Electronic Telegram No. 862 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION M.S. 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 SUPERNOVA 2007Y IN NGC 1187 G. Folatelli, Las Campanas Observatory (LCO), together with N. Morrell, M. Phillips, and M. Hamuy, on behalf of the Carnegie Supernova Project, report spectroscopic observations of SN 2007Y (cf. CBET 845, IAUC 8813) obtained on Feb. 19.04 and 25.02 UT with the 2.5-m du Pont telescope (+ WFCCD spectrograph) at LCO. The spectra show that 2007Y is a type-Ib/c supernova of peculiar evolution, in most aspects resembling the case of SN 2005bf at early stages (see Folatelli et al. 2006, Ap.J. 641, 1039). The first spectrum is similar to that of SN 2005bf at 32 days before maximum light, showing strong absorptions due to Fe II, Ca II, and other metals. In particular, the Ca II infrared triplet absorption component at about 820 nm is remarkably strong. Another absorption is seen at about 620 nm, which may be identified as Si II or H-alpha, the latter requiring higher expansion velocities. Assuming the NED recession velocity of 1390 km/s for the host galaxy (from Koribalski et al. 2004, A.J. 128, 16), a comparison with synthetic spectra obtained using the SYNOW code (Fisher 2000, Ph.D. thesis, University of Oklahoma) allows us to identify a photospheric velocity of about 7000 km/s. The match of Ca II and Fe II lines improves by adding a high-velocity component appearing beyond 15000 km/s, which would support the identification of the feature at 620 nm as H-alpha at similarly high velocities. The high-velocity components of Ca II and Fe II are not as strong as the ones shown by SN 2005bf. Through the same analysis, a strong absorption trough seen around 420 nm is explained by a mixture of Fe II, Ti II, Mg II, and Sc II. The presence of a weak component of He I cannot be ruled out. The second spectrum resembles the spectra of SN 2005bf at 27 and 24 days before maximum. The Ca II infrared triplet absorption has significantly weakened, although a high-velocity component persists. The trough at 420 nm has also weakened, and the overall slope of the continuum appears bluer, suggesting an increase in temperature. The absorption at about 620 nm has also become weaker, while the presence of He I appears slightly more evident. Acquisition images, obtained with the WFCCD spectrograph prior to each of the spectra, were used to measure B- and V-band photometry of SN 2007Y relative to a field star located 111".8 east and 41".8 north of the supernova; these measurements indicate that 2007Y brightened by about 1 magnitude in V, and its B-V color became bluer by about 0.3 mag between Feb. 19 and 25. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2007 CBAT 2007 February 28 (CBET 862) Daniel W. E. Green