63 research outputs found
Comprehensive Observations of the Bright and Energetic Type Iax SN 2012Z: Interpretation as a Chandrasekhar Mass White Dwarf Explosion
We present UV through NIR broad-band photometry, and optical and NIR
spectroscopy of Type Iax supernova 2012Z. The data set consists of both early
and late-time observations, including the first late phase NIR spectrum
obtained for a spectroscopically classified SN Iax. Simple model calculations
of its bolometric light curve suggest SN 2012Z produced ~0.3 M_sun of (56)Ni,
ejected about a Chandrasekhar mass of material, and had an explosion energy of
~10^51 erg, making it one of the brightest and most energetic SN Iax yet
observed. The late phase NIR spectrum of SN 2012Z is found to broadly resemble
similar epoch spectra of normal SNe Ia; however, like other SNe Iax,
corresponding visual-wavelength spectra differ substantially compared to all
supernova types. Constraints from the distribution of IMEs, e.g. silicon and
magnesium, indicate that the outer ejecta did not experience significant mixing
during or after burning, and the late phase NIR line profiles suggests most of
the (56)Ni is produced during high density burning. The various observational
properties of SN 2012Z are found to be consistent with the theoretical
expectations of a Chandrasekhar mass white dwarf progenitor that experiences a
pulsational delayed detonation, which produced several tenths of a solar mass
of (56)Ni during the deflagration burning phase and little (or no) (56)Ni
during the detonation phase. Within this scenario only a moderate amount of
Rayleigh-Taylor mixing occurs both during the deflagration and fallback phase
of the pulsation, and the layered structure of the IMEs is a product of the
subsequent denotation phase. The fact that the SNe Iax population does not
follow a tight brightness-decline relation similar to SNe Ia can then be
understood in the framework of variable amounts of mixing during pulsational
rebound and variable amounts of (56)Ni production during the early subsonic
phase of expansion.Comment: Submitted to A&A, manuscript includes response to referee's comments.
39 pages, including 16 figures, 9 table
The Carnegie Supernova Project I: photometry data release of low-redshift stripped-envelope supernovae
The first phase of the Carnegie Supernova Project (CSP-I) was a dedicated
supernova follow-up program based at the Las Campanas Observatory that
collected science data of young, low-redshift supernovae between 2004 and 2009.
Presented in this paper is the CSP-I photometric data release of low-redshift
stripped-envelope core-collapse supernovae. The data consist of optical
(uBgVri) photometry of 34 objects, with a subset of 26 having near-infrared
(YJH) photometry. Twenty objects have optical pre-maximum coverage with a
subset of 12 beginning at least five days prior to the epoch of B-band maximum
brightness. In the near-infrared, 17 objects have pre-maximum observations with
a subset of 14 beginning at least five days prior to the epoch of J-band
maximum brightness. Analysis of this photometric data release is presented in
companion papers focusing on techniques to estimate host-galaxy extinction
(Stritzinger et al., submitted) and the light-curve and progenitor star
properties of the sample (Taddia et al., submitted). The analysis of an
accompanying visual-wavelength spectroscopy sample of ~150 spectra will be the
subject of a future paper.Comment: Updated a couple of small error
Light Curves of the Neutron Star Merger GW170817/SSS17a: Implications for R-Process Nucleosynthesis
On 2017 August 17, gravitational waves were detected from a binary neutron
star merger, GW170817, along with a coincident short gamma-ray burst,
GRB170817A. An optical transient source, Swope Supernova Survey 17a (SSS17a),
was subsequently identified as the counterpart of this event. We present
ultraviolet, optical and infrared light curves of SSS17a extending from 10.9
hours to 18 days post-merger. We constrain the radioactively-powered transient
resulting from the ejection of neutron-rich material. The fast rise of the
light curves, subsequent decay, and rapid color evolution are consistent with
multiple ejecta components of differing lanthanide abundance. The late-time
light curve indicates that SSS17a produced at least ~0.05 solar masses of heavy
elements, demonstrating that neutron star mergers play a role in r-process
nucleosynthesis in the Universe.Comment: Accepted to Scienc
Early ultraviolet emission in the Type Ia supernova LSQ12gdj: No evidence for ongoing shock interaction
We present photospheric-phase observations of LSQ12gdj, a slowly-declining,
UV-bright Type Ia supernova. Classified well before maximum light, LSQ12gdj has
extinction-corrected absolute magnitude , and pre-maximum
spectroscopic evolution similar to SN 1991T and the super-Chandrasekhar-mass SN
2007if. We use ultraviolet photometry from Swift, ground-based optical
photometry, and corrections from a near-infrared photometric template to
construct the bolometric (1600-23800 \AA) light curve out to 45 days past
-band maximum light. We estimate that LSQ12gdj produced
of Ni, with an ejected mass near or slightly above the
Chandrasekhar mass. As much as 27% of the flux at the earliest observed phases,
and 17% at maximum light, is emitted bluewards of 3300 \AA. The absence of
excess luminosity at late times, the cutoff of the spectral energy distribution
bluewards of 3000 \AA, and the absence of narrow line emission and strong Na I
D absorption all argue against a significant contribution from ongoing shock
interaction. However, up to 10% of LSQ12gdj's luminosity near maximum light
could be produced by the release of trapped radiation, including kinetic energy
thermalized during a brief interaction with a compact, hydrogen-poor envelope
(radius cm) shortly after explosion; such an envelope arises
generically in double-degenerate merger scenarios.Comment: 18 pages, 10 figures, accepted to MNRAS; v2 accepted version. Spectra
available on WISEReP (http://www.weizmann.ac.il/astrophysics/wiserep/).
Natural-system photometry and bolometric light curve available as online
tables in MNRAS versio
Early ultraviolet emission in the Type Ia supernova LSQ12gdj: No evidence for ongoing shock interaction
We present photospheric-phase observations of LSQ12gdj, a slowly declining, UV-bright Type Ia supernova. Classified well before maximum light, LSQ12gdj has extinction-corrected absolute magnitude MB = -19.8, and pre-maximum spectroscopic evolution similar to SN 1991T and the super-Chandrasekhar-mass SN 2007if. We use ultraviolet photometry from Swift, ground-based optical photometry, and corrections from a near-infrared photometric template to construct the bolometric (1600-23 800 Å) light curve out to 45 d past B-band maximum light. We estimate that LSQ12gdj produced 0.96 ± 0.07 M· of 56Ni, with an ejected mass near or slightly above the Chandrasekhar mass. As much as 27 per cent of the flux at the earliest observed phases, and 17 per cent at maximum light, is emitted bluewards of 3300 Å. The absence of excess luminosity at late times, the cutoff of the spectral energy distribution bluewards of 3000 Å and the absence of narrow line emission and strong Na I D absorption all argue against a significant contribution from ongoing shock interaction. However, ~10 per cent of LSQ12gdj's luminosity near maximum light could be produced by the release of trapped radiation, including kinetic energy thermalized during a brief interaction with a compact, hydrogen-poor envelope (radius <1013 cm) shortly after explosion; such an envelope arises generically in double-degenerate merger scenarios
Carnegie Supernova Project-II: Extending the Near-Infrared Hubble Diagram for Type Ia Supernovae to
The Carnegie Supernova Project-II (CSP-II) was an NSF-funded, four-year
program to obtain optical and near-infrared observations of a "Cosmology"
sample of Type Ia supernovae located in the smooth Hubble flow (). Light curves were also obtained of a "Physics"
sample composed of 90 nearby Type Ia supernovae at selected for
near-infrared spectroscopic time-series observations. The primary emphasis of
the CSP-II is to use the combination of optical and near-infrared photometry to
achieve a distance precision of better than 5%. In this paper, details of the
supernova sample, the observational strategy, and the characteristics of the
photometric data are provided. In a companion paper, the near-infrared
spectroscopy component of the project is presented.Comment: 43 pages, 10 figures, accepted for publication in PAS
SN 2009md: Another faint supernova from a low mass progenitor
We present adaptive optics imaging of the core collapse supernova (SN)
2009md, which we use together with archival \emph{Hubble Space Telescope} data
to identify a coincident progenitor candidate. We find the progenitor to have
an absolute magnitude of mag and a colour of mag, corresponding to a progenitor luminosity of log
/L dex. Using the stellar evolution code STARS,
we find this to be consistent with a red supergiant progenitor with M. The photometric and spectroscopic evolution of
SN 2009md is similar to that of the class of sub-luminous Type IIP SNe; in this
paper we compare the evolution of SN 2009md primarily to that of the
sub-luminous SN 2005cs. We estimate the mass of Ni ejected in the
explosion to be M\ from the luminosity
on the radioactive tail, which is in agreement with the low Ni masses
estimated for other sub-luminous Type IIP SNe. From the lightcurve and spectra,
we show the SN explosion had a lower energy and ejecta mass than the normal
Type IIP SN 1999em. We discuss problems with stellar evolutionary models, and
the discrepancy between low observed progenitor luminosities (log
/L dex) and model luminosities after the
second-dredge-up for stars in this mass range, and consider an enhanced carbon
burning rate as a possible solution. In conclusion, SN 2009md is a faint SN
arising from the collapse of a progenitor close to the lower mass limit for
core-collapse. This is now the third discovery of a low mass progenitor star
producing a low energy explosion and low Ni ejected mass, which
indicates that such events arise from the lowest end of the mass range that
produces a core-collapse supernova (7-8 M).Comment: MNRAS accepted, revised version following referee's comment
The Carnegie Supernova Project II. The shock wave revealed through the fog: The strongly interacting Type IIn SN 2013L
We present ultra-violet to mid-infrared observations of the long-lasting Type
IIn supernova (SN) 2013L obtained by the Carnegie Supernova Project II
(CSP-II). The spectra of SN 2013L are dominated by H emission features
characterized by three components attributed to different regions. A unique
feature of this Type IIn SN is that the blue shifted line profile is dominated
by the macroscopic velocity of the expanding shock wave of the SN. We are
therefore able to trace the evolution of the shock velocity in the dense and
partially opaque circumstellar medium (CSM), from at +48
d, decreasing as to after a year. We perform
spectral modeling of both the broad- and intermediate-velocity components of
the H line profile. The high-velocity component is consistent with
emission from a radially thin, spherical shell located behind the expanding
shock with emission wings broadened by electron scattering. We propose that the
intermediate component originates from pre-ionized gas from the unshocked dense
CSM with the same velocity as the narrow component, , but
also broadened by electron scattering. The spectral energy distributions (SEDs)
of SN 2013L after +132 d are well reproduced by a two-component black-body (BB)
model. The circumstellar-interaction model of the bolometric light curve
reveals a mass-loss rate history with large values () over the 25 - 40 years before explosion. The drop
in the light curve at days and presence of electron scattering wings
at late epochs indicate an anisotropic CSM. The mass-loss rate values and the
unshocked CSM velocity are consistent with the characteristics of a massive
star, such as a luminous blue variable (LBV) undergoing strong eruptions,
similar to Carina.Comment: Replaced after language editor corrections, accepted for publication
on Astronomy and Astrophysics, 43 pages, 29 figures. Abstract abridge
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