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IAUC 6890: 1998bp; C/1998 H1

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                                                 Circular No. 6890
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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SUPERNOVA 1998bp IN NGC 6495
     G. M. Hurst, Basingstoke, England, reports the discovery by
Mark Armstrong, Rolvenden, of an apparent supernova (mag 14.8) on
unfiltered CCD images taken on Apr. 29.074, 29.101 and 29.128 UT
with a 0.26-m Schmidt Cassegrain telescope in the course of the
U.K. Nova/Supernova Patrol.  The new star was reported at R.A.
= 17h54m50s.71, Decl. = +18o19'49".3 (equinox 2000.0), or about 15"
due north of the nucleus of NGC 6495.  No star was recorded at this
position on a CCD frame taken by Armstrong on Mar. 20.283 (limiting
mag 16.7).  Hurst estimated mag 14.7 from a CCD frame obtained by
T. Boles, Wellingborough, on Apr. 29.135 in strong twilight.  S.
Nakano, Sumoto, Japan, forwards the following position end figures
measured by A. Sugie at Dynic Astronomical Observatory, from CCD
frames taken under poor conditions on Apr. 30.54 (V = 14.9-15.1):
50s.72, 50".2, which is 1" west and 13" north of the galaxy's
     F. Patat, European Southern Observatory (ESO); and M. Maia,
Observatorio Nacional, Rio de Janeiro, report on their observations
of SN 1998bp with the ESO 1.5-m telescope (+ Boller & Chivens
spectrograph; 10-min exposure, range 360-750 nm, resolution 0.5 nm)
obtained on Apr. 30.38 UT at La Silla:  "A full reduction of the
CCD spectrogram shows that this object is indeed a supernova.  The
spectral features are consistent with a peculiar type-Ia object,
roughly around maximum light.  The usual Si II feature (635.5 nm)
is much less deep than in normal type-Ia supernovae, if compared
with all of the other spectral lines.  The spectrum is dominated by
P-Cyg profiles, superimposed on a slightly blue continuum.  The
most prominent features are identified as Ca II H and K, Si II, Mg
II, and S II.  From the spectrophotometry we estimate B-V about
+0.4 and V-R about +0.4, which are rather red for a normal type-Ia
supernova at this phase.  Since the host galaxy is elliptical and
there is no evident signature of Na I D absorption in the spectrum,
the red observed color is intrinsic.  The expansion velocities
measured from the minima of Ca II H and K, Mg II 448.1-nm, and Si
II 635.5-nm are 13 600, 13 700, and 12 800 km/s, respectively.  The
recession velocity of the parent galaxy, deduced from the emission
peak of the Si II 635.5-nm line, is 4500 km/s."

     Visual m_1 estimates:  Apr. 27.83 UT, 10.4 (K. Hornoch,
Lelekovice, Czech Rep., 0.35-m refl.); 28.92, 10.4 (M. Reszelski,
Szamotuly, Poland, 20x60 binoc.); 29.95, 10.4 (A. Baransky, Kiev,
Ukraine, 0.20-m reflector).

                      (C) Copyright 1998 CBAT
1998 April 30                  (6890)            Daniel W. E. Green

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