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IAUC 7307: HD 209458; SAX J1752.3-3138

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                                                  Circular No. 7307
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
URL http://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
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HD 209458
     G. W. Henry, Tennessee State University; G. Marcy, University
of California at Berkeley; R. P. Butler, Department of Terrestrial
Magnetism, Carnegie Institution of Washington; and S. S. Vogt, Lick
Observatory, report: "The G0 V star HD 209458 = BD +18 4917 (R.A. =
22h03m10s.78, Decl. = +18o53'03".5, equinox 2000.0; V = 7.65)
exhibits sinusoidal velocity variations with a semiamplitude of 81
m/s, indicating the presence of a companion with M sin i = 0.63
Jupiter mass and an orbital period of 3.523 days.  Photometry
reveals a transit ingress on Nov. 8.20 UT with a depth of 0.017 mag,
consistent with the transit time predicted from the velocities.
Further measurements of transits and velocities would be valuable.
The next three predicted times of ingress occur at Nov. 15.263,
18.787, and 22.311 (all times uncertain by 1 hr).  If correct, the
inferred mass is 0.63 that of Jupiter, and radius 1.6 that of
Jupiter, implying a density of 0.21 g/cm**3.  HD 209458 resides at a
distance of 47 pc, with rotational v sin i = 3 km/s, and is
chromospherically inactive, with an estimated age of 4.5 Gyr."

SAX J1752.3-3138
     M. Cocchi, A. Bazzano, L. Natalucci, and P. Ubertini, Istituto
di Astrofisica Spaziale, CNR, Rome; R. Cornelisse and E. Kuulkers,
Space Research Organization Netherlands (SRON), Utrecht, and
Astronomical Institute, Utrecht University; and J. in 't Zand and
J. Heise, SRON, communicate:  "A post-facto analysis of monitoring
observations of the galactic-center region with the Wide Field
Cameras onboard BeppoSAX has led to the discovery of a new x-ray
burster, SAX J1752.3-3138.  This source was seen only during a
burst on Oct. 2.14 UT; no steady emission was observed in 50~000 s
net observation time, the upper limit being 6 mCrab.  The burster
is localized at R.A. = 17h52m24s, Decl. = -31o37'.7 (equinox 2000.0;
99-percent-confidence error radius 2'.9).  No previously known x-ray
sources are contained within the burst-position confidence circle.
The burst showed a peak intensity of 0.7 Crab (2-26 keV), and its
spectrum (integrated over 28 s of data) is consistent with a
blackbody emission with kT = 1.8 keV.  The time profile of the
burst is consistent with fast rise and exponential decay.  The above
characteristics suggest the burst to be a thermonuclear flash on
a neutron star, that is likely located in a low-mass x-ray binary."

                      (C) Copyright 1999 CBAT
1999 November 12               (7307)            Daniel W. E. Green

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