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IAUC 7434: 2000ck; C/1999 S4

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                                                  Circular No. 7434
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
URL http://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7244/7440/7444 (for emergency use only)

SUPERNOVA 2000ck IN IC 4355
     S. Benetti, R. Cosentino, J. Licandro, F. Paulli, M. Pedani,
G. Trancho, A. Zacchei, and E. Giro, Telescopio Nazionale Galileo
(TNG); P. Conconi, G. Crimi, and E. Molinari, Osservatorio
Astronomico di Brera; and A. Caproni, M. Comari, C. Corte, S.
Monai, and M. Pucillo, Osservatorio Astronomico di Trieste, report:
"A fully reduced CCD spectrum (range 333.3-722.3 nm, resolution 1
nm), obtained on May 31.03 UT with the TNG reflector (+ D.o.lo.res
spectrograph), tentatively shows SN 2000ck (cf. IAUC 7431) to be a
type-II supernova near maximum light.  The spectrum is dominated by
a very blue continuum (T_bb about 17 000 K), upon which we identify
(even if faint) H-delta, H-gamma, and H-beta lines with relatively
narrow P-Cyg profiles (from which we derive an expansion velocity
of about 6200 km/s).  There is no sign of a broad H-alpha feature.
From weak interstellar lines due to the Na I D absorption feature
(EW about 0.12 nm) seen at about 605.3 nm, we derive a parent-galaxy
recession velocity of about 8150 km/s."
     S. Jha, P. Challis, and R. Kirshner, Harvard-Smithsonian
Center for Astrophysics; and P. Garnavich, University of Notre Dame,
write:  "Spectra of SN 2000ck, taken by P. Berlind and Garnavich on
May 27.4, 28.3, 29.2, 30.2, and 31.3 UT with the Whipple
Observatory 1.5-m telescope (+ FAST spectrograph), show it to be an
unusual type-II supernova at an early epoch.  The spectra exhibit a
blue continuum with narrow emission lines of [O II], H-gamma,
H-beta, [O III], [O I], [N II], H-alpha, and [S II] from a
superimposed H II region at the recession velocity of IC 4355 (8048
km/s in the NASA/IPAC Extragalactic Database).  From the supernova
itself, there are broad but very weak absorption features of H-beta
(expansion velocity 6700 km/s) and He I (rest 587.6 nm, expansion
velocity 5300 km/s) that have developed only very slowly.  Strong
interstellar Na I absorption (with equivalent width 0.1 nm) at the
host-galaxy redshift implies significant extinction by dust."
     A. V. Filippenko and A. C. Coil, University of California at
Berkeley, communicate:  "A CCD spectrum (range 320-1000 nm) of SN
2000ck obtained on May 31 UT with the Shane 3-m reflector at Lick
Observatory exhibits a blue, nearly featureless continuum.  It
resembles the spectrum of the peculiar type-II supernova 1993J at
very early times (Filippenko 1997, ARAA 35, 309), but the type-II
classification is not yet certain."

     Visual m_1 estimates by N. Biver, Oahu, HI (0.26-m reflector):
May 25.61 UT, 11.3; 29.61, 11.0.

                      (C) Copyright 2000 CBAT
2000 June 1                    (7434)            Daniel W. E. Green

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