2006CBET..587....1F

R. J. Foley, J. S. Bloom, D. A. Perley, and N. R. Butler, University of California, Berkeley, report that inspection of CCD spectra (range 330-920 nm), obtained on July 25 UT with the Keck I 10-m telescope (+ LRIS) show that SNe 2006di (IAUC 8726) and 2006dv (IAUC 8733) are both of type Ia. The spectrum of 2006di is consistent with a type-Ia supernova approximately 40 days after maximum light. SN 2006dv has a spectral-feature age (Riess et al. 1997, A.J. 114, 722) of 1.5 ± 2.0 days relative to maximum light; adopting a recession velocity of 9940 km/s, found from weak Na D absorption, the minimum of the Si II 635.5-nm absorption is found to be blueshifted by 11200 km/s.

Spectra obtained on July 26 show that SNe 2006dr (cf. IAUC 8731), 2006dw (cf. IAUC 8733), and 2006dy (cf. CBET 586) are also all type-Ia supernovae. SN 2006dw has a spectral-feature age of -0.6 ± 2.0 days relative to maximum light. Adopting a recession velocity of 8107 km/s (from Sloan Digital Sky Survey Data Release 3; Abazajian et al. 2005, A.J. 129, 1755), the minimum of the Si II 635.5-nm absorption is found to be blueshifted by 11300 km/s. In addition, two velocity components are seen for both Ca H and K and the Ca infrared triplet. The minima of the Ca H and K absorption are blueshifted to 11900 and 18600 km/s, while the minima of the Ca II infrared triplet is blueshifted to a significantly smaller 9000 and 13600 km/s (gf-weighted rest wavelength of 857.9 nm; Thomas et al. 2004, Ap.J. 601, 1019). The Ca II infrared triplet velocities are smaller than that found in other type-Ia supernovae at a similar age with multiple velocity components (for example, SN 1999ee; see Mazalli et al. 2005, MNRAS 357, 200). The spectrum of 2006dw also appears to have a large near-ultraviolet (blueward of the Ca H and K absorption) excess. In light of the current brightness of SN 2006dw, its age, and its high-velocity features, spectropolarimetry is encouraged.

SN 2006dy has a spectral-feature age of -9.4±2.0 days relative to maximum light; adopting a recession velocity of 2420 km/s, found from weak Na D absorption, the minimum of the Si II 635.5-nm absorption is found to be blueshifted by 13000 km/s. SN 2006dr has a spectral-feature age of 6.5 ± 2.0 days relative to maximum light; adopting a recession velocity of 4640 km/s, found from weak Na D absorption, the minimum of the Si II 635.5-nm absorption is found to be blueshifted by 10200 km/s.