The peculiar type Ia supernova 1999by: Spectroscopy at early epochs

We present medium-resolution (lambda/Delta lambda approximate to 2500) opti cal spectroscopy of SN 1999 by in NGC 2841 made around its light maximum. T hat the depth ratio of the two Si II features at 5800 and 6150 Angstrom are R(Si II) approximate to 0.63 at maximum indicates that this SN belongs to the peculiar subluminous Type SNe Ia. Radial velocities inferred from the m inimum of the 6150 Angstrom trough reveal a steeper decline of the velocity curve than expected for normal SNe Ia, consistent with the behavior of pub lished V RI light curves. A revised absolute magnitude of SN 1999 by and di stance to its host galaxy NGC 2841 are estimated based on the multicolor li ght-curve shape (MLCS) method, resulting in mag and M-V(max) = -18.06 +/-0. 1 mag and d =17.1 +/-1.2 Mpc, respectively. An approximate linear dependenc e of the luminosity parameter Delta on R(Si II) is presented.