TY - JOUR
T1 - The diversity of type Ia supernovae
T2 - Evidence for systematics?
AU - Benetti, S.
AU - Cappellaro, E.
AU - Mazzali, P. A.
AU - Turatto, M.
AU - Altavilla, G.
AU - Bufano, F.
AU - Elias-Rosa, N.
AU - Kotak, R.
AU - Pignata, G.
AU - Salvo, M.
AU - Stanishev, V.
PY - 2005/4/20
Y1 - 2005/4/20
N2 - The photometric and spectroscopic properties of 26 well-observed Type Ia Supernovae (SNe Ia) were analyzed with the aim of exploring SN Ia diversity. The sample includes (Branch) normal SNe, as well as extreme events such as SN 1991T and SN 1991bg, while the truly peculiar SNe Ia, SN 2000cx and SN 2002cx, are not included in our sample. A statistical treatment reveals the existence of three different groups. The first group (FAINT) consists of faint SNe Ia similar to SN 1991bg, with low expansion velocities and rapid evolution of Si II velocity. A second group consists of normal SNe Ia, also with high temporal velocity gradient (HVG), but with brighter mean absolute magnitude 〈M B〉 = -19.3 and higher expansion velocities than the FAINT SNe. The third group includes both normal and SN 1991T-like SNe Ia: these SNe populate a narrow strip in the Si II velocity evolution plot, with a low-velocity gradient (LVG), but have absolute magnitudes similar to HVGs. While the FAINT and HVG SNe Ia together seem to define a relation between R (Si II) and Δm15(B), the LVG SNe either do not conform to that relation or define a new, looser one. The R(Si II) premaximum evolution of HVGs is strikingly different from that of LVGs. We discuss the impact of this evidence on the understanding of SN Ia diversity, in terms of explosion mechanisms, degree of ejecta mixing, and ejecta-circumstellar material interaction.
AB - The photometric and spectroscopic properties of 26 well-observed Type Ia Supernovae (SNe Ia) were analyzed with the aim of exploring SN Ia diversity. The sample includes (Branch) normal SNe, as well as extreme events such as SN 1991T and SN 1991bg, while the truly peculiar SNe Ia, SN 2000cx and SN 2002cx, are not included in our sample. A statistical treatment reveals the existence of three different groups. The first group (FAINT) consists of faint SNe Ia similar to SN 1991bg, with low expansion velocities and rapid evolution of Si II velocity. A second group consists of normal SNe Ia, also with high temporal velocity gradient (HVG), but with brighter mean absolute magnitude 〈M B〉 = -19.3 and higher expansion velocities than the FAINT SNe. The third group includes both normal and SN 1991T-like SNe Ia: these SNe populate a narrow strip in the Si II velocity evolution plot, with a low-velocity gradient (LVG), but have absolute magnitudes similar to HVGs. While the FAINT and HVG SNe Ia together seem to define a relation between R (Si II) and Δm15(B), the LVG SNe either do not conform to that relation or define a new, looser one. The R(Si II) premaximum evolution of HVGs is strikingly different from that of LVGs. We discuss the impact of this evidence on the understanding of SN Ia diversity, in terms of explosion mechanisms, degree of ejecta mixing, and ejecta-circumstellar material interaction.
KW - Supernovae: general
UR - http://www.scopus.com/inward/record.url?scp=20444421309&partnerID=8YFLogxK
U2 - 10.1086/428608
DO - 10.1086/428608
M3 - Article
SN - 0004-637X
VL - 623
SP - 1011
EP - 1016
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2 I
ER -