IAUC No. 7133

Central Bureau for Astronomical Telegrams


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SUPERNOVAE 1999bc AND 1999bd

P. Nugent, Lawrence Berkeley Laboratory, on behalf of the Supernova Cosmology Project and the Near-Earth Asteroid Tracking project (cf. IAUC 7125, 7128), reports two supernovae discoveries on unfiltered CCD frames:

SN 1999 UT R.A. (2000.0) Decl. Mag. Offset

1999bc Feb. 19 8 28 31.08 +17 28 15.4 18.9: 4".2 W, 17".1 N

1999bd Feb. 19 9 30 29.17 +16 26 07.8 17.7: ?

A CCD spectrum (range 420-850 nm) of SN 1999bc, located in UGC 4433, taken by G. Aldering on Mar. 5 UT at the MDM 2.4-m telescope, showed a few narrow emission features (463, 537, and 586 nm) about 4000 km/s across, along with some contamination from a superposed H II region. A CCD spectrum (range 365-930 nm) taken by M. M. Phillips on Mar. 22 with the Las Campanas 2.5-m duPont telescope shows that these features have broadened somewhat over this time period. Phillips classifies SN 1999bc as a type-Ic supernova at a redshift of 0.022, the spectrum being similar to that of SN 1983V at about 30 days after peak brightness.

SN 1999bd has no apparent host on the discovery images (limiting mag about 19). A CCD spectrum obtained at the ARC 3.5-m telescope on Mar. 10 by G. Richards, H. Newberg, and S. Kent showed a blue continuum with several narrow features and H-alpha emission, strongly absorbed by the atmospheric A band. Phillips took another spectrum of this object (range 365-930) on Mar. 22, and he classifies it as a type-II supernova at a redshift of 0.151. Once again, several narrow features are present in the spectrum, along with a weak, broad component visible below H-alpha.

(C) Copyright 1999 CBAT

1999 March 27 (7133) Daniel W. E. Green