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IAUC 8220: CXOU J010043.1-721134; 2003 SS_84

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                                                  Circular No. 8220
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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CXOU J010043.1-721134
     R. C. Lamb and T. A. Prince, California Institute of
Technology; D. J. Macomb, Boise State University; and W. A. Majid,
Jet Propulsion Laboratory, report that the possible anomalous x-ray
pulsar (AXP) designated CXOU J010043.1-721134 has a pulse period of
8.02 s, rather than the previously reported 5.4-s period (Lamb et
al. 2002, Ap.J. 574, L29) from Chandra ACIS-I data, which yield a
Nyquist frequency of 0.154 Hz (6.48-s period):  "In the Fourier
transform of these data, two strong peaks at 0.125 and 0.184 Hz
were observed with power values of 40, where the average power is
normalized to 1.  ROSAT data for this same source favored the
higher frequency.  However, new data for this source, from the XMM-
Newton satellite (observation 0018540101), clearly show that the
correct frequency is near 0.125 Hz.  The XMM data were obtained
with the PN detector, which has a digitization interval of 0.0734
s, giving a Nyquist frequency of 6.8 Hz, well above the region of
interest.  The times of arrival of 4048 source photons, collected
in the 27300-s observation (epoch 2001 Nov. 21.015 UTC), were
corrected to the solar-system barycenter.  The Fourier transform of
these corrected times show a strong peak at 0.124699(5) Hz with a
normalized power value of 28.  Power peaks at the second and third
harmonics are present as well.  The luminosity of the source
(0.2-10 keV), corrected to the 60000-pc distance of the Small
Magellanic Cloud, is 2.6 x 10**35 erg/s.  By combining this
observation with the Chandra observation made 189.934 days earlier,
we derive a frequency time derivative of -4 +/- 3 x 10**-13 s.  The
relative constancy of the luminosity of this source, its magnitude,
and its small spin-down rate [time scale P/(dP/dt) about 10000 yr]
are consistent with the characteristics of AXPs (cf. Mereghetti et
al. 2002, http://xxx.lanl.gov/abs/astro-ph/?0205122)."

2003 SS_84
     M. C. Nolan, A. A. Hine, and E. S. Howell, National Astronomy
and Ionosphere Center; and L. A. M. Benner and J. D. Giorgini, Jet
Propulsion Laboratory, report that Arecibo radar delay-Doppler
images (2380 MHz, 12.6 cm) obtained on Oct. 4-8 show that 2003
SS_84 (cf. MPEC 2003-S40) is a binary system.  Preliminary
estimates of average diameters, based on range extents at 15-m
resolution, are 120 and 60 m.  The pair was seen at approximately
the same orbital phase at Oct. 4.073, 5.083, 7.034, and 8.003 UT,
indicating an orbital period of just under 24 hr or an integer
fraction thereof.  Optical lightcurve observations of this object
would be valuable.

                      (C) Copyright 2003 CBAT
2003 October 10                (8220)            Daniel W. E. Green

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