95 research outputs found
Type Ib/c Supernovae with and without Gamma-Ray Bursts
While the connection between Long Gamma-Ray Bursts (GRBs) and Type Ib/c
Supernovae (SNe Ib/c) from stripped stars has been well-established, one key
outstanding question is what conditions and factors lead to each kind of
explosion in massive stripped stars. One promising line of attack is to
investigate what sets apart SNe Ib/c with GRBs from those without GRBs. Here, I
briefly present two observational studies that probe the SN properties and the
environmental metallicities of SNe Ib/c (specifically broad-lined SNe Ic) with
and without GRBs. I present an analysis of expansion velocities based on
published spectra and on the homogeneous spectroscopic CfA data set of over 70
SNe of Types IIb, Ib, Ic and Ic-bl, which triples the world supply of
well-observed Stripped SNe. Moreover, I demonstrate that a meta-analysis of the
three published SN Ib/c metallicity data sets, when including only values at
the SN positions to probe natal oxygen abundances, indicates at very high
significance that indeed SNe Ic erupt from more metal-rich environments than
SNe Ib, while SNe Ic-bl with GRBs still prefer, on average, more metal-poor
sites than those without GRBs.Comment: 5 pages, 2 Figures. To appear in the Proceedings of IAU Symposium 279
"Death of Massive Stars: Supernovae and Gamma-ray Bursts". Contains updates
with respect to Modjaz et al (2011
The Host Galaxies of Fast-Ejecta Core-Collapse Supernovae
Spectra of broad-lined Type Ic supernovae (SN Ic-BL), the only kind of SN
observed at the locations of long-duration gamma-ray bursts (LGRBs), exhibit
wide features indicative of high ejecta velocities (~0.1c). We study the host
galaxies of a sample of 245 low-redshift (z<0.2) core-collapse SN, including 17
SN Ic-BL, discovered by galaxy-untargeted searches, and 15 optically luminous
and dust-obscured z<1.2 LGRBs. We show that, in comparison with SDSS galaxies
having similar stellar masses, the hosts of low-redshift SN Ic-BL and z<1.2
LGRBs have high stellar-mass and star-formation-rate densities. Core-collapse
SN having typical ejecta velocities, in contrast, show no preference for such
galaxies. Moreover, we find that the hosts of SN Ic-BL, unlike those of SN
Ib/Ic and SN II, exhibit high gas velocity dispersions for their stellar
masses. The patterns likely reflect variations among star-forming environments,
and suggest that LGRBs can be used as probes of conditions in high-redshift
galaxies. They may be caused by efficient formation of massive binary
progenitors systems in densely star-forming regions, or, less probably, a
higher fraction of stars created with the initial masses required for a SN
Ic-BL or LGRB. Finally, we show that the preference of SN Ic-BL and LGRBs for
galaxies with high stellar-mass and star-formation-rate densities cannot be
attributed to a preference for low metal abundances but must reflect the
influence of a separate environmental factor.Comment: Accepted by ApJ 9 May 2014 with only minor revision
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