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