Department of Astronomy, The Oskar Klein CentreStockholm
2 The Oskar Klein Centre, Department of Physics, Stockholm University, AlbaNova, 10691 Stockholm, Sweden
3 Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
4 Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark
5 Las Cumbres Observatory Global Telescope Network, 6740 Cortona Dr., Suite 102, Goleta, CA 93117, USA
6 Department of Physics, University of California, Santa Barbara, Broida Hall, Mail Code 9530, Santa Barbara, CA 93106-9530, USA
7 Millennium Institute of Astrophysics, Universidad de Chile, Casilla 36- D Santiago, Chile
8 Departamento de Astronomía, Universidad de Chile, Casilla 36- D Santiago, Chile
9 Department of Astronomy and Astrophysics, The University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA
10 Kavli Institute for Cosmological Physics, The University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA
11 Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802, USA
12 Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA 16802, USA
13 Department of Astronomy, University of Texas at Austin, Austin, TX 78712, USA
Received: 31 March 2014
Accepted: 20 October 2014
Context. Type Ib/c supernovae (SNe Ib/c) have been investigated in several single-object studies; however, there is still a paucity of works concerning larger, homogeneous samples of these hydrogen-poor transients, in particular regarding the premaximum phase of their light curves.
Aims. In this paper we present and analyze the early-time optical light curves (LCs, ugriz) of 20 SNe Ib/c from the Sloan Digital Sky Survey (SDSS) SN survey II, aiming to study their observational and physical properties, as well as to derive their progenitor parameters.
Methods. High-cadence, multiband LCs are fitted with a functional model and the best-fit parameters are compared among the SN types. Bolometric LCs (BLCs) are constructed for the entire sample. We also computed the black-body (BB) temperature (TBB) and photospheric radius (Rph) evolution for each SN via BB fits on the spectral energy distributions. In addition, the bolometric properties are compared to both hydrodynamical and analytical model expectations.
Results. Complementing our sample with literature data, we find that SNe Ic and Ic-BL (broad-line) have shorter rise times than those of SNe Ib and IIb. The decline rate parameter, Δm15, is similar among the different subtypes. SNe Ic appear brighter and bluer than SNe Ib, but this difference vanishes if we consider host galaxy extinction corrections based on colors. Templates for SN Ib/c LCs are presented. Our SNe have typical TBB of ~10 000 K at the peak and Rph of ~1015 cm. Analysis of the BLCs of SNe Ib and Ic gives typical ejecta masses Mej≈ 3.6−5.7 M⊙, energies EK≈ 1.5−1.7×1051 erg, and M(56Ni) ≈ 0.3 M⊙. Higher values for EK and M(56Ni) are estimated for SNe Ic-BL (Mej≈ 5.4 M⊙, EK≈ 10.7×1051 erg, M(56Ni) ≈ 1.1 M⊙). For the majority of SNe Ic and Ic-BL, we can put strong limits (<2−4 days) on the duration of the expected early-time plateau. Less stringent limits can be placed on the duration of the plateau for the sample of SNe Ib. In the single case of SN Ib 2006lc, a >5.9 days plateau seems to be detected. The rising part of the BLCs is reproduced by power laws with index <2. For two events (SN 2005hm and SN 2007qx), we find signatures of a possible shock break-out cooling tail.
Conclusions. Based on the limits for the plateau length and on the slow rise of the BLCs, we find that in most of our SNe Ic and Ic-BL the 56Ni is mixed out to the outer layers, suggesting that SN Ic progenitors are de facto helium poor. The derived progenitor parameters (56Ni, EK, Mej) are consistent with previous works.
Key words: supernovae: general
Figures 1, 7 and Tables 1–7 are available in electronic form at http://www.aanda.org
Light curve templates are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (126.96.36.199) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/574/A60
© ESO, 2015