MXB 1636-53; SN IN ESO 356-G20; 1980 QA; GX 17+2; HONDA'S Var IN Cyg

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IAUC number 

                                                  Circular No. 3628
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM     Telephone 617-864-5758


V801 ARAE = 4U 1636-53 = MXB 1636-53
     J. V. Paradijs, University of Amsterdam; H. Pedersen, European
Southern Observatory; and W. H. G. Lewin, Massachusetts Institute
of Technology, report the detection of ~ 4-hr modulation in the
broad-band optical flux of the optical counterpart V801 Ara of the
x-ray burst source 4U/MXB 1636-53.  The observations were made in
1980 July and 1981 Aug. with the Danish 1.5-m telescope at La Silla
and cover a total of ~ 23 hr of observing.  If the modulation is
strictly periodic, only three periods are possible: 3.28, 3.78 or
4.42 hr, the uncertainty in each case being +/- 0.05 hr.  The full
amplitude of the modulation was ~ 25 percent in the 1980 data and
40 percent in the 1981 data.  An orbital period of ~ 4 hr is consistent
with an M0V star (~ 0.4 Ms) that fills its Roche lobe.


SUPERNOVA IN ESO 356-G20
     L. Alday, J. Graham and A. Landolt, Cerro Tololo Interamerican
Observatory, have confirmed the existence of this object (cf. IAUC
3627).  Preliminary results from UBV photometry on Aug. 13.4 UT are
V = 16.18, B-V = +0.42, U-B = +0.18.


1980 QA
     C. Torres, Department of Astronomy, University of Chile, informs
us that the observations reported on IAUC 3506 are somewhat
in error and that the object observed was in fact 1979 BA.  The
designation 1980 QA is therefore to be eliminated.


GX 17+2
     M. Oda and the Hakucho Team inform us that the duration of the
second burst reported on IAUC 3624 (the one on May 25d00h08m UT)
should be ~ 5 min, not ~ 0.5 min.


HONDA'S VARIABLE IN CYGNUS
     M. Verdenet, Bourbon-Lancy, France, writes that this object
(IAUC 3546, 3553, 3565, etc.)  had brightened from mv = 15.0 in May
to mv = 13.8 in late July.


1981 August 21                 (3628)              Brian G. Marsden

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