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IAUC 7835: 2002ap; RX J0806.3+1527

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IAUC number

                                                  Circular No. 7835
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)

     K. S. Kawabata, G. Kosugi, T. Sasaki, Y. Ohyama, N. Kashikawa,
Y. Saito, and M. Iye, National Astronomical Observatory of Japan;
and K. Nomoto, University of Tokyo, write:  "We carried out
sequential optical spectropolarimetry (range 385-830 nm; resolution
0.56 nm and 0.14 nm/pixel) of SN 2002ap (IAUC 7810) on Feb. 9.24,
10.28, 11.26 and 12.26 UT with the Subaru 8.2-m telescope (+ FOCAS).
The polarization bump corresponding to the broad absorption feature
in the wavelength range 650-800 nm (cf. IAUC 7820) was still
prominent, but the wavelength of the maximum polarization had
shifted to 748 nm and the FWHM of the feature had narrowed to 45 nm.
A significant variation in the position angle of the polarization
with respect to wavelength was observed around this feature.  The
position angle showed a broad dip of about 15 deg over the feature
at 650-800 nm, superposed on a local (720-770 nm) asymmetric bump
of 20 deg in height that peaked at 760 nm.  These findings suggest
a complicated asymmetric geometry of the explosion."

RX J0806.3+1527
     G. L. Israel and L. Stella, Astronomical Observatory, Rome; W.
Hummel, European Southern Observatory (ESO); and S. Covino and S.
Campana, Astronomical Observatory of Brera, on behalf of a larger
collaboration, report on spectroscopic and photometric optical
observations, obtained with the the ESO Very Large Telescope (on
1999 Nov. 12-19, 2000 Feb. 5, 2001 Jan. 16-24, and Nov. 11) and the
Telescopio Nazionale Galileo (on 2001 Jan. 1), of the blue star
(R.A. = 8h06m22s.9, Decl. = +15o27'31", equinox 2000.0; V = 21.1)
suggested as the optical counterpart of the 321-s x-ray pulsator RX
J0806.3+1527 (Israel et al. 1999, A.Ap. 349, L1):  "B-, V-, and
R-band time-resolved photometry revealed the presence of 15-percent
pulsed-fraction modulation at the 321-s x-ray period, confirming
the correctness of the identification.  Broad (v about 1500 km/s),
low equivalent-width (0.1-0.5 nm) emission lines from the He II
Pickering series (possibly blended with H Balmer lines) were
clearly detected.  These findings, together with the period
stability and the absence of any additional modulation in the
period range 1-300 min, argue in favor of the orbital
interpretation of the 321-s pulsations.  The most likely scenario
is that RX J0806.3+1527 is a double-degenerate system of the AM
CVn class.  This would make it the binary with the shortest
orbital period currently known and one of the best candidates for
gravitational-wave detection."

                      (C) Copyright 2002 CBAT
2002 February 22               (7835)            Daniel W. E. Green

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