P. Garnavich, S. Jha, R. Kirshner, and P. Challis, Harvard- Smithsonian Center for Astrophysics; and D. Balam, University of Victoria, report: "Recent CCD images of SN 1997ef obtained with the Whipple Observatory 1.2-m telescope by P. Berlind, with the MDM 2.4-m telescope by J. Thorstensen, and with the Dominion Astrophysical Observatory's 1.8-m Plaskett telescope indicate that this object has begun to decline in brightness. Visual magnitude estimates relative to the star (V = 17.05) located 1' southwest of UGC 4107: Dec. 16.3 UT, 16.56; 27.3, 16.84; 28.3, 16.94. Spectra obtained at the Tillinghast telescope by Berlind and L. Macri, and at the MDM 2.4-m telescope by Thorstensen, between Dec. 17 and 27 show that the rapid velocity shift seen in the major spectral features has slowed. After correcting for the redshift of UGC 4107, a number of peaks can now be identified at 397 nm (Ca II), 457 nm (?), 486 nm (H-beta), 547 nm (?), 587 nm (He I), 614 nm (?), and 655 nm (H-alpha). The H-alpha emission peak is rounded, while the unidentified maxima have a triangular shape. Currently, the spectrum appears similar to the peculiar type-Ib supernovae 1988L (Filippenko 1988, A.J. 96, 1941) and 1983I (Wheeler et al. 1987, Ap.J. 313, L69), which also displayed broad maxima near the wavelength of H-alpha. These objects and SN 1997ef appear to be extreme examples of massive stars that have lost all but a small amount of hydrogen through mass loss."
International Astronomical Union Circular
- Pub Date:
- December 1997