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Discovery of the Brightest T Dwarf in the Northern Hemisphere
We report the discovery of a bright (H=12.77) brown dwarf designatedSIMP J013656.5+093347. The discovery was made as part of a near-infraredproper-motion survey, SIMP (Sondage Infrarouge de Mouvement Propre),which uses proper motion and near-infrared/optical photometry toidentify brown dwarf candidates. A low-resolution(λ/Δλ~40) spectrum of this brown dwarf covering the0.88-2.35 μm wavelength interval is presented. Analysis of thespectrum indicates a spectral type of T2.5 +/- 0.5. A photometricdistance of 6.4 +/- 0.3 pc is estimated, assuming it is a single object.Current observations rule out a binary of mass ratio ~1 and separation>~5 AU. SIMP J013656.5+093347 is the brightest T dwarf in thenorthern hemisphere and is surpassed only by ɛ Indi Bab over thewhole sky. It is thus an excellent candidate for detailed studies andshould become a benchmark object for the early T spectral class.
| Optical Spectropolarimetry of SN 2002ap: A High-Velocity Asymmetric Explosion
We present spectropolarimetry of the Type Ic supernova SN 2002ap andgive a preliminary analysis: the data were taken at two epochs, close toand 1 month later than the visual maximum (2002 February 8). Inaddition, we present June 9 spectropolarimetry without analysis. Thedata show the development of linear polarization. Distinct polarizationprofiles were seen only in the O I λ7773 multiplet/Ca II IRtriplet absorption trough at maximum light and in the O I λ7773multiplet and Ca II IR triplet absorption troughs a month later, withthe latter showing a peak polarization as high as ~2%. The intrinsicpolarization shows three clear position angles: 80° for the Februarycontinuum, 120° for the February line feature, and 150° for theMarch data. We conclude that there are multiple asymmetric components inthe ejecta. We suggest that the supernova has a bulk asymmetry with anaxial ratio projected on the sky that is different from 1 by an order of10%. Furthermore, we suggest very speculatively that a high-velocityejecta component moving faster than ~0.115c (e.g., a jet) contributes topolarization in the February epoch. Based on data obtained at the SubaruTelescope, which is operated by the National Astronomical Observatory ofJapan (NAOJ).
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