Circular No. 7421

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) BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science) URL http://cfa-www.harvard.edu/iau/cbat.html Phone 617-495-7244/7440/7444 (for emergency use only)

SUPERNOVA 2000ch IN NGC 3432

A. V. Filippenko, University of California at Berkeley, writes: "The descriptions of the 'variable star' in NGC 3432 (cf. IAUC 7415, 7417, 7419) strongly suggest that it is a subluminous type-IIn supernova similar to SN 1997bs in NGC 3627 (cf. IAUC 6627) and SN 1999bw in NGC 3198 (cf. IAUC 7152). The progenitors of these subluminous objects may be very massive, powerful stars such as luminous blue variables (e.g., SN 1961V, cf. Goodrich et al. 1989, Ap.J. 342, 908; SN 1997bs, cf. Van Dyk et al. 1999, A.J. 118, 2331). If so, the 'explosion mechanism' might not be core collapse, and the star may survive (e.g., SN 1961V, cf. Filippenko et al. 1995, A.J. 110, 2261). Indeed, the 'explosion' is actually just a super-outburst of the luminous variable. Some of these outbursts last longer than others, and that of the object in NGC 3432 seems to have been short-lived."

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Host galaxy info: V = 616 km/s, 6.8' x 1.5', SB(s)m;LINER HII; mag 11.67

SN type info: SN IIn

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