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IAUC 7616: C/2001 A2; 2001bb

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                                                  Circular No. 7616
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 617-495-7440/7244/7444 (for emergency use only)

     C. W. Hergenrother, M. Chamberlain, and Y. Chamberlain, Lunar
and Planetary Laboratory, University of Arizona, report that 60-s
R-band images of C/2001 A2 taken on Apr. 30.12 UT with the Catalina
1.54-m reflector show a double nucleus.  The two components are
nearly equal in brightness and 3".5 apart and aligned precisely on
an east-west line.  Both components are highly condensed.
Observations (with the same telescope) on Apr. 24.14 show only a
single nucleus.
     Visual m_1 estimates:  Apr. 20.93 UT, 7.2 (J. G. de S. Aguiar,
Campinas, Brazil, 11x80 binoculars); 21.46, 7.4 (M. Mattiazzo,
Wallaroo, S. Australia, 7x50 binoculars); 23.16, 6.7 (C. S. Morris,
Fillmore, CA, 20x80 binoculars); 25.35, 6.4 (S. T. Rae, Whakatane,
New Zealand, 8x21 binoculars); 27.48, 6.4 (A. Pearce, Nedlands, W.
Australia, 8x40 binoculars); 29.95, 6.3 (W. Souza, Sao Paulo,
Brazil, 11x80 binoculars); 30.49, 6.3 (Pearce).

SUPERNOVA 2001bb IN IC 4319
     R. Chornock, M. Modjaz, and A. V. Filippenko, University of
California at Berkeley, write:  "Inspection of a noisy CCD spectrum
(range 320-1000 nm), obtained on Apr. 30 UT with the Shane 3-m
reflector at Lick Observatory, reveals that SN 2001bb (cf. IAUC
7614) is a supernova, probably of type Ic, but perhaps type Ia.  No
obvious H or He lines are visible, although weak Si II 615-nm
absorption might be present.  The classification is quite uncertain
at present."
     P. Nugent and L. Wang, Lawrence Berkeley National Laboratory,
report:  "A spectrum (range 400-800 nm) obtained on Apr. 30.21 at
the Kitt Peak 2.1-m telescope (+ GCAM) shows that SN 2001bb is a
type-I supernova.  Adopting the NASA/IPAC Extragalactic Database
recession velocity of 4653 km/s for the host galaxy, the minimum of
the Si II feature (rest 635.5 nm) is at a velocity of 13 800 km/s.
Ca II, O I, and Fe II features also appear at this velocity.
Several interesting absorption features between 500 and 600 nm have
yet to be identified conclusively, leaving its subtype unknown at
present.  The supernova most closely resembles SN 1999as (cf. IAUC
7128), a type-Ic hypernova event (cf. Paczynski 1998, Ap.J. 494,
L45) that peaked at absolute V magnitude brighter than -21."

                      (C) Copyright 2001 CBAT
2001 May 1                     (7616)            Daniel W. E. Green

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