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IAUC 6668: eta Car; SLX 1735-269

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                                                 Circular No. 6668
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)
URL http://cfa-www.harvard.edu/cfa/ps/cbat.html
Phone 617-495-7244/7440/7444 (for emergency use only)


eta CARINAE
     K. Ishibashi and K. Davidson, University of Minnesota; M. F.
Corcoran, Goddard Space Flight Center (GSFC) and Universities Space
Research Association; and J. H. Swank, R. Petre, and K. Jahoda,
GSFC, report:  "The Proportional Counter Array on board the Rossi
X-ray Timing Explorer (RXTE) has been monitoring the hard-x-ray
emission from the peculiar luminous star eta Car since 1996 Feb. 9.
Using a conversion factor of 3.22 x 10E-12 erg sE-1 cmE-2 per PCA
count, the 2-10-keV lightcurve (in PCU0-2) shows a significant
long-term rise, with flux increasing from 6.8 x 10E-11 to 1.0 x
10E-10 erg sE-1 cmE-2 in the interval 1996 Dec.-1997 May.  Highly
significant, shorter-duration flaring has been observed on 1996 May
3, July 22, Oct. 24, 1997 Jan. 19, and Apr. 10, with peak fluxes of
6.5, 7.8, 7.3, 9.2, and 12.0 x 10E-11 erg sE-1 cmE-2, respectively,
representing a flux increase of about 9-40 percent over the non-
flare emission.  Timings of the flare peaks suggest a recurrence
every 85.1 +/- 5.4 days, with a duration of 20 days.  The next
flare event should occur in the interval 1997 June 23-July 13, with
peak intensity predicted to occur on July 3.  We encourage
coordinated observations of eta Car at all wavebands during this
interval to determine if this is a persistent property and to
search for the cause of this activity.  Dates of upcoming and
previous RXTE observations of eta Car are available, along with the
most recent RXTE x-ray lightcurve, from
http://lheawww.gsfc.nasa.gov/users/corcoran/eta_car/eta_car_xte.html."


SLX 1735-269
     A. Bazzano, M. Cocchi, and P. Ubertini, Istituto di
Astrofisica Spaziale, CNR, Frascati; and J. Heise, J. in 't Zand,
and J. M. Muller, Space Research Organization of the Netherlands,
Utrecht, report:  "On Apr. 13.668 UT, an x-ray burst was detected
with Wide Field Camera Number 1 on the BeppoSAX satellite from R.A.
= 17h38m17s.8, Decl. = -27o00'08" (equinox 2000.0, error circle
radius 5').  The only known x-ray source within this error circle
is SLX 1735-269.  This is the first report of bursting behavior
from this source, suggesting a neutron star as a likely source.
The burst lasted 30 s and had a peak intensity of 900 mCrabs (2-8
keV).  The steady emission of SLX 1735-269 had an average value of
about 10 mCrab during monitoring observations between Apr. 13.02
and 16.80."

                      (C) Copyright 1997 CBAT
1997 May 23                    (6668)            Daniel W. E. Green

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