IAUC 7294: 1999em; XTE J1859+226

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                                                  Circular No. 7294Central Bureau for Astronomical TelegramsINTERNATIONAL ASTRONOMICAL UNIONMailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)URL http://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304Phone 617-495-7244/7440/7444 (for emergency use only)SUPERNOVA 1999em IN NGC 1637     W. D. Li, University of California at Berkeley, on behalf ofthe Lick Observatory Supernova Search, report the discovery, on anunfiltered CCD frame taken on Oct. 29.44 UT with the 0.8-m KatzmanAutomatic Imaging Telescope, of a supernova (mag about 13.5)located at R.A. = 4h41m27s.04, Decl. = -2 51'45".2 (equinox 2000.0),which is 15".2 west and 25".1 north of the nucleus of NGC 1637.SN 1999em was confirmed at the Beijing Astronomical Observatory onOct. 29.7.  A KAIT image of the same field on Oct. 20.45 showednothing at the position of SN 1999em (limiting mag about 19.0).XTE J1859+226     R. I. Hynes, Southampton University; and C. A. Haswell, A. J.Norton, and S. Chaty, Open University, write:  "Following opticaland near-infrared monitoring of XTE J1859+226 (IAUC 7279,7284),Hubble Space Telescope (HST) STIS observations were performed onOct. 18.10-18.38 UT spanning 112-1026 nm.  The ultraviolet spectrumshows broad (12 000 km/s FWZI) and deep Ly-alpha absorption, strongC IV 155-nm emission (EW = 1.1 nm; 4000 km/s FWZI) and weakeremission lines of C III, N V, O III, O IV, O V, Si IV, and He II.Sharp absorption lines of Si II, Si III, Mg II, and other speciesalso appear with possible interstellar origin.  Preliminaryanalysis of the 220-nm interstellar feature suggests E(B-V) = 0.58+/- 0.07.  The dereddened optical spectral energy distribution canbe represented by a steep blue power law (spectral index +1.2),flattening in the ultraviolet.  This resembles energy distributionsof other short-period soft-x-ray transients, suggesting that XTEJ1859+226 has a binary period < 1 day.  A 20-percent decline in110-170-nm fluxes during the observation coincides with an x-raydecline seen in RXTE/ASM lightcurves.  Shorter timescale variationsare present, but no persistent coherent modulation was detected.Preliminary analyses of 33 hr of optical time-series data collectedbetween Oct. 13.86 and 20.24 at the Nordic Optical Telescope (J. E.Solheim, R. Ostensen, T. M. C. Abbott), Braeside Observatory (R.Fried, J. McFarland), the Jacobus Kapteyn Telescope (D. J. Rolfe,D. A. Lott), Keele (Z. Ioannou), Mt. Laguna (A. Shafter), St.Andrews (K. O'Brien, K. Horne), and Manastash Ridge Observatory (K.Krisciunas), and also 2.5 hr of infrared time-series data at theU.K. Infrared Telescope (R. J. Ivison) on Oct. 18.19-18.31,suggests a 1-percent modulation with period 22-23 min.  Further HSTobservations are scheduled for Nov. 6.82-6.93 and 19.43-19.55;coordinated groundbased observations are encouraged."                      (C) Copyright 1999 CBAT1999 October 30                (7294)            Daniel W. E. Green

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