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IAUC 6601: SAX J1750.8-2900; NOVALIKE Var IN Sgr; 81P

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                                                  Circular No. 6601
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, 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)
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Phone 617-495-7244/7440/7444 (for emergency use only)


SAX J1750.8-2900
     J. Marti, I. F. Mirabel and S. Chaty, Service d'Astrophysique,
Centre d'Etudes de Saclay; and L. F. Rodriguez, Instituto de Astronomia,
Universidad Nacional Autonoma de Mexico, report: "We tentatively
identify the radio counterpart of the galactic center x-ray transient
SAX J1750.8-2900 with a variable VLA radio source, NVSS J175050-290311,
the second of the three candidates listed on IAUC 6597.  The 20-cm flux
density of this object (which has positional uncertainty 10") was reported
in the NRAO/VLA Sky Survey (NVSS) database to be 3.5 mJy (a measurement in
1993), whereas Helfand et al. (1992, Ap. J. Suppl. 80, 211) give a 20-cm flux
density of 34 mJy (a measurement in 1989) for what is evidently the same radio
source, 0.491-1.042, located at R.A. = 17h50m51s.47, Decl. = -29d03'13".6
(equinox 2000.0, uncertainty 1")."


NOVALIKE VARIABLE IN SAGITTARIUS
     F. Kerber and H. Gratl, University of Innsbruck; and M. Roth,
Las Campanas Observatory, report: "We have found dramatic changes in
the spectrum of the novalike object reported by Y. Sakurai in Feb. 1996
(cf. IAUC 6322, 6323) at R.A. = 17h52m32s.69, Decl. = -17d41'07".7
(equinox 2000.0), compared to our observations from one year ago.
The object was suspected to be undergoing a late He-flash (IAUC 6325, 6328),
and our group has been monitoring the object's evolution since discovery.
Spectra obtained on 1997 Mar. 23.33 UT at the 2.5-m du Pont telescope
show very prominent lines in the C2 Swan bands (bandheads 473, 516 and 558 nm)
not seen before.  In addition, the H Balmer lines seem to have weakened
considerably compared to a year ago.  The object was expected to change
quickly in astronomical terms, but the observed change is certainly much
faster and much more massive than expected."


COMET 81P/WILD 2
     Further to the report concerning comet C/1995 O1 on IAUC 6600,
J. Sarmecanic, D. J. Osip, M. Fomenkova and B. Jones report
that mid-infrared imaging of comet 81P with the 1.5-m reflector at
Mt. Lemmon during Mar. 5.27-5.33 UT yields the following photometric
magnitudes (10-arcsec circular aperture, uncertainties 0.2 mag):
[8.7 microns] = 4.3, [10.3 microns] = 3.2, [11.7 microns] = 2.4 and
[12.5 microns] = 2.1.  The resulting color temperature is
200 +/- 20 K, consistent with the equilibrium blackbody
temperature of 213 K at r = 1.7 AU.  There is no evidence for
excess silicate emission.

                      (C) Copyright 1997 CBAT
1997 March 24                  (6601)              Brian G. Marsden

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