Electronic Telegram No. 396
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138,
U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX
617-495-7231 (subscriptions)
CBAT@CFA.HARVARD.EDU (science)
URL
http://cfa-www.harvard.edu/iau/cbat.html
SUPERNOVA 2006X IN NGC 4321 = M100
C. J. Stockdale and M. Kelley, Marquette University; R. A.
Sramek, National Radio Astronomy Observatory; S. D. Van Dyk,
Spitzer Science Center, California Institute of Technology; S.
Immler, Goddard Space Flight Center and Universities Space Research
Association; K. W. Weiler and C. L. M. Williams, Naval Research
Laboratory; and N. Panagia, Space Telescope Science Institute,
report the lack of detection of radio emission near the position
of supernova 2006X (cf. IAUC 8667, CBET 393) with the Very Large
Array: "Upper limits (3 sigma) to any radio flux density were
established on Feb. 9.37 UT of < 0.162 mJy (spectral luminosity <
5.6 x 10^25 erg/s/Hz) at 22.460 GHz (wavelength 1.3 cm) and <
0.047 mJy (spectral luminosity < 1.5 x 10^25 erg/s/Hz) at 8.460 GHz
(wavelength 3.5 cm), among the deepest and earliest limits yet
obtained for radio emission from a type-Ia supernova. Under
standard assumptions, this implies a mass-loss rate from the
pre-supernova system of < (a few) x 10^-8 solar mass per year.
The search for radio emission was conducted within about 10" of
the published optical position of SN 2006X (R.A. = 12h22m53s.99,
Decl. = +15o48'33".1, equinox 2000.0; IAUC 8667), and no radio
emission was detected near the supernova position exceeding three
times the map rms at any of the times or in any of the frequency
bands listed above."
L. Wang, Lawrence Berkeley National Laboratory; D. Baade
and F. Patat, European Southern Observatory; and J. C. Wheeler,
University of Texas, Austin, report on their acquisition of
spectropolarimetric data (range 330-850 nm) of SN 2006X using
the Very Large Telescope at the European Southern Observatory
on Feb. 9 UT: "The polarization is as high as 8 percent in the
blue and decreases approximately linearly to about 3.5 percent
in the red. The spectropolarization is significantly different
from that typical for extinguished Galactic stars. This may
suggest that the dust properties in NGC 4321 are very different
from the Galaxy or that the dust and polarizations are of
circumstellar origin (see Wang 2005, Ap.J. 635, L33). The data
also show polarized spectral features from most spectral lines,
noticeably from the Ca II infrared triplet and Si II 635.5-nm,
at levels around 1 percent."
NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
superseded by text appearing later in the printed IAU Circulars.
(C) Copyright 2006 CBAT
2006 February 9 (CBET 396) Daniel W. E. Green
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