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IAUC 7605: 2001ai; C/2001 A2

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                                                  Circular No. 7605
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)


SUPERNOVA 2001ai IN NGC 5278
     M. Modjaz and W. D. Li, University of California at Berkeley,
on behalf of LOTOSS (cf. IAUC 7514), report the discovery of an
apparent supernova on unfiltered CCD images taken on Mar. 28.4 (mag
about 17.6) and 29.4 UT (mag about 17.5) with the 0.8-m Katzman
Automatic Imaging Telescope.  SN 2001ai is located at R.A. =
13h41m39s.35, Decl. = +55o40'05".1 (equinox 2000.0), which is 2".0
west and 9".0 south of the nucleus of NGC 5278.  An unfiltered
image taken by M. Schwartz with the Tenagra III 0.5-m automatic
telescope on Mar. 19.4 showed nothing at this position (limiting
mag about 19.0).  NGC 5278 is one of an interacting connected pair
of galaxies (with the center of NGC 5279 about 0'.5 away from that
of NGC 5278).
     T. Matheson, S. Jha, P. Challis, and R. Kirshner, Harvard-
Smithsonian Center for Astrophysics, report that a spectrum of SN
2001ai, obtained by P. Berlind on Mar. 29.25 UT with the F. L.
Whipple Observatory 1.5-m telescope (+ FAST spectrograph), shows it
to be a type-Ic supernova before maximum.  The spectrum is similar
to that of SN 1994I, about 5 days before V maximum (see Figure 1 of
Filippenko et al. 1995, Ap.J. 450, L11), although it is much more
blue.  This may be due to contamination by stars associated with a
very bright underlying H II region.  Adopting the NASA/IPAC
Extragalactic Database recession velocity of 7541 km/s for the host
galaxy, the supernova expansion velocity is about 11 700 km/s for
Ca II (rest 395.1 nm).


COMET C/2001 A2 (LINEAR)
     This comet has apparently undergone a rapid brightening
(ephemeris on IAUC 7600).  M. Mattiazzo, Wallaroo, South Australia,
notes that the total visual magnitude has brightened by about 2.5
mag in the 24 hr ending Mar. 30.5 UT, with the comet becoming
noticeably more condensed in the same period.  Visual m_1 estimates
and coma diameters:  Mar. 26.82, 10.8, 2'.5 (R. J. Bouma, Groningen,
The Netherlands, 0.25-m reflector); 28.44, 10.7, 3'.5 (Mattiazzo,
0.20-m reflector); 28.98, 10.9, 3' (P. M. Raymundo, Salvador,
Brazil, 0.25-m reflector); 29.27, 10.9, 2'.0 (M. Linnolt, Honolulu,
HI, 0.25-m reflector); 29.46, 10.8, 3'.0 (Mattiazzo); 29.94, 9.5,
3'.5 (A. Amorim, Florianopolis, Brazil, 0.14-m reflector); 30.45,
8.6, 2'.9 (Y. Nagai, Yamanashi, Japan, 0.32-m reflector); 30.40,
8.2, 5' (S. T. Rae, Whakatane, New Zealand, 10x50 binoculars);
30.52, 8.0, 3'.0 (Mattiazzo, McLaren Vale, S. Australia, 25x100
binoculars); 30.81, 7:, 5' (K. Cernis, Vilnius, Lithuania, no
instrument given).

                      (C) Copyright 2001 CBAT
2001 March 30                  (7605)            Daniel W. E. Green

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