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IAUC 7769: 51P; 4U 0142+61

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                                                  Circular No. 7769
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
Phone 617-495-7440/7244/7444 (for emergency use only)

     P. Manteca, Observatorio de Begues (near Barcelona), reports
that his observations on Dec. 6.1 UT (0.31-m f/6.3 Schmidt-
Cassegrain reflector + CCD) showed this comet to have split, the
two components being separated by some 10" on an east-west line.
Each around mag 17.0-17.4, the western component was perhaps up to
0.4 mag brighter than the eastern, which is evidently the one that
was under observation during July-November.  On Dec. 7.0 and 7.9
Manteca gave m_1 = 16.4 for the eastern component and m_1 = 16.6
for the western.  The eastern component is also clearly the object
defined as component A at the comet's 1994 apparition, when two
much fainter components, B and C, were also recorded with an
effective perihelion time almost 0.3 day later (cf. IAUC 6089).
The current western component is therefore to be denoted as
component D, and its effective perhelion time on 2001 June 5 is
only about 0.006 day later than that of component A.  The splitting
was confirmed by R. Naves and M. Campas (Observatorio Montcabre,
also near Barcelona; 0.25-m f/3.3 Schmidt-Cassegrain reflector +
CCD), who gave m_1 as 16.9 for component A and 16.7 for component D
on Dec. 6.9 and 16.2 for component A and 16.3 for component D on
Dec. 7.9.  R. Ferrando (Observatorio Pla D'Arguines, near Valencia;
0.30-m Schmidt-Cassegrain reflector + CCD) gave m_1 as 16.5 for
component A and 16.7 for component D on Dec. 7.9.  The comet is
noticeably brighter than the predicted magnitude given in the
ephemeris on MPC 43692.

4U 0142+61
     B. Kern and C. Martin, California Institute of Technology,
communicate:  "We observed the anomalous x-ray pulsar (AXP) 4U
0142+61 on Nov. 16-17 UT with the Palomar 5-m telescope, using an
unfiltered CCD observing in a periodic frame-transfer mode,
synchronized with the known 8.7-s x-ray period (Gavriil and Kaspi
2001, http://xxx.lanl.gov/abs/astro-ph/?0107422).  In 10-phase
bins, we find optical pulsations with a 30-percent pulsed fraction.
The pulse profile is similar in morphology and agrees within 0.1 in
phase with the soft x-ray pulse profile.  This is the first
detection of optical pulsations in an AXP.  Our discovery
unambiguously confirms the optical counterpart (Hulleman et al.
2000, Nature 408, 689), and the large pulsed fraction rules out
x-ray reprocessing as the source of pulsed optical emission."

                      (C) Copyright 2001 CBAT
2001 December 8                (7769)            Daniel W. E. Green

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