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IAUC 6193: (2060); QZ Vul

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                                                  Circular No. 6193
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)

     M. Womack, Pennsylvania State University, Erie; and S. A.
Stern, Southwest Research Institute, report:  "We obtained a first
detection of CO in Chiron via the molecule's J=1-0 rotational
transition at 115 GHz (2.6 mm), during June 10-12 UT with the
National Radio Astronomy Observatory 12-m telescope on Kitt Peak.
The line was observed in two polarizations, with each of two
independent filterbanks of 100- and 250-kHz spectral resolution.
The line was blueshifted by about 0.5 km/s from the ephemeris
velocity.  The CO line area was measured to be 0.013 +/- 0.005 K
km/s in both sets of data (at 5 sigma in the 100-kHz spectrum and 3
sigma in the 250-kHz data).  Assuming that the CO fills the 50"
NRAO beam and that the excitation, rotational, and kinetic
temperatures of the gas are all between 10 and 50 K, we derive a CO
column density of (2 +/- 1) x 10E13 cmE-2.  A Haser model
calculation, assuming an isotropic coma expansion at velocities of
0.5 km/s, implies a production rate of Q(CO) = (4 +/- 2) x 10E28
mol sE-1 if CO is a parent molecule.  Additional observations of CO
in Chiron's coma during the upcoming perihelion passage are encouraged."

     P. A. Charles and J. Casares, Oxford University, write:
"Optical spectroscopy of QZ Vul obtained with the 4.2-m William
Herschel Telescope on La Palma shows broad (FWHM 2000 km/s),
double-peaked H-alpha emission superposed on the late-type spectrum
of the secondary star, detected here for the first time and
constrained to be in the range K3-K7; QZ Vul is the quiescent (mag
21) counterpart of the 1988 soft x-ray transient GS 2000+25.  Using
the known photometric period of 8.25836 hr (Chevalier and Ilovaisky
1993, A.Ap. 269, 301), we measure a velocity semiamplitude of 490
+/- 22 km/s for the secondary star by cross-correlation with a K5 V
'template'.  This leads to a mass function of 4.2 +/- 0.5 solar
masses, which --- combined with the absence of eclipses and the
observed ellipsoidal modulation (Callanan and Charles 1991, MNRAS
249, 573) --- suggests a compact object mass of > 5.5 solar masses
(for inclinations < 70 deg), establishing it firmly as a strong
blackhole candidate.  This is further supported by the H-alpha
double-peak separation of 1200 km/s, implying an outer-disk velocity
of 600 +/- 30 km/s, a value that is typically 10-20 percent greater
than the K velocity in other x-ray transients (e.g., Orosz and
Bailyn 1994, IAUC 6103).  QZ Vul thus has the second largest mass
function known amongst the blackhole x-ray binaries, after V404 Cyg
(Casares and Charles 1994, MNRAS 271, L5)."

1995 July 28                   (6193)            Daniel W. E. Green

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